Darwin & Natural Darwin & Natural SelectionSelection

Darwin & Natural Darwin & Natural SelectionSelectionUnit 6: Evolution

Chapter 15

Unit 6: Evolution

Chapter 15

Learning GoalsLearning 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.

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 EvolutionTheory 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

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 DarwinCharles 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

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 FinchesDarwin’s Finches

Natural SelectionNatural SelectionNatural SelectionNatural Selection

Natural Selection: Organisms that are best adapted to an environment survive and reproduce more than others

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 steps: Overproduction Variation Competition Selection

Darwin’s Theory of Natural Selection occurs in four steps: Overproduction Variation Competition Selection

1. Overproduction1. Overproduction1. Overproduction1. Overproduction

Each species produces more offspring that can survive

Each species produces more offspring that can survive

2. Variation2. Variation2. Variation2. Variation

Each individual has a unique combination of inherited traits. Adaptation:Adaptation: an inherited

trait that increases an organism’s chances of survival

Each individual has a unique combination of inherited traits. Adaptation:Adaptation: an inherited

trait that increases an organism’s chances of survival

What adaptations do you see?

What adaptations do you see?

Why is Variation Important?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

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?

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. Competition3. Competition3. Competition3. Competition

Individuals COMPETE for limited resources: Food, water, space, mates

Natural selection occurs through “Survival of the fittestSurvival of the fittest” FitnessFitness: the ability to survive and

reproduce

Not all individuals survive to adulthood

Individuals COMPETE for limited resources: Food, water, space, mates

Natural selection occurs through “Survival of the fittestSurvival of the fittest” FitnessFitness: the ability to survive and

reproduce

Not all individuals survive to adulthood

4. Selection4. Selection4. Selection4. Selection 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. Natural selection acts on the phenotype

(physical appearance), not the genotype (genetic makeup)

Ex: When a predator finds its prey, it is due to the prey’s physical characteristics, like color or slow speed, not the alleles (BB, Bb)

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. Natural selection acts on the phenotype

(physical appearance), not the genotype (genetic makeup)

Ex: When a predator finds its prey, it is due to the prey’s physical characteristics, like color or slow speed, not the alleles (BB, Bb)

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.

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.

Peppered MothPeppered Moth

Which moth will the bird catch? Which moth will the bird catch?

A

B

Descent with Descent with ModificationModificationDescent with Descent with ModificationModification Descent with Modification Descent with Modification – each

living species has descended, with changes, from other species over time.

Common Descent Common Descent – all living organisms are related to one another

Descent with Modification Descent with Modification – each living species has descended, with changes, from other species over time.

Common Descent Common Descent – all living organisms are related to one another

Evidence for Evolution:Evidence for Evolution:

Fossil Record Homologous Body Structures Vestigial Organs Embryology Biochemical Evidence

Fossil Record Homologous Body Structures Vestigial Organs Embryology Biochemical Evidence

The Fossil RecordThe Fossil RecordThe Fossil RecordThe Fossil Record

FossilsFossils: a record of the history of life on Earth

FossilsFossils: a record of the history of life on Earth

Archaeopteryx Archaeopteryx

Missing link between reptiles and birds

Missing link between reptiles and birds

Homologous Body Homologous Body StructuresStructuresHomologous Body Homologous Body StructuresStructures Homologous Homologous

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

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

Vestigial OrgansVestigial OrgansVestigial OrgansVestigial Organs

Vestigial Organs: “leftover” traces of evolution that serve no purpose

Vestigial Organs: “leftover” traces of evolution that serve no purpose

EmbryologyEmbryologyEmbryologyEmbryology

EmbryologyEmbryology: embryos of all vertebrates are very similar early on

EmbryologyEmbryology: embryos of all vertebrates are very similar early on

Biochemical EvidenceBiochemical EvidenceBiochemical 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

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 GoalsLearning 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.

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