Population Ecology

Question 1

What are the 6 words for the definition of ecology as of now?

Answer 1

Relationships, species, interactions, environment, distribution, abundance

Question 2

How is the space a population is limited to defined as?

Answer 2

The person conducting the study determines the geographical area or habitat type a population is limited to

Question 3

What are the 4 limiting factors that determine where a population is and how abundant it is?

Answer 3

Abiotic tolerances, resource supplies, predation, mortality factors

Question 4

What does density show about a population? Why doesn’t high density necessarily mean that is the best habitat for that species?

Answer 4

Reflects the carrying capacity, species are more common where there are more resources. Organisms could be migrating or moving around a lot, so where they are may not necessarily be the best habitat.

Question 5

How does density change as organism size changes? Why is that relationship there?

Answer 5

Density decreases as organism size increases. Bigger things need more resources, so the environment can support less of them

Question 6

What is distribution?

Answer 6

The geographical range of the organism, where they could be

Question 7

What determines the distribution of an organism?

Answer 7

The presence or absence of suitable habitat, if it contains the range of ecological conditions needed for survival

Question 8

How do generalists and specialists differ in geographic range, habitat tolerance, and local population size?

Answer 8

Generalists have a large geographic range, can tolerate a broad range of habitats, and a large local population size. Specialists have a restricted geographic range, a narrow range of habitat tolerance, a small local population size

Question 9

Which 5 factors determine density and distribution?

Answer 9

Climate, tolerance, predators, resources, habitat availability

Question 10

What causes a random distribution?

Answer 10

When the position of a species is not influenced by other species. Is determined by probability, not a biological process

Question 11

What causes a uniform distribution?

Answer 11

Competition for resources and direct interactions establishes a minimum distance between neighbours

Question 12

What causes a clumped distribution?

Answer 12

Individuals form groups due to clumped resources or social behaviour

Question 13

What are relative counts?

Answer 13

Hints used to estimate the population size: pellets counts, catch per unit effort, frog calling codes

Question 14

What are 5 reasons for potential bias when counting a population?

Answer 14

Time of day, stratification, detectability, misidentification, miscounting

Question 15

What is the removal sampling method?

Answer 15

A sample of the population is taken and removed, then new samples are taken and they get smaller each time one is removed

Question 16

What are the assumptions about the removal sampling method?

Answer 16

Same proportion is removed every time, every individual has an equal chance of being caught, population is closed during sampling, sampling does not affect the catchability of others

Question 17

What is the mark re-capture method?

Answer 17

An initial sample is taken, marked, and released back into the population. A second sample is taken and uses N=MC/R to determine population size (total marked x size of second sample/ number of recaptures)

Question 18

Using mark re-capture, how could the population size be overestimated or underestimated?

Answer 18

Can be overestimated by having immigration into the population after marked individuals are released. Can be underestimated if individuals that were already captured like being captured

Question 19

What is dispersal?

Answer 19

Movement of an organism away from birthplace/ high density areas

Question 20

How do organisms disperse?

Answer 20

Passive by gravity, wind, water and hitching a ride on animals. Active by using animals and by active movement

Question 21

What would be the advantages and disadvantages to staying in the natal population?

Answer 21

Advantages: safety in numbers, avoid unknown conditions, know what works, familiar landscape, avoid dying while dispersing. Disadvantages: environmental variability, competition for resources, inbreeding, lower reproductive potential

Question 22

Which organisms are more likely to disperse and which ones are more likely to go farther away?

Answer 22

Juveniles and carnivores usually leave. Bigger organisms go farther

Question 23

What is a metapopulation?

Answer 23

A group of subpopulations that all live on separate patches that are connected by immigration and emigration among the patches.

Question 24

What 4 conditions must be present for a population to be a metapopulation?

Answer 24

Suitable habitat occurs in discrete patches, all populations have a risk of extinction, patches aren’t too isolated, dynamics of each subpopulation aren’t synchronized

Question 25

What is migration? Why do organisms migrate?

Answer 25

Non-permanent dispersal. Round-trip movement of species. Migrate for climate, food, and/or reproduction

Question 26

How does age structure and age classes affect population. growth?

Answer 26

Reproduction only occurs in certain age classes, and mortality rates change with age.

Question 27

Why would sex ratios not be 1:1?

Answer 27

Differential survival rates of the sexes, energy cost to produce certain sexes, sex based dispersal, environmental sex determination

Question 28

What is the difference between type 1, type 2, and type 3 survivorship curves?

Answer 28

Type 1 has high juvenile survivorship, high mortality at senescence (most mammals). Type 2 has constant mortality rates throughout life (most birds)
Type 3 has low juvenile survivorship (insects, fish, amphibians)

Question 29

What kinds of species will typically show geometric growth instead of exponential?

Answer 29

Species with discrete breeding periods

Question 30

What is the carrying capacity (K)?

Answer 30

The maximum number of individuals the environment can support

Question 31

How is logistic population growth different from exponential population growth?

Answer 31

Logistic levels off at K, exponential will keep growing as long as resources aren’t limited

Question 32

At what point in logistic population growth is the growth rate the highest?

Answer 32

K/2

Question 33

How can changes in birth and death rates lead to logistic growth?

Answer 33

If either one or both doesn’t stay constant, will have logistic growth and populations will grow to K

Question 34

What is an Allee effect?

Answer 34

Inverse density dependence which causes small populations to decline

Question 35

What causes an Allee effect?

Answer 35

Mates are hard to find, group dynamics, genetic fitness