Chapter 16: Darwin’s Theory of Evolution Darwin’s Voyage of Discovery

Darwin’s Journey Charles Darwin – British scientist and naturalist – 5 year journey around the world on the HMS Beagle – Hit Australia, Africa, and South America – Collected plants and animals – This journey was the foundation for his theory of evolution

Observations aboard the Beagle 1. Species vary globally – Ex: Emus, Rheas, and Ostriches – Flightless birds found on 3 continents – Similar habitats but different animals 2. Species vary locally – Ex: Tortoises of the Galapagos Islands – Different animals in the same environment 3. Species vary over time – Ex: Fossils of organisms – Some looked similar to animals today; others didn’t

Chapter 16: Darwin’s Theory of Evolution Ideas that shaped Darwin’s Thinking

Role of Geology People believed Earth was not old and not changing Geology was emerging and showing something else James Hutton ( ) – Geological processes shape the land – Forces push mountains up – Deep time: Earth’s history so long we can’t imagine it Charles Lyell ( ) – Principles of Geology Laws of nature don’t change over time Changes in landscape take millions of years

Lamarck’s Evolutionary Hypothesis Jean Baptiste Lamarck ( ) – Created the first theory of evolution All organisms born with desire to become better Organisms could change bodies to adapt to environment Acquired characteristics: Traits that change during organism’s life Acquired traits can be passed onto offspring – Although most ideas were wrong, he was on the right track – Made the connection between an organism’s body and its environment

Role of Economics Thomas Malthus ( ) – English economist – Ideas designed for human population but can be used for all organisms People born quicker than people dying This leads to overcrowding Overcrowding lead to conditions that slow growth Important that only a few survive but which ones

Artificial Selection People chose best traits within organisms and breed them Object is to create bigger and better products Variation can occur in the wild as well as domestic Ex:

Chapter 16: Darwin’s Theory of Evolution Darwin Presents his Case

Evolution by Natural Selection 1. Struggle for Existence – Members of population compete for food, water, and living space – Those that don’t get enough won’t survive 2. Variation and Adaptation – Variation Heritable traits: traits passed onto offspring Heritable traits make survival easier – Adaptation Any heritable trait that allows an organism to survive in the environment

Evolution by Natural Selection 3. Survival of the Fittest – Differences in adaptations affect fitness – Fitness: How well an organism and survive and reproduce in its environment – Individuals with these adaptations will survive more than those without the adaptations

Evolution by Natural Selection 4. Natural Selection – Organisms with the best traits to match their environment will survive – 3 conditions needed for it to exist 1. More individuals being born than dying 2. Heritable traits in the population (variation) 3. Some individuals have traits that all them a better chance to survive – If environment changes, the population will change

Common Descent Every organism today descended from parents who survived and reproduced Descent with modification – Older species evolve into new species – Deep time allows Darwin to validate natural selection – Fossil Record is evidence of descent with modification Common Descent – All organisms share an ancient common ancestor

Chapter 16: Darwin’s Theory of Evolution Evidence of Evolution

Biogeography – Study of where organisms live and where ancestors lived – 2 patterns arose: 1. Closely related organisms that lived in different environments showed many differences – Each environment is different and forces organisms to adapt differently 2. Distantly related organisms that live in similar environments are often similar – Organisms will have similar adaptions if they are in similar environments

Evidence of Evolution Body Structures – Homologous Structures Similar structures found in different organisms allow us to say they have been inherited from a common ancestor

Evidence of Evolution Analogous Structures Show us that organisms that have structures with similar functions but different structures are not as closely related as thought to be Ex: different wings in flying animals

Evidence of Evolution Vestigial Structures Structure in an organism that was once useful to a previous ancestor but no longer has a function in organism Ex: Hip bone in whales and dolphins

Evidence to Evolution Embryology – At an embryonic stage, all organisms look and develop in the same way