Unit 3: Populations

Question 1

The five levels of nature

Answer 1

1. Organism/individual
2. Population
3. Community
4. Ecosystem
5. Biosphere

Question 2

Population ecology

Answer 2

The study of factors that cause populations to increase or decrease

Question 3

Basic characteristics of populations

Answer 3

○ Size
○ Density
○ Distribution
○ Sex ratio
○ Age structure

Question 4

Population size (n)

Answer 4

The total number of individuals within a defined area at a given time

Question 5

Population density

Answer 5

• The number of individuals per unit area at a given time
  ○ Helps scientists to determine if a species is rare or abundant

Question 6

Population distribution

Answer 6

• A description of how individuals are distributed with respect to one another
  ○ Distributions can be random, uniform, or clumped

Question 7

Population sex ratio

Answer 7

The ratio of males to females in a population

Question 8

Population age structure

Answer 8

A description of how many individuals fit into particular age categories in a population

Question 9

Density-dependent factor

Answer 9

A factor that influences an individual’s probability of survival and reproduction in a manner that depends on the size of the population

Question 10

Limiting resource

Answer 10

A resource that a population can’t live without and that occurs in quantities lower that the population would require to increase in size

Question 11

Carrying capacity (K)

Answer 11

The maximum population of a particular species that a given habitat can support over a given period

Question 12

Density-independent factors

Answer 12

A factor that has the same effect on the individual’s probability of survival and the amount of reproduction at any population size

Question 13

Population growth rate

Answer 13

The number of offspring an individual can produce in a given time period, minus the deaths of the individual or its offspring during the same period

Question 14

Instrinsic growth rate (r)

Answer 14

The maximum potential for growth of a population under ideal conditions with unlimited resources

Question 15

Exponential growth model

Answer 15

• A growth model that estimates a populations future size after a period of time based on the intrinsic growth rate and the number of reproducing individuals currently in the population, without considering limiting factors
  □ This model produces a J-shaped curve
  □ Exponential growth is a density-independent factor

Question 16

Logistic growth model

Answer 16

• A growth model that describes a population whose growth is initially exponential, but slows as the population approaches the carrying capacity of the environment
  □ This model produces a S-shaped curve
  □ Logistic growth is a density-dependent factor

Question 17

Overshoot

Answer 17

When a population becomes larger than the environment’s carrying capacity

Question 18

Die-off

Answer 18

A rapid decline in a population due to death

Question 19

K-selected species

Answer 19

• A species with a low intrinsic growth rate that causes the population to increase slowly until it reaches carrying capacity
  ○ Large mammals and most birds are K-selected species

Question 20

r-selected species

Answer 20

A species that has a high intrinsic growth rate, which often leads to population overshoots and die-offs
○ These species reproduce often and produce many offspring
○ Small organisms are r-selected species

Question 21

Survivorship curves

Answer 21

Graphs that represent the distinct patterns of species survival as a function of age

Question 22

Type I survivorship curve

Answer 22

A pattern of survival over time in which there is a high survival throughout most of the life span, but then individuals start to die in large numbers as they approach old age

Question 23

Type II survivorship curves

Answer 23

A pattern of survival over time in which there is a relatively constant decline in the survivorship throughout most of the life span

Question 24

Type III survivorship curve

Answer 24

A pattern of survival over time in which there is low survivorship early in life with few individuals reaching adulthood

Question 25

Metapopulations

Answer 25

• A group of spatially distinct populations that are connected by occasional movements of individuals between them
  ○ Metapopulations can provide protection to certain species from factors like diseases and can increase the size of smaller populations and introduce new genetic diversity

Question 26

Inbreeding depression

Answer 26

When individuals with similar genotypes - typically relatives - breed with each other and produce offspring that have an impaired ability to survive and reproduce

Question 27

Malthusian theory

Answer 27

• Claimed that human population is growing exponentially while food supply grows linearly (fixed amount)
  ○ Innovation and creativity will solve our problems -> Technological advances can/will increase our carrying capacity

Question 28

Factors that influence human population

Answer 28

• Population size
• Birth/death rates
• Fertility
• Life expectancy
• Migration

Question 29

Crude birth rate

Answer 29

births per 1,000 individuals/year

Question 30

Crude death rate

Answer 30

deaths per 1,000 individuals/year

Question 31

Global population growth rate

Answer 31

(CBR - CDR)/10

Question 32

National growth rate

Answer 32

[(CBR + immigration) - (CDR + emigration)]/10

Question 33

Doubling time

Answer 33

• When a population grows exponentially and the number of years it takes for it to double
  ○ 70 / % growth rate

Question 34

Rule of 70

Answer 34

• n = 70/R
  ○ R = growth rate

Question 35

Total fertility rate (TFR)

Answer 35

Average number of children each woman will have

Question 36

Replacement fertility rate

Answer 36

• The total fertility rate for a nation that would keep its population stable
  ○ For most nations, this number is 2.1%
  □ Greater number = increase ; lesser number = decrease

Question 37

Population growth characterisitics of developing countries

Answer 37

○ Higher fertility, infant mortality, and death rates
○ Lower life expectancy
○ Low per capita resource use

Question 38

Population growth characteristics of developed countries

Answer 38

○ Lower fertility, infant mortality, and death rates
○ Higher life expectancy
○ High per capita resource use

Question 39

Factors affecting life expectancy, infant mortality and child mortality

Answer 39

• Available health care/prenatal care
• Adequate food supply
• Portable drinking water
• Good sanitation
• Moderate to low levels of pollution

Question 40

Factors affecting life spans (gender)

Answer 40

• Gender-specific diseases
• Hazardous lifestyle choices
• Wars
• Dangerous jobs

Question 41

Theory of demographic transition

Answer 41

The theory that as a country moves from a subsistence economy to industrialization and increased affluence, it undergoes a predictable shift in population growth

Question 42

Stage 1 of demographic transition

Answer 42

○ CBR = CDR
○ Short life expectancy, high infant mortality
○ US/Europe = before 18th century
○ No countries in stage 1 now

Question 43

Stage 2 of demographic transition

Answer 43

○ Death rates decline
○ Fertility rates remain high -> imbalance
○ US = early 19th century ; India = now

Question 44

Stage 3 of demographic transition

Answer 44

○ # of births decline -> more birth control available
○ CBR = CDR again
○ Economy/education improves

Question 45

Stage 4 of demographic transition

Answer 45

○ CBR < CDR
○ High affluence/economic development
○ More elderly
○ Government may encourage immigration or gives incentives to have more children

Question 46

Three stages of age structure

Answer 46

○ Pre-reproductive
○ Reproductive
○ Post-reproductive