Module 8

Module 8—Populations, Individuals, and Gene Pools

 

Glossary

 

Consult the glossary in the textbook for other definitions that you may need to complete your work.

 

antibiotic resistance: the ineffectiveness of an antibiotic that results if a bacterial cell has alleles that make it resistant to being destroyed by antibiotics

Each dose of antibiotics will allow these bacteria to survive and pass on their resistant traits to the next generation—more of each generation are resistant until the resistant allele is the most common; at this point, the antibiotic is no longer effective.

 

behavioural defences: actions and gestures that are meant to communicate that the organism is dangerous and should be avoided or is harmless and not threatening

 

biotechnology: manipulation of genes or traits

 

biotic potential (r): highest per capita growth rate possible

 

bottleneck effect: a type of genetic drift similar to the founder effect; occurs when a natural disaster thins the population to a small group that happens to be unrepresentative of the original group

 

Allele frequencies of the two groups will be dissimilar.

 

carrying capacity (K): the theoretical maximum population size that the environment can sustain over an extended period of time; may change as the quality of the habitat changes; the population is at carrying capacity when it levels off during logistic growth

 

chemical defences: toxic, bad-tasting, or bad-smelling chemicals secreted by an organism that either discourage consumers from eating it, poison consumers, or prevent competitors from growing or living nearby

 

climax species: the last species of plant in the succession; is used to name the succession

 

clumped distribution: organisms grouped together; occurs in highly competitive environments

 

commensalism: a type of symbiosis in which one species benefits and the other is not affected one way or another

 

cryptic colouration (camouflage): colours or patterns that allow an organism to blend into its environment and avoid being seen

 

density (Dp): the number of individuals in a given unit of area (land) or volume (air or water) 

 

 

density-dependent limiting factors: biotic factors that limit a habitat’s carrying capacity (e.g., parasites, disease, increase in predators, lack of water, food, or territory); the impact increases with the density of the population

 

density-independent factors: abiotic factors that limit a habitat’s carrying capacity (e.g., fire, flood, frost); the impact is not affected by the density of the population

 

emigration: number of individuals that leave the population; due to the same reasons as immigration

 

environmental resistance: the combined effects of factors that limit population growth; prevents a population from growing at its biotic potential; determines the carrying capacity of the environment

 

exponential growth: a growth pattern exhibited by a population that doubles with each generation; results in a J-shaped curve; begins with a lag phase, followed by a steep rise

 

exponential phase: the second phase of a growth graph in which population size increases significantly because limiting factors are not yet significant

 

fecundity: fertility; the ability of an organism to be fertile or to reproduce

 

founder effect: a type of genetic drift that occurs when a small population that is not representative of the main population migrates away

 

Allele frequencies of the two groups will be dissimilar.

 

frequency: number/total; how common something is; usually expressed as a decimal percentage; e.g., an incidence of “2 in 5” gives the same information as a frequency of 0.4 or 40%

 

gene flow: movement of alleles into or out of a population by immigration or emigration

 

genetic drift: a change in allele frequencies caused by chance events in a small gene pool, such as inbreeding caused by isolation of a small non-representative group or a few non-breeding individuals (bachelors)

 

Founder effect and bottleneck effect are examples of genetic drift.

 

growth rate (gr): the change in the number of individuals in a unit of time

 

gr will be positive if the population size is increasing, and negative if it is decreasing.

 

Hardy-Weinberg equation: an equation used to determine the frequency of genotypes:  p2 + 2pq + q2 = 1, where p = frequency of the dominant allele and q = frequency of the recessive allele

 

If the frequency of genotypes is known, the equation can be used to work backwards to find the frequency of alleles in the gene pool.

 

Hardy-Weinberg Equilibrium: a principle that states that allele frequencies in a population will remain the same over time as long as the population is large, there is no gene flow, natural selection is not occurring, there is no change in mutation rate, and no mate selection is occuring

 

If allele frequencies do change, it indicates that microevolution is occurring in the population.

