Evidence of

Evolution

There are 5 main categories of

evidence that support evolution• Fossils

• Biogeography

• Embryology

• Comparative Anatomy

• DNA and proteins

Fossils

• 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.

• Paleontology- study of ancient items

• We can use morphology to determine

information about an organism’s ancestors.

Here are some famous examples of

transitional fossils:

Archaeopteryx

Archaeopteryx

So is Tiktaalik.

Horses

Whale

Progression

BIOGEOGRAPHY

The study of geography provides evidence of

evolution.– island species most closely resemble nearest

mainland species

– populations can show variation from one island to

another

Check your Understanding

• What are the 2 categories of

paleontology?

• What is morphology? How is it used in

looking at fossils?

Embyology

• 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.

Check your Understanding

• What is embryology?

• How does the similarity of embryos related

to how the organism are related?

Comparative AnatomyComparing structures between different

organisms to find if they are related.

Comparative Anatomy

• Structures analyzed will be in 1 of 3

outcomes;

• 1) structures are homologous-they have

the SAME ancestors but DIFFERENT

function.

• 2) structures are analogous-they have

DIFFERENT ancestors but SAME function

• 3) Vesitigal-the structure functions in one

group but serves no function in another

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Homologous structures:Structures that come from the SAME or common

ancestor

Ex: The bones in the front limbs of a bird, dolphin,

and human are all homologous structures.

Check your understanding

• “Homo” means the same…so what exactly

is the same about homologous structures

like a bat wing and your arm?

Analogous structures:

• structures that function the same but evolved

from different ancestors.

• These can’t be used as evidence or

relatedness. To pinpoints true relatedness,

internal structures such

as cells, organs and

developing embryos need

to be studied.

An example could be the wing of a bird and

the wing of an insect.

Check your understanding

• Bee wings and bird wings both function for

flight, so why are they analogous? What

do they NOT share?

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

Check your Understanding

• What are the 3 categories of comparative

anatomy?

• What do organisms share that have

homologous structures?

• What do organisms NOT share that have

analogous structures?

• Can we use analogous structures to show

relatedness? Why/why not?

• Why do vestigial structures exist if they are

not used?

DNA and proteins

• An organism’s history is written in the sequence

of nucleotides making up its DNA

• If species have changed

over time, their genes

should have changed.

• The more the molecules

are alike the more in

common the organisms

are!

• Therefore, closely related species will show

more similarities in nucleotide sequences than

will distantly related species