Evolution two-

EvolutionEvolution

Day 2Day 2

Lamarck is SillyLamarck is Silly

Key TermsKey Terms

EvolutionEvolution: Changes in a population of : Changes in a population of organisms over long periods of time.organisms over long periods of time.

Natural SelectionNatural Selection: process by which : process by which individuals that are better suited to their individuals that are better suited to their environment survive and reproduce environment survive and reproduce successfullysuccessfully “AKA, Survival of the Fittest” “AKA, Survival of the Fittest”

Remember: Individuals do not evolve, populations do.

Summary of Darwin’s Theory: Summary of Darwin’s Theory: EvolutionEvolution

Observation 1Observation 1: Left unchecked, the : Left unchecked, the number of organisms of each species will number of organisms of each species will increase exponentiallyincrease exponentially, from generation to , from generation to generation. generation.

Example: Exponential KittenExample: Exponential Kitten

Example: Exponential KittenExample: Exponential Kitten

Every day, this kitten will reproduce by Every day, this kitten will reproduce by splitting. The total number of kittens will splitting. The total number of kittens will double each day.double each day.

Day One, One KittenDay One, One Kitten

Example: Exponential KittenExample: Exponential Kitten

Day Two, Two Kittens.Day Two, Two Kittens.

Example: Exponential KittenExample: Exponential Kitten

Day Three, Four KittensDay Three, Four Kittens

Example: Exponential KittenExample: Exponential Kitten

Day Four, Eight Kittens.Day Four, Eight Kittens.

Example: Exponential KittenExample: Exponential Kitten

Day Five, Sixteen Kittens.Day Five, Sixteen Kittens.

Example: Exponential KittenExample: Exponential Kitten

Day Six, Thirty-Two Kittens.Day Six, Thirty-Two Kittens.

Example: Exponential KittenExample: Exponential Kitten

Day Seven, Sixty-Four Kittens. Day Seven, Sixty-Four Kittens.

Example: Exponential KittenExample: Exponential Kitten

Day Seven, 128 kittensDay Seven, 128 kittens

Summary of Darwin’s Theory: Summary of Darwin’s Theory: EvolutionEvolution

Observation 2Observation 2: In nature, populations : In nature, populations tend to tend to remain stable in sizeremain stable in size. .

Observation 3Observation 3: Environmental resources : Environmental resources are limited.are limited.

Summary of Darwin’s Theory: Summary of Darwin’s Theory: EvolutionEvolution

Inference 1: Inference 1: Production of more Production of more individuals than can be supported by the individuals than can be supported by the environment leads to a environment leads to a struggle for struggle for existenceexistence among individuals, with only a among individuals, with only a fraction of offspring surviving in each fraction of offspring surviving in each generation.generation.

Examples: Plants competing for sunlight, Examples: Plants competing for sunlight, Ants competing for space and food.Ants competing for space and food.

Examples: CompetitionExamples: Competition

Ant Fight.

Plant Fight.

Summary of Darwin’s Theory: Summary of Darwin’s Theory: EvolutionEvolution

Observation 4: Observation 4: Individuals of a population Individuals of a population vary extensively in their characteristics vary extensively in their characteristics with no two individuals being exactly alike.with no two individuals being exactly alike.

Observation 5Observation 5: Much of this variation : Much of this variation between individuals between individuals is heritableis heritable..

Variation and HeritabilityVariation and Heritability

-Differences between individual organisms -Differences between individual organisms exist exist due to differences in genetics.due to differences in genetics.

-These genetic differences arise from -These genetic differences arise from genetic mutations.genetic mutations.

Variation and HeritabilityVariation and Heritability

Mutations are not all good. Many of them Mutations are not all good. Many of them do nothing at all, while others are do nothing at all, while others are absolutely harmful. absolutely harmful. Mutations occur Mutations occur randomly and have random effects.randomly and have random effects.

When a mutant breeds, these genetic When a mutant breeds, these genetic mutations mutations are inherited by the offspringare inherited by the offspring. .

Examples: Extra Fingers, Sickle Cell Examples: Extra Fingers, Sickle Cell AnemiaAnemia

Examples: MutationsExamples: MutationsExtra Fingers

(Polydactyl)

Sickle Cell Anemia

Summary of Darwin’s Theory: Summary of Darwin’s Theory: EvolutionEvolution

Inference 2: Survival in the struggle for Inference 2: Survival in the struggle for existence is not random, but depends existence is not random, but depends in part on the heritable characteristics in part on the heritable characteristics of individuals. Individuals who inherit of individuals. Individuals who inherit characteristics most fit for their characteristics most fit for their environment are likely to environment are likely to leave more leave more offspring than less fit individualsoffspring than less fit individuals..

Summary of Darwin’s Theory: Summary of Darwin’s Theory: EvolutionEvolution

Inference 3: The unequal ability of Inference 3: The unequal ability of individuals to survive and reproduce individuals to survive and reproduce leads to a gradual change in a leads to a gradual change in a population, with favorable population, with favorable characteristics characteristics accumulating over accumulating over generationsgenerations (natural selection). (natural selection).

Darwin’s Theory: The Short VersionDarwin’s Theory: The Short Version

1. Organisms differ; variation is inherited1. Organisms differ; variation is inherited

2. Organisms produce more offspring than 2. Organisms produce more offspring than survivesurvive

3. Organisms compete for resources3. Organisms compete for resources

4. Organisms with advantages survive to pass 4. Organisms with advantages survive to pass those advantages to their childrenthose advantages to their children

5. Species alive today are descended with 5. Species alive today are descended with modifications from common ancestorsmodifications from common ancestors

Example: Colored MothsExample: Colored Moths

The traits that The traits that help an organism help an organism survive in a survive in a particular particular environment are environment are “selected” in “selected” in natural selectionnatural selection

Key Terms for EvolutionKey Terms for Evolution

Adaptation: An inherited characteristic that increases an organism’s ability to survive and reproduce in its specific environment.

Fitness: The ability to survive and reproduce in a specific environment. Adaptations make an organism more fit.

Key Terms for EvolutionKey Terms for Evolution

Descent with Modification: Over long periods, natural selection produces organisms that continually adapt to their environment, eventually becoming separate species.

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

Artificial Selection: Nature provides the variation and human select those variances they find useful.

• Example: a farmer breeds only his best livestock.

Evidence for EvolutionEvidence for Evolution• 1. The Fossil Record: These imprints

allow scientists to see an entire evolutionary history, including “in between” fossils.

• 2. Homologous Body Structures: Why else use the same skeletal plan for very different appendages?

• 3. Similarities in Embroyology: During the very early stages of life (in the womb), many organisms go through similar stages of development.

FossilFossil

Homologous StructuresHomologous Structures

EmbryologyEmbryology