Topic 10: Population Growth and Regulation

Question 1

what is meant by r when calculating birth and death rates?

Answer 1

birth rate - death rate = r or the instantaneous rate of growth.

Question 2

Define the exponential growth model and what are the assumptions for the exponential growth model?

Answer 2

the rate of population growth is directly proportional to population size and the intrinsic growth rate r.

assumptions of model:
1. that there is unlimited resources.
2. that the environment is constant and stable (no seasonality or variation or change of any kind).

Question 3

What does it mean if:

r = 0
r > 0
r < 0

Answer 3

1. birth rate = death rate
2. birth rate is greater than death rate
3. birth rate is less than death rate

Question 4

How is the r-value influenced?

Answer 4

r-value is influenced by life history, such as the frequency of reproduction, number of individuals born and environmental conditions.

Question 5

What type of organisms does the exponential growth model work best for?

Answer 5

works best for r-type organisms.

Question 6

What happens when the population grows?

Answer 6

as the population grows interactions between individuals causes an increase in mortality and a decrease in birth rate.

Question 7

What is (1- N/K)?

Answer 7

(1- N/K) is a correction factor added to the exponential growth model.

Question 8

What happens to (1- N/K) as the population increases in size?

Answer 8

as population increases in size and comes closer to carrying capacity the effect of the correction factor becomes stronger.

Question 9

What is the assumption of the logistic growth model? What does it NOT assume?

Answer 9

1) constant/ stable environmental conditions.

does not assume infinite resources.

Question 10

What kind of species does the logistic growth model work well with?

Answer 10

k-type species

Question 11

What is meant by density independent factors?

Answer 11

typically includes changing environmental conditions beyond the optimal or even tolerance level for a species.

Question 12

What does a life table do?

Answer 12

a life table quantifies mortality and survivability in different age classes within a population.

Question 13

What assumptions do the life tables make?

Answer 13

1) the cohort will be representative of the larger population.

2) the environment is stable.

Question 14

Define the variable: age class (years)

Answer 14

a given time interval after birth of the individuals (x).

Question 15

Define the variable: cohort

Answer 15

a group of individuals born at the same time (n)

Question 16

Define the variable: survivorship

Answer 16

the probability at birth of an individual surviving to any age (Ix)

Question 17

Define the variable: age specific mortality

Answer 17

number of individuals from the cohort who have died during a time interval (dx).

Question 18

Define the variable: mortality rate

Answer 18

the probability of death at any given age (qx)

Question 19

There are 3 idealized types of survivorship curves. Name them and give an example of a species that follow that curve.

Answer 19

a) type 1 - very high initial survivability, very low initial mortality, indicative of k-type species. ex- reindeer, moose, elephant.

b) type 2 - no trend. survivorship and mortality is consistent over lifetime. ex- birds.

c) type 3 - very low initial survivability, very high initial mortality, indicative of r-type species. ex- insects, mice.

Question 20

The estimation of birth rate involves 2 important factors. What are these factors?

Answer 20

a) in a sexually reproducing population, only females give birth

b) the birth rate w/n the female population will vary with age (some immature and others past age of fertility)

Question 21

How do you determine net reproductive rate (R0)?

Answer 21

with birth rate (Bx) and survivorship (Ix).

Question 22

When does competition occur?

Answer 22

competition occurs when individuals use a common resource that is in short supply relative to the numbers seeking to use it.

Question 23

What is intraspecific VS interspecific competition?

Answer 23

intra - competition w/n the same species.

inter - competition b/w two species.

Question 24

Intraspecific competition can be categorized into 4 categories; what are they?

Answer 24

a) scrambled competition: all individuals suffer a depression of growth and reproduction. (happens in herds)

b) contest competition: only some individuals suffer a depression of growth and reproduction.

c) exploitation: the presence of individuals leads to reduced availability of a resources with NO CONTACT.

d) interference: individuals interact DIRECTLY with each other preventing others from occupying a habitat or accessing resources within it.