If you want to print this document out, here’s a link to this same document as an easier-to-print google doc.



I wrote this outline for you: an AP Bio student who’s studying for the upcoming AP Bio exam. My goal was to give you an easy-to-use study outline that you can use to assess your familiarity with key AP Bio concepts and skills.

My main source was the College Board’s AP Biology Course and Exam Description. However, based on my own experience preparing students for the AP Bio exam and consultation with other AP Bio teachers, I’ve combined some topics, changed the order of topics, and (rarely) added or cut topics.

If you want to go see the sources upon which I based this study outline, here are two ways to do that.

  • AP Biology Course and Exam Description. This is the official College Board Document. Including its introductory material and appendices, it’s over 200 pages. Filled with illustrative examples, learning objectives, and key concepts, it’s a fantastic design document. But if you’re studying for the AP Bio exam, it can be a bit much.
  • My reformatted Google Doc version of the CB document. By cutting and pasting, I was able to get the College Board’s original document to fit into 40 pages. However, the language can still be confusing, which is why I wrote the study outline below.

How to Use this Study Outline

Use this document to do retrieval practice. That means recalling information from memory (as opposed to just reading). As you move through the outline below, look at the numbered learning objective, and say (or write down) everything you know. If you can’t respond to an objective, mark that as a topic that you’ll need review.

Where possible and feasible, I’ve put brief bullet points below the learning objective so you can tell if you’re on the right track. However, to keep the length of this document reasonable, many objectives have no bullets.

Links in the lists of topics or objectives go to interactive tutorials on Learn-Biology.com’s AP Biology curriculum. 

Other Resources for Studying

The best material for you to use to study are questions created by the College Board. You can download the FRQs and scoring guidelines from the 2021 exam here. You can access FRQs from previous years at this link (but remember that the course was redesigned in 2019: skip questions relating to topics that are no longer on the exam, such as the immune system or the nervous system).

You’ll be able to access high quality multiple choice questions from the College Board through your teacher, who can give these to you directly or make them available through AP Classroom.

In addition to the outline below, please look at these review resources that I’ve created to help you review for the AP Bio exam.

Unit 1. Chemistry of Life

Unit 1 Topics

Unit 1 Learning Objectives

Topic 1.1. Structure of Water and Hydrogen Bonding

  1. Describe water’s molecular structure.
  2. Explain the key physical and chemical properties that result from water’s molecular structure.
  3. Describe cohesion, adhesion and surface tension, and explain how these key properties of water result from hydrogen bonding.
  4. List examples of ways in which living things depend on water’s physical and chemical properties

Topic 1.2 – 1.4. Life’s Key Elements; Monomers and Polymers; Carbohydrates and Lipids

  1. Describe the key roles of carbon, nitrogen, and phosphorus in the molecules found in living things.
    • Carbon is the key structural atom in all biomolecules
    • Nitrogen is in proteins and nucleic acids; phosphorus is in ATP, nucleic acids and phospholipids.
  2. Compare and contrast dehydration synthesis and hydrolysis reactions.
    1. Dehydration synthesis reactions are endergonic, and are used to build the complex molecules in living things.
    2. Hydrolysis reactions are exergonic, and are used to release energy and to digest polymers into monomers.
  3. Describe the structure and function of carbohydrates.
    • Simple sugars (monosaccharides) are the monomers of carbohydrates. These monomers are combined to create more complex carbohydrates.
    • Glucose (a six-carbon simple sugar) is used to power synthesis of ATP during cellular respiration.
  4. Describe the structure and function of lipids
    • Differences in saturation determine the differences between fats and oils.
    • The structure of phospholipids gives them polar/hydrophilic regions and nonpolar/hydrophobic regions.

Topics 1.4, 1.5, 1.6: Proteins and Nucleic Acids

  1. Describe the role and structure of amino acids.
    • Amino acids are the monomers of proteins
    • They have a central carbon, a hydrogen atom, an amine group, a carboxyl group, and a variable R-group/side chain
  2. List the types of R groups/side-chains
    • hydrophobic, hydrophilic, basic, or acidic.
  3. Explain how proteins are directional,
    • They have an amino terminus and a carboxyl terminus.
  4. Explain how the four levels of protein structure give rise to a protein’s 3D shape and function
    • primary: the sequence of amino acids .
    • secondary: interaction between carbonyl and amino residues leading to alpha helices and beta pleated sheets.
    • tertiary: interactions between R-Groups
    • Quaternary: interactions between polypeptide chains.
  5. Compare and contrast the structure of DNA and RNA.
    • Both are polymers of nucleotides, which have  5 carbon sugar, a phosphate group, and a nitrogenous base.
    • Both encode information in their sequence of nucleotides.
    • In DNA, the sugar is deoxyribose, and the bases are A,T, C, and G.
    • In RNA the sugar is ribose, and the bases are A, U, C, and G.
    • DNA is a double helix in which the complementary strands are antiparallel; RNA is single stranded.
  6. Explain directionality of DNA, and connect directionality to DNA replication
    • DNA (and RNA) has a 5′ to 3′ orientation. During replication, new nucleotides can only be added to the 3′ end of a growing strand.

Unit 2. Cell Structure and Function

Unit 2 Topics

Unit 2 Learning Objectives

Topics 2.1 and 2.2: Cell Structure and Function.

  1. Explain the basic ideas of the cell theory
    • Cells are the basic units of life, all living things are made of cells, and cells come from other cells.
  2. Compare and contrast the basic features of prokaryotic and eukaryotic cells.
  3. Describe the structure and functions of the following cell parts
    1. nucleus
    2. cytoplasm
    3. cell membrane
    4. ribosomes
    5. Rough endoplasmic reticulum
    6. Smooth endoplasmic reticulum
    7. Golgi complex
    8. lysosomes
    9. mitochondria
    10. vacuoles
    11. chloroplasts
    12. cell wall

Topic 2.3: The Size of Cells (surface area to volume relationships)

  1. Explain how surface area-to-volume ratios affect the ability of biological systems (cells, organisms, and groups of organisms) to obtain resources; eliminate wastes; or absorb or dissipate heat or other forms of energy from the environment.
  2. Explain how membrane surface area influences the size and shape of cells and organisms. Specifically:
    1. Why are cells small?
      • Cells are small because smaller size enables cells to increase their surface area-to-volume ratio to more efficiently exchange materials and energy with their environment.
    2. Explain how, despite the limitation described above, organisms were able to increase in size.
      • Through multicellularity, which required various adaptations to increase internal surface area to allow for diffusion of nutrients and wastes into or out of cells, or to control heat exchange with the environment.
    3. Explain various adaptations to increase or decrease surface area-to-volume ratios.
      • Increase: branch vessels or flat surfaces to increase the efficiency of exchange.
      • Decrease: opposite of above.

Topics 2.4 – 2.9: Cell Membrane Structure and Function; Osmosis

  1. Describe the fluid mosaic model of the cell membrane. Descriptions should include
    • The overall function of the membrane
    • The role of phospholipids (and how their structure results in the formation of phospholipid bilayers).
    • The role of embedded proteins (how they fit into the bilayer, and their various roles)
    • The functions of cholesterol, glycolipids, and glycoproteins.
  2. Define selective permeability.
  3. Explain how selective permeability arises from the fluid mosaic structure of the membrane.
    1. How small, nonpolar molecules like N2, CO2, and O2 can pass across the membrane
      • simple diffusion through the phospholipid bilayer.
    2. How ions and large polar molecules move across the membrane
      • facilitated diffusion through embedded protein channels
    3. How small polar molecules (like water) pass through the membrane
      • Water passes through aquaporins.
  4. Compare and contrast passive transport, active transport, and facilitated diffusion. Connect each process to membrane structure.
    • Protein pumps use energy for active transport
    • Protein channels allow for facilitated diffusion.
  5. Compare and contrast endocytosis and exocytosis.
  6. Explain membrane potential
    • A charge created by an imbalance in ions across a membrane.
  7. Connect membrane potential to processes such as ATP synthesis.
    • Proton gradients are used to drive ATP synthesis through chemiosmosis (more on this below in Topics 3.5 and 3.6.
  8. Define the term osmosis, and be able to predict and explain the flow of water into or out of cells in hypotonic, hypertonic, and isotonic environments.
  9. Explain the movement of water into or out of cells (and entire organisms) in relationship to water potential
    • Water always flows from high water potential to lower water potential.
  10. Be able to understand and use (but don’t memorize) the two water potential equations
    1. the general water potential equation (Ψ = ΨS + ΨP : water potential = pressure potential + solute potential)
    2. The equation for solute potential:   ΨS = – iCRT .

Topic 2.10: Cellular Compartmentalization (and its origins)

  1. Define the term “endomembrane system,” and describe that system’s overall function. Descriptions should include:
    • Creating cellular compartments that segregate cellular functions such as hydrolysis, export of cell materials through exocytosis, import of materials through endocytosis, capture of food or pathogens in phagocytosis, and assembly of macromolecules.
    • Creating compartments with optimal conditions for enzymatic reactions
    • Increasing surface area for membrane-bound enzymatic reactions (in the E.R. and Golgi).
  2. List the key membrane-bound organelles found within eukaryotic cells, and describe the structure and function of each.
    • List should include: rough E.R., smooth E.R., Golgi, lysosomes, vacuoles, vesicles, mitochondria, and chloroplasts.
  3. Explain how compartmentalization is different in eukaryotic and prokaryotic cells
    • Extensive compartmentalization is primarily a feature of eukaryotic cells.
    • Prokaryotic cells do have some internal compartments (such as the thylakoids in cyanobacteria)
  4. Explain the evolutionary origins of mitochondria and chloroplasts, with supporting evidence.
    • Both mitochondria and chloroplasts arose through endosymbiosis. Free-living bacterial ancestors of mitochondria and chloroplasts were taken up by and took up residence inside a larger archaeal cell.
    • All eukaryotic cells originate from the uptake/incorporation of mitochondria into a larger cell.
    • Plants and algae originate from an early eukaryotic uptake of a photosynthetic cyanobacterium.
  5. Describe the evidence for the endosymbiotic theory.
    • Both mitochondria and chloroplasts have their own bacteria-like chromosomes, with their own DNA.
    • Both have a double membrane (the inner one a vestige of their own ancestral membrane; the outer one a vestige of an ancient endocytotic vesicle)
    • Both reproduce themselves through binary fission.

