Ch. 11 Population Dynamics Flashcards Preview

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Flashcards in Ch. 11 Population Dynamics Deck (57)
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1

Eutrophication

Excessive richness of nutrients in a lake or other body of water

2

Populations can change in size as a result of four processes:

Birth, death, immigration, and emigration

3

Population dynamics

The ways in which populations change in abundance over time

4

Populations exhibit a wide range of growth patterns, including..

- exponential growth
- logistic growth
- fluctuations
- regular cycles

5

Exponential growth usually happens when..

- when conditions are favorable
- when a species reaches a new geographic area

6

Logistic curve

- some populations reach a stable size that changes little over time
- fluctuate by a small amount around what appears to be carrying capacity

7

Logistic equation

K

- assumed to be constant
- the population size for which birth and death rates are equal

8

Logistic growth example

- when sheep were first introduced to Tasmania, the population increased rapidly
- later, population numbers fluctuated above and below a maximum sustainable population size

9

Birth and death rates vary over time, thus we expect..

Carrying capacity to fluctuate

10

Carrying capacity

An equilibrium with their environmental resources

11

Logistic growth

Near exponential growth when..

Resources are unlimited

12

Environmental resistance

Growth slows as species approaches carrying capacity of environment

13

___ factors reduce population growth rates.

Density-dependent

14

Density-dependent factor examples

- predation
- food abundance
- parasite load
- intraspecific competition

15

Population fluctuation

Rise and fall in population size over time

16

Population outbreak (bloom)

Populations may explode, causing a bloom

17

Population cycles

Some populations have alternating periods of high and low abundance at regular interval

18

Internal factors that may drive population cycles in rodents:

Hormonal or behavioral changes in response to crowding

19

External factors that may drive population cycles in rodents:

Weather, food supplies, or predators

20

Example of top-down regulation in lemmings

Used field observations and mathematical models to argue that their 4-year cycle is driven by predators

21

Example of bottom-up regulation in lemmings

In other studies, predator removal had no effect on population cycles

These cycles were driven by food supply

22

Effects of population density often have a ___ or delay.

Lag time

23

What may this lag be due to?

Need time to reproduce

24

Delayed density dependence

- delays in effect that density has on population size

25

Example of delayed density dependence

When a predator reproduces more slowly than its prey

26

__ can cause fluctuations in population size.

Time lags

27

Stable limit cycle

Pattern when the population fluctuates indefinitely about the carrying capacity

28

Many factors can drive populations to extinction:

- predictable factors
- fluctuation in population growth rate and population size
- chance events

29

If you fluctuate to zero ->

Extinction

30

Fluctuations increase risk of ___.

Extinction