AP Biology Study Guide PDF

1.1: Development of Life on Earth ❖ Introduction The Big Bang - 14 Billion Years ago Formation of our Sun - 5 BYA Earth Formation - 4.6 BYA Crust Formation by Condensation, Cooling, Etc. - 4.1 BYA Cooling and condensation led to for...

1.1: Development of Life on Earth ❖ Introduction The Big Bang - 14 Billion Years ago Formation of our Sun - 5 BYA Earth Formation - 4.6 BYA Crust Formation by Condensation, Cooling, Etc. - 4.1 BYA Cooling and condensation led to formation of ocean that completely covered Earth’s surface ❖ Conditions of Early Earth Reducing Atmosphere (electron adding) CO (volcanoes), CH4, NH3, H2O, N2, H2 No free O2 and no O3 (ozone layer) No oxidation Lots of mutations → high rates led to increased diversity Stability/longevity for the products of chemical reactions Earth was bombarded with energy ←no ozone layer UV radiation Frequent severe lightning storms Ionizing radiation Geothermal activity Lots of chemical reactions happened then that could never occur today ❖ Steps to Modern Earth and its Life Forms ❖ 1. Biomolecular Building Blocks Created Miller Urey Experiment provided evidence that biomolecules can arise spontaneously from the early earth's atmospheric conditions Amino acids, simple sugars, nucleotide precursors, and fatty acids No oxidation → complex biomolecules will survive and increase over time ❖ 2. Membrane Structures and Cells Emerge Protobionts: cell precursors - molecules inside a membrane Early “cells” contained biomolecules Simple sugars, amino acids, lipids, catalytic RNA molecules Membranes allowed self-containment and concentration of molecules Higher [molecules] → faster reaction rate Reproduced by fission - membrane like outer layer split into two cells RNA is a catalyst  Drove earliest metabolic reactions - acts like an enzyme → ribozymes Self replicating All reactions are completely random and took a billion years to actually wind up building cells! ❖ 3. Inheritance & Cell Division Proto-cells had no inheritance capability and just split in half to divide RNA molecules played a big role Can store information and replicate itself DNA came later Early organisms were haploid → later became diploid Diploid advantages Possession of two alleles for each gene If one is bad, the good one can cover for it Most traits are determined by gene interactions → two alleles increases the variety of phenotypes → increase survivability Production of haploid gametes → sexual reproduction is now possible → diversity ❖ 4. From Heterotroph to Autotroph Earliest organisms: Prokaryotes Single celled anaerobic heterotrophs Absorbed nutrients Photosynthesis emerged → sugars created Produced O2 → increased in the atmosphere Aerobic metabolism emerged More energy per glucose molecule ❖ 5. Eukaryotic & Multi-Celled Organisms Eukaryotes took another billion years to arise Compartmentalization Infolding of membranes Organelles that allow for complex metabolism Created by membrane proliferation and endosymbiosis Protists were the first eukaryotes → more diverse  Endosymbiont Theory Archaebacteria engulfed bacteria that could perform aerobic respiration or photosynthesis Eubacteria that could do aerobic respiration became mitochondria Cyanobacteria gave rise to chloroplasts Evidence for Endosymbiosis Mitochondria & Chloroplast ◆ Reproduce independently ◆ Have their own DNA (similar to modern eubacteria) ◆ Double Membrane ← original membrane and membrane from being engulfed  Multicellularity Differential and specialization allows for efficiency, unique tasks Larger size → fewer predators, greater access to food and resources If one cell is damaged, others can replace it Pre-Cambrian → aggregate multicellularity (clumps and no differentiation) Cambrian Explosion → true multicellularity with differentiation All modern invertebrates have their roots in this period High mutation rates and slow development of protective ozone layer ❖ 6. Emergence of Larger Land Masses Pangaea - supercontinent Continental drift split Pangaea into the continents we know today As land masses moved, organisms were isolated from one another → fueled diversity through natural selection Index Fossils Remains of organisms that lived in specific geological periods in specific locations Used to date the rock layer in which they are found Their geological distribution helps us figure out how land masses have moved use d to assign a date to newly found fossils in the same rock strata 1.2: Phylogeny and Cladistics ❖ Adaptations support life on land Improved support - wood and skeletons Water transport in plants - roots, stems, vascular tissue New means of transport - limbs and muscles Water retention mechanisms - tough skin, internalized lungs, advanced excretory systems Waxy cuticle on plants UV protection Reproduction without water - seeds in plants, internal fertilization in animals ❖ Levels of Classification Taxon - hierarchical classification level Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species Species - a group of organisms that can breed and produce fertile offspring ❖ Homology Similar