Unit 3. Cellular Energetics

Unit 3 Topics

Unit 3 Learning Objectives

Topics 3.1 to 3.3: Enzymes

  1. Describe the key properties and function of enzymes. This description should include the following:
    • Enzymes are complex, large proteins that facilitate chemical reactions by reducing activation energy.
    • Enzymes are highly specific, and generally interact with only one substrate.
    • Enzyme specificity is based on the complementary shape and charge between the enzyme’s active site and the substrate.
  2. Explain how changes in an enzyme’s shape affect the enzyme’s function. Connect this explanation to the idea of denaturation.
    • Because enzymes are proteins, their shape is stabilized by internal bonds that can be disrupted by changes in the enzyme’s environment.
    • Denaturation is when a change in an enzyme’s shape reduces its ability to bind with its substrate.
    • Denaturation can be reversible or irreversible.
  3. Explain the effect of moderate and extreme changes in temperature on enzyme activity
    • At moderate temperatures, temperature increase will increase enzyme-substrate collisions, increasing enzyme activity. Temperature decrease will (for the opposite reason) decrease enzyme activity.
    • At high temperatures, enzymes can denature, reducing their activity
  4. Explain the effect of changes in pH or ion concentration on enzyme activity.
    • Because enzymes are proteins and because protein shape is a function of various internal bonds, enzymes have a pH and ion concentration optimum.
    • Environmental changes that move the pH and ion concentration above or below that optimum will disrupt the enzyme’s internal bonds, changing the shape of the enzyme’s active site, reducing its activity.
  5. Explain the effects of enzyme and substrate concentration on enzyme activity
    • Enzyme activity will increase with increased enzyme and substrate activity until the enzymes’ active sites are saturated. At that point, enzyme activity reaches its maximum rate.
  6. Explain the role of competitive and non-competitive inhibitors on enzyme activity
    • Competitive inhibitors reduce enzyme activity by competing with substrates for the enzyme’s active site.
    • Non-competitive inhibitors bind at a region away from the active site (an allosteric site). However, that binding changes the shape of the active site, reducing the enzyme’s activity.
  7. *Explain how cells can regulate enzyme activity through feedback inhibition and allosteric regulation.
    • In feedback inhibition, the product of an enzymatic reaction acts as a competitive or non-competitive inhibitor of enzyme activity, creating negative feedback that reduces enzyme activity.
    • In allosteric regulation, a substance produced by a metabolic pathway binds with an enzyme at an allosteric site. This can inhibit or stimulate enzyme activity.

Topic 3.4: Cell Energy

  1. Explain how living things create and maintain their complex order.
    • Through a constant input of energy.
    • For autotrophic organisms, that energy input is almost always energy from the sun (the exceptions are chemoautotrophs, which get energy by oxidizing inorganic compounds).
    • For heterotrophs, the energy is from organic compounds that are eaten or absorbed.
  2. Describe the energy input/output balance required for life to be maintained.
    • For life to be maintained, energy input has to exceed energy loss.
  3. Using the terms endergonic and exergonic, describe energy coupling.
    • In energy coupling, energy-requiring processes (endergonic processes) are typically coupled with energy releasing (exergonic) processes.
  4. Describe the structure of ATP.
    • ATP is adenosine triphosphate. It consists of the 5-carbon sugar ribose, connected to three phosphate groups on one side and the nitrogenous base adenine on the other side.
  5. Describe some common coupled reactions.
    • Oxidizing food or food by-products in order to reduce electron carriers.
    • Oxidizing electron carriers to power proton pumping during chemiosmotic production of ATP.
    • Hydrolyzing ATP to ADP and phosphate (an exergonic reaction) in order to power any endergonic process (synthesis, movement, or any other kind of work).
  6. Describe the ATP/ADP cycle.
    • In an endergonic reaction powered by chemiosmosis or energy from an organic substrate,  ATP is made from ADP and phosphate. The breakdown of ATP to ADP and phosphate makes energy available to power cellular work.

Topic 3.5: Photosynthesis

  1. Describe the cellular location of the reactions of photosynthesis
    • Chloroplasts are the organelle that carries out photosynthesis.
    • Within chloroplasts are thylakoids: membrane-bound sacs, organized into stacks called grana.
    • The photosystems and electron transport chain involved in the light reaction are located in the thylakoid membranes.
    • The carbon-fixing reactions of the Calvin cycle occur in the stroma.
  2. Describe key evolutionary milestones in the evolution of photosynthesis
    • Photosynthesis first evolved in photosynthetic bacteria (cyanobacteria)
    • Prokaryotic photosynthesis created Earth’s oxygen-rich atmosphere.
    • Chloroplasts are endosymbionts, descended from a cyanobacterium that took up residence inside a eukaryotic cell. These cells evolved to become the cells making up algae, then plants.
  3. Explain the light reactions of photosynthesis
    • Light energy is converted into electron energy by two chlorophyll rich photosystems. (PS II and PS I)
    • Electron flow through the electron transport chain of photosystem II is used to create a proton gradient that powers ATP synthesis. The mechanism (pumping protons to a compartment, followed by chemiosmotic flow through ATP synthase) parallels what happens in mitochondrial ATP synthesis.
    • Electron flow through the ETC of photosystem I is used to reduce NADP+ into NADPH.
  4. Explain the key reactions of the Calvin cycle
    • The Calvin cycle is responsible for carbon fixation (bringing organic carbon into the biosphere)
    • The inputs are the products of the light reactions (NADPH and ATP), and carbon dioxide
    • NADPH  provides reducing power (for hydrogenating CO2)
    • The reduction of carbon dioxide into carbohydrate is endergonic. Hydrolysis of ATP provides the energy to drive this reaction forward.
    • Rubisco is the key enzyme involved in carbon fixation (and is the most abundant protein on Earth).

Topic 3.6: Cellular Respiration

  1. Explain the overall pathway of aerobic cellular respiration
    • Glycolysis, link reaction, Krebs, and the electron transport chain.
  2. Explain what happens during glycolysis
    • Oxidation of glucose is coupled to the reduction of NAD+ to NADH, and the phosphorylation of ADP to ATP.
    • The end product is pyruvic acid, an energy-rich 3 carbon compound that powers the link reaction and Krebs cycle.
  3. Explain what happens during the link reaction
    • Pyruvic acid enters the mitochondria, and gets converted to acetyl CoA.
    • Oxidation of pyruvate generates NADH.
  4. Explain the key reactions of the Krebs cycle
    • Oxidation of acetyl-CoA to power reduction of NAD+ and FAD to NADH and FADH2;
    • Phosphorylation of ADP to ATP
    • Release of carbon dioxide.
    • Regeneration of the four carbon compound oxaloacetate.
  5. Explain the roles of  NADH and FADH2 in cellular respiration
    • Electron energy from oxidation of these two electron carriers is used to power proton pumping to create a proton gradient between the intermembrane space and the mitochondrial matrix.
  6. Describe what happens in chemiosmosis
    • Diffusion of protons through the ATP synthase channel is used to power ATP synthesis from ADP and P.
  7. Explain the role of oxygen in the electron transport chain.
    • Final electron acceptor
  8. Compare and contrast lactic acid and alcohol fermentation.
    • Both reduce pyruvate so that NAD+ can be regenerated, allowing glycolysis to continue to yield two ATPs/glucose.
  9. Connect the structure of the mitochondrion to the key processes of aerobic respiration
    • Krebs occurs in the mitochondrial matrix;
    • The ETC happens along the inner membrane;
    • Protons are pumped to the intermembrane space;
    • Inner membrane folding increases surface area, allowing for more ETC components and more ATP synthases
  10. Explain how the pathways of cellular respiration can be used for thermoregulation
    • Uncoupling electron flow from oxidative phosphorylation allows electron flow to generate heat.

Unit 4: Cell Communication, Cell Cycle, Feedback

Unit 4 topics

Unit 4 Learning Objectives

Topics 4.1.-4.4: Cell Signaling, Cell Communication and Signal Transduction

  1. Describe three ways that cells communicate with one another, and provide examples of each one.
    • Cell-to-cell contact (examples: immune signaling, plasmodesmata)
    • Short distance signaling using local regulators (examples: neurotransmitters, quorum sensing, morphogens during embryonic development)
    • Long distance signaling (examples: endocrine signaling)
  2. Describe the function of signal transduction
    • linking signal reception with a cellular response)
  3. List the three components of signal transduction systems
    • reception, transduction, response
  4. Describe the key features of reception
    • specific receptors — usually membrane proteins — binding with ligands.
  5. Describe the key features of signal transduction
    • ligand binding leading to changes in the intracellular domain of a membrane protein; propagation of the signal to and through second messengers such as cyclic AMP; amplification of the signal through phosphorylation cascades.
  6. List examples of cellular responses that result from signal transduction
    • Examples: cell division, secretion of molecules, gene expression, apoptosis.
  7. Explain how changes in the components of a signaling system (ligand, receptor, transduction components) can alter cellular responses.
    • Mutations in receptors (changes in shape or number) can affect downstream signal transduction.
    • Chemicals interfering with any part of a signaling system component can change transduction.

Topic 4.5: Feedback and Homeostasis

  1. Describe the function of feedback mechanisms
    • Maintaining internal environments and responding to internal and external environmental changes.
  2. Define the physiological concept of a set point.
    • The value around which a physiological process fluctuates. Example: the temperature set point in humans is 37 degrees C.
  3. Explain how negative feedback helps to maintain homeostasis
    • By returning a perturbed system back to its target set point.
  4. Explain how positive feedback works
    • By amplifying responses and processes in a way that increases the initial stimulus, which further activates the response.

Topic 4.6: Cell Division and the Cell Cycle

  1. Compare and contrast cell division in prokaryotes and eukaryotes
    • binary fission v. mitosis
  2. Describe the functions of cell division in eukaryotes
    • Asexual reproduction, growth and repair.
  3. List the phases of the cell cycle, and explain what happens during each phase
    • List: interphase, G1, S, G2, M
  4. Explain the importance of the G0 phase.
  5. Describe, on a big-picture level, what happens in mitosis
    • Cloning of a parent cell’s entire genome into two genetically identical daughter cells
  6. List and describe the phases of mitosis.

Topic 4.7: Cell Cycle Regulation

  1. Describe how the cell cycle is regulated
    • answers should include a general description of internal checkpoints, and how these checkpoints work to control progression through the cycle
  2. Explain how interactions between cyclins and cyclin-dependent kinases control the cell cycle.
  3. Describe how disruptions to the cell cycle can lead to cancer.
    • Cancer can result from any process that increases cell division, removes inhibition or cell division, or both.
    • Processes that increase cell division are connected to mutations in oncogenes. Processes that remove cell division inhibitors are connected to mutations in tumor suppressor genes.
  4. Define apoptosis
    • A regulated process resulting in cell death.

