Evidence for Evolution

Evolution

• Biological evolution is descent with

modification.

It is important to remember that:

• Humans did not evolve from chimpanzees. Humans and chimpanzees are evolutionary cousins and share a recent common ancestor that was neither chimpanzee nor human.

• Humans are not "higher" or "more evolved" than other related species.

• humans and chimpanzees have each evolved traits unique to their own lineages.

Common ancestor

Peppered Moth •During the Industrial Revolution, industrial wastes

darkened tree trunks and killed off lichens. Light moths became rare and the dark moths

became abundant.

•In 1819, the first dark moth was seen; by 1886, it was far more common: rapid

evolutionary change.

Before Industrial revolution

• Eventually light moths

were common only far

from industrial areas.

• The cause of this

change was thought

to be selective

predation by birds,

which favored

camouflage coloration

in the moth.

After the Industrial

Revolution

Selective Breeding

• Selective breeding (or

artificial selection)

occurs when humans

choose two organisms

with desirable

characteristics and

breed them together to

get offspring that also

have these

characteristics.

• Short-legged dogs (bassets and dachshunds)

developed from a single mutation on 1 gene

• The short-legged dogs were allowed to

reproduce, passing the gene on

• Darwin used

pigeons as an

example of how

variation could be

inherited and that

the form of

organisms was not

fixed.

These common vegetables were cultivated from forms of wild

mustard.

Similarity among Embryos

• In the embryo stage,

most vertebrates

look the same and

follow a comparable

development.

• This similarity seems

to indicate a

common ancestor

among vertebrates.

Homologous structures • A dolphin flipper, a

human hand, and a

bat wing are all just

variations in size

and shape of the

same number of

bones.

These structures appear to have a similar origin and

indicate a shared ancestor.

• Homologous structures are produced

through divergent evolution

• Same basic structure has changed to perform

different tasks

Analogous Structures

• Organisms facing the

same environmental

selective pressures

may evolve towards a

similar form.

Tasmanian wolf

North American

wolf

Analogous structures: wing of an insect, bird bat and

pterosaur.

Same purpose, different internal structure

• Analogous structures are produced through

convergent evolution.

Analogous structures: flying

lemur and fruit bat

Bat’s wing is homologous with

human hand

Vestigial Structures

• The presence of structures that have no apparent use

• implies that the organism's ancestors had a more useful version of the body part.

Wisdom teeth

•Over time through adaptation the role for these

structures has been lost.

• Fish species that live in caves have vestigial, non-functional eyes.

• When their sighted ancestors ended up living in caves, there was no longer any natural selection that maintained the function of the fishes' eyes.

• fish with better sight no longer out-competed fish with worse sight.

• these fish still have eyes — but they are not functional

Biochemistry – “chemical

relatedness”

• All higher organisms share the same basic

biochemistry including: Amino acids,

proteins, lipids, carbohydrates and many

enzymes

• All higher organisms use DNA as a

genetic code.

• DNA is a double helix

molecule

• DNA sequences can

be compared

between species. The

more similar the

sequence, the more

related.

• Humans and

chimpanzees share

98.7% of the same

DNA sequences

Biogeography

• Organisms that are more closely related

are found geographically closer together.

Geology

• A study of the earth's geology shows that

the planet is a place of both slow gradual

change and sudden catastrophic change.

• If organisms were unchanging they would

not be able to keep up with the changes.

Fossil Record

• If evolution is occurring, organisms found

in the fossil record should be different than

those found today.

• The fossil record shows the appearance,

change, and extinction of many

organisms throughout time.

Increasing Complexity

• Principle of Superposition: Organisms found

in the lowest rock layers must be the oldest

• We see the least

complex organisms in

the oldest layers and

most complex in the

youngest.

Punctuated Equilibrium

• The evolutionary process involving long

periods without change (stasis)

punctuated by short periods of rapid

speciation.

• Gradualism is selection and variation that

happens more gradually.

• Explains why some species seem to

change very slowly (sharks, crocodiles)

over millions of years

• Some species seem to change very

rapidly (Hawaiian birds, etc.)