Population ecology

Question 1

A population

Answer 1

• All the individuals of the same species
• That occupy the same area in a particular ecosystem
• i.e. They are all potentially able to interbreed

Question 2

A community

Answer 2

• The different populations of species
• That occupy a specific area in an ecosystem

Question 3

Ecological niche

Answer 3

The job or role that an organism has in a particular ecosystem

Question 4

Ecosystem

Answer 4

• A system formed by the interaction of a community of organisms with their physical environment
• Includes both biotic and abiotic factors

Question 5

Population size

Answer 5

The number of individuals making up a particular population

Question 6

Population parameters

Answer 6

Factors influencing population size

• Births
• Immigration
• Mortality/deaths
• Emigration

Question 7

Population parameters increasing populations

Answer 7

• Births
• Immigration

Question 8

Population parameters decreasing populations

Answer 8

• Mortality/deaths
• Emigration

Question 9

Formula to calculate change in population size

Answer 9

N = (B + I) - (D + E)

Question 10

B + I > D + E

Answer 10

Increasing population size

Question 11

B + I < D + E

Answer 11

Decreasing population size

Question 12

B + I = D + E

Answer 12

Stable population size

Question 13

Two main approaches to finding the population size

Answer 13

• direct counting / census
• estimating / indirect methods

Question 14

A tool often used for direct counting of organisms

Answer 14

Aerial photography

Question 15

Two indirect methods of estimating population size

Answer 15

• Mark-recapture
• Quadrats

Question 16

Population estimation technique for stationary or slow moving populations

Answer 16

• Quadrats
• direct methods

Question 17

Quadrats are used for estimating…

Answer 17

• population size of stationary or slow moving organisms
• in which there are large numbers
• e.g. barnacles, plants

Question 18

Mark-recapture methods are used for estimating…

Answer 18

• population size of mobile organisms
• e.g. fish, birds and insects

Question 19

Population estimation formula for Mark-recapture

Answer 19

N = (M x C) / R

• N estimated population size
• M total captured and marked
• C total recaptured
• R total marked individuals recaptured

Question 20

Population estimation formula for Quadrats

Answer 20

Estimated population = (Total area x number in quad) / area of quad

Question 21

Precautions required when using Mark-recapture method

Answer 21

• do not harm organisms
• do not affect behaviour of organisms
• return marked animal where originally caught
• limit time between first and return samples to limit population parameter effects e.g. emigration
• enough time for organisms in population to mingle
• second catch should be larger than first to increase accuracy of estimate

Question 22

Example ways of marking organisms in the Mark-recapture method

Answer 22

• Fish - metal or plastic tag on fin
• Insects - a dot of non-toxic paint
• Mammals - collared
• Birds - ring on leg

Question 23

Types of interactions in a community

Answer 23

• Predation
• Competition
• Parasitism
• Mutualism

Question 24

Predator

Answer 24

• Any organism that hunts a a prey species
• predators benefit by gaining food

Question 25

The environment benefits from predation

Answer 25

• By keeping herbivore numbers down.
• Keeps carrying capacity stable.

Question 26

Five examples of predators

Answer 26

• Spiders
• Snakes
• Lions
• Wild cats
• Wild dogs

Question 27

Population cycles

Answer 27

• Periods where populations vary in density from high to low
• Shorter for smaller organisms e.g. mice
• Longer for larger organisms e.g. antelope

Question 28

Cyclical fluctuations between predator and prey

Answer 28

• When a predator population relies heavily on one prey population.
• The population cycle of the predator follows the pattern of the prey population.
• When prey numbers increase, predators increase as food available.
• When prey decrease, predators soon decrease as food becomes scarce.
• time lag in predator numbers response to increasing or decreasing prey.

Question 29

Individuals in a prey population most likely to be killed

Answer 29

Old, young or sick

• easier to catch
• lower stamina or speed
• less agile to outmaneuver
• didn’t recognize danger

Question 30

Why effects of predators on prey population might be less than expected

Answer 30

• Old, young or sick usual targets
• These animals wouldn’t be reproducing or would have died anyway.