Unit 5 : Evolution

Chapter 15 - Darwin’s Theory of Evolution

Charles Darwin

• English

• Born 1809

• HMS Beagle - 1831

• Naturalist

• Very Religious

Darwin’s Observations

• Animals and plants were well adapted

• Diverse reproductive strategies

• Puzzled by location of animals– Rabbits in Argentina, not in Australia

• Fossils– similar, dissimilar, Extinction

The Beagle’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 Islands

Section 15-1

The Galapagos Islands

DesertLarge rainfall

Intermediate Shell

Domed Shell

Saddle backed Shell

Climate variation throughout

Tortoises of the Galapagos

Saddleback• long neck, curved

shell, found on Hood Island, desert like

Dome Shaped• shorter neck, domed

shell, lush vegetation, covers the ground, Isabela island

Many different varieties in different locations

Finches

Journey Home

• Animals and plants varied a great deal from island to island

• Did the organisms on different islands belong to the same species?

• Was the ancestor from S. America?

Influences on Darwin

• Fossil Record

James Hutton - 1785

• Earth - millions of years old, not 5700

Charles Lyell - 1833• Past events are explained by the processes

that scientists can see today.

Jean-Baptiste Lamarck - 1809

• Proposes 1st theory of evolution– use vs. disuse– acquired traits are passed on– leads to changes in species

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

Thomas Malthus - 1798

• Economist - unchecked population growth leads to a lack of space and food

Frog Eggs - What detemines survival?

Artificial Selection

• Farmers and breeders– Selective Breeding

Darwin’s View - On the Origin of the Species - 1859

Darwin: Reluctant Rebel

Natural Variation passed on to future generations

Struggle for Existence

                                                                                                                                                                                                                                                                                                 

                                                                                                                                                                                             

Fitness

• Ability to survive and reproduce successfully

Adaptations - physical characteristics or behaviors

Camouflage

Survival of the Fittest - (Natural Selection)

• Individuals that are best suited for their environment have high levels of fitness and therefore survive and reproduce

Descent with Modification

• Species change overtime

• All organisms share a common ancestor (common descent)

Darwin’s Evidence of Evolution

• Fossil Record

• Distribution of Living Species

• Homologous Body Structures

• Embryo Development

Fossil Record

• Evidence of change over time

• Age of the Earth

Distribution of Living Species - I

Unrelated organisms look similar because of common ecological conditions - Convergent Evolution

Beaver

NORTH AMERICA

Muskrat

Capybara SOUTH AMERICA

Coypu

Figure 15–14 Geographic Distribution of Living Species

Beaver

Muskrat

Beaver andMuskrat

Coypu

Capybara

Coypu andCapybara

Distribution of Living Species - II

Finches - all share a common mainland ancestor, differences are due to the environment

Homologous Structures - same basic design, modifications

Vestigial Organs - traces of homologous structures

Embryo Development

Embryonic Cells develop in the same group and similar patterns

Reviewing Darwin’s Theory• Variation

• Large amounts of offspring

• Competition

• Struggle for Existence

• Survival of the Fittest

• Descent with Modification via Natural Selection

• Common Descent

How does evolution really work?