Flashcards in Chapter 53: Population Ecology Deck (35)

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1

## What is a population?

### A group of individuals of the same species that occupy the same general area

2

## What 4 factors influence population?

###
Density

Dispersion

Structure

Growth Rate

3

## What is density?

###
The number of individuals per unit area or volume

- density is the result of an interplay between processes that add individuals to a population and those that remove individuals

4

## What is dispersion?

### The pattern of spacing among individuals within the boundaries of the population

5

## ______ and ______ affect population size.

### Births; deaths

6

## What are the 3 types of dispersion?

###
1. Clumped dispersion

2. Uniform dispersion

3. Random dispersion

7

## What is clumped dispersion?

###
When organisms aggregate (group) in patches

- this is due to resource availability and behavior

8

## What is uniform dispersion?

###
When organisms are evenly distributed

- this is due to social interactions such as territoriality (claiming territory)

9

## What is random dispersion?

###
When the position of each organism is independent of other organisms

- this is due to the absence of strong attractions or repulsions

10

## What is demography?

### The study of vital statistics of a population and how they change over time

11

## What factors affect demography?

###
1. Population size

2. Density and Distribution

3. Age Structure, Sex Ratio

4. Birth, Death, Immigration and Emigration

12

## What is age structure?

### The relative number of individuals at each age

13

## What is immigration?

### The influx of new individuals from other areas

14

## What is emigration?

### The movement of individuals out of a population

15

## What is a life table?

### An age specific summary of the survival pattern of a population

16

## What is the best way to construct a life table?

### Follow the fate of a cohort, a group of individuals of the same age.

17

## What is a Type I species?

###
Species that invest a lot of energy into caring for their young

- have low death rates early in life

E.g., humans and large vertebrates

18

## What is a Type II species?

###
Species that have an equal probability of dying at any age

E.g., mammals and birds

19

## What is a Type III species?

###
Species that invest little energy raising their young

- high death rages among offspring

E.g., fish, invertebrates, plants

20

## What are the 3 types of population growth models?

###
1. Constant Growth

2. Exponential Growth

3. Logistic Growth

21

## What is constant growth?

### When the population continues to grow constantly

22

## What is exponential growth?

###
The increase of a population in an ideal, unlimited environment.

Equation:

^N/^t = rN

^N = change in population size

^t = change in time

If r>0 = increasing population

If r<0 = decreasing population

N = current population size

23

## What is the intrinsic rate of increase (r)?

### The rate at which the population increases

24

## What is per capita rate of increase?

###
A population's growth rate, which equals the birth rate minus the death rate.

^N/^t = B - D

^N = change in population size

^t = change in time

25

## What is expected of exponential growth?

###
It cannot continue on forever.

It has a 'Carrying Capacity' (K) (limit).

Either:

- the population will crash

- slower population growth

26

## What is the J-shaped curve?

### An exponentially growing population that is rebounding after being reduced.

27

## What is logistic growth?

###
A population's change over time in response to feedback from the environment or its own population density. (S curve!)

Equation:

dN/dt = rN (K-N)/K

dN = rate of change in population size

dt = rate of change in time

If r>0 = increasing population

If r<0 = decreasing population

N = current population size

K = carrying capacity

28

## What are density-dependent factors?

###
Factors that cause a change in the population size that are related to the population density.

E.g., if you have a small density of 20 birds in a large forest, their population will continue to increase because they have plenty of resources. However, if you have a large density of 6,000 birds in a smaller forest, the birds will compete for their resources and the population may start to decline.

29

## What are density-independent factors?

###
Factors that cause a change in the population size that are unrelated to the population density.

E.g., if you have a population of 20 deer, or 50 deer, or 100 deer, and there's a fire, it doesn't matter how many deer you started with, what matters is that the population got affected regardless of how many there were.

30