Lecture 14

Question 1

What does it mean when we say populations have structure

Answer 1

Population structure refers to how individuals in a population differ in age, stage, and sex, which influences per capita rates (birth, death, emigration, immigration)

Question 2

How does age influence population dynamics

Answer 2

Different age groups can have different per capita rates of birth (b), death (d), emigration (e), and immigration (i).

Question 3

What is an example of a stage-structured population?

Answer 3

Insects with life stages (egg, larva, pupa, juvenile, adult) where each stage has different survival and reproduction rates

Question 4

Why is stage structure important in population studies?

Answer 4

Individuals in different stages of life (e.g., juvenile vs. adult) can have different vital rates, affecting overall population growth and survival.

Question 5

How does sex impact population structure?

Answer 5

Males and females may have different per capita rates; for example, females may experience higher mortality due to the energy costs of reproduction.

Question 6

What might be the implications of structure on the population?

Answer 6

Impacts N and dN/dt

Question 7

What do we need to know to determine the effect of the structure on the population?

Answer 7

What the structure represent and how it impacts vital rates

Question 8

Demography

Answer 8

The branch of population biology
dealing with population projections for age- structured populations

Question 9

Two factors are important when examining age structured populations

Answer 9

1. survivorship vs. age
2. reproduction vs. age

Question 10

How is survivorship represented?

Answer 10

l(x), l is life table, x is specific cohort

Question 11

Survivorship

Answer 11

the pattern of survival for individuals in a population as a function of age

Question 12

What is a cohort table?

Answer 12

A cohort table (dynamic life table) tracks a group of individuals (a cohort) from birth to death, recording survival and reproduction rates

Question 13

What is a static life table?

Answer 13

A static life table is a snapshot of a population at one point in time, assuming a constant age distribution

Question 14

How does a cohort table differ from a static life table?

Answer 14

A cohort table follows the same group of individuals over time, while a static life table records data from all individuals at a single time point

Question 15

Why do both cohort and static life tables give similar results?

Answer 15

If population age distribution is stable, both methods will estimate similar survival and reproduction rates, so we often refer to both as cohort tables

Question 16

What assumption does a static life table make?

Answer 16

It assumes that survival and reproductive rates remain constant over time

Question 17

Type I surviorship

Answer 17

Juvenile survival is high and most mortality occurs among older individuals

Question 18

Type II survivorship

Answer 18

Die at equal rates regardless of age

Question 19

Type III survivorship

Answer 19

Die at high rate as juvelniles and then at much lower later in life

Question 20

Which population has Type I survivorship?

Answer 20

K selected, producing few costly offspring and providing lots of parental care

Question 21

Which population has Type II survivorship?

Answer 21

Population that has constant vulnerability to diseases and predators

Question 22

Which population has Type III survivorship?

Answer 22

Typical of r, lots of offspring, don’t look after them

Question 23

Fecundity schedule

Answer 23

the average number of
offspring produced for each age per female

Question 24

Semelparity

Answer 24

organisms have a single
reproductive event

Question 25

Iteroparity

Answer 25

organisms reproduce more than once in a lifetime

Question 26

How is fecundity (reproduction) mentioned?

Answer 26

m(x)

Question 27

What do life tables help determine in an age-structured population?

Answer 27

They help determine the growth rate by considering survivorship and fecundity for each age group

Question 28

What two key factors are combined in a life table?

Answer 28

Survivorship (probability of surviving to a certain age) and fecundity (number of offspring produced per female at each age)

Question 29

What is the net reproductive rate (R₀)?

Answer 29

R₀ is the average number of offspring produced per female over her lifetime, calculated using a life table

Question 30

Why do life tables usually only track females in species with two sexes?

Answer 30

Because females directly determine population growth by producing offspring

Question 31

How can life tables be used in population ecology?

Answer 31

They help estimate whether a population is growing (R₀ > 1), stable (R₀ = 1), or declining (R₀ < 1)

Question 32

What is a stable age distribution?

Answer 32

A population state where the proportion of individuals in each age class remains constant over time

Question 33

What condition must be met for a population to reach a stable age distribution?

Answer 33

The life table values (survivorship and fecundity) must remain fixed over time

Question 34

Does a stable age distribution mean population size is constant?

Answer 34

No, the population can still grow or decline, but the relative proportions of age classes stay the same

Question 35

Why is stable age distribution important in population ecology?

Answer 35

It allows for accurate population growth predictions and helps in conservation and management efforts

Question 36

Why might stage be more important than age in population models?

Answer 36

Because individuals in different stages (e.g., juvenile, adult) often have more similar vital rates than individuals of the same age

Question 37

In which type of organisms is stage structure more relevant than age structure?

Answer 37

Organisms where only one stage reproduces, like insects (e.g., only adults reproduce)

Question 38

How are stage-structured populations often visualized?

Answer 38

Using life cycle diagrams, which show transitions between different life stages (e.g., Loggerhead Sea Turtles)

Question 39

What is a stable stage distribution?

Answer 39

When the proportion of individuals in each stage remains constant over time, assuming life table values are fixed

Question 40

Why are stage-structured models important for conservation?

Answer 40

They help identify which life stage has the biggest impact on population growth and should be prioritized for conservation efforts

Question 41

What is the difference between stable age distribution and stable age structure/abundance?

Answer 41

-Stable age distribution → Proportion of age classes is constant over time. - Stable age structure/abundance → The population has reached a steady abundance with similar proportions of different age classes.