Unit 5. Heredity

Unit 5 topics

Unit 5 Learning Objectives

TOPIC 5.1: Meiosis

  1. Explain how meiosis transmits genetic material from one generation to the next.
  2. Compare and contrast diploid and haploid cells, and explain how these terms connect to somatic cells and germ cells.
    • Diploid: two chromosome sets (one maternal, one paternal). Haploid: one set
    • Somatic: body cells. Germ cells: gametes.
  3. Compare and contrast mitosis and meiosis (the types of daughter cells, the number of cell divisions)
    • Mitosis: 2 diploid daughter cells that are clones of the parent.
    • Meiosis: 4 haploid daughter cells that are genetically unique.

Topics 5.2 and 5.6. Meiosis, Chromosomal Inheritance, and Genetic Diversity

  1. Explain how meiosis generates genetic diversity.
    • By creating genetically unique offspring that are genetically distinct from their parents, and siblings who are genetically distinct from each other.
  2. Define “homologous” chromosomes (their origin, their relationship in term of genetic information) and explain what happens to homologous pairs during meiosis
    • Homologous pairs are the matched chromosomes inherited from each parent. They have the same genes, but possibly different alleles.
    • During meiosis 1, homologous pairs independently assort, creating gametes with unique combinations of maternal and paternal chromosomes.
  3. Explain what crossing over is, and how it generates genetic diversity.
    • Homologous pairs exchange pieces of DNA, creating unique, never-before-seen recombinant chromosomes.
  4. Explain fertilization (in terms of haploid and diploid chromosome numbers), as well as fertilization’s contribution to genetic diversity.
  5. Compare meiosis 1 and meiosis 2, and explain what happens during each process.
    • Meiosis 1: diploid to haploid, independent assortment.
    • Meiosis 2: sister chromatids are pulled apart.
  6. Connect the events of meiosis and fertilization to how sexual reproduction creates variation.
    • Through independent assortment; crossing over, and fertilization.
  7. Connect the events of meiosis to Mendel’s laws of segregation and independent assortment; and to recombination of linked alleles.
  8. Explain how certain aspects of human genetic variation (Down’s syndrome, etc.) can be explained by chromosomal changes resulting from meiosis (nondisjunction).

Topic 5.3. Mendelian Genetics

  1. Explain Mendel’s laws of segregation and independent assortment, and connect them to what happens during meiosis.
  2. Explain relevant rules of probability that apply to genetics.
    • The rule of multiplication is the most important of these.
  3. Be able to solve genetics problems involving
    1. Monohybrid and dihybrid crosses with autosomal genes;
    2. Multiple alleles, with blood type (A, B, O system) as an illustrative example. Note that while blood type isn’t explicitly in the College Board’s standards, it can show up in problems related to inheritance patterns that involve multiple alleles.

Topic 5.4. Non-Mendelian Genetics

  1. Explain the chromosomal basis of linkage and recombination. When given data about linkage, be able to determine the distance (in map units) between linked alleles.
    • Genes on nonhomologous chromosomes independently assort.
    • Genes on the same chromosome are linked, but can recombine because of crossing over.
  2. Explain the inheritance patterns of sex linked genes, and be able to solve genetics problems involving sex linkage.
    • Sex linked genes are on the X chromosome
    • Males (who much more frequently express these genes) always inherit sex-linked genes from their mother.
  3. Explain non-XY sex determination systems, such as the ZZ/ZW system in birds, haplodiploidy in bees, and temperature dependent sex determination in certain reptilian clades.
  4. Define polygenic traits, and describe why these usually have a bell-curve shaped distribution pattern.
  5. Explain non-nuclear inheritance
    • Inheritance of genes in mitochondria of chloroplasts.
    • Gene transmission is exclusively maternal.

Topic 5.5. Environmental Effects on Phenotype

  1. Explain how the interaction between genotype and environment is a major determinant of phenotype.

[note: Topic 5.6 was covered above with topic 5.2].

Unit 6. Gene Expression and Regulation

Unit 6 topics

Unit 6 Learning Objectives

Topic 6.1: DNA and RNA Structure and Function

[note: some of this is also covered in 1.6 above]

  1. Compare eukaryotic and prokaryotic chromosomes.
    • Prokaryotes have circular chromosomes. Eukaryotes have linear chromosomes. Prokaryotes also have plasmids
  2. Compare and contrast the functions of DNA and RNA
    • DNA is the molecule of heredity in organisms. RNA can play that role in viruses.
    • In organisms, RNA’s function is information transfer related to protein synthesis (mRNA, tRNA, and rRNA)
    • RNA also has a catalytic role in certain processes (splicing out introns, influencing gene expression).
  3. Describe the features of DNA that make it suited to be the molecule of heredity.
    • Stability of double helix allows for stable information storage.
    •  Base pairing rules allow for accurate replication.

Topic 6.2: DNA Replication

  1. Explain the basic chemistry of DNA replication.
    • DNA polymerase adds new nucleotides at the 3’ end of a growing strand (5′ to 3′ synthesis)
    • Because DNA polymerase can only add to an existing strand, an RNA primer is required.
  2. Explain how DNA replication is semiconservative
    • One strand acts as the template for synthesis of a new complementary strand.
  3. List the key enzymes involved in DNA Replication (and describe the function of each)
    • Helicase, topoisomerase, DNA polymerase, ligase
  4. Describe the leading and lagging strands, and explain how replication is different on each.
    • Leading strand: continuous replication.
    • Lagging strand: discontinuous replication (Okazaki fragments).

Topic 6.3: Transcription

  1. Describe the flow of genetic information within cells (AKA the central dogma)
    • DNA makes RNA makes protein
  2. Describe what happens during transcription
    • RNA polymerase binds at a promoter, a DNA sequence just upstream of the transcription start site.
    • Binding of RNA polymerase can be regulated by transcription factors (see topics 6.5 and 6.6 below)
    • RNA polymerase uses the sequence of DNA nucleotides in the template strand (AKA the noncoding strand, minus strand, or antisense strand) to synthesize complementary RNA.
    • RNA polymerase synthesizes in the 5’ to 3’ direction as it reads DNA in the 3’ to 5’ direction
  3. Describe the roles and key features of the 3 types of RNA in protein synthesis
    • mRNA:  carries information from DNA to the ribosome. Information is encoded in codons: 3 RNA nucleotides that specify a particular amino acid.
    • tRNAs: have an amino acid binding site and an anticodon (a sequence complementary to a codon). The specific binding of anticodon to codon ensures that the amino acid sequence in a polypeptide matches the sequence specified in mRNA
    •  rRNA is the catalytic part of the ribosome, connecting amino acids in a polypeptide chain.
  4. Describe the additional RNA processing the occurs in eukaryotic cells
    • Addition of a poly-A tail.
    • Addition of a GTP cap.
    • Excision of introns and splicing and retention of exons.
  5. Explain how organization of eukaryotic genetic material into introns and exons can increase phenotypic variation.
    • Through alternative splicing, exons can be spliced together in alternative ways allowing for the production of multiple protein versions from the same mRNA transcript.

Topic 6.4. Translation

  1. Compare translation in prokaryotes and eukaryotes
    • In all cells, translation occurs at ribosomes. In eukaryotes, some ribosomes are embedded into the rough E.R.
    • In prokaryotes, translation and transcription can occur simultaneously. In eukaryotes transcription is in the nucleus, and translation in is the cytoplasm.
  2. Define the genetic code, and describe its key features.
    • The genetic code is a set of 3-letter sequences of nucleotides called codons that code for specific amino acids.
    • The code is redundant, with many codons coding for the same amino acid.
    • The code is nearly universal, with only a few variants throughout the living world.
    • The code includes punctuation: codons that signal for translation to start and stop.
  3. Describe the process of translation.
    • Initiation: the small subunit of a ribosome binds with the start codon. A tRNA with an anticodon matching the start codon binds, bringing the first amino acid. The large subunit binds the small subunit.
    • Elongation: As specified by the codon on the mRNA, tRNAs with the designated amino acid bind with the mRNA at the ribosome. The ribosome catalyzes a peptide bond between the newly arrived amino acid and the growing polypeptide chain.
    • Termination: when a stop codon is reached, a release factor causes the polypeptide to be released, and the ribosome dissociates from the mRNA.
  4. Explain how retroviruses violate the central dogma.
    • Retroviruses use RNA as their genetic code.
    • Reverse transcriptase uses the RNA as a template for creating DNA, which then incorporates into the host’s chromosome. The incorporated virus (a provirus) then exploits the host cell’s replication, transcription and translation machinery for replication of new retroviruses.

Topics 6.5 and 6.6. Regulation of Gene Expression and Cell Specialization

  1. Define regulatory sequences.
    • Regulatory sequences are segments of DNA that control the expression of genes, usually by increasing or decreasing the rate of transcription.
  2. Describe how prokaryotic cells use operons to control gene expression.
    • Operons are clusters of genes under the control of a single promoter.
    • Expression of operons is under the control of a regulatory protein, which binds to an operator region that is just downstream from the promoter.
  3. Define epigenetics.
    • Reversible modifications to DNA that influence gene expression without changing the DNA sequence.
  4. Explain the role of transcription factors in regulating eukaryotic gene expression.
    • Transcription factors are proteins that bind near or at the promoter to regulate the binding of RNA polymerase.
    • Transcription factors can block, promote, or inhibit transcription.
  5. Explain how the phenotype of a multicellular organism is determined by gene expression.
    • All cells in a eukaryotic organism have the same DNA. Cells differentiate into specific tissues because they express genes for tissue-specific proteins.
    • These tissue-specific genes are activated through induction of transcription factors during embryonic development. Induction unfolds in a hierarchical sequence.
    • Small RNAs also play a role in regulation of transcription and translation.
  6. Explain how gene expression can be coordinated in eukaryotes
    • In eukaryotes, genes in different tissues can share regulatory sequences that can be activated or repressed by transcription factors to coordinate gene expression.

