Chapter 13 - How Populations Evolve

adaptation

inherited characteristic that increases an organism's chance of survival

artificial selection

selection by humans for breeding of useful traits from the natural variation among different organisms

balancing selection

Natural selection that maintains stable frequencies of two or more phenotypic forms in a population (balanced polymorphism)

biogeography

the study of the past and present distribution of species

Bottleneck effect

Genetic drift resulting from a drastic reduction in population size

differential

Selection that causes a shift in allele frequency such that one more more alleles become more common over time

directional selection

occurs when natural selection favors one of the extreme variations of a trait

disruptive selection

natural selection that favors individuals with either extreme of a trait

evolution

the gradual change in a species over time

evolutionary fitness

The contribution an individual makes to the gene pool of the next generation, relative to the contribution of other members of the population

evolutionary tree

a diagram that reflects evolutionary relationships among groups of organisms

extinction

disappearance of a species from all parts of its geographical range

fitness (differential reprod. success)

offspring that survive to reproduce themselves

fossil record

chronological collection of life's remains in sedimentary rock layers

Founder effect

Random change in the gene pool that occurs from a small starting colony size for a population

Gene flow

The gain or loss of alleles from a population by the movement of individuals into our out of a population

Gene Pool

All the genes (alleles) in a population at a given time

Genetic Drift

A change in the gene pool of a population due to chance

Hardy Weinberg Equilibrium(HWE)

a 'null model' of no evolution within a population, i.e. allele frequencies remain constant through generations

homologous structures

similar structures that related species have inherited from a common ancestor

homology

similarity in characteristics resulting from a shared ancestry

Microevolution

evolution resulting from small specific genetic changes that can lead to a new subspecies / a change in a population's gene pool over successive generations; evolutionary changes in species over comparably brief periods of time

Modern Synthesis

A comprehensive theory of evolution that incorporates genetics and includes most of Darwin's ideas, focusing on populations as the fundamental units of evolution

Mutation

A change in the nucleotide sequence of DNA; the ultimate source of genetic diversity

natural selection

The process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species

paleontologist

scientist who studies fossils

Population

A group of interacting individuals belonging to one species and living in the same geographic area (that therefore can potentially interbreed)

Population Genetics

The study of genetic changes in populations; the science of microevolutionary changes in populations

sexual dimorphism

marked differences between the sexes in secondary sexual characteristics, which are not directly associated with reproduction

Sexual selection

Change in the gene pool due to behavior that causes preferential mating with one or more genotypes / results from differences in traits affecting access to mates

stabilizing selection

intermediate forms are favored and extreme forms are eliminated/ Selection that maintains generally unchanging allele frequencies over time

strata

layers of sedimentary rock

vestigial organs

organs that serve no useful purpose for the organism; these suggest that sometime in the past they were useful

The Fossil Record

shows that organism have appeared in a historical sequence, and many fossils link ancestral species with those living today (Evidence of Evolution)

Biogeography

observations of the geographical distribution of species when closely related species tend to be found in the same geographical region (Evidence of Evolution)

comparative anatomy

Homologous structures among species and vestigial organs provide evidence of evolutionary history. (Evidence of Evolution), the study of the structures of different organisms. Looking at homologous parts: parts that have similar structure provide evidence

Comparative embryology

closely related species often have similar stages in their embryonic development (Evidence of Evolution)

molecular biology

all species share a common genetic code, suggesting that all forms of life are related through branching evolution from the earliest organisms. Comparisons of DNA and proteins provide evidence of evolutionary relationships.(Evidence of Evolution)

Darwin's theory of natural selection

Individuals best suited for a particular environment are more likely to survive and reproduce than less fit individuals

Natural selection in action

can be observed in the evolution of pesticide -resistent insects, drug-resistant microbes and horned lizards among many other organisms

Hardy-Weinberg formula

p^2 + 2pq = q^2 = 1

population genetics and health science

Hardy-Weinberg formula can be used to estimate the frequency of a harmful allele, which is useful information for public heath programs dealing with genetic diseases

homology

similarity in characteristics resulting from a shared ancestry

vestigial organs

organs that serve no useful purpose for the organism; these suggest that sometime in the past they were useful

Lamarck

French naturalist who proposed that evolution resulted from the inheritance of acquired characteristics. , He thought that use or disuse of a particular body part could cause it to grow or shrink � just like using your arms a lot might cause the muscles t

Charles Darwin

british biologist who introduced the ideas of natural selection and evolution; argued that specific behaviors evolved because they led to advantages in survival or reproduction

evolutionary adaptation

An accumulation of inherited characteristics that enhance organisms' ability to survive and reproduce in specific environments

gradualism

the idea that large changes on Earth can result from the accumulation of small changes over a very long time.

p

in Hardy-Weinberg represents the frequency of the dominant allele

q

in Hardy-Weinberg represents the frequency of the recessive allele

p^2

in Hardy-Weinberg represents frequency of homozygous dominants

q^2

in Hardy-Weinberg represents frequency of homozygous recessives

2pq

in Hardy-Weinberg represents frequency of heterozygotes

bottleneck effect

changes in the gene pool caused by a rapid reduction in population size. Reduces genetic variability

founder effect

Genetic drift that occurs when a few individuals become isolated from a larger population, with the result that the new population's gene pool is not reflective of the original population.

directional selection

form of natural selection in which the entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve

disruptive selection

form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle