Evidence For Evolution

Common Descent (See earlier notes/slideshow)

Anatomy - Homologous/Analogous/Vestigial Structures

Fossil Evidence

Embryological Evidence

Biochemical Evidence

Anatomy

structural features with common evolutionary origin

similar in arrangement, function, or both

suggest a common ancestor

Homologous Structures

AnatomyHomologous Structures

AnatomyHomologous Structures

Darwin’s Finches

Anatomy

structural features without common evolutionary origin

similar only in function

common ancestor does not have that structural feature

Analagous StructuresAnatomy

Analagous Structures

The supports for insect wings are not homologous with bones of bat/bird wings.

Bones are homologous

Insect and bird wings evolved separately when difference ancestors adapted differently to similar ways of life

Anatomy

Living in the open ocean as a fish eater requires a streamlined body and the ability to move very quickly when needed. These pressures caused first sharks, then ichthyosaurs and finally dolphins, to all adopt a very similar body shape and method of movement.

In all these animals the tail is the major motor, other flippers and fins are used merely for steering and the body has taken on a shape that has the least resistance to water.

They come from three animal groups that have been separate for hundreds of millions of years yet there they are, all looking so much alike.

Ichthyosaurs, Dolphins, and Sharks

Analagous StructuresVestigial Structures

body structure with no function in a present-day organism, but was probably useful to an ancestor

a structure becomes vestigial when the species no longer needs the feature

Vestigial StructuresThe Wings

of Flightless BirdsHind Leg Bones

in Whales

Vestigial StructuresErector Pilli

and Body HairThe Human Tailbone

(Coccyx)

Vestigial StructuresThe Blind Fish,

Astyanax mexicanusWisdom Teeth In

Humans

Vestigial StructuresThe Human

AppendixMale Breast Tissue

and Nipples

Fossils

provide record of early life

similarities suggest ancestral relationships between difference species

Fossils used to trace the

evolution of the modern camel.

Ancestors were as small as rabbits.

Embryologyembryo - earliest stage of growth and development in plants and animals

gill slits and tail in each embryo, not present in any of these as adults, except fish

similarities in embryos suggest evolution from distant, common ancestors

Biochemistrystructure of molecules of life reflect descent from common ancestors

similar vital molecules in all species “molecular fossils”

nucleic acids came first (RNA), still in all organisms,and then DNA-based inheritance developed

comparison of DNA and RNA identifies how closely related species are

triplet code to make proteins used in bacteria to man