Evolution

Objective: K1 - Analyze & evaluate how natural selection produces changes in a population, not individuals & describe the three types of isolation that cause speciation

I. Population Genetics - study of the traits in a population

A. Population – a group of interbreeding organisms (a species) living in a given area

B. Gene Pool – combined genetic material of all the members of a population

C. Allele – forms that a gene can take

D. Allele Frequency – the number of each allele for a trait as a fraction of all the alleles for a particular trait

a. Example: 8 alleles total, 4 are green. Allele frequency of green = 4/8 or 1/2

II. How do you get NO EVOLUTION - NO evolution = genetic equilibrium - Five conditions must be met to have genetic equilibrium. 1. Random mating 2. Large Populations 3. No Immigration or Emigration 4. No Mutation 5. No Natural Selection - Genetic Equilibrium does not occur - It is only theoretical

III. Generalization 1. If gene pools do not remain the same

over time, they must change. 2. This “changing of the gene pool” (allele

frequency) has a name —› Evolution. 3. Evolution – the changes in the gene pool

of a population over time.

IV. Speciation – formation of a new species

1. Behavioral Isolation

- occurs when 2 populations are capable of interbreeding but have differences in courting rituals or other reproductive strategies

2. Geographic Isolation

- 2 populations are separated by geographic barriers

●examples: rivers, mountains, bodies of water

3. Temporal Isolation

- 2 or more species reproduce at different times

What a Beak! Lab

Objective: K2 - Analyze & evaluate the relationship of natural selection to adaptation and to the development of diversity in & among species & how the elements of natural selection result in differential reproductive success

V. Natural Selection: a. Artificial Selection – humans select for variations

in plants and animals that they find useful. b. Natural Selection

– also means “Survival of the Fittest”.

- Fitness in this sense does not mean strongest.

- Fitness in Darwin terms means reproduction. The one who survives long enough to reproduce the most is the one with the highest fitness.

VI. Types of Selection -Evolution acts on the phenotype of the

individual, not the genotype. - There are 3 types of selection that can

occur on a population. i. Directional Selection – when individuals at one end of the curve have a

higher fitness than individuals in the middle or at the other end of the curve.

ii. Stabilizing Selection – when individuals near the center of the

curve have higher fitness than individuals at either end of the curve, narrowing of the graph.

iii. Disruptive Selection– when individuals at either end have a higher

fitness and individual near the middle of the curve are selected against.

- Over time with enough selection a population can go through genetic drift.

a. genetic drift – random change in allele frequency.

VII. Adaptation- an inherited trait that increases a population’s chance of survival and reproduction in a particular environment A. Through adaptations, populations often

become suited to a specific job called a niche.

1. niche – a habitat and the role a population plays in that habitat

- job, profession, role 2. Competition arises when 2 populations

occupy the same niche.

B. Mimicry - Definition: The advantageous

resemblance of one species to another

Purpose:Deceives predatorsProvides a form of camouflage for protectionExample: The viceroy butterfly is a mimic of

the monarch butterfly because the monarch is toxic and the viceroy is non-toxic.

M & M Allele Activity