Population Ecology II

Question 1

What is carrying capacity (K)?

Answer 1

the maximum population size that a particular environment can sustain

Question 2

What are some varying factor for carrying capacity?

Answer 2

Energy, shelter, predation, nutrient availability, water, etc.

Question 3

What is the logistic growth model?

Answer 3

the per capita rate of increase declines as carrying capacity is reached

Question 4

What is the formula for the logistic growth model?

Answer 4

(dN/dt) = r(max) * N * [ (K-N)/K ]

Question 5

How to calculate the difference between growth of the logistical model and exponential model

Answer 5

[ (K-N)/K ]

Question 6

What is some assumptions about the logistic growth?

Answer 6

• Density-dependent factors affect population
• Populations adjust growth instantaneously and smoothly approach K
• Each individual added to the population has the same negative effect on its growth rate

Question 7

What is the Allee Effect?

Answer 7

At small population sizes, growth rate increases with increasing density

Question 8

What are some potential reasons as to why the Allee Effect occurs?

Answer 8

Problems finding mates at low densities
Species that form groups
* Foraging success
* Predation avoidance

Question 9

What is life history?

Answer 9

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

Question 10

What are three main variables from a life history?

Answer 10

• The age at which reproduction begins
• How often the organism reproduces
• How many offspring are produced per reproductive episode

Question 11

How does life history traits involve trade-offs?

Answer 11

Animals must allocate energy to one or the other, giving rise to a trade-off
High growth = advantages of body size
High reproduction = advantages of birth rate

Question 12

What is an example of trade offs and life histories?

Answer 12

The lower the brood size for a European kestrels increase the survivability of the family.

Question 13

What is the difference between semelparity and iteroparity?

Answer 13

Semelparity- big-bang reproduction, reproduce once and die
Iteroparity- produce offspring repeatedly
Highly variable or unpredictable environments favor semelparity, while dependable environments favor iteroparity.

Question 14

How does selection influence the trade-off between offspring number and size?

Answer 14

*Some plants produce a large number of small seeds, ensuring that at least some of them will grow and eventually reproduce
*Other plants produce a moderate number of large seeds that provide a large tore of energy that will help seedlings become established.

Question 15

What is K-selection?

Answer 15

density-dependent selection, selects for life history traits that are advantageous at high population densities
usually found at the top of the S curve of a logistic model.

Question 16

What is r-selection?

Answer 16

Density-independent selection, selects for life history traits that maximize reproduction in uncrowded environments
usually found at the bottom of the S curve

Question 17

What is the difference between density-independent and density-dependent populations?

Answer 17

In density-independent populations, birth rate and death rate do NOT change with population density
In density-dependent populations, birth rates fall and death rate rises with population density

Question 18

What are mechanisms of density-dependent population regulation?

Answer 18

Density dependent birth and death rates are an example of negative feedback that regulates population growth
*Competition for resources, territoriality, disease, intrinsic factors, toxic wastes

Question 19

What are some population dynamics?

Answer 19

The size of populations doesn’t always remain stable
The study of population dynamics focuses on the complex interactions between biotic and abiotic factors that cause variation in population size

Question 20

What are some factors that can affect population size over time?

Answer 20

weather and predator population (wolves and moose in the winter example)
Regular boom and bust cycles (lynx populations follow the 10 year boom-and-bust cycle of hare populations

Question 21

What are metapopulations?

Answer 21

groups of populations linked by immigration and emigration
When a population becomes crowded and resource competition increase, emigration often increases