Chapter 15

Darwin’s Theory of Evolution

Charles Darwin

• Charles Darwin- the father of evolution (1809-1882).

Darwin traveled around the world for 5 years on the HMS Beagle. He collected data and made observations of many unique organisms.

Darwin’s Journey

Pinta IslandIntermediate shell

Pinta

Isabela IslandDome-shaped shell

Hood IslandSaddle-backed shellHoodFloreana

Santa Fe

Santa Cruz

James

Marchena

Fernandina

Isabela

Tower

Giant Tortoises of the Galápagos IslandsSection 15-1

Hutton and Lyell

• Proposed that the earth rocks moved up beneath the earth.

• This process is extremely slow.• The conclusion was that earth is extremely old.• Lyell said that the only way to explain what

occurred in the past is to use processes that occur today.

Sea level

Sedimentary rocks form in horizontal layers.

When part of Earth’s crust is compressed, a bend in a rock forms, tilting the rock layers.

As the surface erodes due to water, wind, waves, or glaciers, the older rock surface is exposed.

New sediment is then deposited above the exposed older rock surface.

Movement of Earth’s Crust

Section 15-2

Sea level

Lamarck

• Recognize living things change.

• Proposed his own evolutionary hypothesis.

• 1. Tendency towards perfect.

• 2. Use and disuse.

• 3. Inheritance of acquired traits.

Figure 15–7 Lamarck’s Theory of EvolutionSection 15-2

Origin of Species

• Was published 25 years after his famous voyage.

• He was prompted by Alfred Wallace’s work.

Darwin’s Conclusions

• Artificial selection helped spur the creation of new species.

• Example: breeding of fast horses.

Darwin’s Conclusions

• Natural selection had no human involvement.

• All life goes through a struggle to exist.

• The genes that allowed an organism to survive would be passed to another generation.

• Over time a new species would develop.

Evidence of Evolution #1

• Fossil Record

• Showed through the process of time the animals that existed on the planet.

• By comparing fossils and rock layers one can find the relationships in changing life.

Evidence: Fossils

Evidence of Evolution #2

• BIOGEOGRAPHY: Geographic Distribution• Different continents had different species of

animals.• The reason is because each species descended from

different animals.• However if the species had the same conditions on

two different continents they evolved the same.

Beaver

NORTH AMERICA

Muskrat

Capybara SOUTH AMERICA

Coypu

Geographic Distribution

Beaver

Muskrat

Beaver andMuskrat

Coypu

Capybara

Coypu andCapybara

Evidence of Evolution #3

• COMPARATIVE ANATOMY

• Homologous structures

• Structures in different species that share similar structure, function, or both.

• These show that the species have a common ancestor.

Turtle Alligator Bird Mammal

Ancient lobe-finned fish

Homologous Body Structures

Homologous Structures

• Vestigial structures- A structure that has no function in a present-day organism but was probably useful to an ancestor.

• Natural selection does not get rid of the organ.

Evidence of Evolution #4

• EMBRYOLOGY

• Embryo- the earliest stage of growth of an organism.

Fish chicken rabbit human

Embryology

Evidence of Evolution #5

• MOLECULAR BIOLOGY

• DNA and proteins are shared in common between related individuals.

• Species that are closely related will have higher amounts of their DNA and proteins in common. Ex – Humans and chimps share 99% of their DNA!

A summary of Darwin’s Theory

• 1. Individual organisms are different and some of these difference can be inherited.

• 2. Organisms produce more offspring than can survive in an environment. The organisms that do not survive do not reproduce.

A summary of Darwin’s Theory• 3 Because more organisms are produced than

survive, they compete for resources.• 4. Organisms has different advantages and

disadvantages in their struggle for existence. The organisms that are best suited to their environment survive and reproduce a lot more.

• 5. Species alive today are descended with modifications from ancestral species that lived in the past.