 

host: the organism in a type of symbiotic relationship that provides food or a means to complete reproduction for the parasitic organism of another type of species

 

immigration: number of individuals entering the population from outside; can be due to abiotic factors (e.g., escape from fire, drought, flood, climate change) or biotic (e.g., increased competition)

 

interspecific competition: when members of two different species compete for scarce resources and survival; competition only occurs when there are too many organisms and not enough resources

 

intraspecific competition: when members of the same species compete against each other for scarce resources and survival; causes microevolution because one phenotype or allele will have better survival than another

 

The scarcer the resources, the more extreme the competition and the faster microevolution occurs.

 

invasive species: species that are introduced to an area and that out-compete the indigenous species in its trophic level for nutrients and/or prey; are less affected by limiting density-dependent and density-independent factors

 

J curve: population growth with a brief lag phase and a steep increase in the growth curve

 

K-selected strategy: takes advantage of stable conditions; characterized by few offspring with much investment and nurturing to increase offspring survival

 

K-selected organisms: species that have K-selected strategies, such as longer life span, later reproductive age, few offspring, and parental care

 

lag phase: the first phase of a growth graph showing little increase in population numbers

 

logistic growth: a population increase resulting in an S-shaped curve; begins with slow growth, steepens to exponential growth, and then levels to a carrying capacity due to competition because of environmental resistance

 

mate selection (non-random mating): the process of choosing mates based on the presence of certain traits or phenotypes and, thus, genotypes

 

Traits are usually displayed in some form of courtship ritual.

 

microevolution: a change in the frequency of alleles in the gene pool that results in a change in the characteristics of the population; does not result in a new species

 

mimicry: when a harmless organism has the same bright colouration of an organism that has protective colouration

 

monoculture: the cultivation of a single crop

 

mortality: death; may be due to kill-off (predation) or die-off (disease, starvation, or exposure)

 

mutualism: a type of symbiosis involving two organisms of different species in which both benefit or depend on the relationship to survive

 

natality: number of births; tends to increase with food supply and decrease with competition

 

natural selection: the process by which organisms with heritable traits survive in a particular environment, passing on their successful traits to the next generation

 

Those selected have greater reproductive fitness that either increases fertility or decreases mortality.

 

niche: a position or role taken by an organism within its community

 

parasite: the organism in a symbiotic relationship that benefits by living on or in another organism (host) as a source of food or means of reproduction 

 

The host is harmed in this relationship.

 

per capita growth rate (cgr): the rate of change per individual; the amount of change each individual in the initial population is responsible for

 

cgr can be positive or negative depending on what the initial N is.

 

pioneer species: the first species of plant to invade a cleared site in a succession

 

population: organisms of a particular species in a particular place at a particular time

 

population determiners: four factors that change the numbers of individuals in the population: natality, mortality, immigration, and emigration

 

predator-prey: a relationship in which one organism (predator) hunts and kills another organism (prey) for food

 

primary succession: a succession that begins with bare rock; soil-building organisms (e.g., lichen) are pioneers

 

protective colouration: bright colours that give clear warning to potential attackers

 

random distribution: no pattern exists in organism distribution; occurs in environments with little competition

 

reproductive strategy: the strategies used in reproduction to ensure survival of a species; may be r- or K-selected strategies

 

r-selected strategy: takes advantage of favourable conditions; characterized by early reproduction and high reproductive rate with little investment in offspring survival

 

r-selected organisms: species that have r-selected strategies, such as a short life span, early reproductive age, large numbers of offspring, and little parental care

 

S curve: a logistic growth pattern with a lag phase, growth phase, and stationary phase in which limiting factors become significant

 

secondary succession: a succession that begins with soil

 

stationary phase: the third stage of a population growth graph in which population size stabilizes because of the balance between environmental resistance and biotic potential

 

structural defences: physical parts of the organism that either protect the organism from being consumed or allow the organism to compete better for scarce resources

 

succession: the orderly replacement of one species with another over time; occurs after a disruption, such as fire

 

symbiotic relationship: any close relationship in which individuals of different species live together in a feeding or protective relationship

 

transgenic organism: an organism that has genes from more than one species

 

uniform distribution: organisms are equally spaced apart; occurs in artificial environments (e.g., agricultural crops)

 

wildlife corridor: a route used by wildlife to move from one territory to another

 

Wildlife corridors are often part of a migratory pattern.

Biology 30 Learn EveryWare © 2009 Alberta Education