Topic 6.7. Mutation

  1. Define mutation
  2. Compare and contrast somatic and germline mutations: where they occur, and what their consequences are.
  3. Describe various types of point mutations
    • silent (no change in protein coded for by the mutated gene)
    • missense (one amino acid is substituted for another one)
    • nonsense (a stop codon is substituted for an amino acid)
    • insertions and deletion errors leading to a frameshift (change in reading frame), causing extensive missense (or nonsense).
  4. Explain how mutations come about.
    • Causes can include radiation, reactive chemicals, or errors in DNA replication or DNA repair.
  5. Explain how mutations can be harmful, beneficial, or neutral.
    • Harmful: result in a protein that is nonfunctional or harmful.
    • Beneficial: improves the function of a protein
    • Neutral: the resulting protein is the same (silent mutation) or similar (because of the type of amino acid substitution).
  6. Explain the overall importance of mutation to evolution.
    • Mutation provides the raw material upon which natural selection acts.
  7. Connect the events of mitosis or meiosis to mutation.
    • Changes in chromosome number (polyploidy) resulting from mitosis or meiosis can create new species.
    • Changes in chromosome number caused by nondisjunction during meiosis results in a variety of human developmental disorders (Down syndrome), or in chromosomal differences (Turner Syndrome)
  8. Define horizontal gene transfer, and describe various types of mechanisms of horizontal gene transfer
    • Horizontal gene transfer is uptake of genetic information (as opposed to inheritance of genetic information from a parent.
    • It  occurs primarily in prokaryotes and viruses via transformation, conjugation, and transduction.
    • When two viruses infect the same cell, their genetic information can be combined, leading to viral progeny with novel gene sequences.

Topic 6.8. Biotechnology

  1. Explain the basic goals of genetic engineering.
    • Analyzing or manipulating DNA.
  2. Describe the basic method and purpose of electrophoresis
    • Separating molecules of DNA, RNA, or protein according to size and charge, usually for analytical purposes.
  3. Describe the polymerase chain reaction (PCR)
    • During PCR, DNA or RNA fragments are amplified (small amounts are made into larger samples that can be analyzed).
  4. Describe the purpose of bacterial transformation
    • Introduces DNA into bacterial cells, usually for the purpose of getting these cells to express desired proteins (such as with genetically engineered insulin or clotting factor)
    • Transformation is usually preceded by inserting novel genes into plasmids, which are then used as a vector to introduce these genes into bacterial cells where these genes can be replicated and expressed.
  5. Describe the purpose of nucleic acid sequencing
    • Determining the order of nucleotides in DNA or RNA.

Unit 7.  Evolution

Unit 7 topics

Unit 7 Learning Objectives

Topic 7.1: Introduction to Natural Selection

  1. Define adaptation.
  2. Explain how while evolution is non-random, the mutations that lead to adaptation are themselves random.
    • Selection is non-random. But If it weren’t for mutation (which is random), all that selection could do would be to cull the population of less adaptive phenotypes. Mutation is what makes the process of natural selection creative and open-ended.
  3. Explain how natural selection works:
    •  Inherited variation, followed by selection for beneficial traits and against harmful traits, shifts the average phenotype in a population, leading to adaptation.
  4. Describe how evolutionary fitness can be measured
    • As an organism’s ability to survive and reproduce.

Topics 7.2 and 7.3: Natural Selection and Artificial Selection

  1. Explain the importance of phenotypic variation to natural selection.
    • Natural selection acts on phenotypic variation in populations. If selective pressure is maintained in the same direction over multiple generations, different phenotypic variations will become more or less common, depending on fitness.
  2. Explain how artificial selection works.
    • During artificial selection, humans select favored phenotypes within plant or animal gene pools, shifting the average phenotype in a desired direction.
  3. Explain how natural selection acts on phenotypes to shift allele frequencies within populations.
    • The result of selection (artificial or natural) is a shift in allele frequencies. But what’s being selected are phenotypes.
  4. Explain the relationship between environmental change and selective pressure
    • As environments change, so do selective pressures. If selective pressure continues in the same direction, there’s directional selection for specific phenotypes. If change is fluctuating, then so will the average phenotype in a population.
  5. Distinguish between directional, disruptive, and stabilizing selection*

Topics 7.4 and 7.5: Population Genetics and Hardy Weinberg

  1. Define gene pool
  2. Define allele frequency
  3. Describe evolution in terms of a population’s gene pool.
    • Evolution is a change in the genetic makeup of a population over time.
  4. Describe the Hardy-Weinberg equilibrium model.
    • The Hardy-Weinberg model is a mathematical model of a non-evolving population. That means a population in which allele frequencies stay constant over time.
  5. Be able to solve problems related to the two Hardy-Weinberg equations. [Note: you’ll be giving the formulas, so you don’t need to memorize them). The formulas are:
    • p + q = 1, and
    • p2 + 2pq +q2 = 1
  6. State the five conditions associated with non-evolving populations in Hardy Weinberg equilibrium
    • Large population size
    • isolation (no outside alleles coming into or leaving the gene pool)
    • no net mutation
    • random mating (no sexual selection or assortative mating).
    • no beneficial or harmful alleles
  7. Define genetic drift.
    • Genetic drift is a change in gene frequencies caused by random sampling of alleles in small populations.
  8. List and describe two ways in which genetic drift can occur.
    • The founder effect
    • The bottleneck effect.
  9. State the conditions that lead to evolution (change in allele frequencies). These are all violations of the Hardy-Weinberg conditions listed above
    • Violate large population size, and you have genetic drift, shown either by population bottlenecks, or by the founder effect.
    • Violate isolation, and you have gene flow.
    • Violate no net mutation, and you have alleles changing frequency as they mutate from one form to another.
    • Violate random mating, and you have evolution caused by sexual selection or assortative mating.
    • Violate no harmful or beneficial alleles, and you have evolution caused by natural selection.

Topic 7.6: Evidence for Evolution, Continuing Ancestry, and Continuing Evolution

  1. Explain what fossils are, and how fossils can be dated.
    • Radioactive decay can show the age of igneous rocks in sedimentary strata adjacent to fossils.
    • Decay of carbon-14 can show the age of relatively recent fossils.
    • Geological strata and use of index fossils can show relative dates.
  2. Describe homologous structures
    • Structures that show evidence of common ancestry because of similarity in structure or similar embryological origin.
  3. Describe vestigial structures
    • Structures that have lost their function, and only exist because of their inheritance from a common ancestor.
  4. Describe molecular homologies and vestigial features at the molecular levels
    • Shared sequences in proteins and nucleic acids that show evidence of common ancestry.
    • Pseudogenes are inactive gene sequences that persist in the genome.

Topic 7.7. Evidence for Common Ancestry

  1. List and describe the molecular homologies that indicate that all living things share a common ancestor.
    • DNA, RNA, ribosomes, the genetic code, and shared metabolic pathways (chemiosmosis)
  2. List and describe the cellular and genetic homologies that indicate that all eukaryotes share a common ancestor.
    • Membrane bound organelles, linear chromosomes,  genes with introns, mitochondria

Topic 7.8: Evidence for Continuing Evolution

  1. List and describe the evidence that evolution continues

Topic 7.9: Phylogeny

  1. Describe the types of evidence that can be used to infer evolutionary relationships.
    • Morphological similarities that show homology
    • DNA and RNA sequences
  2. Be able to construct and analyze phylogenetic trees and cladograms. The key things to be able to identify are
    • Common ancestors
    • Which clades are most closely related (and why)
  3. With regards to phylogenetic trees, define (and be able to identify) clades, shared derived features, ancestral features, outgroups, nodes, and common ancestors.
  4. Understand what phylogenetic trees represent in terms of evolutionary understanding.
    • Phylogenetic trees and cladograms are hypotheses about evolutionary relatedness that need to be revised in light of new information.
  5. Compare the value of sequence data and morphological data in terms of constructing phylogenetic trees.
    • Molecular data typically provide more accurate and reliable evidence than morphological traits
  6. Explain how molecular clocks work.
    • Nodes are dated based on correlation with the fossil record. This enables extrapolation of divergence times in other branches of the same phylogenetic tree.

Topics 7.10-7.12: Speciation, Variation and Extinction

  1. Explain the biological species concept (what it is, and what its limits are)
    • A species is a population that can interbreed to produce viable, fertile offspring.
    • Doesn’t work for fossil species or asexual species
  2. Describe prezygotic and postzygotic reproductive isolating mechanisms
  3. Explain what speciation is, and the mechanisms by which is occurs
    • Definition: when an ancestral species splits into two or more reproductively isolated daughter species.
    • Mechanisms: allopatric and sympatric
  4. Compare punctuated equilibrium with gradualism
    • Punctuated equilibrium: long  periods of stasis, followed by rapid change.
    • Gradualism: slow evolution at a steady pace over long periods of time.
  5. Define adaptive radiation and describe its importance
    • Multiple speciation events from a common ancestor.
    • Key pattern of life’s reemergence following mass extinction. Also a key pattern on island chains.
  6. Connect a population’s genetic diversity with its ability to withstand environmental pressures.
    • Populations with more genetic diversity are better able to respond to environmental change.
    • Populations with little genetic diversity (because of genetic drift or human manipulation) are at higher risk of extinction.
  7. **Connect variation at the molecular level with fitness
    • Molecular variation can increase fitness.
    • Example: Multiple chlorophylls enhance photosynthesis
    • Example: Multiple hemoglobins (fetal vs adult) maximize oxygen absorption at different developmental stages
  8. Distinguish between extinction and mass extinction.
    • Extinctions occur at a regular background rate.
    • During mass extinction events (of which there have been very few), geological or astronomical events increase extinctions well beyond the background rate.
  9. Explain how human activity is related to extinction
    • Currently, humans are modifying ecosystems to a degree that’s creating a human-caused mass extinction event (see Topic 8.7 below).
  10. Explain the connection between extinction and biodiversity
    • In any particular ecosystem, the level of diversity results from the rate of speciation and the rate of extinction.
    • Mass extinctions create vacant ecological niches that are filled during subsequent adaptive radiations (such as the adaptive radiation of the mammals following the extinction of the dinosaurs).

Topic 7.13: Origin of Life

  1. List the key dates for the emergence of life on Earth.
    • Based on geological evidence, Earth formed about 4.5 bya.
    • Based on biological and geological evidence, life was well established by 3.5 bya.
    • Based on geological and biological evidence, life probably first emerged on Earth about 3.8 bya.
  2. Explain some of the key steps associated with the origin of life on Earth.
    • Conditions in a few locations on the early Earth would have made the abiotic formation of biological monomers possible.
    • A  likely spot for that to have happened is alkaline hydrothermal vents.*
    • Additional prebiotic molecules could have come down from space via meteorites (but this is not nearly as plausible as the hydrothermal vents) 
    • Formation of monomers would have to be followed by formation of polymers.
    • Next would be the formation of self-replicating polymers. *
    • At some point, the encapsulation of self-replicating polymers within a lipid bubble led to the formation of cells.*
  3. Describe the progress that’s been made in verifying theories related to the origin of life.
    • Organic monomers, including nucleotide precursors and amino acids, have been synthesized in laboratories under abiotic conditions designed to simulate the conditions on the early Earth.
    • The next step —creating complex self replicating polymers — has not yet been achieved, but there are promising approaches.
  4. Describe the RNA world hypothesis.
    • The RNA world hypothesis promotes the idea that RNA, rather than DNA, served as the first genetic material.

