Chapter 53: Population Ecology

Question 1

What is a population?

Answer 1

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

Question 2

What 4 factors influence population?

Answer 2

Density
Dispersion
Structure
Growth Rate

Question 3

What is density?

Answer 3

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

Question 4

What is dispersion?

Answer 4

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

Question 5

______ and ______ affect population size.

Answer 5

Births; deaths

Question 6

What are the 3 types of dispersion?

Answer 6

1. Clumped dispersion
2. Uniform dispersion
3. Random dispersion

Question 7

What is clumped dispersion?

Answer 7

When organisms aggregate (group) in patches

• this is due to resource availability and behavior

Question 8

What is uniform dispersion?

Answer 8

When organisms are evenly distributed

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

Question 9

What is random dispersion?

Answer 9

When the position of each organism is independent of other organisms

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

Question 10

What is demography?

Answer 10

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

Question 11

What factors affect demography?

Answer 11

1. Population size
2. Density and Distribution
3. Age Structure, Sex Ratio
4. Birth, Death, Immigration and Emigration

Question 12

What is age structure?

Answer 12

The relative number of individuals at each age

Question 13

What is immigration?

Answer 13

The influx of new individuals from other areas

Question 14

What is emigration?

Answer 14

The movement of individuals out of a population

Question 15

What is a life table?

Answer 15

An age specific summary of the survival pattern of a population

Question 16

What is the best way to construct a life table?

Answer 16

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

Question 17

What is a Type I species?

Answer 17

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

Question 18

What is a Type II species?

Answer 18

Species that have an equal probability of dying at any age

E.g., mammals and birds

Question 19

What is a Type III species?

Answer 19

Species that invest little energy raising their young
- high death rages among offspring

E.g., fish, invertebrates, plants

Question 20

What are the 3 types of population growth models?

Answer 20

1. Constant Growth
2. Exponential Growth
3. Logistic Growth

Question 21

What is constant growth?

Answer 21

When the population continues to grow constantly

Question 22

What is exponential growth?

Answer 22

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

Question 23

What is the intrinsic rate of increase (r)?

Answer 23

The rate at which the population increases

Question 24

What is per capita rate of increase?

Answer 24

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

Question 25

What is expected of exponential growth?

Answer 25

It cannot continue on forever. It has a 'Carrying Capacity' (K) (limit). Either: - the population will crash - slower population growth

Question 26

What is the J-shaped curve?

Answer 26

An exponentially growing population that is rebounding after being reduced.

Question 27

What is logistic growth?

Answer 27

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 ```

Question 28

What are density-dependent factors?

Answer 28

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.

Question 29

What are density-independent factors?

Answer 29

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.

Question 30

The effects of density-dependent factors _________ as the population density ______.

Answer 30

Increases; rises

Question 33

What is life history?

Answer 33

The events of an organism from conception to death. - it's main focus is the adaptations that influence reproductive success

Question 34

How many humans can the earth support? | What is the carrying capacity of humans?

Answer 34

Average estimate is 10-15 billion

Question 35

What is the ecological footprint?

Answer 35

The aggregate (total) land and water area needed to sustain the people of a nation - how to measure our carrying capacity

Question 36

Which growth model explains human population growth?

Answer 36

Exponential | - slowly increased in 1650 No longer growing exponentially, but still increasing

Question 37

Life histories fall into two patterns shaped by natural selection. a) Opportunistic species (r-selected) b) Equilibrium species (K-selected) Explain the differences between these two.

Answer 37

a) These organisms are short-lived, reproduce at an early age and have many offspring and provide little care. - e.g., insects b) These organisms are long-lived, reproduce later in life and provide extensive parental care. - e.g., birds, large mammals