BellringerEvolution -What is it? -Is it a Fact? -Do you agree with it? Why or Why Not?

-Is there evidence? - What is natural selection?

Camouflage- makes it possible for animals to live in their natural habitat. Increases their survival.

Evolution: Darwin vs. LamarckEvolution: change over time; modern organisms descend from ancient organisms

Theory: Well-supported, testable explanation of phenomena

Don’t copy

Voyage of Beagle: Charles Darwin observed and collected fossils; proposed evolutionary hypothesis about way life changes

Patterns of Diversity: plants/animals well-Suited to environment; variety of ways to reproduce

Evolution: Darwin and LamarckDon’t copy

Galapagos Islands: islands west of South America; all have different climates

Darwin’s Thoughts:He noticed that individual birds collected from one island looked different from birds collected from other

islandsHe wondered if animals living on different islands had once been members of the same species—

meaning that separate species would have evolved from an original South American ancestor species after becoming isolated from one another.

Evolution: Darwin

Evolution: LamarckJean Baptiste Lamarck: French naturalist noticed living things changed over time—all species desended from other species

Lamarck’s Theory: selective use/disuse of organs organisms acquired or lost traits during lifetime….traits passed to offspring…change over time (tendancy toward perfection)

Evolution: LamarckAnimals continually change and acquire features that help them live more successfully in the environments (Bird’s Wings-inc. sizefly)

Alter size or shape of particular organs by using bodies in new way (no use of wingsdec. size, lose)

Ex. Weightlifting all lifetime, children big muscles too. Study hardchildren geniuses

Evaluating Lamarck’s & Darwin’s theory: No knowledge of how traits inherited—organism’s behavior has no effect on inheritable characteristics

Don’t Copy Evolution: DarwinDarwin’s Theory:

Natural Variation: Differences among individuals of a species

Ex. Aquilegia flowers

Artificial Selection: Nature provides variation among different organisms, humans select

Ex. Largest hogs, fastest horses

*Natural Selection favors traits that benefit organism in environment Environment does “selective breeding”

Don’t Copy Evolution: Darwin

Fitness: ability to survive & reproduce in environment

Adaptation: inherited characteristics that increases organisms chance for survival

Survival of the Fittest (natural selection): Individuals better suited to environment, with high level of fitness, survive and reproduce successfully

Evolution: Darwin vs. Lamarck

Don’t Copy Natural Selection: struggle for existence. Species compete for food, living space…etc. (mutations & genetic recombination lead to this)

Don’t copy

*Over time, natural selection results in changes in the inherited characteristics of a population.

These changes increase a species fitness in its environment.

Natural Selection

Evolution of PopulationsChapter 16

Genes and VariationDarwin and Mendel were

unaware of each others work.

Neither could fully develop their theories

In the 1930’s scientists connected their ideas in one unifying theory

Variation and Gene PoolsGenetics variation is studied in

populationsPopulation: a group of the same

species that can interbreed.A population shares a common

group of alleles called a gene pool a gene pool is all of the

different genes that exist in a population

Sample Population48 % heterozygous black16% homozygous black36% homozygous brown

Variation and Gene Pool, cont.The relative frequency of an

allele is the number of times that a gene occurs in a gene pool.

this is expressed as a percentage

(40% black, 60% brown)Evolution is any change in the

relative frequency in alleles in a population

So evolution would be in action if the relative frequency changed from 40% black to 30%

Sources of VariationMutations: changes in the DNA sequence caused by error in replication, radiation,

chemicals in the environmentOnly some mutations change the phenotype and

affect fitnessGene Shuffling: results from sexual reproduction 23 pairs of chromosomes can produce 8.4

million different gene combinationsCrossing over causes differences in genes.Gene shuffling does not change the relative

frequency of alleles in a population- you will still have the same number of alleles in the population, they are just recombined differently.

Single Gene vs. polygenic traits (pg 395-396)

The number of phenotypes produced for a single trait depends on how many genes control the trait.

Single Gene Trait (395): controlled by a single gene (2 alleles)

expressed in a bar graphPolygenetic Trait (396): traits controlled by

two or more genes – offers a great deal of variation

expressed in a bell shaped curve

Natural Selection on a Single Gene TraitNatural Selection can act on a single gene

trait that can change the allele frequency in a population and lead to evolution

Ex: lizards pg 397

Natural Selection on Polygenic TraitsNatural selection can affect the distribution

of phenotypes in 3 ways1.Stabilizing Selection2.Disruptive Selection3.Directional Selection

Stabilizing Selection

Individuals at the center have the greatest fitness

Pg 399

Disruptive SelectionBoth ends have greater fitness than the

middle.Page 399

Directional SelectionIndividuals at one end have greater fitness

than the middle or other endPage 398

Genetic Drift Page 400Genetic Drift: the random change in allele frequency. Occurs in small populations that break away

from a larger groupCaused by individuals entering and exiting the

populations this adjusts the allele frequencies in the gene

pool and results in a change from the original group’s gene pool.

Ex: Founder Effect when the allele frequency changes as a result of

the migration of a small group

Evolution vs. Genetic EquilibriumHardy –Weinberg principle States that the allele frequency will stay

in genetic equilibrium (no evolution is occurring) if certain conditions are met

1.Random Mating2.Large population ( so no genetic drift)3.No movement in and out of the population4.No mutation5.No Natural Selection

SpeciationSpeciation: The formation of a new species Species: a group of organisms that

breed together and produce fertile offspring.Reproductive Isolation: As new species

evolve, populations become reproductively isolated from each other.

Reproductive isolation

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