Evolution

Evolution Simply said it means… “Descent with modification” ……. What does descent with modification mean? It means a change in the genetic frequency in a population over time.

Two Opposing Views on Evolution DARWIN: Father of Evolution Believed traits were INHERITED LAMARK: Believed traits were AQUIRED “Use it or Lose it”

Darwin & Galapagos Islands Darwin’s Theory of Evolution was based on his studies in the Galapagos Islands (off the northwest coast of South America) during his voyage in the Beagle ship. He noticed that the animal and plant species in the islands were similar but not the same.

Mechanisms of Evolution Natural Selection Mutations Gene Flow Genetic Drift Nonrandom Mating Bottleneck Effect Founder Effect

Darwin’s Natural Selection: Population has variations of a trait. Some variations are favorable. More offspring are produced than survive. Those that survive have favorable traits. A population will change over time. SURVIVAL OF THE FITTEST!!!

MICHAEL PHELPS ARNOLD SCHWARZENEGGER

Darwin’s Natural Selection: In summary: when organisms with favorable variation (trait) in its environment survive, reproduce, and pass these variations on to the next generation Reminder: •INDIVIDUAL ORGANISMS DO NOT EVOLVE! •Natural selection does not act on individuals, but only in the sense that it affects one individual’s ability to survive and reproduce •The smallest unit that can evolve is a population, a collection of individuals of the same species living in an area together

Mutations Changes in DNA introduce variations in a population

Gene Flow (migration) Movement of alleles between populations “shuffles up” characteristics Breeding of individuals creates unique combinations

Non-random mating Mating that does not occur by chance Sexual selection: males compete for females

Genetic Drift Changes in allele frequency (common characteristics of a population) due to chance Types: Bottleneck Effect Founders Effect

Bottleneck Effect A sudden shrinking of a population Changes genes in population drastically Less diversity Ex: natural disasters

Founder Effect A small population is isolated from another Different allele frequency than original population

Adaptation Any trait that aids in the chances of survival and reproductive success of an organism Darwin’s theory of natural selection can be used to explain the evolution of various adaptation in organisms

Structural adaptations Change in the structure of body parts May be used as a defense mechanism Mimicry – a structural adaptation that provides protection for an organism by copying the appearance of another, more dangerous species Camouflage – a structural adaptation that enables an organism to blend in with its surroundings

                                                                

Physiological adaptations Changes in an organism’s metabolic or internal processes Ex. Antibiotic resistance

Types of Natural Selection Stabilizing: • Intermediate phenotype favored • Population moves toward norm Directional: • Extreme phenotype is favored • Population shifts in that direction Disruptive: • 2 or more extreme phenotypes favored • Population splits

Types of Natural Selection

Evidence for Evolution Fossils Comparative Anatomy Biogeography Embryology Biochemical

Evidence for Evolution Fossils can show evolutionary changes over time Horse Evolution

Evolution & The Geologic Time Scale Using fossil records and different dating techniques, scientists can determine the approximate dates for events on Earth The Geologic Time Scale is divided up to represent different times during which the Earth and its organisms evolved

Evidence for Evolution Comparative Anatomy: Anatomical structure indicates evolutionary relationships Vestigial Structures: Functionless structures indicate evolutionary pathways Ex.: wisdom teeth, appendix

Evidence for Evolution Comparative Anatomy: ANALOGOUS STRUCTURES: Same function, but no common descent. -HOMOLOGOUS STRUCTURES: Different function, common descent. Genetic and embryological comparisons reveal hidden relationships

Evidence for Evolution Biogeography Related organisms found close together on globe

Evidence for Evolution Embryology: Embryological development shows evolution from a common ancestor

Evidence for Evolution Biochemical: Genetic (DNA) comparisons may reveal hidden relationships

Patterns of Macroevolution: Mass Extinction: more than 99% of all species that ever lived are extinct Punctuated Equilibrium: rapid evolution after long periods of equilibrium Gradualism: gradual transformation of a species

Patterns of Macroevolution Coevolution: 2 species evolve in response to changes in each other over time Convergent Evolution unrelated organisms come to resemble another Divergent Evolution or Adaptive Radiation a species or group of species evolves into many new species

Mechanisms of Speciation Species: A group of organisms that can breed amongst each other and produce fertile offspring The gene pool of the population is isolated from other gene pools due to: Seasons/weather Geographic location Reproductive isolation Reproductive isolation: Morphological differences in damsel fly reproductive organs Damsel fly penises

Hardy-Weinberg Equilibrium How do we measure evolution? “Evolution is the change in the allele frequency over time.” Can we measure allele frequency?

Breeding Bunnies  Bunnies in England either have hair (dominant) or are hairless (recessive) We can measure the frequency of each in the population. But is evolution happening? How do we know?

Hardy-Weinberg Equilibrium A population that is not changing genetically is said to be at Hardy–Weinberg equilibrium assumptions that underlie the Hardy–Weinberg equilibrium: mating is random population is large no migration mutation can be ignored Natural selection is not acting on the population. If these are true and no change is occurring, population is in equilibrium

Back to the bunnies  SO… p= frequency of dominantallele F (haired bunnies) q= frequency of recessiveallele f (hairless bunnies) Frequencies meaning percentages of a whole SO… p+q= 1(because that makes up 100% of the population)

For example… If hairless bunnies exist in 20% of the population, q = .2 Consequently, the haired bunnies would be 80%, or p=.8 SO, p+qstill equals 1. BUT, what about heterozygotes? How do those factor into the equation?

Hardy-Weinberg Equilibrium p2 + 2pq + q2 = 1 Homozygous dominant Heterozygous Homozygous recessive everyone

Breeding Bunnies Example If p = .8, then p2= .64 If q = .2, then q2= .04 Then, to find out the frequency of the heterozygotes, you have 2 options: 2 * .8 * .2 OR 1 -.64 -.04 Both = 2pq = .32

Let’s do a Lab!

Mechanisms of Speciation A group of organisms that can breed amongst each other and produce fertile offspring The gene pool of the population is isolated from other gene pools due to: Seasons/weather Geographic location Reproductive isolation Reproductive isolation: Morphological differences in damsel fly reproductive organs Damsel fly penises

Evolution Theory in a Nutshell DESCENT WITH MODIFICATION ECOLOGICAL COMPONENT: Life experiences by individuals in a population can influence the flow of genetic information from one generation to the next. GENETICS COMPONENT: If the genetic makeup of a population is different in one generation from the genetic makeup of the population in a previous generation, this is an evolutionary result.