Evolution

Breaking Down the Definitions Honors1. Evolution2. Natural selection3. Adaptation4. Fitness5. Convergent evolution6. Divergent evolution7. Adaptive radiation8. Artificial selection9. Coevolution

10. Population genetics11. Microevolution12. Bell curve13. Gene pool14. Allele frequency15. Phenotype frequency16. Hardy-Weinberg

Genetic Equilibrium17. Gene flow18. Genetic drift

19. Sexual selection20. Stabilizing selection21. Disruptive selection22. Directional selection23. Speciation24. Geographic isolation25. Allopatric speciation26. Reproductive isolation27. Sympatric speciation

Breaking Down the Definitions Regular1. Evolution 2. Natural variation3. Artificial selection4. Fitness5. Adaptation6. Natural selection7. Gene pool8. Directional selection9. Stabilizing selection

10. Disruptive selection11. Genetic drift12. Hardy-Weinberg Principle13. Genetic equilibrium14. Speciation15. Reproductive isolation16. Behavioral isolation17. Geographic isolation18. Temporal isolation

History of Evolution

• Originally most scientists believed species were permanent and unchanging• With the discovery of fossils of unique organisms, CATASTOPHISM,

was a theory that sudden geologic changes caused extinction of large groups of organisms.• Jean Baptiste Lamarck came up with an early idea of evolution, that

individuals could acquire traits during their lifetimes and pass those traits on to offspring

Charles Darwin

•Darwin spent years traveling the globe and making detailed observations to develop the theory of NATURAL SELECTION.•Brainpop! Charles Darwin•Darwin’s Finches Activity

Fill in the missing boxes. Food Choices: Fruit, Cactus, Seeds, Insects

Natural Selection

•Natural Selection= the mechanism (the ‘how’) for descent with modification. Basically, organisms best suited for an environment will survive to pass on their traits to their offspring. Organisms lacking traits to make them successful will die and therefore not be able to pass on the unsuccessful traits.

4 Parts of Natural Selection

Overproduction Genetic Variation

Struggle to Survive

Differential Reproduction

Overproduction

•Species produce more individuals than will survive to maturity•The environment will limit the number of individuals that reach adulthood

Genetic Variation

•Individuals of a population differ in traits such as size, color, strength, speed, ability to find food, resistance to disease

Struggle to Survive

• Individuals within a population must compete with each other for limited resources (food, shelter, etc).•A trait that makes an individual successful in its environment (thick fur in cold climates) is called an ADAPTATION.•Giraffe Video Clip

Differential Reproduction

•Organisms with the best adaptations are the most likely to survive and therefore pass on those successful adaptations to offspring• Through inheritance the adaptations will become

more frequent in the population• The environment, ‘selects’, the most favorable traits =

NATURAL SELECTION•Natural Selection Crash Course

Survival of the Fittest

•Fitness is a measure of an individual’s hereditary contribution to the next generation. •A ‘fit’ individual is one that has offspring that live long enough to also reproduce.•Lion Fitness Activity

Modeling Natural Selection

• Bird Beak Lab with write up• Battle of the Bird Beaks!

Types of Evolution

•CONVERGENT EVOLUTION: The process by which different species evolve similar traits. •The anole lizard evolved on 2 separate islands from 2 distinct ancestors, but since each species had similar habitats they both evolved with similar twig-dwelling traits, but remain 2 separate species.

Types of Evolution

•DIVERGENT EVOLUTION: process in which descnedants of a single ancestor diversify into separate species that fit different environments•ADAPTIVE EVOLUTION: a new population will evolve traits to fit its new environment

Honors Homework!

•Quick Lab on p.309• Find at least 2 organisms (at least one of which must

by wild) and make observations (written AND drawn) of the organism• For each organism also explain why you think they

have developed certain traits or adaptations.

Population Genetics

• The study of evolution from a genetic point of view• Variation of traits within a population can be shown on a bell curve,

with most organisms falling in the middle range

Causes of Genetic Variation

•Environmental factors•Heredity•Mutation•Recombination

The Gene Pool

• The GENE POOL = the total genetic information available in a population (all of the possible alleles)•ALLELE FREQUENCY= the specific allele (A or a)

divided by the total number of alleles in the population•PHENOTYPE FREQUENCY= the specific phenotype

(Red or Pink) divided by the total number of organisms• Flower Color Activity

Hardy-Weinberg Genetic Equilibrium

•Genotype frequencies in a population tend to remain the same from generation to generation unless acted upon by an outside influence.• Ideal population in Hardy-Weinberg Equilibrium:

1. No mutations occur2. No individuals enter or leave the population3. The population is large4. Individuals mate randomly5. Natural Selection does not occur

Disruption of Genetic Equilibrium•Mutation• Gene Flow—immigration and emigration• Genetic Drift—allele frequencies change as a result of

random events, leading to a particular allele (A or a) disappearing completely and thereby reducing genetic variation. GENETIC DRIFT is only significant in small populations• Nonrandom Mating—Sexual selection • Natural Selection—stabilizing, disruptive, directional

selection

Population Genetics Crash Course

• Hardy-Weinberg Practice!

Formation of Species

•SPECIATION is the process of the formation of a new species.•A species is a group of organisms that can successfully interbreed (and the offspring can also reproduce) and have similar morphological (internal and external structures) features.

Isolation and Speciation

•Geographic (allopatric) Isolation- populations become physically separated (canyon, river,mountains) and gene flow between the 2 groups stops. Natural selection and genetic drift then make the 2 groups incompatible for mating and the 2 groups evolve separately.

Isolation and Speciation

•Reproductive (sympatric) Isolation– barriers to successful breeding between 2 populations. Examples: different mating times, different mating calls

Speciation Video Clips

• Geographic Separation

• Speciation Crash Course

Review