genetics, structure, and biochemistry Functions may differ ❖ Analogy Superficial similarities in function with very different underlying genetics, structure, and biochemistry Traits evolved because they are the most efficient way to survive in a common environment ❖ Cladogram Shows relationship based on common ancestors - does NOT indicate time All cladograms are hypotheses - evidence of homologies are used to infer relationships ❖ Phylogenetic Tree Branches are proportional to the amount of time or evolutionary change that has taken place  Logic of Phylogeny DNA governs physical and biochemical traits Similar DNA → similar traits → common ancestor Most DNA is inherited and not obtained from mutations DNA mutates at predictable rates DNA differences establish a timeline for ancestry because mutations happened after organisms stopped interbreeding and sharing genes ❖ Law of Parsimony (Occam’s Razor) Simplest and most likely explanation is probably correct Mutations are an important source of variation but are RARE If 2 organisms have similar DNA/appearance → probably have a recent common ancestor Likelihood that two similar traits evolved independently is very small 1.3: Intro to Evolution ❖ Evolution Collective change in phenotypes/traits of organisms (populations) through time Isolation, natural selection, mutations, random events Is not purposeful and has no goal → if useful traits arise, good for them Does NOT produce “perfect” organisms → selection forces may not act on hidden genes so they persist ❖ Jean-Baptiste Lamark Theory of Use or Disuse - inheritance of acquired characteristics ❖ Charles Darwin Proposed the theory of evolution by natural selection ❖ Natural Selection Variation Competition for limited resources In a specific environment, some variations may be more advantageous than others → allow others to survive and reproduce and pass on their traits Eventually, the advantageous trait will increase in frequency in the population Due to differential success in reproduction Environment selects favorable inherited traits that cause a higher rate of survival and reproduction Population adapts to the environment over a long time frame Why not perfection? “Fittest” organisms has some advantageous traits but not the “best” of every trait Selection favors the best average organisms, not each best gene Mutations fuel diversity by introducing random allele variety If the environment changes, these “best” organisms may no longer be the “best” It's good to have variety in your population ❖ Evolution Trends Simple to complex Haploid to diploid Aquatic to terrestrial Long periods of increasing diversity Occasional extinction events ❖ Biogeography Examine geological strata and locations of fossils to observe differences over long periods of time Fossils provide evidence of natural selection (slow phenotypic changes) and extinction events ❖ Fossil Evidence Fossils are formed when dissolved minerals solidify within bone tissue Homologous Structures Similar underlying body structures due to variations of genes from a common ancestor Vestigial Structures No longer used in one organism, but may be used in related organisms Analogous Structures Similar characteristics in different species that serve the same function but evolve independently Comparative Embryology The embryos of related organisms have many similarities in their early stages of development ❖ Artificial Selection Humans select for desired traits instead of nature 1.4: Evolution of Populations ❖ Five Fingers of Evolution Small Population Random Mating (No Selective Mating) Mutations Genetic Flow Adaptations ❖ Causes of Microevolution Genetic Drift Random events change allele frequencies Bottleneck Effect Founder Effect Nonrandom Mating Selecting a mate based on phenotype gives that phenotype an advantage Mutation Random changes may cause new variations Favorable ones allow increased reproduction for those organisms Gene Flow immigration/emigration change population size which changes allele frequencies in the gene pool Natural Selection Organisms with different phenotypes will have different reproductive successes Survival of the fittest Not all traits are influenced by natural selection ❖ Natural Selection → Phenotype Distributions Directional Selection One phenotype is clearly and consistently advantageous Distribution shifts towards one extreme phenotype Often happens concurrently between two predator/prey species Diversifying/Disruptive Selection Multiple phenotypes can be successful and several emerge as organisms avoid competition Distribution dips down and shifts towards both extremes Stabilizing Selection Clear optimal level of behavior  Reduces diversity in the species and increases their efficiency/improves their survival Distribution spikes upwards ❖ Sexual Selection In species where female prefers certain traits in her mate Sometimes they demonstrate strength/fitness Sometimes they just look pretty → pretty offspring who will also get to mate Leads to sexual dimorphism → different phenotypes for each gender ❖ Macroevolution Large scale changes that can only be