Chapter 10 Evolutionary Biology AP Biology Exam Review

Chapter 10: Evolutionary Biology AP Biology Exam Review

Descent with Modification Theme: • Evolutionary change is based on the interactions between populations & their environment which results in adaptations (inherited characteristics) to increase fitness Evolution = change over time in the genetic composition of a population

Charles Darwin (1809 -1882) • English naturalist • 1831: joined the HMS Beagle for a 5 -year research voyage around the world (stopped at: Galapagos Islands) • 1859 – published Origin of Species • Influenced by Lamarck, Hutton & Lyell, Malthus

Darwin’s Theory of Natural Selection: 1. Populations produce more offspring than can possibly survive. 2. Individuals in a population vary extensively from each other, mostly due to inheritance. 3. Struggle to survive: individuals whose inherited characteristics best fit to environment leave more offspring than less fit. 4. Unequal ability of individuals to survive and reproduce leads to gradual change in pop, with favorable characteristics accumulating over generations.

• Populations evolve, not individuals. • Fitness is determined by the environment. In summary: Natural Selection = differential success in reproduction Product of natural selection = adaptations of populations to environment

Natural Selection Artificial Selection • Nature decides • “Man” decides • Works on individual • Selective breeding • Inbreeding occurs • i. e. beaks • i. e. dalmations Therefore, if humans can create substantial change over short time, nature can over long time.

Evidence for Evolution 1. Biogeography ▫ ▫ Geographic distribution of a species Geographic, reproductive isolation 2. Fossil Record – transitional forms 3. Comparative Anatomy 1. Homologous structures 2. Vestigial structures 4. Embryonic Development 5. Molecular Biology ▫ DNA, proteins

Human embryo Chicken embryo Gill pouches Postanal tail

Population Genetics = Foundation for studying evolution • Darwin’s could not explain how inherited variations are maintained in populations - not “trait blending” • A few years after Darwin’s “Origin of Species”, Gregor Mendel proposed his hypothesis of inheritance: Parents pass on discrete heritable units (genes) that retain their identities in offspring

Hardy-Weinberg Theorem: • Frequencies of alleles & genotypes in a population’s gene pool remain constant from generation to generation unless acted upon by agents other than sexual recombination (gene shuffling in meiosis) • Equilibrium = allele and genotype frequencies remain constant

Hardy-Weinberg Equilibrium Allele Frequencies: • Gene with 2 alleles : p, q p = frequency of allele “A” in a population q = frequency of allele “a” in a population Note: 1–p=q 1–q=p

Hardy-Weinberg Equilibrium Genotype Frequencies: • 3 genotypes (AA, Aa, aa) p 2 = AA 2 pq = Aa q 2 = aa

The Hardy-Weinberg Theorem describes a nonevolving population.

Conditions for Hardy-Weinberg Equilibrium: 1. Extremely large population size (no genetic drift). 2. No gene flow (isolation from other populations). 3. No mutations. 4. Random mating (no sexual selection). 5. No natural selection.

• If any of the Hardy-Weinberg conditions are not met microevolution occurs • Microevolution = generation to generation change in a population’s allele frequencies

Main Causes of Microevolution 1. Mutations – changes in DNA Point mutations Gene duplication Mutation will alter or create new alleles in a population.

Main Causes of Microevolution 2. Sexual Recombination ▫ Rearrange alleles into fresh combinations every generation

Main Causes of Microevolution 3. Natural selection Douglas fir trees only release their seeds during fires. Fire rarely occurs in the river bottom of this valley.

