Population Growth cont.

Question 1

Logistic population growth models

Answer 1

incorporate carrying capacity, such that population growth approaches zero as population size nears K; regulated by density dependent factors and falls into two general reproductive strategies; more realistic model and produces an S-shaped population size curve

Question 2

Carrying capacity (K)

Answer 2

maximum population size the environment can support; varies over space and time w/ abundance of limiting resources

limiting factors include: energy shelter, refuge from predators, nutrient availability, water, and suitable nesting sites

Question 3

During the logistic population growth, the number of individuals added to the population _____

Answer 3

increases then decreases

Question 4

When are new individuals added most rapidly?

Answer 4

at intermediate population size, when the breeding population is substantial and resources are abundant; population growth rate decreases as N approaches K

Question 5

Density independent

Answer 5

birth rate and death rate do not change w/ population density

Question 6

Density dependent

Answer 6

birth rates and death rates are directly or indirectly regulated by population density; population size can only be regulated by density-dependent factors

Question 7

Density dependent factors

Answer 7

predation, competition for resources, disease, intrinsic factors, territoriality, toxic waste

Question 8

Predation

Answer 8

can be density dependent if prey are easier to catch at high density; Ex: kelp populations’ death rate increased as hiding spaces from predators became scarce at high densities

Question 9

Competition

Answer 9

in crowded populations, increasing population density intensifies competition for resources and reduces birth rates; Ex: farmers reduce competition by applying fertilizers to reduce nutrient limitations on crop yield

Question 10

Disease

Answer 10

can regulate population density if its transmission rates increase as population becomes more crowded; Ex; influenza and tuberculosis spreads faster in densely crowded cities compared to rural areas

Question 11

Territoriality

Answer 11

can limit population density when space becomes the resource for which individuals compete; Ex: Cheetahs use chemical markers in urine to warn other cheetahs of their territorial boundaries

Question 12

Intrinsic factors

Answer 12

physiological factors appear to regulate population size; Ex: hormonal changes in white-footed mice delay sexual maturation and depress immune system at high density making birth rates drop even when food and shelter are abundant

Question 13

Toxic wastes

Answer 13

accumulation of toxic wastes at high population density can contribute to density dependent regulation of population size; Ex: concentration of ethanol produced by brewer’s yeast becomes toxic at high population density

Question 14

Which is more common, negative density dependence or positive density dependence?

Answer 14

Negative density dependence

Question 15

Population dynamics

Answer 15

focuses on the complex interactions between biotic and abiotic factors that cause variation in population size

Question 16

Example of a large mammal’s population size fluctuating at unpredictable intervals.

Answer 16

Two major population increases and collapses in the moose population on Isle Royale during the last 50 years; 1st collapse due to increase in wolf population, 2nd collapse due to harsh winter conditions

Question 17

Example of population fluctuating at regular boom and bust cycles.

Answer 17

Snowshoe hares and lynx both follow roughly 10 year population cycles in the forests of northern Cananda and Alaska; overexploitation by predators is an essential factor affecting snowshoe hare cycles; lynx increase and decrease in response to the availability of their prey species

Question 18

Life history

Answer 18

comprises traits that affect an organism’s schedule of reproduction and survival

Question 19

What are the five key components that make up life history?

Answer 19

1. age/size at reproductive maturity
2. allocation of energy to reproduce
3. # and size of reproduction
4. # of reproductive events
5. life span

Question 20

What are the two reproductive events called?

Answer 20

Iteroparity and Semelparity

Question 21

Iteroparity

Answer 21

repeated reproductive events throughout a lifetime

Question 22

Semelparity

Answer 22

a “one-shot” pattern of big-bang reproduction

Question 23

r-selection

Answer 23

selection for life history traits that maximize reproductive success at low density

Question 24

K-selection

Answer 24

selection for life history traits that are advantageous at high population densities

Question 25

Principle of allocation

Answer 25

resources that an organism has to partition among life history functions (growth, maintenance, and reproduction) are finite