Ch 53

World Population

7.6 billion

Which processes increase a population's size? Deaths and emigration. Births and immigration. Births and deaths. Deaths and immigration.

Births and immigration.

Population cycling (boom or bust cycles):

Complex interactions between various factors such as resource availability or predation patterns ex. Snowshoe hare cycles of abundance disappear if predators are experimentally excluded by fences

Density independent vs dependent population regulation

Density independent: Birth/death rate does not change with population density; e.g. environmental conditions like drought • Density dependent: Birth/death rate changes with population density -negative feedback involved • Competition for resources • Disease • Predation • Territoriality • Intrinsic physiological factors (e.g. hormonal changes) • Toxic waste build up

Which of the following statements about density-independent growth is true? The per-capita rate of increase may exceed rmax during density-independent growth. Density-independent growth can continue indefinitely in nature. Density-independent growth is also known as exponential growth. A population that is experiencing density-independent growth levels off at the environment's carrying capacity.

Density-independent growth is also known as exponential growth.

cohorts

Group of individuals of same age

Population

Group of individuals of single species living in same general area • Population members rely on same resources, influenced by similar environmental factors, likely to interact and breed with one another

exponential population growth

Growth of a population in an ideal, unlimited environment, represented by a J-shaped curve when population size is plotted over time.

Which of the following assumptions have to be made regarding the mark-recapture estimate of population size? I. Marked and unmarked individuals have the same probability of being trapped. II. The marked individuals have thoroughly mixed with the population after being marked. III. No individuals have entered or left the population by immigration or emigration, and no individuals have been added by birth or eliminated by death during the course of the estimate. II and III only I, II, and III II only I and II only I only

I, II, and III

Which of the following statements about a population experiencing logistic growth is true? If the K and N values are similar, the amount of available resources is high. If N is greater than K, the population will shrink. If N is less than K, the population will not grow. If the K and N values are far apart, the population will grow very slowly.

If N is greater than K, the population will shrink.

K vs R selection

K-selection: selection for traits that lead to population approaching carrying capacity • Long lives • Investment in a few, large offspring • Parental care common • Maximizes population size and operates in populations living at density near K (carrying capacity) where strong competition between individuals r-selection: Selection for traits that maximize intrinsic rate of increase at LOW population densities. • Short lives • Investment in many small offspring. • Little parental care • Occurs in environments where population densities fluctuate well below K and/or where little competition e.g. in newly formed habitats.

carrying capacity (K)

Largest number of individuals of a population that a environment can support Population growth greatest when population approximately half of carrying capacity

Which factor does not affect a habitat's carrying capacity? Availability of food. Number of nesting sites. Maximum number of individuals in a population. Intensity of predation.

Maximum number of individuals in a population.

logistic population growth model

Per capita rate of increase declines as carrying capacity reached; Produces sigmoid (S-shape) growth curve over time

Population ecology:

Study of how biotic and abiotic factors influence the density, size and age structure of populations

Demography

Study of statistics of populations and how they change over time • e.g. birth and death rates • Cohort: Group of individuals of same age • Life table: Age-specific summary of survival pattern of population • Survivorship curves (plotting of life table data)

life history traits

Traits that affect an organism's schedule of reproduction and survival. product of natural selection When reproduction begins, How often reproduction occurs, number of offspring per reproductive bout, also: size of offspring, frequency of offspring, amount of parental care etc.

demography patterns of survivorship

Type I curve: -Low death rate in early, middle life -Death rates increase in older age groups -Typical if few offspring per parent but high parental care Type II curve: -Intermediate, constant mortality over organism's life -Common in rodents, invertebrates (easy prey) Type III curve: -Very high death rates early in life -Death rates decline for few individuals surviving to critical age -Common with large numbers of offspring per parent but little parental care -Seen in many fish, marine invertebrates

Under which of the following conditions would a population most likely experience exponential growth? Large number of individuals in the starting population. Young populations with few individuals. Habitat with limited resources. Environment with a low carrying capacity.

Young populations with few individuals.

Which of the following best defines a cohort? the number of individuals that annually die or emigrate out of a population a group of the individuals from the same age group, from birth until they are all dead all of the individuals that are annually added to a population by birth and immigration the reproductive males and females within the population a group of individuals that inhabits a small isolated region within the range for the species

a group of the individuals from the same age group, from birth until they are all dead

The three basic variables that make up the life history of an organism are how often reproduction occurs, life expectancy of females in the population, and number of offspring per reproductive episode. number of reproductive females in the population, age structure of the population, and life expectancy. the number of reproductive females in the population, how often reproduction occurs, and death rate. age when reproduction begins, how often reproduction occurs, and how many offspring are produced per reproductive episode. life expectancy, birth rate, and death rate.

age when reproduction begins, how often reproduction occurs, and how many offspring are produced per reproductive episode.

In wild populations, individuals most often show a _____ pattern of dispersion. uniform density-dependent clumped random equilibrium

clumped

Which of the following causes populations to shift most quickly from an exponential to a logistic population growth? increased birth rate decreased death rate favorable climatic conditions removal of predators competition for resources

competition for resources

Which of the following sets of measurements would best describe a population's physical structure and vital statistics? minimum and maximum amounts of precipitation and annual temperature extremes density, dispersion, and demographics ratio of predators and the number of immigrants and emigrants annual precipitation averages and mean annual temperatures gene frequency over time and the ratio of reproductive to nonreproductive individuals

density, dispersion, and demographics

Which of the following is most likely to contribute to density-dependent regulation of populations? floods intraspecific competition for nutrients the removal of toxic waste by decomposers fires earthquakes

intraspecific competition for nutrients

Resource competition, territoriality, disease, and toxic wastes are some of the factors that provide _____ and help regulate population. metapopulations zero population growth negative feedback population dynamics positive feedback

negative feedback

Which of the following is characteristic of K-selected populations? small offspring early parental reproduction many offspring per reproductive episode a high intrinsic rate of increase offspring with good chances of survival

offspring with good chances of survival

the models that describe population growth, r stands for _____. carrying capacity total number of individuals in the population per capita population growth rate a time interval population density

per capita population growth rate

Exponential growth of a population is represented by dN/dt= r max N rNK rNN−KK rNK−NK rN(K+N)

r max N

Which of the following groups would be most likely to exhibit uniform dispersion? moths, in a city at night lake trout, which seek out cold, deep water high in dissolved oxygen cattails, which grow primarily at edges of lakes and streams dwarf mistletoes, which parasitize particular species of forest tree red squirrels, who actively defend territories

red squirrels, who actively defend territories

Dispersion

the pattern of spacing among individuals within the boundaries of the population

To determine the density of a rabbit population, you would need to know the number of rabbits and _____. their pattern of dispersion the factors that limit population growth for that rabbit population the birth rate the size of the area in which they live the growth rate of the population

the size of the area in which they live

Which equation represents the logistic growth rate of a population? r=b−d ΔNΔt=rmaxN ΔNΔt=rMmaxN(K−N)/K ΔNΔt=rN

ΔNΔt=rMmaxN(K−N)/K