UNIT VIII EVOLUTION Big Campbell v Ch 22

UNIT VIII EVOLUTION • Big Campbell v Ch 22 -28, 31 • Baby Campbell v. Ch 13 -17 • Hillis v. Ch 15 -18

I. EVOLUTION - WHAT IS IT? o “Descent with Modification” Earth’s many species are descendants of ancestral species that were diff. than present day species o Evolution – change in the genetic of a population over time. composition v “Change” – in the genetic composition (the alleles) v Population – group of organisms of one species in a certain habitat that interbreed to produce fertile offspring. November 24, 1859

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

II. Hardy-Weinberg Principle, cont • Five Conditions for Hardy-Weinberg Equilibrium: 1) No Mutations – gene pool is modified if mutations alter alleles or if entire genes are deleted or duplicated 2) Random Mating – if individuals mate preferentially within a population (inbreeding), random mixing of gametes does not occur and gene frequency changes. 3) No natural Selection – differences in the survival and reproductive success of individuals carry diff. genotypes and can alter allele frequencies. 4) Extremely large population size – the smaller the pop the more likely allele frequencies will fluctuate by chance from one generation to the next (genetic drift) 5) No gene flow (migration) – moving alleles into or out of populations can alter allele frequencies. If any of these conditions are not met, evolutionary change will occur!

II. Hardy-Weinberg Principle, cont • Hardy-Weinberg Equation Ø p = frequency of one allele (A) Ø q = frequency of other allele (a) Ø p + q = 1 (sum of 2 alleles = 1 or 100%) • Therefore, Øp=1 -q Øq=1 -p • Genotype Frequency Ø AA = p 2 Ø aa = q 2 Ø Aa = 2 pq • To determine distribution of genotype frequencies in a population → Øp 2 + 2 pq + q 2 = 1

Ex: PKU in the US Autosomal Recessive Occurs 1 in 10, 000 births q 2 =. 0001 q =. 01 p = 1 -. 01 =. 99 What % of individuals are carriers for PKU? • 2 pq = 2(. 99)(. 01) =. 0198 or 2% • • •

II. Hardy-Weinberg Principle, cont Hardy-Weinberg Practice Problems 1. If you know that you have 16% recessive fish (bb), . . . • q 2= • q= • Therefore, p = v To calculate the frequency of each genotype … • p 2 = • 2 pq = v What is the expected percentage of heterozygous fish?

II. Hardy-Weinberg Principle, cont • Hardy-Weinberg Practice Problems, cont 2. If in a population of 1, 000, 90 show recessive phenotype (aa), use Hardy-Weinberg to determine frequency of allele combinations. 3. 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 4. The ability to roll the tongue is a dominant trait. … 75% of the students at Kingwood Park High School have the ability to roll the tongue. Assuming the student population is 1700, a) How many students would exhibit each of the possible genotypes? b) How many students would exhibit each of the possible phenotypes?

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

III. A HISTORY OF EVOLUTIONARY THEORY, cont

III. A HISTORY OF EVOLUTIONARY THEORY, cont • Charles Darwin (1809 -1882)

III. A HISTORY OF EVOLUTIONARY THEORY, cont • Darwin, cont o Observed many examples of adaptations ØInherited characteristics that enhance organisms’ survival and reproduction o Based on principles of natural selection ØPopulations of organisms can change over the generations if individuals having certain heritable traits leave more offspring than others ØDifferential reproductive success

III. A HISTORY OF EVOLUTIONARY THEORY, cont • Darwin’s Conclusions § Based on his own observations and the work of other scientists, Darwin realized … o Members of a population often vary greatly in their traits. o Traits are inherited from parents to offspring. o All species are capable of producing more offspring that their environment can support, therefore …

III. A HISTORY OF EVOLUTIONARY THEORY, cont § Darwin concluded … o Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals. o This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations. § Descent with Modification

IV. EVIDENCE FOR EVOLUTION • Direct Observation o Antibiotic/Drug Resistance

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

IV. EVIDENCE FOR EVOLUTION, cont • Homology o Homologous structures o Vestigial organs ØSnakes ØCetaceans ØFlightless birds

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

IV. EVIDENCE FOR EVOLUTION, cont • Biogeography o Geographical distribution of species o Continental Drift ØPangaea o Endemic species o Islands are inhabited by organisms most closely resembling nearest land mass