Unit 8. Ecology

Unit 8 topics

Unit 8 Learning Objectives

Topic 8.1: Responses to the Environment

[Note from Mr. W]. In terms of understanding how organisms respond to their environments, these exclusion statements by the College Board tell you what you don’t have to know.

  • In relationship to how changes in the environment are related to physiological or behavioral changes, no specific physiological mechanism is required.
  • In relationship to communication and behavioral systems, the details of these systems are outside the scope of the exam and course.

As a result, telling you what to study is difficult. The College Board’s objectives are very open-ended (and somewhat obvious). So, while there are bound to be questions on the AP exam that relate to animal behavior and responses to the environment, it’s hard to advise you on what specific terms or concepts you need to know.

Here are the key ideas from the CB outline.

  1. Based on cues in the environment, organisms change their behavior and physiology.
  2. Communication between organisms in response to internal or external changes can change behavior.
  3. Signaling changes the behavior of other organisms, and is subject to natural selection.
  4. A variety of signals (visual, auditory, tactile, chemical, electrical) are used to indicate social dominance, to find food, and to induce or solicit mating.
  5. Learned and innate behaviors are subject to natural selection.
  6. Cooperation between members of the same population can increase fitness.

One strategy might be to familiarize yourself with illustrative examples. However, don’t overdo it. You don’t need to memorize anything. If these examples show up on the AP exam, they’ll be used as parts of data sets or scenarios that you’ll have to analyze and explain (with no previous knowledge expected).

  • Photoperiodism and phototropism in plants
  • Taxis and kinesis in animals
  • Nocturnal and diurnal activity
  • Pack behavior in animals
  • Herd, flock, and schooling behavior in animals
  • Predator warnings
  • Colony and swarming behavior in insects
  • Kin selection
  • Parent and offspring interactions
  • Courtship and mating behaviors
  • Foraging in bees and other animals
  • Fight-or-flight response
  • Predator warnings
  • Plant responses to herbivory
  1. Compare and contrast endotherms and endotherms.
    • Endotherms use thermal energy generated by metabolism to maintain homeostatic body temperatures.
    • Ectotherms lack efficient internal mechanisms for maintaining body temperature. Their temperature can fluctuate widely, though they may regulate their temperature behaviorally by moving into the sun or shade or by aggregating with other individuals.
  2. Describe the relationship between metabolic rate and size.
    • Generally, the smaller the organism, the higher the metabolic rate.
  3. Describe the relationship between energy gain or loss and growth/survival/reproduction
    • Net energy gain results in energy storage or the growth of organisms or populations.
    • Net energy loss results in loss of mass, death, and population decline.
  4. Describe how energy flow through ecosystems can be graphically represented.
    • Through food chains, foods webs, and energy pyramids.
  5. *Define biogeochemical cycle, and (as a representative example) explain the carbon cycle.
  6. Explain the effects of changes in energy availability on trophic levels and ecosystem structure.
    • Changes in energy availability can affect the number and size of the trophic levels. Specifically, a change in the producer level can affect the number and size of other trophic levels.
  7. Compare autotrophs and heterotrophs
    • Autotrophs capture energy from physical or chemical sources in the environment;
    • Heterotrophs capture energy by eating or absorbing chemical energy in organic compounds.
  8. Compare photoautotrophs with chemoautotrophs
    • Photoautotrophs use light in order to synthesize organic compounds. Plants, algae and cyanobacteria are photoautotrophs.
    • Chemoautotrophs power the creation of organic compounds by oxidizing small inorganic molecules (such as iron). This process can occur in the absence of oxygen. All chemoautotrophs are bacteria or archaea.

Topics 8.3 and 8.4: Population Ecology

  1. Explain the general factors behind population growth, and the general equation for this growth  (dN/dt = B – D)
  2. Explain what exponential growth is, when it occurs, and be able to use its relevant equation (dN/dt = rmaxN)
  3. Define limiting factors.
  4. Compare and contrast Density Dependent and Density Independent Limiting Factors
  5. Define carrying capacity.
  6. Be able to use the Logistic Growth equation (dN/dt = rmaxN (K-N/K))
  7. Explain how population growth can be influenced by resource availability and predator prey interactions.

Topics 8.5: Community Ecology

  1. Explain how communities change over time during the process of ecological succession.
  2. Describe the key Interactions that occur between the species in a community. This includes the following interactions, and being able to describe the positive and negative effects on each species.
    • Mutualism
    • Parasitism
    • Commensalism, amensalism
    • Competition (leading to niche partitioning and character displacement)
    • Predator/Prey interactions (leading to evolutionary arms races)
  3. Explain what keystone species are, and what happens when keystone species are removed from their ecosystems.
    • An organism whose activity defines the structure of the entire ecosystem.
    • Often these are carnivores which control herbivores, increasing productivity and overall biodiversity.
    • When keystone species are removed, ecosystems can collapse.

Topic 8.6: Biodiversity

  1. Define Biodiversity, and describe its key components.
    • Species composition and richness.
  2. Know how to use the Simpson’s Biodiversity index.
  3. Explain the connection between biodiversity and ecosystem resilience.
    • Less biodiversity and less ecosystem complexity often equates to less resilience to environmental change.

Topic 8.7: Disruptions to Ecosystems

  1. List and describe the traits that predispose a species to become an invasive species.
    • High reproductive rates, tolerance of a wide range of conditions, generalist ecological niche.
  2. Explain how invasive species affect ecosystem dynamics and biodiversity.
    • When invasive species enter a new habitat, they tend to grow exponentially.
    • As invasive species are freed from control by their former predators or competitors, they can outcompete or overexploit the species in their new environment, or overrun their new habitat.
    • The overall effect is a decrease in biodiversity.
  3. Describe the human activities that lead to changes in ecosystem structure and/ or dynamics.
    • Destruction or degradation of habitat, habitat fragmentation, introduction of invasive species,
    • Introduction of new diseases that can devastate native species.
    • Climate disruption that is altering habitats worldwide.
  4. Explain how geological and climatic changes can change ecosystem structure and/or dynamics.
    • Changes in geology and climate can alter habitats and change ecosystem distribution.

Unit 8 Flashcards


[h]Unit 8 Flashcards (no animal behavior)

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|129530cd07110″ question_number=”298″ topic=”8.1.Responses_to_the_Environment”] Describe the differences between regulators and conformers.

Importance for the AP exam: Medium 

[a] Regulators are organisms that keep a specific internal condition (such as body temperature) confined within a narrow range. Conformers allow that condition to fluctuate with the external environment. For example, mammals and birds are body temperature regulators. Reptiles, fish and amphibians are conformers.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|128c05de35510″ question_number=”299″ topic=”8.2.Energy_Flow_Through_Ecosystems”] What’s the difference between an ectotherm and an endotherm?

Importance for the AP exam: High 

[a] An endotherm is an organism that generates its heat internally through its metabolism. An ectotherm generates its heat from the environment (for example, from the sun’s heat).

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|b439044b534c7″ question_number=”300″ unit=”8.Ecology” topic=”8.2.Energy_Flow_Through_Ecosystems”] Compare and contrast the benefits of being an endotherm or an ectotherm.

Importance for the AP exam: High 

[a] The advantage of being an endotherm is that it enables an organism to be active regardless of the environmental temperature. That’s why the predominant animals in Arctic or Antarctic environments are mammals (think of polar bears) and birds (think of penguins). The disadvantage of being an endotherm is that it requires a lot of energy. Ectotherms can survive on about 1/10th the food energy required by an endotherm of similar mass.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|1282906de7110″ question_number=”301″ topic=”8.2.Energy_Flow_Through_Ecosystems”] What are some strategies that ectotherms use to regulate their body temperature?

Importance for the AP exam: Medium 

[a] Ectotherms have variety of behavioral means of optimizing their body temperature. In larger animals such as lizards and snakes, this this includes basking in the sun, or resting in the shade. In honeybees, huddling together and moving their wing muscles generates heat that can raise the temperature of the hive in cold weather, or create air currents to cool the hive in warm weather.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|12736e209d110″ question_number=”302″ topic=”8.2.Energy_Flow_Through_Ecosystems”] What is metabolic rate? How can it be measured?

Importance for the AP exam: Low

[a] An organism’s metabolic rate is the amount of energy that the organism expends during a given amount of time. It can be measured by oxygen consumption, carbon dioxide production, or heat production.

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|2a44063e5605″ question_number=”303″ unit=”8.Ecology” topic=”8.2.Energy_Flow_Through_Ecosystems”] How can the metabolic rates of animals of different sizes be compared? What’s the general relationship between metabolic rate and size (and why)?

Importance for the AP exam: Low

[a] To compare metabolic rates in animals that are of different sizes, we use the relative metabolic rate: the metabolic rate/unit of body mass.

Among endothermic animals (for example, mammals) the general rule is that as size increases, relative metabolic rate decreases. For example, a gram of mouse tissue metabolizes up to 10 times faster than a gram of elephant tissue.

Why? Smaller animals have a larger surface area to volume ratio than do larger animals. As a result, smaller animals will lose heat more easily than a larger animal will. To replace that heat, the smaller animal will need to perform more cellular respiration, increasing its relative metabolic rate.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|126839a763d10″ question_number=”304″ topic=”8.2.Energy_Flow_Through_Ecosystems”] What’s the relationship between energy availability, producer population size, and ecosystem complexity? List two examples of ecosystems that demonstrate high energy input and high complexity.

Importance for the AP exam: Medium 

[a] All other things being equal, the more energy (such as sunlight) coming into an ecosystem, the higher the productivity and population size of ecological producers, and the more trophic levels that ecosystem will be able to support. This partly explains the diversity and complexity of tropical rainforest and coral reef ecosystems.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|125f0eb892110″ question_number=”305″ topic=”8.2.Energy_Flow_Through_Ecosystems”] What are autotrophs? Compare and contrast photoautotrophic and chemoautotrophic organisms.

Importance for the AP exam: Medium 

[a] Autotrophs are organisms that can produce their own food. Photoautotrophs use the energy in light to create the organic compounds they need to survive through photosynthesis. Chemoautotrophs derive the energy for their life processes by chemosynthesis: oxidizing inorganic substances, including iron, sulfur, or hydrogen sulfide. 

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|1253ff8017110″ question_number=”306″ topic=”8.2.Energy_Flow_Through_Ecosystems”] What are heterotrophs, and how do they get the energy and matter they need to live, grow, and reproduce?

