Evolution

SC.912.L.15.1 Explain how the scientific theory of evolution is supported by the fossil record, comparative anatomy,

comparative embryology, biogeography, molecular biology, and observed evolutionary change

Darwin wasn’t the only one

• Lamarck – Changes in a phenotype

occur because of an environmental need

• Giraffe – Modifications were

passed onto the next generation

• Inheritence – “need” was dictated by

environmental change and that change involved movement towards perfection

Now we know

• No evidence that changes in environment can initiate changes in organisms that can be passed on to future generations – Change originates in the

process of gamete formation

• Environment does not create these variations it determines the survival of these variations

“Decent with Modification”

• Organic Evolution: “Decent with modification” - Charles Darwin – Species change gradually through adaptation.

• Chance

• FLASH CARD ALERT– ADAPTATION: A single individual has a random

mutation/trait that creates a change in phenotype, which increases the organism’s chance of successful reproduction.

– Leads to: NATURAL SELECTION

• FLASH CARD ALERT: NATURAL SELECTION: The adapted individual is able to survive and reproduce in the new environment better than others

Then: The adapted individual reproduces, creating more individuals with the same adaptations.

These adaptations become predominant in the population, thus altering the genetic makeup of the entire population… OR…

A new species arises that co-exists with the ancestor

THE STEPS OF EVOLUTION• 1. Random mutation. A single individual has a random

mutation/trait that is beneficial in its environment.

• 2. Natural selection: The adapted individual is able to survive and reproduce in the new environment better than others

• 3. Reproduction of adaptive trait: The adapted individual reproduces, creating more individuals with the same adaptations.

• 4. These adaptations become predominant in the population, thus altering the genetic makeup of the entire population… OR…

• 5. A new species arises that co-exists with the ancestor

Flightless Birds: Penguin

• Random Mutation: – Can be advantageous (adaptation) neutral, or

maladaptive

• Adaptation: characteristics that increase the potential of an organism to successfully reproduce in a specified environment

• Adaptations are characteristics that increase an individual's evolutionary fitness.

• FLASH CARD ALERT: – EVOLUTIONARY FITNESS: measure of

the capacity for successful reproduction in a given environment relative to others of that same species.

Example: The Hedgehog

How Natural Selection Works

• All organisms have a far greater reproductive potential than is ever realized– Starfish

• Struggle of survival: – Not enough resources to go around– Changes in the environment: climate change, food

shortages, environmental stressors.

• Inherited Variations exist– Genetic mutation & recombination

• These genetic changes MAY BE an advantage – Chance.

• Because individuals with maladaptive traits are less likely to reproduce the maladaptive traits become less frequent and are eventually eliminated