BIO 189: Chapter 12- Forces of Evolutionary Change

What is evolution?

A change in the genetic makeup of a population of organisms over many generation

Populations evolve as different alleles come into existence (_______) and then change in ____ over time

mutations and frequency

What is a gene pool?

Total # of alleles for each gene in a population

What is the allele frequency formula?

#specific allele in population/ total allele # for gene in population

What are two key principles of evolutions?

Common descent with modification and natural selection

Who was Charles Darwin and what did he do?

He was hired as a naturalist on HMS Beagle (took a 5-year journey around the world studying and collecting animals)

What was gradualism?

New species result from an ancestral species undergoing slow constant changes over long periods of time

What are Darwin’s Galapagos finches?

multiple modern species evolved from a single ancestor specific from South America

Who was Alfred Russel Wallace?

Darwin’s contemporary

Natural history collector and explorer

Conducted field studies of species diversity in the Amazon and in Indonesia

Independently developed a nearly identical theory of evolution as Darwin

What was Wallace’s evolution theory?

Descent with modification and Natural selection as mechanism

Finished work in 1858 (wanted to co-publish both papers)

Darwin gets most of the credit

What is the particulate theory?

Packets of heredity and they come in pairs

What were the different branches of science that were incorporated by biologist in modern evolutionary synthesis?

Genetics, Botany, Paleontology, Morphology, Ecology, Cell biology

What are selective pressures?

Elements of environment that determine good and bad traits (biotic or abiotic)

What do embryos not do?

Compete for environmental resources

Compete for reproductive partners

Directly contribute genes to the next generation

What was Hardy-Weinberg’s Equilibrium?

A “negative model” (easier to define what something is not rather than what it is)

What happens in the absence of evolutionary forces?

Allele frequencies will not change over time, non-evolving populations are in genetic equilibrium

What are the 5 major causes that are clearly defined by the Hardy- Weinberg Model?

Natural Selection

Mutations (new alleles)

Small population size

Non-random mating

Migration between populations

What does the H.W.E model help determine?

If evolution is occurring and sometimes what mechanisms evolution is occurring through

If we know the allele frequencies we can calculate?

Genotype frequencies

What are the three outcomes of natural selection at population level?

Stabilizing (reduces variation to a smaller window)

Directional (one extreme is better/favorable)

Disruptive (both extremes are better/favorable than intermediate)

What are the five agents of evolution?

Mutation (alteration in an organism’s DNA)

Natural Selection (Survival of the fittest)

Gene Flow (Movement of alleles from one population to another)

Genetic Drift (chance of alteration of gene frequencies in a population)

Sexual Selection (Some members of a population mate more than others)

What is gene flow?

Mixing alleles between separate populations

What is a genetic drift?

The allele frequencies in population can change dramatically by events of pure random chance

What is a bottleneck event?

A sudden and dramatic reduction in a population’s size resulting in only a few survivors (only the survivor’s alleles make up new populations gene pool, reduced genetic diversity)

What is the founder effect?

A small group of individuals establishes a new population in an isolated settlement (fewer founders= stronger founder effect)

What is dimorphism?

2 distinct forms (usually males & females look very different)

What is intersexual in sexual selection?

Between sexes, organisms spend energy and resources to attract the opposite sex

What is intrasexual in sexual selection?

Within sex, intimidate, outcompete, defeat same sex competitor

What is artificial selection/selective breeding?

Human interjections, humans changed organisms based on desired traits due to exploiting selection mechanisms