Importance for the AP exam: High 

[a] Heterotrophs are organisms that capture the energy present in organic compounds produced by other organisms. Heterotrophs can be ecological consumers, decomposers, or parasites. They get their energy and matter by metabolizing the organic compounds in organisms that they eat or absorb, or in the dead remains of organisms.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|1248f0479c110″ question_number=”307″ topic=”8.2.Energy_Flow_Through_Ecosystems”] What are food chains and food webs? 

Importance for the AP exam: High 

[a] A food chain shows the passage of energy and matter from one organism to the next within an ecosystem. A food web shows all the interconnected food chains in an ecosystem.

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|274602f65205″ question_number=”308″ unit=”8.Ecology” topic=”8.2.Energy_Flow_Through_Ecosystems”] What are trophic levels?

Importance for the AP exam: High 

[a] A trophic level is an organism’s position in a food chain or food web.

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|26a307b5fa05″ question_number=”309″ unit=”8.Ecology” topic=”8.2.Energy_Flow_Through_Ecosystems”] Describe the basic trophic levels found in most ecosystems.

Importance for the AP exam: High 


  • Food chains begin with producers, which create energetic organic compounds, almost always through photosynthesis.
  • Next are primary consumers, which eat producers. These organisms are also known as herbivores.
  • Next are secondary consumers, or carnivores, which eat the primary conumers. Secondary consumers cn be consumed by tertiary consumers. In some oceanic food chains, there are even higher levels, but rarely more than four or five.
  • When organisms at any level die their remains are broken down by decomposers.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|123d4c0c28110″ question_number=”310″ topic=”8.2.Energy_Flow_Through_Ecosystems”] What do ecological pyramids represent? List the three types of ecological pyramids,

Importance for the AP exam: High 

[a] Ecological pyramids are a way of showing the structure of an ecosystem, usually by trophic level. There are three types: energy, biomass, and numbers.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|1232ac95e7d10″ question_number=”311″ topic=”8.2.Energy_Flow_Through_Ecosystems”] In relationship to ecology, describe a pyramid of energy, and explain the 10% rule.

Importance for the AP exam: High 

[a] A pyramid of energy shows the amount of harvestable chemical energy in each trophic level. In this pyramid, each trophic level has 10% of the chemical potential energy of the level beneath it. Thus, if the producers in an ecosystem had 10,000 units of energy (measured in units like kilojoules or kilocalories), the primary consumers would have 1000 units, and the secondary consumers would have 100 units.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|1221a5fef4910″ question_number=”312″ topic=”8.2.Energy_Flow_Through_Ecosystems”] In relationship to ecology, compare and contrast a pyramid of biomass with a pyramid of numbers.

Importance for the AP exam: High 

[a] A pyramid of biomass shows the biomass (living matter) available at each trophic level in an ecosystem. No 10% rule applies, and in some aquatic ecosystems in which there’s high productivity and high rates of conversion of producers to primary consumers, the shape might not be pyramidal, because there might be less biomass in the producers than in the primary consumers.

A pyramid of numbers shows the number of organisms at each trophic level. Again, no 10% rule applies. Imagine a tree — one organism, supporting thousands of insects, supporting hundreds of birds — and you can see how the shape of this pyramid is not at all pyramidal.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|1215b74204110″ question_number=”313″ topic=”8.2.Energy_Flow_Through_Ecosystems”] 1) What is a biogeochemical cycle? 2) What are the key components of biogeochemical cycles?

Importance for the AP exam: High 

[a] 1) Biogeochemical cycles show the movement of elements or compounds between the biotic (living) and abiotic (non-living) parts of an ecosystem.

2) Components of biogeochemical cycles include reservoirs (locations where elements or compounds accumulate, often in chemically different forms) and fluxes or flows(ways in which these compounds or elements move from one reservoir to another one.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|120c1c90f7910″ question_number=”314″ topic=”8.2.Energy_Flow_Through_Ecosystems”] Describe the carbon cycle. Note that for AP Bio, you can leave out dissolved CO2 in the oceans, absorption into rocks, and release from volcanoes. 

Importance for the AP exam: High 

[a] Through photosynthesis, producers fix carbon dioxide in air or water into carbohydrates, which can be then converted into lipids, proteins, etc.). Some of this carbon moves to animals via consumption. Both plants and animals respire, which returns CO2 to the atmosphere. When plants or animals die, their organic remains are decomposed. Decomposition renders the carbon in dead organic matter back into carbon dioxide, which rejoins the atmosphere.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|11e5420a8ad10″ question_number=”315″ topic=”8.2.Energy_Flow_Through_Ecosystems”] What is the 10% rule?

Importance for the AP exam: High 

[a] The 10% rule is the key principle behind the pyramid of energy. Specifically, in any ecosystem, only 10% of the available energy gets passed from one trophic level to the next.

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|1556beb88c40a3″ question_number=”316″]Describe some of the reasons behind the 10% rule.

[a]The 10% rule results from:

  • Entropy: Whenever energy is transformed from one form to another (from the bodies of herbivores to the bodies of carnivores, for example), some energy is lost as heat.
  • Inefficient harvest: Consumers don’t eat everything in the trophic level below.
  • Not everything that gets consumed will be absorbed into the body: everything that’s defecated out constitutes matter and energy that aren’t passed on the the organism.
  • Much energy goes to staying alive, and not  to growth that can be passed on to the next trophic level.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|11dc171bb9110″ question_number=”317″ topic=”8.2.Energy_Flow_Through_Ecosystems”] What is nitrogen fixation?

Importance for the AP exam: Medium 

[a] Nitrogen fixation involves capturing atmospheric nitrogen and bringing it into organic compounds. The organisms that can do this are nitrogen fixing bacteria, which use energy to reduce nitrogen to ammonia (NH3)  and the ammonium ion  (NH4+).

Some nitrogen-fixing bacteria live freely in the soil. Others live in root nodules in legumes (which includes peas, beans, clover, and peanuts). The relationship is mutualistic: the nitrogen fixing bacteria provide accessible nitrogen, while the legumes provide food energy to support the bacteria.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|11d2a1ab6ad10″ question_number=”318″ topic=”8.2.Energy_Flow_Through_Ecosystems”] Describe the processes of ammonification, nitrification and assimilation that occur in the nitrogen cycle.

Importance for the AP exam: Medium 

[a]Ammonification involves taking the nitrogen compounds in organic matter, and converting them into ammonia and  ammonium. This process is carried out by decomposers. Then, during nitrification, nitrifying bacteria convert the ammonia into nitrates (NO3) and nitrites (NO2). Through assimilation, the nitrates and nitrates can be absorbed by the roots of non-legume plants.

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|2280c4bb34a09e” question_number=”319″ unit=”8.Ecology” topic=”8.2.Energy_Flow_Through_Ecosystems”] Describe the process of denitrification.

[a] Nitrates and nitrates can be used in anaerobic respiration by denitrifying bacteria. This returns nitrogen gas (N2) to the atmosphere.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|11c15092fb110″ question_number=”320″ topic=”8.2.Energy_Flow_Through_Ecosystems”] Describe how human activity has affected the nitrogen cycle.

Importance for the AP exam: Medium 

[a] For about the past 100 years, humans have significantly altered the nitrogen cycle through application of nitrogen fertilizers (usually in the form of nitrates) to food crops. This energy intensive process has vastly increased agricultural productivity. It has also had significant environmental effects caused by runoff of nitrogen fertilizer into streams, lakes, bays, and oceans.

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|1f222d643605″ question_number=”321″ unit=”8.Ecology” topic=”8.2.Energy_Flow_Through_Ecosystems”] Describe what happens when excess nitrogen and/or phosphorus enters lakes, streams, ponds, or oceans.

Importance for the AP exam: Medium 

[a] Excess flows of nitrogen and phosphorus into lakes, streams, ponds or oceans can cause a process called eutrophication. Eutrophication starts with excess growth of algae and other producers, which are stimulated by the nitrogen and phosphorus. When the algae die, their biomass is broken down by decomposers. Decomposition (which involves cellular respiration) depletes the oxygen level in the water. Low oxygen levels kill off other aquatic life, reducing biodiversity.

[!]8.3-8.4.Population Ecology[/!]

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|11b6669b3e510″ question_number=”322″ topic=”8.3-4.Population_Ecology”] Ultimately, only four variables affect the size of any population. What are they?

[a] Population size is a function of births, deaths, immigration, and emigration.

Importance for the AP exam: High 

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|11a5aa85c7910″ question_number=”323″ topic=”8.3-4.Population_Ecology”] What is exponential growth?

Importance for the AP exam: High 

[a] Exponential growth is growth of a population in which the number of individuals added is proportional to the amount already present. As a result, the bigger the population, the bigger the increase.

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|8bc500335071b” question_number=”324″ unit=”8.Ecology” topic=”8.3-4.Population_Ecology”] Explain the formula for exponential growth.

[a] The formula for exponential growth is change in N/t = rN, where

  • N = population size
  • t = time
  • r= rate of increase

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|8badb7bc6871b” question_number=”325″ unit=”8.Ecology” topic=”8.3-4.Population_Ecology”] In a graph, what does exponential growth look like?

[a] When exponential growth is plotted (with time as the X axis and population size as the Y axis) the result is a J shaped curve: a slow takeoff followed by an increasingly steep rise in population.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|1195837349d10″ question_number=”326″ topic=”8.3-4.Population_Ecology”] In biological systems, when does exponential growth occur?

Importance for the AP exam: High 

[a] In any biological system, exponential growth can only happen for a limited period of time, during which a population has the resources (food, space, etc) that let it grow without constraints. This might happen when an invasive species arrives in a new environment, freed from the predators that might have held it in check in its previous environment. It can also happen during the early phases of a bacterial infection, or during a disease outbreak (when a pathogen can spread exponentially).

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|11886ab067510″ question_number=”327″ topic=”8.3-4.Population_Ecology”] What is biotic potential? How is it represented?

Importance for the AP exam: High 

[a] Biotic potential is the maximum rate at which a population can expand. It’s represented by rmax.

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|1c0f35b12e05″ question_number=”328″ unit=”8.Ecology” topic=”8.3-4.Population_Ecology”] What is carrying capacity?

[a] Carrying capacity is the maximum number of individuals that a particular environment can support.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|1178fde1a0d10″ question_number=”329″ topic=”8.3-4.Population_Ecology”] What is the logistic growth model?

Importance for the AP exam: High 

[a] The logistic model of population growth shows how a population’s growth decreases as it reaches its carrying capacity.

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|8b3769203731b” question_number=”330″ unit=”8.Ecology” topic=”8.3-4.Population_Ecology”] Describe the equation for logistic growth.

