Evidence of Evolution

There are 4 main bodies of

evidence that support evolution• Paleontology

• Embryology

• Comparative Anatomy

• Molecular Biology

Paleontology• Study of ancient items

• Fossil: preserved bone or other trace of an

ancient organism

• Formed when the dead animal, or something an

animal left behind, is buried by sediment.

• This is a relatively rare event, conditions must

be just right in order for a fossil to form.

By looking at how the organisms progressed in

the fossil record we can see how they have

changed gradually.

• We can use morphology and location of

fossils to determine information about an

organism’s ancestors.

Transitional Fossils• Every fossil is a transitional fossil.

The location of those fossils, and also

currently living organisms provides evidence

as well. – island species most closely resemble nearest

mainland species

– populations can show variation from one island to

another

Developmental patterns in embryos

• Embryology-using stages of development

to determine relatedness. The closer the

stages of development the more related

the organisms are.

• Early in development, human embryos and

embryos of all other vertebrates (organisms

with a backbone) are similar. Ex: tailbone,

fur, gills.

Comparative Anatomy• Comparing how organisms are put together

provides important evidence for evolution.

Homologous structures:Structures that are derived from a common

ancestor. SAME ancestry NOT same function!

These ARE

used to

determine

evolution

relationships

Analogous structures:

• structures that look similar but evolved from

different ancestors.

• These can’t be used as evidence or

relatedness. Why not??

An example could be the wing of a bird and

the wing of an insect.

Vestigial structures: remnants of an organism’s evolutionary past and has no function

Ex: Whales and snakes

each have a vestigial

pelvis that serves no

apparent function.

This pelvis is a

remnant of the

evolutionary past

Molecular Biology

• Determine similarities in common biological

molecules like DNA or proteins.

• Closely related species will show more

similarities in bio molecule than will distantly

related species

Molecular clocksUse differences between molecules (like DNA, RNA Hemoglobin,

cytochrome C ) to determine how closely related 2 groups are.

The greater the divergence, the higher the % difference in the

compared molecules.

• The molecular clock is a technique that

uses the mutation rate of biomolecules to

deduce the time in prehistory when two or

more life forms diverged. Over the course of

millions of years, mutations build up in any

given stretch of DNA at a reliable rate.

For example, the gene that codes for the protein alpha-globin

(a component of hemoglobin) experiences base changes at a

rate of .56 changes per base pair per billion years.

2 special areas of molecular

biology are:

1) Psuedogenes

2) Hox genes

Pseudogenes are sequences

providing evidence of

evolution– Non-functioning sections of DNA

– carried along with functional DNA

– can be clues to a common ancestor

Think: How is this related to RNA Processing?

Hox genes indicate a very distant common

ancestor.

– Determines head to tail development in embryos

– Are genes that are shared by all organisms, they

are called “master genes”.

– Position of cell

differentiation:

creates

segments of

cells in embryos

that will develop

into certain

tissues or

structures.