Evolution = change over time

Evolution

• Individuals do NOT evolve! Populations evolve.

• Evolution occurs at conception, when new combinations of DNA are made.– The only role you have left in evolution will be

when you have children!

Jean-Baptiste Lamarck (1744-1829)

3 ideas of Lamarck:

1. Organisms desired to change and better themselves.

2. The law of use and disuse.3. The inheritance of acquired traits.

Darwin and Wallace: Similar ideas, different places & times

• Both founders of the theory of evolution

Alfred Russell Wallace• Was also voyaging and observing

similar things that Darwin was seeing.

• He sent an essay to Darwin, and Darwin published their ideas in a paper on the theory of evolution.

Darwin’s Ideas

• Darwin proposed evolution occurred through the process of Natural Selection.

• “Survival of the Fittest” means the organism that has traits that are more suitable to the environment will survive and reproduce.

• The principles of Natural Selection are:

• 1. Organisms have more offspring than is needed to replace themselves.

• 2. There is a variation of traits amongst the offspring.

• 3. Some of these traits are better suited to the environment than others.

• 4. The offspring that possess these favorable traits will survive and reproduce.

• 5. These favorable traits will be passed on to future generations.

Adaptations• A favorable trait that makes an organism more

likely or “fit” to survive.– **Traits are controlled by genes.

Adaptations1. Mimicry – An individual gains an advantage by

looking like the individuals of a different species."Red touch yellow, kills a fellow. Red touch black,

venom they lack.“ Scarlet king snake and coral

snake.

Evidence for Evolution

1. Fossil record 2. Anatomical3. Embryological 4. DNA5. Artificial Selection

Evidence for Evolution

• Fossil record: Fossils show change over time.

Anatomical Evidence• Homologous

structures: – A common limb

that has evolved to perform a different function.

– Ex: Bird wing, human arm, elephant leg all have the same bones

Analogous structure: • Different structures

that perform the same function

• Ex: Bird wing, grasshopper wing

• Vestigial structures: A structure that is reduced in function. (snake hips)

• Embryological evidence: Comparing the embryos of different species can give clues to evolutionary relationships.

• DNA Evidence: Comparing DNA of organisms can show hidden relationships. (scrub jays)

Mechanisms of Evolution:• Evolution occurs when the genes in a

population change.*Populations evolve, individuals don’t!

• Basic mechanisms of evolutionary change.1. Natural Selection2. Mutations3. Genetic Drift4. Migration

Mechanisms of Evolution:

1. Mutations: Changes in DNA sequences that result from environmental factors (ex: radiation or chemicals) or just by chance.

Mechanisms of Evolution2. Genetic Drift: A random change in allele

frequencies that cause changes in populations.– By chance, some individuals leave behind more offspring than others.

The genes of the next generation are the genes of the "lucky" ones, not necessarily the healthier or "better" individuals.

Mechanisms of Evolution3. Migration or Gene Flow: When new

individuals enter or leave a population. As a result the allele frequencies change.

Speciation: a new species is created.

• Species- A group of organisms that breed with one another and produce fertile offspring.

How do new species form?1. Geographic isolation: occurs when a natural physical

barrier separates a population and they evolve separate from each other.– Ex: Body of water, landslides, mountains, deserts

How do new species form?

2. Reproductive Isolation occurs when formerly interbreeding population can no longer breed and produce fertile offspring.– Geographic isolation can lead to reproductive

isolation.

1. Mechanical- Failure due to physical interference

2. Behavioral- Sexual selection differences

3. Biological- Failure to create fertile offspring

4. Time- Two or more species reproduce at different times

Patterns of Evolution

• Divergent Evolution: When animals evolve away from their common ancestors to become more successful in their niches. – Ex. Galapagos Finches, and Hawaiian

Honeycreepers

• Convergent Evolution: When two or more distantly related organisms evolve similar characteristics because they occupy the same niches.

Convergent Evolution

• The “Fish” body form has evolved several times in very different organisms.

Convergent Evolution

• Placental vs. Marsupial mammals. In Australia, marsupials evolved in isolation. Their body forms match their placental counterparts.