[a] The logistic growth model can be represented by the equation N/t = rN (K-N)/K, where

  • N = population size
  • t = time
  • r= rate of increase
  • K = carrying capacity

As a population reaches its carrying capacity, there will be increased environmental resistance, as density dependent limiting factors slow and then stop a population’s growth.

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|8b0992761e71b” question_number=”331″ unit=”8.Ecology” topic=”8.3-4.Population_Ecology”] When plotted on a graph, what does logistic growth look like?

[a] When logistic growth is plotted (with the X axis representing time and the Y axis representing population size), the result is an “S-shaped” or “sigmoid” curve. The curve initially looks like an exponential growth curve (a J-curve) with a slow takeoff followed by a rapid rise. But as N approaches K, the amount of increase slows and then drops to zero as the population stabilizes at K.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|1139665cdd910″ question_number=”332″ topic=”8.3-4.Population_Ecology”] In relationship to population growth, what are limiting factors?

Importance for the AP exam: High 

[a] Limiting factors prevent a population from increasing at its biotic potential, and cause a population’s size to stabilize at or below the environment’s carrying capacity.

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|1a2d4013d205″ question_number=”333″ unit=”8.Ecology” topic=”8.3-4.Population_Ecology”] Define and describe density dependent limiting factors.

[a] Density dependent limiting factors intensify as the density of individuals within a population increases. These factors can be extrinsic (coming from outside the growing population) or intrinsic (from within the population).

Extrinsic factors include predation pressure, parasitism, and competition for increasingly scarce resources. Intrinsic factors can include the stress that’s induced by increased crowding and competition, lowering the birth rate. Territoriality can similarly decrease a population’s ability to expand beyond a certain density.

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|198a44d37a05″ question_number=”334″ unit=”8.Ecology” topic=”8.3-4.Population_Ecology”] Define and describe density independent limiting factors.

[a] Density independent limiting factors are those that are unrelated to a population’s size (symbolized by N).  For example, hurricanes,  floods, or earthquakes can all cause significant death in a population, lowering population size, regardless of that population’s density.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|1125c13889d10″ question_number=”335″ topic=”8.3-4.Population_Ecology”] When a population grows reaches its carrying capacity, the result might be stable oscillation around carrying capacity. Explain.

Importance for the AP exam: Medium 

[a] In this scenario, the population overshoots the carrying capacity, lowering the available resources. This causes the population to decline. As the resource base recovers, the population resumes its growth until it again overshoots the carrying capacity, repeating the cycle.

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|22226ae15b55a5″ question_number=”336″]Sometimes, a population overshoots carrying capacity, which is followed by a catastrophic population decline. Explain.

Importance for the AP exam: Medium

[a]An overshoot is where population exceeds the environment’s carrying capacity. If this causes a significant depletion in environmental resources from which the environment can’t recover, then the population that caused the depletion, if it can survive at all, will do so at significantly reduced numbers.

[!]8.5.Community Ecology and Biodiversity[/!]

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|111a423dd4110″ question_number=”337″ topic=”8.5-6.Community_Ecology_and_Biodiversity”] Define coevolution. Relate coevolution to the idea of the evolutionary arms race. Provide examples.

Importance for the AP exam: High 

[a] Coevolution involves the reciprocal evolutionary adaptations that occur between two or more species. Each species becomes a selective force eliciting counter adaptations in the other species.

Because the two species are involved in a positive feedback loop, the result can be an evolutionary arms race, with extreme reciprocal adaptations in both coevolving species. Examples include the deep tubular flowers of some species and the long proboscis or beak of the moths or birds that pollinate them; the speed of predators and the matching speed of their prey (think of cheetahs and antelopes).

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|1109f5ea98110″ question_number=”338″ topic=”8.5-6.Community_Ecology_and_Biodiversity”] What is symbiosis? What are the three most common forms of symbiosis, and how are these relationships symbolized?

Importance for the AP exam: High 

[a] Symbiosis occurs whenever two species live together in close proximity.

  • In parasitism, one species (the host) is harmed, while the other species (the parasite) benefits. This can be represented as “+/-.”
  • In commensalism, one species benefits, while the other species is unharmed. This is represented as “+/0.”
  • In mutualism, both species benefit from the interaction, represented as “+/+.”

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|10f6c0887f110″ question_number=”339″ topic=”8.5-6.Community_Ecology_and_Biodiversity”] The Simpson’s index of biodiversity is based on the relationship between species richness, the overall abundance of individuals, and the evenness of species distribution. Explain the meaning of each part of the index, and describe the conditions that lead to high species diversity.

Importance for the AP exam: High 

[a] In the Simpson’s index of biodiversity, species richness means the overall number of species in a specific area. Abundance is the number of organisms of all species. Evenness is how evenly distributed abundance is among the species living in a specific area.

For biodiversity to be high, an ecosystem needs to have high species richness, and the abundance of individuals within each species needs to be evenly distributed. For example, if there are 100 individuals of species A, 100 individuals of species B, and 10 individuals of species C, then evenness is lower than it would be  the number of individuals of each species were the same.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|10eaac8ad0510″ question_number=”340″ topic=”8.5-6.Community_Ecology_and_Biodiversity”] What is Gause’s competitive exclusion principle?

Importance for the AP exam: High 

[a] According to Gause’s principle of competitive exclusion, two competitive species can’t coexist in the same ecological niche. That’s because any advantage that one species has over its competitor will lead the species with the advantage to outcompete the other.

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|8a79a7572131b” question_number=”341″ unit=”8.Ecology”] What results from ecological competition?

[a] There are two possible results of competition. Either one species will become extinct, or the two species will evolve in a way to partition the resource that they’re competing for. The result of this niche partitioning is specialization, with simultaneous character displacement so that each species will dominate its sub-niche more effectively. Thus we see, for example, species of shorebirds with slightly different beaks, each one taking a slightly different type of prey; or species of grazing mammals with different sizes, enabling them to specialize on a particular plant or part of a plant.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|10d9f07559910″ question_number=”342″ topic=”8.5-6.Community_Ecology_and_Biodiversity”] What’s the difference between a species’ fundamental niche and its realized niche?

Importance for the AP exam: High 

[a] The fundamental niche of a species is the range of resources that it could exploit in the absence of competition. However, because species that are competing differentiate (character displacement caused by niche partitioning), the actual resources each competing species exploits is narrower than the full resource. The actual resource that’s exploited by each species is the realized niche, and it’s always narrower than the fundamental niche.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|10cc42af7e110″ question_number=”343″ topic=”8.5-6.Community_Ecology_and_Biodiversity”] Using the barnacle species Chthalamus and Semibalanus as examples, explain the difference between a species’ fundamental niche and its realized niche.

Illustrative Example: Competition

Importance for the AP exam: High 

[a] Chthalamus and Semibalanus are two barnacle species found in  rocky intertidal zone habitats. When the two species live together, Chthalamus is limited to the upper reaches of the intertidal zone (close to the high tide line), while Semibalanus inhabits the lower reaches (down to the low tide line). If Semibalanus is experimentally removed from the habitat, then Chthalamus shows itself of being capable of inhabiting the entire intertidal zone (from the high tide line to the low tide line). Chthalamus’s fundamental niche, in other words, is the entire intertidal zone. Because of competition, it is limited to the upper part of the zone, which is said to be that species realized niche.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|10c0c3b4c8510″ question_number=”344″ topic=”8.5-6.Community_Ecology_and_Biodiversity”] What’s the relationship between ecosystem diversity and an ecosystem’s resilience to environmental change?

Importance for the AP exam: High 

[a] Resilience is defined as an individual’s or a system’s ability to recover from adverse circumstances. In general, ecosystems with high diversity are more resistant to change than ecosystems with low diversity, and more resilient in terms of their ability to recover from adverse conditions.  As ecosystems become simpler, with fewer parts and less diversity within the parts, they become less able to adapt to changes in the environment. In this context, “fewer component parts” means fewer species, and “less diversity within the parts” means, for example, more genetic homogeneity. A field of corn in which every plant is a clone would represent the lowest possible diversity (only one part, and no diversity within the parts) and the lowest expected resilience.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|10b315eeecd10″ question_number=”345″ topic=”8.5-6.Community_Ecology_and_Biodiversity”] What are keystone species? In your response, use the example of sea stars in the intertidal zone.

Importance for the AP exam: High 

[a] A keystone species is one whose action within a biological community structures the entire community. Frequently, keystone species are predators who keep a particular herbivore in check. The result is an increase in the overall biodiversity of the community. A famous example is the role of sea stars in controlling mussel populations in the rocky intertidal zone. By controlling the mussels, the sea stars create ecological space for a variety of other invertebrates to live in this community. Similarly, sea otters, by controlling populations of sea urchins, keep the urchins from overgrazing kelp. This maintains the kelp forests, which in turn support many other species.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|10a701f13e110″ question_number=”346″ topic=”8.5-6.Community_Ecology_and_Biodiversity”] As it relates to ecosystem diversity and structure, what is a “trophic cascade?”

Importance for the AP exam: High 

[a] Trophic cascades occur when a trophic level within an ecosystem is suppressed, usually by a predator that reduces the activity of an herbivore. The activity of this predator, in turn, can increase the overall biodiversity of an ecosystem by increasing the ecosystem’s overall productivity, and by creating ecological space for other herbivores and producers. The idea of a trophic cascade is thus closely connected to the idea of a keystone species (since the keystone species is usually the predator that’s controlling the herbivore).

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|1094d15458d10″ question_number=”347″ topic=”8.5-6.Community_Ecology_and_Biodiversity”] What is ecological succession? In your answer, distinguish between primary and secondary succession.

Importance for the AP exam: Medium 

[a] Ecological succession is the process by which a community changes following a disturbance. Primary succession is what happens in a lifeless area where there’s no soil, such as what happens after a volcanic eruption, a rockslide, or retreat of a glacier. Secondary succession is what happens in an area where the biological community has been destroyed or removed, but the topsoil is still intact. This occurs after a fire, a flood, a forest clearing, etc.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|108ba66587110″ question_number=”348″ topic=”8.5-6.Community_Ecology_and_Biodiversity”] Describe how primary ecological succession typically unfolds.

Importance for the AP exam: Medium 

[a] Primary succession starts with colonization by pioneer species that can live on bare rock, and which can be dispersed into this area via wind which carries their spores. These pioneers include lichens and algae, which begin a slow process of biomass accumulation and soil development. These are followed by sun-tolerant mosses and herbs, which continue to break down the rock. The remains of the mosses and herbs increase the amount of soil for the next group of organisms, sun-tolerant grasses and ferns.