Main Causes of Microevolution 4. Genetic drift: a change in a population’s allele frequencies due to chance bottleneck and founder effect

A. Bottleneck Effect – genetic drift due to drastic reduction in population size ▫ Certain alleles may be over/under represented Northern elephant seals hunted nearly to extinction in California

B. Founder effect – few individuals become isolated from larger population certain alleles over/under represented Polydactyly in Amish population

Main Causes of Microevolution 5. Gene flow – genetic exchange due to migration of fertile individuals i. e. wind storm blows pollen to another field Reduces differences between populations Gain/lose alleles

Fitness : the contribution an individual makes to the gene pool of the next generation Natural selection can alter frequency distribution of heritable traits in 3 ways: 1. Directional selection 2. Disruptive (diversifying) selection 3. Stabilizing selection

Directional Selection: eg. beak sizes of birds during wet/dry seasons in Galapagos Diversifying Selection: eg. small beaks for small seeds; large beaks for large seeds Stabilizing Selection: eg. average human birth weight

Preserving Genetic Variation • Diploidy: inherit 2 alleles § Recessive alleles less favorable § Heterozygote protection • Heterozyote Advantage: § People hybrid for sickle cell anemia protected against malaria.

Darwinian Fitness : ability to survive AND reproduce AND pass on alleles to offspring • Sexual selection for mating success ▫ Intra (within same sex) – competition for mate ▫ Inter (out) – mate choice Sexual selection may lead to pronounced secondary differences between the sexes

Evolution of Populations • Remember: ▫ Individuals are selected ▫ Populations evolve • Terms: ▫ Population = localized group belonging to same species ▫ Species = members of a population that can interbreed and produce fertile viable offspring ▫ Gene pool = total combo of genes in a population at any one time ▫ Fixed population = all members are homozygous for trait (usually not the case)

Speciation = origin of species • Microevolution: changes within a single gene pool • Macroevolution: evolutionary change above the species level ▫ cumulative effects of speciation over long periods of time Similarity between different species.

Two Patterns of Evolutionary Change Anagenesis Cladogenesis

Two Patterns of Evolutionary Change Anagenesis (“new” “race”) Cladogenesis (“branch” “race”) • Phyletic evolution • A single species gradually changes into a different species • No original group left • Evolution in single direction • Branching evolution • One species stays same, but small portion leaves and changes to another species • Gene pool splits • Original + new groups • Increase in diversity/# of species

Biological Species Concept • Proposed by Ernst Mayr (1942) • Species = population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring ▫ Reproductively compatible • Reproductive isolation = barriers that prevent members of 2 species from producing viable, fertile hybrids

Types of Reproductive Barriers Prezygotic Barriers: ▫ Impede mating/fertilization Types: ▫ Habitat isolation ▫ Temporal isolation ▫ Behavioral isolation ▫ Mechanical isolation ▫ Gametic isolation Postzygotic Barriers: ▫ Prevent hybrid zygote from developing into viable adult Types: ▫ Reduced hybrid viability ▫ Reduced hybrid fertility ▫ Hybrid breakdown

Types of Reproductive Barriers Prezygotic barriers impede mating or hinder fertilization if mating does occur Habitat isolation Temporal isolation Behavioral isolation Individuals of different species Mechanical isolation Gametic isolation Mating attempt HABITAT ISOLATION Fertilization TEMPORAL ISOLATION BEHAVIORAL ISOLATION MECHANICAL ISOLATION GAMETIC ISOLATION Postzygotic barriers prevent a hybrid zygote from developing into a viable, fertile adult Reduced hybrid viability Reduced hybrid fertility Hybrid breakdown Viable, fertile offspring Fertilization REDUCED HYBRID VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN

Other definitions of species: • Morphological – by body shape, size, and other structural features • Paleontological – fossil record • Ecological – niche/role in community • Phylogenetic – unique genetic history, branch on tree of life

Two main modes of speciation Allopatric speciation Sympatric speciation

Two main modes of speciation: Allopatric Speciation Sympatric Speciation “other” “homeland” “same” “homeland” Geographically isolated Evolves by natural selection & genetic drift Eg. Galapagos finches Overlapping populations within home range Subset of population isolated from parent pop. change due to: • chromosomal changes • nonrandom mating • habitat differentiation Eg. polyploidy in plants (oats, cotton, potatoes, wheat)

