Population Ecology

Question 1

Population ecology

Answer 1

Explores how biotic and abiotic factors influence the density distribution size and age structure of populations

Question 2

Population

Answer 2

A group of individuals of the same species that live in the same area

Question 3

Density

Answer 3

Number of individuals per unit area or volume (how many units in a given space)

Question 4

Dispersion

Answer 4

Pattern of spacing among individuals

Question 5

B.I.D.E. model

Answer 5

Increase/decrease in local density (B.I. = increase, D.E. = decrease)

• birth
• immigration
• deaths
• emigration

Question 6

3 types of dispersion:

Answer 6

1. clumped dispersion
2. uniform dispersion
3. random dispersion

Question 7

Clumped dispersion

Answer 7

Individuals aggregate in patches

-things that give rise to clumped dispersion are resource distribution/availability and behavior

Question 8

Uniform dispersion

Answer 8

Individuals are evenly distributed

-given rise by social interactions (territoriality)

Question 9

Random dispersion

Answer 9

The position of each individual is independent of other individuals
-given rise by absence of strong attractions or repulsions

Question 10

Demography

Answer 10

Study of population attributes and how they change over time

1. composition of the population (population structure)
2. rates that describe population change

Question 11

Population structure

Answer 11

• sex ratio = number of males:number of females
• age structure = percent of individuals in different age groups in the population
• age groups based on reproductive status (pre-reproductive, reproductive, post-reproductive)

Question 12

Population structure shapes

Answer 12

• urn-shaped: a few kids, many parents, even more seniors (non-growing or declining population)
• pyramid-shaped: lots of kids, some parents, fewer seniors (rapidly growing population)
• bell-shaped: some kids, more parents, few seniors (slow [non] growing population)

Question 13

Population rates

Answer 13

• birth rate = number of births/population size
• fecundity/fertility rate = number of offspring per unit time
• death rate = number of deaths/population size

Question 14

Generation time

Answer 14

Average amount of time between the birth of an individual and the birth of its offspring

Question 15

Survivorship

Answer 15

Tracks the changes in the number of individuals in a cohort over time

Question 16

Cohort

Answer 16

Group of individuals born at the same time

Question 17

3 types of survivorship curves

Answer 17

• type I = low death rates during early and middle life then an increase among older age groups (humans)
• type II = the death rate is constant over the organism’s life span (rodents)
• type III = high death rates for the young then a slower death rate for survivors (oysters)

Question 18

Rate of increase

Answer 18

• r = per capita birth rate - per capita death rate
• r = b - d
• exponential growth model: dN/dt = rN
• N = number of individuals in the population
• t = time

Question 19

Exponential growth

Answer 19

Rate of increase (r) determines speed at which population size increases

• when population grows, eventually something will give out (resources, disease, accidents/disasters)
• populations cannot exponentially grow forever

Question 20

2 controls on population size

Answer 20

1. density-independent controls

2. density-dependent controls

Question 21

Density-independent controls

Answer 21

Not sensitive to size of population

-i.e. disasters, etc.

Question 22

Density-dependent controls

Answer 22

Sensitive to density of population

• changes as size of population increases
• i.e. competition, disease, predation

Question 23

Logistic growth

Answer 23

Some populations will increase then level off
-point of population stabilization = carrying capacity (K)
-exponential growth + a “buffering” term that keeps the population at/near carrying capacity (K)
-change in a population over time (dN/dt) =
rN * (K-N)/K
-(K-N)/K describes density-dependent control