As soil increases, pioneers are replaced by small shrubs. These are followed by trees, which create a shady understory, creating a niche for shade-tolerant shrubs. Ultimately, a self-perpetuating climax community develops. Note that while this description focused on plant life, the animal life changes as well.

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|112095dca605″ question_number=”349″ unit=”8.Ecology” topic=”8.5-6.Community_Ecology_and_Biodiversity”] How is primary ecological succession different from secondary succession.

[a] Primary succession starts from bare rock, and requires a slow process of soil creation. In secondary succession, the soil is intact, and the succession process can unfold much more quickly.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|107cf3da77d10″ question_number=”350″ topic=”8.5-6.Community_Ecology_and_Biodiversity”] What are the overall trends associated with ecological succession?

Importance for the AP exam: Medium 

[a] Here are the overall trends associated with ecological succession:

  • abiotic conditions are replaced by biotic conditions
  • soil mass increases
  • overall biodiversity increases
  • the number of interspecific interactions increases
  • the community becomes more stable and more resilient to change.

[!]8.7.Disruptions to Ecosystems[/!]

[q json=”true” yy=”4″ dataset_id=”AP_Bio_Flashcards_2022|1073c8eba6110″ question_number=”351″ unit=”8.Ecology” topic=”8.7.Disruptions_to_Ecosystems”] What are five things that humans are doing that are causing the current extinction crisis.

Importance for the AP exam: High 

[a] In recent years, extinction rates have risen up to 1000 times beyond the background rate. These extinctions have been caused by human activities. These activities include

  • Overhunting.
  • Habitat destruction.
  • Habitat fragmentation.
  • Invasive species.
  • Climate change

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|10614dcd44510″ question_number=”352″ topic=”8.7.Disruptions_to_Ecosystems”] What’s the # 1 cause current extinction crisis. Name the cause, and elaborate.

Importance for the AP exam: Medium

[a]Habitat destruction and degradation is the number 1 cause of species extinction. For example, cutting down natural forests, and replacing them with much less diverse second growth forests designed for timber harvest, reduces the ecological complexity of forests, making it impossible for the species that formerly lived in them to survive. Destructive fishing practices can destroy coral reef ecosystems. Every time a habitat is destroyed or significantly altered, the species living in them have to flee or perish.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|1055f4134cd10″ question_number=”353″ topic=”8.7.Disruptions_to_Ecosystems”] What is habitat fragmentation? Explain how habitat fragmentation is contributing to the current extinction crisis.

Importance for the AP exam: Medium 

[a] Habitat fragmentation occurs when human transformation of forests, prairies, and other habitats into farms and other developed areas breaks apart a species’ range into several smaller areas. Because each of these areas is too small to support a viable population, and because gene flow is usually not possible between these areas, subpopulations in each of these areas decline.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|1042e3f1f2110″ question_number=”354″ topic=”8.7.Disruptions_to_Ecosystems”] Explain how climate change is contributing to the sixth mass extinction.

Importance for the AP exam: Medium

[a]  Alteration of climate is changing the conditions in various ecosystems at a rate that exceeds the ability of species within those ecosystems to adapt. It’s also changing the geographical range of species, often pushing them further north in the northern hemisphere, or further south in the southern hemisphere. This is pushing many species, already stressed, to the point of extinction.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|10363af14a510″ question_number=”355″ topic=”8.7.Disruptions_to_Ecosystems”] What are invasive species? How can they affect ecosystem dynamics?

Importance for the AP exam: High 

[a] Invasive species are those that 1) are not native to an ecosystem, 2) spread rapidly and persistently once introduced into an ecosystem, and 3) cause ecosystem disruption. Once introduced into a new area, invasive species are freed from the controlling forces such as predators or competitors they faced in their native environment. With these controls gone, invasive species often expand exponentially, outcompeting native species, destroying an ecosystem’s resource base, and spreading disease (such as parasites that they might carry).

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|11fd44c52a110″ question_number=”356″ topic=”8.7.Disruptions_to_Ecosystems”] One feature of the carbon cycle is that carbon can become fossilized as fossil fuels, and then return to the atmosphere when these fossil fuels are burned for energy. Describe this part of the carbon cycle, and explain how it’s affecting the Earth’s climate.

Importance for the AP exam: Low

[a] At certain times in Earth’s history, rates of photosynthesis have exceeded rates of decomposition. As a result, carbon from plants wasn’t decomposed, causing it to accumulate as deposits of coal, petroleum, and natural gas (fossil fuels).

Since the start of the Industrial Revolution, humans have been burning these fuels for energy, releasing carbon dioxide. The current CO2 level of 400 parts per million is 40% higher than the level at the start of the Industrial revolution.

The added carbon dioxide has been trapping heat within the atmosphere. This is slowly increasing planetary temperatures, causing the polar ice caps to shrink, increasing the intensity of storms, intensifying droughts, intensifying seasonal wildfires, melting permafrost, and increasing sea levels.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|11f2a54ee9d10″ question_number=”357″ topic=”8.7.Disruptions_to_Ecosystems”] What is ocean acidification, and what’s causing it?

Importance for the AP exam: Low

[a] The oceans can absorb carbon dioxide from the atmosphere, and much of the carbon dioxide released by industrial processes has been absorbed into ocean waters. However, this is causing the pH of the oceans to decrease, as dissolved carbon dioxide becomes carbonic acid, a process known as ocean acidification. Ocean acidification, in turn, is having widespread ecological impacts. That’s because lower pH makes it difficult for many marine creatures to create their calcium carbonate shells. This is one of many factors negatively impacting coral reefs, which are in decline around the globe.

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|2208c06647fda5″ question_number=”358″]What are some key principles for nature reserve design that can help preserve biodiversity.


  • Make the reserves as large as possible so that the populations within them can be of viable size.
  • Create corridors between adjacent reserves to allow for gene flow between the populations within the reserves.
  • Choose reserves that have a wide variety of habitat types within them


Science Practices

[This is word-for-word from the College Board’s Course and Exam Description]

  1. Concept Explanation: Explain biological concepts, processes, and models presented in written format.
    1. 1.A  Describe biological concepts and/or processes.
    2. 1.B  Explain biological concepts and/or processes.
    3. 1.C  Explain biological concepts, processes, and/or models in applied contexts.
    4. Assessment on the AP Exam: Students will need to identify or pose a testable question, state the null and alternative hypotheses or predict the results of an experiment, identify experimental procedures, and/or propose new investigations.
  2. Visual Representations: Analyze visual representations of biological concepts and processes.
    1. 2.A  Describe characteristics of a biological concept, process, or model represented visually.
    2. 2.B  Explain relationships between different characteristics of biological concepts, processes, or models represented visually
      1. In theoretical contexts.
      2. In applied contexts.
    3. 2.C  Explain how biological concepts or processes represented visually relate to larger biological principles, concepts, processes, or theories.
    4. 2.D  Represent relationships within biological models, including
      1. a. Mathematical models.
      2. b. Diagrams.
      3. c. Flowcharts.
    5. Assessment on the AP exam: Students will need to describe characteristics of a biological concept, process, or model represented visually, as well as explain relationships between these different characteristics. Additionally, students will need to explain how biological concepts or processes represented visually relate to larger biological principles, concepts, processes, or theories.
  3. Questions and Methods: Determine scientific questions and methods.
    1. 3.A  Identify or pose a testable question based on an observation, data, or
    2. a model.
    3. 3.B  State the null and alternative hypotheses, or predict the results of an experiment.
    4. 3.C  Identify experimental procedures that are aligned to the question, including
      1. a. Identifying dependent and independent variables.
      2. b. Identifying appropriate controls.
      3. c. Justifying appropriate controls.
    5. 3.D  Make observations, or collect data from representations of laboratory setups or results. (Lab only; not assessed)
    6. 3.E  Propose a new/next investigation based on
      1. a. An evaluation of the evidence from an experiment.
      2. b. An evaluation of the design/methods.
    7. Assessment on the AP Exam: Students will need to identify or pose a testable question, state the null and alternative hypotheses or predict the results of an experiment, identify experimental procedures, and/or propose new investigations.
  4. Representing and Describing Data: Represent and Describe Data
    1. 4.A  Construct a graph, plot, or chart (X,Y; Log Y; Bar; Histogram; Line, Dual Y; Box and Whisker; Pie).
      1. a. Orientation
      2. b. Labeling
      3. c. Units
      4. d. Scaling
      5. e. Plotting
      6. f. Type
      7. g. Trend line
    2. 4.B  Describe data from a table or graph, including
      1. a. Identifying specific data points.
      2. b. Describing trends and/or patterns in the data.
      3. c. Describing relationships between variables.
    3. Assessment on the AP exam: Students will need to identify specific data points, describe trends or patterns, and describe relationships between variables
  5. Statistical Tests and Data Analysis: Perform statistical tests and mathematical calculations to analyze and interpret data.
    1. 5.A  Perform mathematical calculations, including
      1. a. Mathematical equations in the curriculum.
      2. b. Means.
      3. c. Rates.
      4. d. Ratios.
      5. e. Percentages.
    2. 5.B  Use confidence intervals and/ or error bars (both determined using standard errors) to determine whether sample means are statistically different.
    3. 5.C  Perform chi-square hypothesis testing.
    4. 5.D  Use data to evaluate a hypothesis (or prediction), including
      1. a. Rejecting or failing to reject the null hypothesis.
      2. b. Supporting or refuting the alternative hypothesis.
    5. Assessment on the AP exam: Students will need to perform mathematical calculations, use confidence intervals, perform chi-square hypothesis testing, and use data to evaluate a hypothesis or prediction.
  6. Argumentation: Develop and justify scientific arguments using evidence.
    1. 6.A  Make a scientific claim.
    2. 6.B  Support a claim with evidence from biological principles, concepts, processes, and/or data.
    3. 6.C  Provide reasoning to justify a claim by connecting evidence to biological theories.
    4. 6.D  Explain the relationship between experimental results and larger biological concepts, processes, or theories.
    5. 6.E  Predict the causes or effects of a change in, or disruption to, one or more components in a biological system based on
      1. a. Biological concepts or processes.
      2. b. A visual representation of a biological concept, process, or model.
      3. c. Data.
    6. Assessment on the AP exam: Students will need to make scientific claims, support claims with evidence, and provide reasoning to justify claims. Additionally, students will need to explain relationships between experimental results and larger biological concepts, processes, or theories. Finally, students will need to predict the causes or effects of a change in, or disruption to, one or more components in a biological system.

* Not explicitly in the standards, but recommended

** The College Board put this concept in Cellular energetics, which looks like a mistake.