Darwin & Natural Darwin & Natural SelectionSelection

Learning Goals 1. Define "Evolution" & "Natural Selection". 2. Describe the 4 steps of Natural Selection,

giving an example of each. 3. Explain the importance of "Variation". 4. Does Natural Selection act on an

organism phenotype or genotoype? Explain! 5. List the 5 evidences that support the

Theory of Evolution.

Theory of EvolutionTheory of Evolution Evolution: The process of change

over time Specifically, a change in the frequency

of a gene or allele in a population over time

Charles DarwinCharles Darwin Father of Evolution Proposed a mechanism for

evolution, natural selectionnatural selection Darwin went on a 5-year trip

around the world on the ship, the HMS Beagle As the ship’s naturalist, he

made observations of organisms in South America and the Galapagos Islands

•Wrote a book, “Wrote a book, “Origin of the SpeciesOrigin of the Species””

Darwin’s Finches

Natural SelectionNatural Selection Natural Selection: Organisms that are

best adapted to an environment survive and reproduce more than others

Darwin’s Theory of Natural Selection occurs in four parts: Overproduction Variation Selection Adaptation

1. Overproduction1. Overproduction Each species produces more

offspring than can survive

2. Variation2. Variation Each individual has a

unique combination of inherited traits.

These natural differences are called variations

Why is Variation Important? Because the environment changes. The more variation variation withinwithin a species a species, the

more likely it will survivesurvive EX: If everyone is the same, they are all

vulnerable to the same environmental changes or diseases

The more variation of variation of types of types of speciesspecies in an habitat, the more likely at least some some will survivewill survive EX: Dinosaurs replaced by mammals

Which community has a better Which community has a better chance of surviving a natural chance of surviving a natural disaster?disaster?

Community ACommunity A Community BCommunity B

3. Selection3. Selection Individuals COMPETE for limited resources:

Food, water, space, mates Natural selection occurs through “Survival Survival

of the fittestof the fittest” FitnessFitness: the ability to survive and reproduce-the

advantageous trait will be passed to the next generations

Not all individuals survive to adulthood

4. Adaptation4. Adaptation

The individuals with the best traits / best traits / adaptations will survive and have the adaptations will survive and have the opportunity to pass on it’s traitsopportunity to pass on it’s traits to offspring.

Adaptation:Adaptation: an inherited trait that increases an organism’s chances of survival

Individuals with traits that are not well suited to their environment either die or leave few offspring.

Evolution occurs when good traits good traits build up in a populationbuild up in a population over many generations and bad traits are bad traits are eliminated by the death of the eliminated by the death of the individualsindividuals.

What adaptations do you see?

What adaptations do you see?

Peppered Moth Which moth will the bird catch?

A

B

Evidence for Evolution: Fossil Record Homologous Body Structures Vestigial Organs Embryology Biochemical Evidence

The Fossil RecordThe Fossil Record FossilsFossils: a record of the history of life

on Earth

Archaeopteryx Missing link between

reptiles and birds

Homologous Homologous (Common) (Common) Body Body StructuresStructures Homologous Homologous

Body StructuresBody Structures: similar anatomy in different types of animals because of common ancestor

Vestigial OrgansVestigial Organs Vestigial Organs: “leftover” traces of

evolution that serve no purpose

EmbryologyEmbryology EmbryologyEmbryology: embryos of all

vertebrates are very similar early on

Biochemical EvidenceBiochemical Evidence BiochemistryBiochemistry: DNA with more similar

sequences suggest species are more closely related EX: Humans and chimpanzees share

more than 98% of identical DNA sequences

Learning Goals 1. Define "Evolution" & "Natural Selection". 2. Describe the 4 steps of Natural Selection,

giving an example of each. 3. Explain the importance of "Variation". 4. Does Natural Selection act on an

organism phenotype or genotoype? Explain! 5. List the 5 evidences that support the

Theory of Evolution.

Coral Snake (Poisonous)

Milk Snake (Not poisonous)

Stick Mantid

Flower Mantid