Population Dynamics

Question 1

Explain Density vs Dispersion.

Answer 1

Density: volume of individuals per area.
Dispersion: how the individuals are spread out

Question 2

Name the two methods of measuring population density. Define both.

Answer 2

Census: a complete count of all individuals
Population sampling: small subsets are counted, data is extrapolated to entire population

Question 3

What are the two population sampling methods for organisms that stay in ONE PLACE?

Answer 3

Quadrant method (series of stationary fixed frames) and transect method (frames moving along a line or path).

Question 4

What is the equation for determining population density?

Answer 4

Total # organisms / total area.

Question 5

Explain how to give the popular estimate of a population of MOBILE organisms.

Answer 5

Take two random samples (making the organisms from the first capture), use formula.

(Total # marked)(total # from 2nd capture) DIVIDED BY (total # recaptured with mark)

Question 6

Name the two types of factors that regulate population numbers, and give an example of each.

Answer 6

Density dependent limits: eg. Food.
Density independent limits: eg. Weather

Question 7

Define competition as a population limiting factor.

Answer 7

Individuals compete for a limiting resource.

Question 8

Define predation as a population limiting factor.

Answer 8

An interaction between species where one species uses another for food. Prey population usually much higher than predator population.

Question 9

Name three defenses against predation.

Answer 9

Cryptic colouring: camouflage
Warning colouration: brightly coloured = poison
Batesian mimicry: harmless species looks like a poisonous one

Question 10

Describe symbiosis

Answer 10

Individuals of two or more species live in direct contact

Question 11

Define mutualism

Answer 11

A relationship between two species where BOTH benefits (symbiotic relationship)

Question 12

Describe commensalism

Answer 12

One organism benefits, other is neutral.

Question 13

Describe amensalism

Answer 13

One partner negatively affected, other is not affected. Eg. Black walnut trees release chemicals that harm plants around it.

Question 14

Describe parasitism

Answer 14

One organism (host) is the source of food or shelter for another organism (parasite). Host harmed, parasite benefits.

Question 15

How do we calculate growth rate?

Answer 15

Growth rate = (births - deaths)/total population

Question 16

Describe exponential growth vs logistic growth. Give equations for each.

Answer 16

Exponential: as population increases, birth increases. (Growth rate x population size)
Logistic : population growth is limited by carrying capacity. As it approaches capacity, growth slows. (Carrying capacity - population size, divided by CC)

Question 17

Define survivorship. Give the three types.

Answer 17

Survivorship is the number of offspring that survive into old age
Type I: most organisms live to old age
Type II: percentage of deaths are consistent across age groups
Type III: most deaths occur shortly after birth

Question 18

Define fecundity

Answer 18

Average number of offspring produced by a female over her lifetime.

Question 19

Describe r vs k selected species. Give another name for both. Which type is prime to extinction?

Answer 19

r-Selected (opportunitists): maximize birth rate. Many offspring, little parental care.
k-Selected (competitors): maximize survivorship of offspring. Prone to extinction, parental care to adulthood.

Question 20

Describe the four theoretical stages of demographic transition.

Answer 20

1 - birth and death rate high. Least developed countries.
2 - birth rate high, death rate falls. Improved healthcare/food production.
3 - birth rates falls. Death rate falls. Low infant mortality. Increase standard of living.
4 - birth/death rates low. Steady population, higher than in stage 1.

Question 21

Give the formula to calculate frequency of a species

Answer 21

(Number of quadrats in which the species occurs)/(total number of quadrats). Exists as a percentage.

Question 22

Explain how relative frequency is calculated. What do these percentages mean about dispersion patterns?

Answer 22

Frequency of a species/total frequency of all species. 0-30% means clumped, 31-80% means random, 81-100% means uniform.

Question 23

Explain how abundance is calculated.

Answer 23

Number of a certain species/total number of plants.

Question 24

Define frequency vs relative frequency.

Answer 24

Frequency: % of quadrats occupied by a species.
Relative frequency: frequency of a species / total frequency of all species

Question 25

Define abundance vs frequency vs density.

Answer 25

Abundance: compares # of a species with total.
Frequency: % of quadrats occupied by a species.
Density: # of plants of a species per unit area.

Question 26

Why do invasive plants demonstrate random dispersion?

Answer 26

Outcompete native species: no predators

Question 27

Name the formula for exponential growth of a population

Answer 27

(Growth rate)(population)

Question 28

Give the formula for LOGISTIC growth of a population

Answer 28

(Growth rate x population)(carrying capacity - population, divided by carrying capacity)

Question 29

Describe a predator/prey population graph

Answer 29

predator population always lower, usually relatively stable. prey population much higher, but has extreme highs and lows depending on season.