Adaptive Radiation • Emergence of numerous species from a common ancestor introduced into new environment • Occurs when: Ø A few organisms make way to new, distant areas (allopatric speciation) Ø Environmental change extinctions new niches for survivors • Eg. Hawaiian archepelago Founding Parents

When 2 splintered groups rejoin geographically: Possibilities: 1. Still one species 2. Two distinct species (no interbreeding) 3. Hybrid zone A B Interbreeding zone

Tempo of Evolution Gradualism • Darwin • Slow, constant change • Less likely Punctuated Equilibium • Eldridge & Gould • Long period of minor change are interrupted by short bursts of significant change • More likely

Convergent Evolution • Independent development of similar features between 2 unrelated species • Similar environments • Analogous structures • Eg. wings on bees & wings on birds

REMEMBER!! • Dear King Philip Came Over For Good Spaghetti • Dear King Philip Crossed Over Five Great Seas • Dear King Philip Came Over From Germany Stoned • Your own? ? ?

ia n ib a Ra n t M ou se m Hu rd Bi Fi sh Am ph La nc el et Dr o so ph ila • Phylogeny = evolutionary history of a species or group of species Phylogram: the length of a branch reflects the number of changes that have taken place in a particular DNA sequence in that lineage

Cladistics : a form of systematics • Cladogram: diagram of evolutionary relationship of organisms ▫ Shared characteristics due to common ancestry ▫ Uses parsimony – simplest explanation, fewest DNA base changes for tree (“keep it simple”) Turtle Leopard Hair Salamander Amniotic egg Tuna LE 25 Lamprey 11 b Lancelet (outgroup) Cladogram Four walking legs Hinged jaws Vertebral column

Comparison of Structures Homology Analogy • Results from: ▫ Adaptive radiation ▫ Common ancestor ▫ Similar origin • Different functions • Eg. wing of bat, human arm, dolphin flipper • Results from: ▫ Convergent evolution ▫ Different ancestors ▫ Different origin • Similar functions • Eg. wings of bird, wings of insect Remember: • Adaptive radiation – emergence of many species from common ancestor • Convergent evolution – unrelated species independently evolve similarities when adapting to similar environments

Major events during each Era • Precambrian: microscopic fossils (stromatolites) ▫ Photosynthesis, atmospheric O 2 ▫ Eukaryotes (endosymbiont theory) • Paleozoic: Cambrian Explosion ▫ Plants invade land, many animals appear ▫ Permian Extinction (-96% species) • Mesozoic: “Age of Reptiles”, dinosaur, plants ▫ Formation of Pangaea supercontinent ▫ Cretaceous Extinction – asteroid off Mexico’s coast • Cenozoic: primates Note: All end with major extinction & start with adaptive radiation

ic o oz o- Ceno. Mes zoic le Pa Humans Land plants Animals Clock Analogy of Earth’s History Origin of solar system and Earth 1 4 Proterozoic Archaean Eon Multicellular eukaryotes Billions of years ago 2 3 Prokaryotes Single-celled eukaryotes Atmospheric oxygen

Evolution of Plants • Non-Vascular (liverworts, hornworts, mosses) Seedless Vascular (ferns) Seed Vascular (gymnosperms, angiosperms) • Mosses: Gametophytes = dominant form • Ferns: 1 st with vascular tissue (xylem, phloem ▫ wet environment (fertilization in water) ▫ Sporophyte = dominant form • Gymnosperms: “naked” seeds on cones ▫ Conifers • Angiosperms: flowering plants

Evolution of Animals – Body Plan

Evolution of Animals – Body Cavities

Evolution of Animals – Development

Evolution of Animals

Evolution of Animals • • Porifera (sponge) Cnidarian (jellyfish, hydra) Flatworms (planaria) Mollusc ▫ Gastropod (snail), bivalve (clams), cephalopod (octopus) • Annelid (earthworm) • Arthropods (insects, crustaceans) • Echinoderms (“spiny skin” = starfish, sea urchins) • Chordates (vertebrates)

Chordate Characteristics

Phylogeny of living chordates