Evolution is a Theory! A theory is a well supported explanation of a phenomena that has occurred in...

Evolution is a Theory!• A theory is a well

supported explanation of a phenomena that has occurred in the natural world

• A theory in science is a well tested, well supported hypothesis, not just a guess

Evidence of Evolution

1. Fossil Record

2. Geographic Distribution of Living Species

3. Homologous Body structures

4. Similarities in Embryology

Evidence of Evolution

Fossil Record provides evidence that living things have evolved

Fossils show the history of life on earth and how different groups of organisms have changed over time

Fossil Formation

1. Ammonite is alive and swimming 2. Ammonite dies and sinks into the sediments

3. Soft body decays, leaving shell (or bones)

4. Minerals gradually replace the bone/shell

Relative vs. Absolute Dating

Relative Dating

• Can determine a fossil’s relative age

• Performed by estimating fossil age compared with that of other fossils

• Drawbacks – provides no info about age in years

Absolute dating

• Can determine the absolute age in numbers

• Is performed by radioactive dating – based on the amount of remaining radioactive isotopes remain

• Drawbacks - part of the fossil is destroyed during the test

Carbon-14 Dating

Primate Fossils

Australopithecus Homo erectus Homo sapien

Primate Brain

Capacity

Primate Bone structure

Human Relatives

Australopithecusafarensis

Homo habilis = handy human1.5 to 2 mya

Homo erectus1.6 mya

bipedal

Neanderthals35,000 to 100,000 ya

Cro-Magnon35,000 to 40,000 ya

2. Geographic Distribution of Living Species

Similar animals in different locations were the product of different lines of descent

Evidence of Evolution

Adaptive Radiation

Turtle

Alligator

Bird

Homologous Body StructuresStructures that have

different mature forms but develop from the same embryonic tissues

e.g. Wing of bat, human arm, leg of turtle

Evidence of Evolution

Homologous Body Structures

Vestigial Organs

– traces of homologous organs in other species

– Organ that serves no useful functione.g. Appendix

Evidence of Evolution

Similarities in Embryology

– In their early stages of development, chickens, turtles and rats look similar, providing evidence that they shared a common ancestry.

Mechanisms for evolution

• Do populations or individuals evolve?

• What is a gene pool?

• How do populations change?

Mechanisms for evolution

• Do populations or individuals evolve?

• What is a gene pool?

• How do populations change?

• Would these types of change effect a large or small population more?

WHAT IS SPECIATION?A single species becomes multiple species.A single species becomes multiple species.

Can result from:Can result from:

- Geographical isolation- Geographical isolation

SPECIATION• GEOGRAPHIC GEOGRAPHIC

ISOLATIONISOLATION

• REPRODUCTIVE REPRODUCTIVE ISOLATIONISOLATION

Coevolution

• Organisms evolve in response to each other.– For every defense mechanism a prey species

develops, a predator develops a way around it.– Pollinators become more and more specialized

to the plants that they pollinate.

Convergent evolution

Unrelated organisms evolve similar structures.

What were these structures called?!?

Homologous structures

Form Fits Form Fits FunctionFunction

Organisms will change Organisms will change over time to become more over time to become more and more efficient. Their and more efficient. Their physical structures will physical structures will

become increasingly become increasingly suited to their specific suited to their specific

tasks. tasks.

Evolution