UNIT VIII EVOLUTION Baby Campbell Ch 19-23, 27 Big Campbell

I. A HISTORY OF EVOLUTIONARY THEORY

I. A HISTORY OF EVOLUTIONARY THEORY, cont Darwin As he traveled, he observed many examples of adaptations He recognized adaptations lead to differential reproductive success Based on his study of other works, he also knew Members of a population often vary greatly in their traits. Traits are inherited from parents to offspring. All species are capable of producing more offspring that their environment can support. His observations and subsequent reflections allowed him to propose his hypothesis for evolutionary change; descent with modification Species are not immutable Divergent species share a common ancestor The mechanism that produces change in species is natural selection: the differential survival and reproduction of individuals in a population based on variation in their traits.

II. Hardy-Weinberg Principle Predicts allele frequency in a non-evolving population; that is, a population in equilibrium States that allele frequencies in a population will remain constant from generation to generation if five conditions are met Used to identify evolving/study populations 4

II. Hardy-Weinberg Principle, cont Five Conditions for Hardy-Weinberg Equilibrium: 5

II. Hardy-Weinberg Principle, cont Hardy-Weinberg Equation p = frequency of one allele (A) q = frequency of other allele (a) p + q = Therefore, p = q = Genotype Frequency AA = aa = Aa = To determine distribution of genotype frequencies in a population → 6

II. Hardy-Weinberg Principle, cont Hardy-Weinberg Practice Problems If you know that you have 16% recessive fish (bb), . . . q 2 = q = Therefore, p = To calculate the frequency of each genotype … p2 = 2pq = What is the expected percentage of heterozygous fish? 7

II. Hardy-Weinberg Principle, cont If in a population of 1,000, 90 show recessive phenotype (aa), use Hardy-Weinberg to determine frequency of allele combinations. 8

II. Hardy-Weinberg Principle, cont In people light eyes are recessive to dark. In a population of 100 people, 36 have light eyes. What percentage of the population would be … Homozygous recessive? Homozygous dominant? Heterozygous?

II. Hardy-Weinberg Principle, cont The ability to roll the tongue is a dominant trait. … 75% of the students at Kingwood High School have the ability to roll the tongue. Assuming the student population is 2526, How many students would exhibit each of the possible genotypes? How many students would exhibit each of the possible phenotypes?

II. Hardy-Weinberg Principle, cont PTC Taster or Non-taster? 75% Tasters 25% Non-tasters

III. EVIDENCE FOR EVOLUTION Direct Observation Antibiotic/Drug Resistance

III. EVIDENCE FOR EVOLUTION, cont Fossil Record Succession of forms over time Transitional Links Vertebrate descent

III. EVIDENCE FOR EVOLUTION, cont Homology Homologous structures Vestigial organs Snakes Cetaceans Flightless birds

III. EVIDENCE FOR EVOLUTION, cont Convergent Evolution Independent evolution of similar features in different lineages Analogous structures

III. EVIDENCE FOR EVOLUTION, cont Biogeography Geographical distribution of species Continental Drift Pangaea Endemic species Islands are inhabited by organisms most closely resembling nearest land mass Comparative Embryology Pharyngeal Pouches Gill slits Tail

III. EVIDENCE FOR EVOLUTION, cont Molecular Biology Similarities in DNA, proteins, genes, and gene products Common genetic code

IV. MICROEVOLUTION A change in the gene pool of a population over a succession of generations Five main causes:

IV. MICROEVOLUTION, cont Genetic Drift Changes in the gene pool due to chance. More often seen in small population sizes. Usually reduces genetic variability. There are two situations that can drastically reduce population size: Bottleneck Effect Founder Effect

IV. MICROEVOLUTION, cont Bottleneck Effect Type of genetic drift resulting from a reduction in population (natural disaster) Surviving population is no longer genetically representative of the original population

IV. MICROEVOLUTION, cont Founder Effect Due to colonization by a limited number of individuals from a parent population Gene pool is different than source population

IV. MICROEVOLUTION, cont Gene Flow Genetic exchange due to the migration of fertile individuals or gametes between populations Tends to reduce differences between populations

IV. MICROEVOLUTION, cont Mutations

IV. MICROEVOLUTION, cont Nonrandom Mating Inbreeding Assortative mating

IV. MICROEVOLUTION, cont Natural Selection Only form of microevolution that adapts a population to its environment

V. VARIATION IN POPULATIONS Genetic Variation Critical for species/population success “Substrate” for evolution Mutation and Recombination Diploidy Balanced Polymorphism Heterozygote Advantage Frequency-Dependent Selection

VI. A CLOSER LOOK AT NATURAL SELECTION Not a random process → Dynamic process Increases frequency of alleles that provide reproductive advantage Fitness Natural selection is the only evolutionary mechanism for adaptive evolution

VI. CLOSER LOOK AT NATURAL SELECTION, cont Three ways in which natural selection may alter variation Directional Disruptive Stabilizing

VI. CLOSER LOOK AT NATURAL SELECTION, cont Sexual Selection Can result in sexual dimorphism - secondary sex characteristic distinction Intrasexual Selection Intersexual Selection

VII. MACROEVOLUTION Macroevolution “Species” Refers to the formation of new taxonomic groups Due to an accumulation of microevolutionary changes AKA Speciation “Species” Biological Species Concept

VII. MACROEVOLUTION Reproduction Asexual vs Sexual Reproduction

VII. MACROEVOLUTION Reproduction, cont Prokaryotes Fungi Plants

VII. MACROEVOLUTION Reproduction, cont Animals Asexual Reproduction Budding Fission Fragmentation/Regeneration Parthenogenesis Sexual Reproduction External Fertilization Internal Fertilization

VII. MACROEVOLUTION Reproduction, cont Sexual Reproduction Strategies Hermaphroditism Sequential Hermaphroditism Protogynous - female first Protandrous – male first Pheromes Chemical signals released by organism Influences behavior, physiology of organisms of same species Active in minute amounts

VII. MACROEVOLUTION, cont Reproductive Isolation Important to maintain integrity & continuity of a species Prevents closely related species from interbreeding when their ranges overlap. Divided into 2 types Prezygotic Postzygotic

VII. MACROEVOLUTION, cont

VII. MACROEVOLUTION, cont

VII. MACROEVOLUTION, cont Speciation Fossil record shows evidence of bursts of many new species, followed by periods of little chance Known as punctuated equilibrium Other species appear to change more gradually Gradualism fits model of evolution proposed by Darwin

VII. MACROEVOLUTION, cont Modes of Speciation Based on how gene flow is interrupted

VII. MACROEVOLUTION, cont Allopatric Populations segregated by a geographical barrier; can result in adaptive radiation (island species)

VII. MACROEVOLUTION, cont Sympatric Reproductively isolated subpopulation in the midst of its parent population (change in genome); polyploidy in plants; cichlid fishes

VIII. HISTORY OF LIFE ON EARTH

VIII. HISTORY OF LIFE ON EARTH, cont Formation of Organic Molecules Oparin/Haldane Hypothesis Primitive Earth’s atmosphere was a reducing environment No O2 Early oceans were an organic “soup” Lightning & UV radiation provided energy for complex organic molecule formation

VIII. HISTORY OF LIFE ON EARTH, cont Formation of Organic Molecules, cont Miller/Urey Experiment Tested Oparin/Haldane hypothesis Simulated atmosphere composed of water, hydrogen, methane, ammonia All 20 amino acids, nitrogen bases, ATP formed Hypothesis was supported 44

VIII. HISTORY OF LIFE ON EARTH, cont 45

VIII. HISTORY OF LIFE ON EARTH, cont

VIII. HISTORY OF LIFE ON EARTH, cont Mass Extinctions

VIII. HISTORY OF LIFE ON EARTH, cont Adaptive Radiation Periods of evolutionary change, increased speciation Often due to increased ecological niches in communities Also seen in organisms with major evolutionary innovations

IX. PHYLOGENY

IX. PHYLOGENY, cont Taxonomy Naming and classifying of organisms Binomial nomenclature Molded by phylogeny

IX. PHYLOGENY, cont Phylogeny, cont Evolutionary history of an organism Represented with a phylogenetic tree A lineage is comprised of ancestor and descendant populations A taxon is any group represented with a name Sister taxa are groups of organisms that share an immediate common ancestor that is not shared by the other groups represented Basal taxon is group that diverges early in the group’s history Each branch point represents the common ancestor of two evolutionary lineages that have diverged

IX. PHYLOGENY, cont Trees Root Node Extant versus Extinct

IX. PHYLOGENY, cont Taxa are sub-categorized as Monophyletic – Includes ancestral group and all descendants Clade Paraphyletic – Includes ancestral group and some, but not all descendants Polyphyletic – Includes taxa with multiple ancestors

IX. PHYLOGENY, cont

IX. PHYLOGENY, cont Tree Construction Homology Heritable traits shared by 2 or more ancestors Example: backbone in all vertebrates Important to distinguish between homologies and analogies Homologies are likenesses attributed to common ancestry Analogies are likenesses attributed to similar ecological roles and natural selection Analogies are also known as homoplasies May also be done at a molecular level 55

IX. PHYLOGENY, cont Tree Construction, cont Ancestral Trait Derived Traits Synapomorphies May see evolutionary reversals Relative term Ingroup Groups of organisms being considered, phylogenetically organized Outgroup Group chosen as point of reference for tree Closely related but diverged before the ingroups

IX. PHYLOGENY, cont Tree Construction, cont Parsimony Also known as Occam’s Razor Principle that if multiple trees are possible, the correct one is most often the one with the fewest evolutionary changes

IX. PHYLOGENY, cont 58

IX. PHYLOGENY, cont - + Derived Trait Taxon Fur Gizzard Claws/ Nails   Taxon Derived Trait Fur Gizzard Claws/ Nails Lungs Feathers Jaws Mammary Glands Keratinous Scales Lamprey - Chimp + Crocodile Lizard Mouse Perch Pigeon Salamander

IX. PHYLOGENY, cont Ring of Life

IX. PHYLOGENY, cont PhyloCode

X. KINGDOM ANIMALIA PHYLOGENY