Population Ecology I - Distribution and Abundance

Question 1

Population

Answer 1

individuals of the same species that co-occur in space and time

Question 2

Characteristics of Populations:

Answer 2

• density: number of individuals
• distribution: size, shape and location of area occupied

Question 3

absolute density

Answer 3

the number of individuals of a population per unit area

Question 4

ecological density

Answer 4

the number of individuals of a population per unit SUITABLE HABITAT

Question 5

What is a metapopulation

Answer 5

a group of subpopulations living on such patches by exchanges of individuals make up the metapopulation

Question 6

essentials of metapopulations

Answer 6

1. are a population of subpopulations
2. subpopulations are connected by movement of individuals from one subpopulation to another
3. any subpopulation can go extinct and be re-colonized repeatedly over time
4. the risk of subpopulation extinction is generally greatest for small subpopulations
5. density-dependent and density-independent population dynamics occur within each populaiton

Question 7

Distribution

Answer 7

the geographic distribution of a species is limited by the physical environment (incl. both abiotic and biotic conditions) and species niche requirements

Question 8

What influences population distribution and abundance?

Answer 8

• habitat suitability
• historical factors
• dispersal limitation

Question 9

Dispersal

Answer 9

the permanent movement of individuals (or propagules), usually from population to another

Question 10

Why disperse?

Answer 10

to avoid inbreeding
- natal dispersal: juveniles undergo permanant dispersal to another location

Question 11

Seed Dispersal Modes

Answer 11

• gravity (short)
• explosive (short)
• by wind (short-to-long)
• water (short-to-long)
• animals (via ingestation and defecation, short-to-long distance)

Question 12

Two major categories of dispersal

Answer 12

1. immigration: movement into a local population
2. emigration: movement out of a local population

Question 13

Drivers of Numerical Responses

Answer 13

1. reproduction: lag time needed for predators to produce offspring
2. dispersal: no lag time as species are highly mobile and can track prey across the landscape

Question 14

Random distribution

Answer 14

• individuals have an equal chance of living anywhere within an area
• results from neutral interactions among individuals of a species, random disturbances, uniform disturbances of resources

Question 15

Regular Distribution

Answer 15

• individuals are uniformly spaced
• results from antagonistic interactions among individuals of the same species, uniform distribution of resources, uniform depletion of resources

Question 16

Clumped distribution

Answer 16

• individuals have a higher probability of being in some areas versus others
• results from mutual interactions, patchy resources, dispersal limitations

Question 17

Large Scale Distributions

Answer 17

how populations are distributed over scales in which there is significant environmental variation

Question 18

On larger scales, what kind of dispersion pattern do many animal and plant species show?

Answer 18

clumped

Question 19

Broader niche usually indicates?

Answer 19

a wider species large-scale distribution

Question 20

Why aren’t all species in all the places?

Answer 20

• principle of allocation
• takes extra energy to survive and reproduce in regions on the edge of their niche
• surviving at the edge of tolerance is not efficient

Question 21

Example of Range expansion in Invasive Species

Answer 21

Africanized bee -hybrid between european bees and african honeybee
- stopped spreading in 2009
- too cold both north and south of their range

Question 23

relationship between organism size and population density

Answer 23

population density declines as organism size increases

Question 24

why does does the relationship between organism size and population density occur?

Answer 24

• body scaling
• metabolic demand vs. resource availability

Question 25

size spectrum and plants

Answer 25

for a given species, density decreases with increasing biomass (age) in a process called self-thinning

Question 26

what influences how common or rare a species is?

Answer 26

- geographic range of species - habitat tolerance - local population size