seen over thousands or millions of years Speciation - new species form Extinction – the end of a species ❖ Patterns of Evolution Divergent Evolution Organisms branch out from a common ancestor Natural selection, competition, mutation, and genetic drift Survival improves when organisms do not directly compete Tends to force diverse ways of finding food/mates within a habitat Evidence: homologous structures Adaptive Radiation Rapid diversification from a common ancestor into diverse new habitats with different selection pressures Significant environment-phenotype connection Convergent Evolution When organisms face an extreme environment or task Few choices about how to survive or few structures that can accomplish the task Evidence: Analogous Structures Coevolution The evolution of one species influences the evolution of another Predator-prey relationships ◆ Mammal predators become stronger and faster ◆ Prey animals are evolving to be more alert and sift ◆ Predators seek out the young/weak 1.5: Chi-Square Analysis ❖ Compare observed results with what you would expect to happen ❖ There will usually be some variation between what you expect and what you observe How much is too much? ❖ Null Hypothesis - general, default position Assume there is no relationship between two or more measured phenomena Results should be evenly divided ❖ ❖ Steps Predict your expected values Collect your observed (actual) data Calculate the X^2 values for each group and add them together to get your X^2 sum Find the degrees of freedom Number of groups - 1 Use the chart to compare your X^2 sum to the critical value at p=0.05 ❖ Use actual values, not percentages/ratios, in the formula ❖ ❖ Interpretation of Results  If the calculated X^2 sum is less than the critical value at p=0.05, the variation is random and not significant. Your data support your hypothesis If the calculated X^2 sum is greater than the critical value at p=0.05, the variation is statistically significant, and not just due to randomness. You must reject the null hypothesis ❖ Format for FRQ Responses The Chi-Square Sum of ____ is (greater/less) than the critical value of ____ at p=___. The variation is statistically (significant/insignificant). We just (accept/reject) the null hypothesis. It is (likely/unlikely) that … 1.6: Hardy Weinberg  ❖ Populations Group of individuals of the same species who interbreed Gene Pool - total aggregate of genes in a population at one time Dominant and Recessive Allele Frequencies p = proportion of dominant alleles Q = proportion of recessive alleles When you observe a population → you see phenotypes and not necessarily the genes ❖ Hardy Weinberg Theorem Allele Frequencies - p + q = 1 The two alleles of a gene population Treat them as frequencies (percentages) and not quantities Genotype Frequencies: p^2 + 2pq + q^2 = 1 Mating in diploid organisms can be represented mathematically ❖ Conditions Populations must be very large Mating is random There is no net mutation There is no immigration or emigration There is no natural selection Opposite of Microevolution 1.7: Speciation ❖ Allopatric Speciation - “Other Country” - Speciation in different places Geographic separation is most common Physical and reproductive isolation Locations have different selection pressures Gene pools do not mix Steps to Allopatry Geographic Isolation Allows for population gene pools to become different from one another ◆ Mutations - new traits appear ◆ Small founder groups w/ unrepresentative gene pool ◆ Differential natural selection in various habitats ◆ Competition that encourages niches Reproductive isolation occurs over time Reproductive barriers develop ◆ Prezygotic - before zygotic interactions Geographic Isolation Species occur in different areas Ecological Isolation Species occur in different habitats of the same area Temporal Isolation Species reproduce in different season/times Behavioral Isolation Species differ in mating rituals Mechanical Isolation Structural differences between species prevent mating Gamete Isolation Gametes of one species function poorly with another ◆ Postzygotic - after zygotic interactions Hybrid Inviability/Infertility Hybrid embryos do not develop properly or do not survive in nature  Hybrid adults are sterile or have reduced fertility New species are formed which cannot interbreed Isolation + time = potential for speciation If genetic differences cause reproductive isolation → speciation If genetic differences do not create barriers → two groups may reunite into one species ❖ Sympatric Speciation - “Close country” - speciation in the same place Rare – mainly in plants Autopolyploidy Single species Meiosis error → self-fertilization Allopolyploidy Two species - hybrid Hybrid gamete merges with one of the parent gametes Diversifying selection (from competition) and behavioral isolation can happen in animals ←polyploidy is generally lethal in animals ❖ Punctuated Equilibrium Long periods of stability that are interrupted by the sudden appearance of new species ❖ Gradualism The slow and steady accumulation of changes leading to a new species