IV. EVIDENCE FOR EVOLUTION, cont • Comparative Embryology o Pharyngeal Pouches Ø Gill slits o Tail

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

V. MICROEVOLUTION • A change in the gene pool of a population over a succession of generations • Five main causes: Ø Mutation Ø Non-Random Mating Ø Natural Selection Ø Genetic Drift Ø Gene Flow

• Genetic Drift o o V. MICROEVOLUTION, cont 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: ØBottleneck Effect ØFounder Effect

V. MICROEVOLUTION, cont • Bottleneck Effect v Type of genetic drift resulting from a reduction in population (natural disaster) v Surviving population is no longer genetically representative of the original population • Founder Effect v Due to colonization by a limited number of individuals from a parent population v Gene pool is different than source population

V. MICROEVOLUTION, cont • Gene Flow Ø Genetic exchange due to the migration of fertile individuals or gametes between populations – tends to reduce differences between populations

V. MICROEVOLUTION, cont • Mutations Ø A change in an organism’s DNA (gametes; many generations); original source of genetic variation (raw material for natural selection)

V. MICROEVOLUTION, cont • Nonrandom Mating Ø Inbreeding – reduces fitness by putting an individual at a greater risk of harmful recessive traits. Ø Assortative mating – individuals with similar genotypes/phenotypes mate more frequently than expected

V. MICROEVOLUTION, cont • Natural Selection Ø Blend of Chance and Sorting chance in the creation of new genetic variations; sorting b/c natural selection favors some alleles over others Ø Relative fitness – contribution an individual makes to the gene pool of the next generation Ø Only form of microevolution that adapts a population to its environment

VI. VARIATION IN POPULATIONS • Genetic Variation is the “substrate” for evolution • Maintained through … Ø Polymorphism § Coexistence of 2 or more distinct forms of individuals (morphs) within the same population Ø Geographical Variation § Differences in genetic structure between populations (cline)

VI. VARIATION, cont Ø Mutation and Recombination Ø Diploidy § 2 nd set of chromosomes hides variation in the heterozygote Ø Balanced Polymorphism § Heterozygote Advantage § Frequency-Dependent Selection o Survival & reproduction of any 1 morph declines if it becomes too common o Parasite/host

VII. A CLOSER LOOK AT NATURAL SELECTION • Natural Selection v. Not a random process → Dynamic process v. Increases frequency of alleles that provide reproductive advantage ØFitness

VII. CLOSER LOOK AT NATURAL SELECTION, cont v Natural selection is the only evolutionary mechanism for adaptive evolution

VII. CLOSER LOOK AT NATURAL SELECTION, cont • Three ways in which natural selection alters variation v. Directional v. Disruptive v. Stabilizing

VII. CLOSER LOOK AT NATURAL SELECTION, cont • Sexual Selection Ø Can result in sexual dimorphism secondary sex characteristic distinction Ø Intrasexual Selection - within the same sex; individuals of one sex compete directly for mates of the opposite sex Ø Intersexual Selection - individuals of one sex are choosy in selecting their mate (male showiness)

• Macroevolution VIII. MACROEVOLUTION Ø Refers to the formation of new taxonomic groups Ø Due to an accumulation of microevolutionary changes Ø AKA Speciation • “Species” • Biological Species Concept Ø Described by Ernst Mayr in 1942 Ø A population or group of populations whose members have the potential to interbreed and produce viable, fertile offspring; in other words, similar organisms that can make babies Ø Can be difficult to apply to certain organisms. .

VIII. MACROEVOLUTION Reproduction • Asexual vs Sexual Reproduction

VIII. MACROEVOLUTION Reproduction, cont • Prokaryotes • Fungi • Plants

VIII. MACROEVOLUTION Reproduction, cont • Animals § Asexual Reproduction v Budding v Fission v Fragmentation/Regeneration v Parthenogenesis

VIII. MACROEVOLUTION Reproduction, cont § Sexual Reproduction v External Fertilization v Internal Fertilization

• Sexual Reproduction VIII. MACROEVOLUTION Reproduction, cont v Strategies Ø Hermaphroditism Ø Sequential Hermaphroditism § Protogynous - female first § Protandrous – male first Ø Pheromones o Chemical signals released by organism o Influences behavior, physiology of organisms of same species o Active in minute amounts

