Ch. 10 Population Growth & Regulation

Question 1

Life tables contain..

Answer 1

Information about births and deaths that is essential to predict trends or future population size

Question 2

___ show how survival and reproductive rates vary with age, size, or life cycle stage.

Answer 2

Life tables

Question 3

Age-specific survival rate (Sx)

Answer 3

Chance that an individual of age x will survive to age x+1

Question 4

Survivorship (Ix)

Answer 4

Proportion of individuals that survive from birth to age x

Question 5

Fecundity (Fx)

Answer 5

Average number of offspring produced by a female while she is of age x

Question 6

Cohort

Answer 6

Individuals born at the same time

Question 7

• Cohort life table

Answer 7

• follows fate of a group of individuals all born at the same time
• mostly used for non-mobile organisms

Question 8

• Static life table

Answer 8

• survival and reproduction of individuals of different ages during a single time period are recorded
• requires estimating the age of individuals
• easier for mobile or long-lived organisms

Question 9

• Survivorship curves

Answer 9

Plot of number of individuals from a hypothetical cohort that will survive to reach certain ages

Question 10

• Survivorship curve

Type I

Answer 10

Most individuals survive to old age

Ex: most Dall mountain sheep survive to old age
Ex: U.S. Females

Question 11

• Survivorship curve

Type II

Answer 11

Chance of surviving remains constant throughout life

Ex: song thrushes have about the same chance of survival at any age

Question 12

• Survivorship curve

Type III

Answer 12

Individuals die at high rates when young, those that reach adulthood survive well

Ex: oysters
Ex: species that produce large numbers of offspring
Ex: out of a million Cleome seeds, only 39 survive to produce 1-year-old plants

Question 13

Survivorship curves can vary…

Answer 13

• among populations of a species
• between males and females
• among cohorts that experience different environmental conditions

Question 14

• Age structure

Answer 14

• proportion of population in each age class

- influences whether a population will increase or decrease in size, and how fast the population will grow

Question 15

• Rapid growth

Answer 15

Younger age groups are larger

Ex: Guatemala, Nigeria, Saudi Arabia

Question 16

• Zero growth

Answer 16

Relatively similar-sized age groups

Ex: Spain, Austria, Greece

Question 17

• Negative growth

Answer 17

Older age groups are larger

Ex: Germany, Bulgaria, Italy

Question 18

Which population can sustain social security longer?

Answer 18

Rapid growth

- more younger people to pay taxes for older people’s social security

Question 19

To predict population size for following year, two things must be calculated:

Answer 19

• survival

- fecundity

Question 20

Growth rate (lambda)

Answer 20

Ratio of population size in year t+1 to population size in year t

Lambda > 1, population grows
Lambda < 1, population declines
Lambda = 1, population is stable

Question 21

Stable age distribution

Answer 21

If age structure does not change from one year to the next

Question 22

Continuous growth

Answer 22

When individuals leave an average of more than one offspring over substantial periods of time

Question 23

Geometric growth

Answer 23

• population reproduces in synchrony at regular time intervals, and growth rate remains the same
• population increases by a constant proportion
• visualize geometric growth as a set of discrete points

Question 24

Translation

Answer 24

The population size at the next period

Predicted to be simply the current population size * the geometric growth rate

Question 25

Exponential growth

Answer 25

- reproduces continuously -> generations overlap | - continuous, a line

Question 26

Exponential growth r =

Answer 26

Exponential population growth rate or intrinsic rate of increase

Question 27

Exponential growth Closed population

Answer 27

b-d (instantaneous birth rate - instantaneous death rate)

Question 28

Exponential growth Open population

Answer 28

(b + immigration) - (b + emigration)

Question 29

Doubling time

Answer 29

Number of years it will take the population to double in size

Question 30

Net reproductive rate

Answer 30

Mean number of offspring produced by an "average" individual during its lifetime

Question 31

Growth rate may change independently of ___ or as a function of ___.

Answer 31

Density

Question 32

* Density-independent factors

Answer 32

- factors such as temperature and precipitation, and catastrophes such as floods or hurricanes - such factors affect density, but the effects are not related to density - birth & death rates are not affected Ex: the insect population size fluctuations are correlated with temperature and rainfall

Question 33

* Density-dependent factors

Answer 33

- cause birth & death rates, and dispersal rates to change as population density changes Ex: when sending a bunch of horses from US to Germany, the horse population density increased, one horse could have gotten infected with a disease, they disease would spread quickly, and all the horses would have mostly been dead by the time they got to Germany. Ex: in song sparrows, number of eggs laid per female decreased with density, as did number of young that survived

Question 34

Density-dependent factors As densities increase...

Answer 34

- birth rates often decrease - death rates increase - dispersal from the population increases - all tend to decrease population size

Question 35

Population regulation

Answer 35

Occurs when density-dependent factors cause population to - increase when density is low - decrease when density is high - can maintain population at relatively stable size in stable environment Density-independent factors can have large effects on population size as well, but they do not regulate population size

Question 36

Logistic growth

Answer 36

- Population increases rapidly at first - then stabilizes at carrying capacity (K) - growth rate decreases as population size nears carrying capacity

Question 37

Carrying capacity (K)

Answer 37

Maximum population size that can theoretically be supported indefinitely by environment

Question 38

At carrying capacity, growth rate is ___.

Answer 38

Zero

Question 39

How does logistic differ from exponential and geometric growth?

Answer 39

- In exponential growth, r is assumed to be constant - in logistic growth, we assume that r declines as density increases - initially, logistic growth is similar to exponential growth - eventually, a population that grows logistically levels off at the carrying capacity

Question 40

N

Answer 40

Population density

Question 41

r

Answer 41

Per capita growth rate

Question 42

K

Answer 42

Carrying capacity

Question 43

1 - N/K

Answer 43

Discounts growth as N approaches K

Question 44

Logistic growth When N is small, As density increases, As density approaches K,

Answer 44

- A population with logistic growth increases at a rate close to r - growth rate decreases - growth approaches zero

Question 45

* Logistic growth curve

Answer 45

- slope of curve at any point = rate of population growth at that time - inclination point has max growth rate -> max sustainable yield - management goal to maintain population close to K/2

Question 46

* Ecological footprint

Answer 46

- total area required to support a human population | - humans are different because of our technologies that can alter K (agriculture, medicine, energy utilization)

Question 47

Ecological footprint approach

Answer 47

Carrying capacity depends on amount of resources used by each person

Question 48

___ is the environmental impact of a population.

Answer 48

Ecological footprint