How do organisms adapt and change

over time?

What makes this flounder fish so

unusual? And, how did it get this way?

Vestigial Structures

Embryonic Structures

HomologousStructures

Fossils

NaturalSelection

Charles Darwin (1809-1882) Sailed around the world 1831-1836

Galapagos Turtles

Darwin’s Travels Revealed

• Lots of different species!

• These island observations led him to develop the theory of evolution!

Natural Selection• The process where plants/animals with

favorable traits survive and reproduce.

• Occur because of a mutation in the DNA or the environment.

Ex. Organisms adapt to their

environment.

Natural Selection is NOTSelective Breeding!

• Nature provides variation, humans select variations that are useful.

Ex a farmer breeds only his best livestock

Natural Selection

• Traits that help an organism survive in the environment are “selected”.

Example of Natural Selection

Peppered Moths Darwin’s Finches

• The isolation of the birds on an island caused the finches to develop lots of different kinds of beaks.

• A study of different colored moths disappearing and appearing in an area.

Summary of Darwin’s Theory

1. Organisms differ; variation is inherited

2. Organisms produce more offspring than survive

3. Organisms compete for resources

4. Organisms with advantages survive to pass those advantages to their children

5. Species alive today are descended with modifications from common ancestors

Is this a correct theory?

Mimicry

• Physically or actively looking like another organism.

Ex. A walking stick insect.

How do we know that organisms use natural

selection?

Fossil Records

• Solid remains or imprints of once-living organisms.

• Are formed from layers of sediment and minerals replacing bone.

Evidence of Evolution

• Shows that living things have evolved

• Show the history of life on earth and how organisms have changed over time.

Relative Dating

• Can determine a fossil’s relative age

• Date age comparing with other fossils

• Drawbacks – provides no info about age in years

Absolute Dating

• Can determine the absolute age in numbers

• Performed by radioactive dating – based on the amount of remaining radioactive isotopes

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

Carbon-14 Dating

What do fossil records and skeletal records show

Similarities!

Vestigial Structures• Once useful structures that are still visible.

Ex. The hind-limb bones deeply embedded inside the whale or the changes in the horse.

Can you find the vestigial structures?

Homologous Structures

• Similar structures in different organisms.

Ex. Hand Bones

Homologous Body Structures

Embryonic Structures

• Embryos of vertebrates are not the same but look similar.

(And, grow into different organisms.)

How do organisms ensure the survival of there

species?

Natural Selection Must Haves:

• Overproduction of off-spring

• Inherited variation or differences

• Struggle to survive

• Successful reproduction

See the pictures and examples on Pg.162 +164

Possible Reasons for Natural Selection

• Variation In Genes

• Competition

• Pollution/Mutations

• Environmental Changes

• Separation

• Adaptation

• Division

So, why is it important that animals and plants adapt to

their environment?List and explain at least 3

reasons or examples you think animals might adapt.