ch 15 Flashcards
(40 cards)
A population consists of
all the individuals of a species that live together in one place at one time. A population can be widely distributed or confined to a small area.
In the exponential model of population growth, the growth rate remains
constant. Rapid, continuous growth is the result.
In the logistic model of population growth, the growth rate ___ as population size rises. The population stabilizes at the carrying capacity, the maximal population size the environment can sustain.
declines
The population stabilizes at the carrying capacity, the maximal population size the environment can sustain.
Populations of species that are r-strategists are characterized by
exponential growth.
reproduce early in life
have many offspring that are small, mature rapidly, and receive little parental care.
Populations of species that are K-strategists are characterized by
slow population growth.
reproduce late in life
have few offspring that are large, mature slowly, and often receive extensive parental care.
Human populations have evolved with many of the characteristics of ___, however, the human population is now growing ___.
K-strategists
explosively.
The Hardy-Weinberg principle states that
the frequencies of alleles and genotypes in a population remain constant unless evolutionary forces act on them.
This principle holds true only for large populations in which individuals mate randomly and in which forces that change the proportions of alleles are not acting.
The five forces that can cause allele frequencies to change are
mutation, migration, nonrandom mating, genetic drift, and natural selection.
Natural selection reduces the frequency of a harmful recessive allele slowly because
very few individuals are homozygous recessive and express the allele.
Population
all the individuals of a species that live in one place at one time.
Demography
statistical study of populations
Population features:
Size
density
dispersion
Size
number of population
Large populations may be doing well, but
if in small area (high density) may run low on resources and more vulnerable to spread of contagious illnesses and excess waste.
Small Populations - may be in danger of going extinct due to:
Inbreeding (mating with relatives) which increase number of homozygous genotypes. If more homozygous recessives, more change of recessive genetic disorder.
Less genetic diversity therefore less able to survive a new pressure
Difficulty in finding mates if in a large area
Density
number per square unit
Dispersion
pattern of positioning
Types of dispersion
Random
Even
Clumped - most common… can indicate where resources are.
Model
hypothetical population that has key characteristics of a real population uses previous data to predict future trends.
Stage 1 Model:
r (rate of growth) = birth rate – death rate (all per 1000 per year)
Stage 2 Model:
N=current pop.
ΔN (number added) = r x N
Stage 3 (logistic)Model:
K = Carrying Capacity, population size the environment can sustain
ΔN = r x N x (k-n /k)
Logistic model
accounts for decreasing resources available to a population as well as more waste and/or spread of contagious diseases… as population reaches K level.
r-strategists characteristics
large populations due to large # of offspring and/or reach maturity fast,
little care of offspring,
exponential pop. growth,
good in unstable environment BECAUSE of the large population size and/or there quick reproduction cycle they have more genetic variation that enables them to respond to changes - they evolve/adapt quicker.
