Chapter 15 Evolution

What is evolution? Change in a population over time Changes occur at genetic level  mutations

Mutations Change in the DNA code Can affect traits / phenotype

The Darwin Dude? 5 year voyage on Beagle (1831-36) Naturalist: surveyed coast of S.A. Wrote “Origin of Species”

Galapagos Island Facts Part of Ecuador 13 main volcanic islands Formed between 5 - 10 MYA

Darwin & Galapagos Organisms adapted to their environment “Darwin’s Finches” Mechanism for evolution = Natural Selection

Noteworthy Species

Darwin’s Finches Adaptive Morphology

Why do species change? Variations & adaptations help organisms survive

Camouflage

Camouflage

Natural Selection Organisms with favorable traits survive & reproduce Variation is key

Natural Selection (cont.) Struggle for existence Species become better fit for their environment

Natural Selection (cont.) 4 Main Principles (pg 421): Variation Heritability Overproduction Reproductive Advantage

Types of Natural Selection 1. Stabilizing Selection: Average phenotype favored Ex. Human baby weight

Stabilizing Selection

Types of Natural Selection 2. Directional Selection: increases “extreme” versions of traits Ex. Peppered Moth, Darwin’s finches

Peppered Moth: Natural Selection

Directional Selection

Types of Natural Selection 3. Disruptive Selection: splits populations into 2 groups Both extremes favored Ex. Marine & Land Iguanas

Disruptive Selection

Evidence of Evolution Fossil Record Fossils: preserved evidence Found in Sedimentary rock

“Soft parts” don’t fossilize Fossil Record (cont) “Soft parts” don’t fossilize Specific conditions needed to form fossils Lack of “transitional” fossils

Evidence of Evolution 2. Homologous Structures: Anatomically similar structures Evidence of common evolutionary origin

Homologous Structures

Evidence of Evolution 3.Comparative Embryology: similarities in embryos

Evidence of Evolution 4.Compararative Biochemistry: Organisms have similar DNA, genes and enzymes

Evidence of Evolution 5. Vestigial Structures: reduced in size, no longer have function

What is Speciation? Formation of new species Become genetically different

What are Species? Group of organisms that can interbreed & produce fertile offspring

Infertile Species Horse + Donkey = Mule

Liger

Species Loop Hole Not a perfect definition Used for classification Some different species can produce fertile offspring

Rate of Speciation Gradualism: Evolution occurring at slow rate Punctuated Equilibrium: Evolution occurring at irregular rates

Cause of Speciation Geographic Barriers Environment Changes Mountains, Rivers, etc. Environment Changes