Holt Biology Chapter 15
Terms
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- Population
- all the individuals of a species that live together in one place at a time
- Population size
- the number of indivuduals in a population
- population density
- the number of indivudials that live in a given area
- disperation
- the way the individuals of the population are arranged in space
- three types of dispersion
- random, even, and clumped
- population model
- a hypothetical population that attempts to exhibit the key characteristics of a real population
- exponential growth curve
- is a curve in which the rate of population grown stays the same, as a result the population size increases steadily
- density-dependent factors
- limited resources amount of water, food
- carrying capaity
- the population size an environment cans sustain
- logistic model
- a population model in which exponential grown is limited by density dependent factors
- r-strategists
- species that adapt and grow rapidly in changing environment, bacteria, mosquitos, cockroaches
- K-strategists
- Organsims that grow slowly and have small populations sizes such as whales
- density imdependent factors
-
growth of speies limited by environmental conditions
ex. weather and climate
Ex mosquitos pop. increase in summer due to warm weather, decrease during winter -
Hardy-
weinberg principle - frequencies of alleles in a population do not change unless evolutionary foreces act on the population
- gene flow
- the movement of alleles into or out of a population
- nonrandom mating
-
mating with others that live nearby or of same phenotype
(mating with relatives, inbreeding - genetic drift
-
change in an allel's frequency (occurs in small populations/changed by chance event fire, landslide
Cheetas - polygenic
- a trait that is influenced by several genes( human height/skin color
- normal distribution
-
hill shaped curve on graph
alleles average value - directional selection
- the frequency of a particular trait moves in one direction in a range.(like pestsicide resistance in insects change of the average value of a population
- stabilizing selection
-
distribution becomes narrower
Increases of the number of average individuals