Chapter 21 * Species- a group of individuals that can exchange genetic material through interbreeding * Gene pool- all alleles present in all individuals in a species * Populations- interbreeding groups of organisms of the same species living in the same geographical area * Mutations- generate new genetic variation * Somatic (occurs in body tissues) * Germ-line- occurring in reproductive cells (passed on to next generation) * Deleterious (harmful), neutral (not functionally important), advantageous (improves chance of carriers’ reproduction or survival) * Fixed populations- exhibit only one allele at a particular gene * Ways to measure variation * Observable traits: not v. useful, most traits rely on multiple genes * Gel electrophoresis: separates proteins based on charge and size, shows homo vs. heterozygous as distinct, only good for enzymes * DNA sequencing: just count occurrences, best method * Evolution- any change in allele or genotype frequencies of a population over time * Hardy-Weinberg Equilibrium- when met, evolutionary mechanisms are not at work 1. No difference in the survival and reproductive success of individuals 2. Populations must not be added to or subtracted from by migration 3. There can be no mutation 4. Population must be sufficiently large to prevent sampling errors- (genetic drift = change in the frequency of an allele due to the random effects of small population size) 5. Individuals must mate at random- (non-random mating is an obvious thing) * Important scientists: Darwin, Wallace, Malthus * Fitness = a measure of the extent to which the individual’s genotype is represented in the next generation * Modern Synthesis = Fisher’s marriage between Darwin’s theory of natural selection and Mendelian genetics, produced current evolutionary theory * Fixation of alleles = allele has frequency of 1 * Positive selection = natural selection that increases the frequency of a favorable allele * Natural selection patterns 1) Stabilizing selection = maintains status quo, acts against extremes 2) Directional selection = selects against one extreme, change over time 3) Artificial selection = successful phenotypes are chosen by breeder, not by competition 4) Disruptive selection = favors extremes, against intermediate forms 5) Sexual selection = promotes traits that increase an individual’s access to reproductive opportunities * Migration = the movement of individuals from one population to another: Gene flow = the movement of alleles from one population to another * Bottleneck * Founder event * Molecular clock- correlation between the time two species have been evolutionarily separated and the amount of genetic divergence between them * Pseudogene- a gene that no longer functions, all mutations are by definition neutral
Section 24.4 * We have relatively low genetic variation 0.1%, but size of genome means ~3 million base pairs differ between any 2 people * Only 7% of total genetic variation in humans occurs between races
Sections 27.2-27.4 * Symbiont- an organism that lives in closely evolved association with another species * Endosymbiosis- symbiosis in which one partner live within the other * 27-7 for 2 hypotheses on eukaryotic origin * Protists- organisms having a nucleus but lacking other features specific to plants/animals/fungi * Algae- photosynthetic protists * Protozoa- heterotrophic protists, almost exclusively single-celled * 7 superkingdoms of eukaryotes * Amoebozoa- amoeba-like cells that move/gather food by pseudopodia, slime molds are coenocytic (multiple nuclei within one giant cell) * Archaepastida- 2nd most diverse/conspicuous, photosynthetic, include land plants * Stramenopila- all have unusual flagellum that bears 2 rows stiff hairs, most are phosynthetic, diatoms