AP Biology Final Exam review

Natural Selection

Organisms with desirable traits are more likely to survive and reproduce, which passes those traits on to the offspring. "Selecting" for the traits that give an advantage.

Prezygotic barriers

block fertilization from occurring by...

1. impeding different species from attempting to mate

2. Preventing the successful completion of mating

3. Hindering fertilization if mating is successful

Habitat isolation

Two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers

Temporal isolation

Species that breed at different times of the day, different seasons, or different years cannot mix their gametes

Behavioral isolation

courtship rituals and other behaviors unique to a species are effective barriers

Mechanical Isolation

Morphological differences prevent successful mating

Gametic isolation

Sperm of one species may not be able to fertilize eggs of another species

Postzygotic barriers

prevent the hybrid zygote from developing into a viable, fertile adult by...

1. Reduced hybrid viability

2. Reduced hybrid fertility

3. Hybrid breakdown

Reduced hybrid viability

genes of the different parent species may interact and impair the hybrid's development or survival

Reduced hybrid fertility

Even if hybrids are vigorous, they may be sterile

Hybrid Breakdown

Some first-generation hybrids are fertile, but when they mate with another species or with either parent species, offspring of the next generation are feeble or sterile

Hardy Weinberg equations

p + q = 1

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

Gene flow

the transfer of genes from one population to another, reducing genetic variation. This can fuse two species into one. Violates H-W

Mutation

The ultimate source of genetic variation. They come from a change in the DNA from an error. Violates H-W

Nonrandom mating

Individuals are more or less likely to mate with others because of genotypes/phenotypes. Violates H-W

Population size

Small populations are more susceptible to genetic drift and reduced genetic diversity. A larger population makes this less likely. A large population would not violate H-W , but a small one might

Stabilizing selection

Selects against the different extremes and for the average.

Directional selection

Selects for one side of the extreme (away from the average)

Disruptive selection

Selects for both extremes but against the intermediate

Speciation

the process by which one species splits into two or more species

Allopatric speciation

gene flow is interrupted when a population is divided into geographically isolated subpopulations

Sympatric speciation

takes place in populations that live in the same geographic area. Occurs through polyploidy, habitat differentiation, and sexual selection

Ecology

the scientific study of the interactions between organisms and the environment. They determine the distribution of organisms and their abundance

Predation

(+/-) refers to an interaction in which one species, the predator, kills and eats the other, the prey

Mutualism

(+/+) an interspecific interaction that benefits both species

Commensalism

(+/0) one species is benefited while the other is neither harmed nor helped

Parasitism

(+/-) one organism, the parasite, derives nourishment from another organism, the host, which is harmed in the process

Endoparasites

live within the body of the host (like a tapeworm)

Ectoparasites

live on the external surface of a host (like a tick)

Competition

(-/-) organisms either within a species or between species compete for the same resources (food, shelter, water) and both are harmed

Herbivory

(+/-) an interaction where a herbivore eats parts of a plant or alga

Carrying capacity (K)

is the maximum population size the environment can support. Varies with the abundance of limiting resources

Exponential growth

results in a J shaped curve. It characterizes populations in new environments or rebounding populations. Cannot be sustained for long

Logistical growth

results in an S shaped curve. The rate of increase declines as carrying capacity is reached

Ecological niche

the specific set of biotic and abiotic resources used by an organism, a role

Abiotic factors

the nonliving chemical and physical attributes of the environment

Examples of abiotic factors

Temperature, water, oxygen, salinity, sunlight, rocks. (soil can be both)

Biotic factors

the other organisms that make up the living component of the environment

Examples of biotic factors

Predation, herbivory, mutualism, parasitism, competition

Clumped distribution

Most common pattern of dispersion, individuals congregate in patches. This may be influenced by resource availability and behavior

Uniform distribution

Individuals are evenly distributed. May be influenced by territoriality

Random distribution

the position of each individual is independent of other individuals. Occurs in the absence of strong attractions or repulsions

Type 1 survivorship curve

low death rates during early/middle life and increase in older age groups

Type 2 survivorship curve

a constant death rate over the organisms life span

Type 3 survivorship curve

high death rates for the young and lower death rate for survivors

K-selection

or density-dependent selection, selects for life history traits that are sensitive to population density

R-selection

or density-independent selection, selects for life history traits that maximize reproduction

Community

a group of populations of different species in an area

Population

a group of individuals of the same species living in an area

Ecosystem

the community of organisms in an area and the physical factors with which they interact

Landscape

is a mosaic of connected ecosystems

Global ecology

is concerned with the biosphere, or global ecosystem, which is the sum of all the planet's ecosystems. It looks at the influence of energy and materials on organisms

Density-dependent factor

birth and death rates fall and rise with population density

Density-independent factor

birth and death rates do not change with population density

Regulator

uses internal mechanisms to control internal change despite external changes

Conformer

allows its internal condition to change in accordance with external changes

Thermoregulation

the process by which animals maintain an internal temperature within a tolerable range

What does species diversity actually measure?

Species richness (the number of different species in the community) and relative abundance (the proportion of each species represents all individuals in the community)