VIII. MACROEVOLUTION, cont • Reproductive Isolation o Prevent closely related species from interbreeding when their ranges overlap. o Divided into 2 types ØPrezygotic ØPostzygotic

VIII. MACROEVOLUTION, cont Prezygotic Reproductive Barriers

VIII. MACROEVOLUTION, cont Postzygotic Reproductive Barriers

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

VIII. MACROEVOLUTION, cont • Modes of Speciation Ø Based on how gene flow is interrupted

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

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

IX. HISTORY OF LIFE ON EARTH

IX. HISTORY OF LIFE ON EARTH, cont • Formation of Organic Molecules o Oparin/Haldane Hypothesis Ø Primitive Earth’s atmosphere was a reducing environment Ø No O 2 Ø Early oceans were an organic “soup” Ø Lightning & UV radiation provided energy for complex organic molecule formation o Miller/Urey Experiment Ø Tested Oparin/Haldane hypothesis Ø Simulated atmosphere composed of water, hydrogen, methane, ammonia Ø All 20 amino acids, nitrogen bases, ATP formed Ø Hypothesis was supported

IX. HISTORY OF LIFE ON EARTH, cont

IX. HISTORY OF LIFE ON EARTH, cont

IX. HISTORY OF LIFE ON EARTH, cont • Mass Extinctions

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

X. PHYLOGENY Phylogeny – study of how living things share common evolutionary history (relationships among organisms) - Constructed based on physical structures, behaviors, and biochemical attributes - Commonly used to depict evolutionary history of species, populations, and genes.

X. PHYLOGENY • Taxonomy Ø Carrolus Linnaeus Ø Binomial nomenclature – 2 part naming system; genus and species Ø Taxon (taxa) – which is any group of species that we designate with a name. EX: humans, primates, mammals Ø KPCOFGS Ø Domain is broadest; organisms not as closely related Ø Species is most specific

X. PHYLOGENY, cont • Phylogenetics Ø Tracing of evolutionary relationships Ø Illustrated with diagrams known as phylogenetic trees Ø May portray all life, or a major evolutionary group such as insects or mammals. Ø Common ancestor is called the “root”

X. PHYLOGENY • Tree Terminology Ø Root – common ancestor of all organisms in the tree. Ø Node – or split when a single lineage divides into two; giving rise to new lineages Ø Clade § Any taxon that consists of all evolutionary descendants of a common ancestor § Clades are sub-categorized as v. Monophyletic – Includes ancestral group and all descendants v. Paraphyletic – Includes ancestral group and some, but not all descendants v. Polyphyletic – Includes taxa with multiple ancestors Ø Sister Clades – any 2 clades that are each other’s closest relatives Ø Sister Species – two species that are each other’s closest relatives

Monophyletic – “single tribe”

Paraphyletic vancestral group and some, but not all descendants “beside the tribe”

Paraphyletic

Polyphyletic Includes taxa with multiple ancestors EX: Kingdom Protista

Polytomy • Unresolved pattern of divergence • More than 2 descendant groups emerge • Evolutionary relationships are not clear

X. PHYLOGENY, cont • Evolutionary history of an organism

X. PHYLOGENY, cont • Important to distinguish between homologies and analogies Ø Homologies are likenesses attributed to common ancestry Ø Analogies are likenesses attributed to similar ecological roles and natural selection • May also be done at a molecular level Ø Known as molecular systematics

X. PHYLOGENY, cont • Tree Construction, cont Ø Ancestral Trait – trait from which organisms evolve; found in common ancestor Ø Derived Traits – new traits that evolved after ancestral trait § Synapomorphies – shared among a group of organisms; viewed as evidence for common ancestry of group. EX: vertebral column of vertebrates § May see evolutionary reversals – a character may revert from a derived state back to an ancestral state. EX: fins tetrapods fins in whales/dolphins Ø Ingroup § Groups of organisms being considered, phylogenetically organized Ø Outgroup § Group chosen as point of reference for tree § Closely related but diverged before the ingroups

X. PHYLOGENY, cont • Tree Construction, cont Ø Parsimony § Also known as Occam’s Razor § Principle that if multiple trees are possible, the correct one is most often the simplest one; one that takes the fewest assumptions

X. PHYLOGENY, cont

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

X. PHYLOGENY, cont Ring of Life

XI. KINGDOM ANIMALIA PHYLOGENY