Learning Target: Evolution of Populations Ch. 11. 1 – 11. 2, pp Learning Target: Evolution of Populations Ch. 11.1 – 11.2, pp. 329 – 333, & Ch. 11.6, pp. 347 - 351 I Can…Describe how genetic variation within a population increases the chance that some individuals will survive and describe different mechanisms of evolution.

Genetic Variation Within Populations Ch. 11.1, pp. 328-329 Key Concept: Populations share a common gene pool Main Ideas: Genetic variation within a population increases the chance that some individuals will survive. Genetic variation comes from Mutation Recombination

Genetic Variation Within Populations Ch. 11.1, pp. 328-329 Gene pool Store of population’s genetic variation All alleles within population Allele frequency Measure of how common a certain allele is within the population Each autosomal gene has two alleles Homozygous Heterozygous

Genetic Variation Within Populations Ch. 11.1, pp. 328-329 Phenotype traits: Monogenic or polygenic Dominant/Recessive Incomplete Dominance Co-Dominance Permissive/Epistasis

Genetic Variation Within Populations Ch. 11.1, pp. 328-329 Allele Variation: Mutations Change in DNA nucleotide sequence Recombination New different combinations of alleles Crossing over during meiosis

Genetic Variation Within Populations Ch. 11.1, pp. 328-329 Allele frequency in a population gene pool can be calculated.

Natural Selection in Populations Ch. 11.2, pp. 330-333 Key Concept: Populations, not individuals, evolve Main Ideas: Natural selection Acts on distribution of traits Can change the distribution of traits in one of three ways Microevolution Observable change in allele frequency of a population over time

Natural Selection in Populations Ch. 11.2, pp. 330-333 Normal Distribution Phenotype frequency highest at mean Decreases as nears extremes “Bell” shaped curve Not undergoing selective pressure

Natural Selection in Populations Ch. 11.2, pp. 330-333 Directional Selection Favors one of the extreme phenotypes Causes shift of highest allele frequency from mean towards one extreme

Natural Selection in Populations Ch. 11.2, pp. 330-333 Stabilizing Selection Favors mean phenotype

Natural Selection in Populations Ch. 11.2, pp. 330-333 Disruptive Selection Favors both extreme phenotypes Selects against mean phenotype

Direction of Evolution ≠ Purpose or Intent Natural Selection in Populations Ch. 11.2, pp. 330-333 Remember: Direction of Evolution ≠ Purpose or Intent

Patterns in Evolution Key Concept: Evolution occurs in patterns Ch. 11.6, pp. 347-351 Key Concept: Evolution occurs in patterns Main Ideas: Evolution is not random Species can shape each other over time Species can become extinct Speciation often occurs in patterns

Patterns in Evolution Evolution occurs in patterns Ch. 11.6, pp. 347-351 Evolution occurs in patterns Evolution through natural selection is NOT random. Mutations cannot be predicted accurately Termed “Random event” Source of genetic variation Natural selection acts upon the variation Not random Selective pressure makes one variation more advantageous in survival and/or reproduction than other variation

Direction of Evolution ≠ Purpose or Intent Patterns in Evolution Ch. 11.6, pp. 347-351 Selective pressures act upon variations in population: Adds up over many generations Advantageous variation becomes more prevalent in population over time. Population becomes “adapted” The adaptation (advantage variation) becomes more prevalent and allele frequencies change. Direction of Evolution ≠ Purpose or Intent

Patterns in Evolution Environment drives natural selection Ch. 11.6, pp. 347-351 Environment drives natural selection Environments can change Convergent Evolution Different species must adapt to similar environmental pressures. Evolution toward similar characteristics in unrelated species Analogous structures e.g. dolphin and shark tail fin

Patterns in Evolution Divergent Evolution Ch. 11.6, pp. 347-351 Divergent Evolution Closely related species evolve in different direction and become increasingly different Common ancestor Homologous structures e.g. Kit fox & Red fox, Galapagos finches, Grey wolf to domestic dogs Question: Both turtles and snails have shells. Is this an example of convergent or divergent evolution?

Patterns in Evolution Coevolution: Ch. 11.6, pp. 347-351 Coevolution: Species react to each other in many different ways Beneficial e.g. ____________________________ Parasitic e.g. _____________________________ Arms race e.g. ____________________________

Patterns in Evolution Extinction: Elimination of a species from Earth Ch. 11.6, pp. 347-351 Extinction: Elimination of a species from Earth Unable to adapt to changing environments Background extinction : Continuous over time Affects one to small number of species in an area Mass Extinction: Rare Global level Many species Five mass extinctions in last 600 million years

Patterns in Evolution Patterns in evolution: Punctuated equilibrium Ch. 11.6, pp. 347-351 Patterns in evolution: Punctuated equilibrium Episodes of speciation followed by long periods of little evolutionary change Adaptive radiation Diversification of one ancestral species into many descendant species Different environmental pressures