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Flashcards in Population ecology Deck (31)
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1

A population

  • 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

2

A community

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

3

Ecological niche

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

4

Ecosystem

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

5

Population size

The number of individuals making up a particular population

6

Population parameters

Factors influencing population size

  • Births
  • Immigration
  • Mortality/deaths
  • Emigration

7

Population parameters increasing populations

  • Births
  • Immigration

8

Population parameters decreasing populations

  • Mortality/deaths
  • Emigration

9

Formula to calculate change in population size

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

10

B + I > D + E

Increasing population size

11

B + I < D + E

Decreasing population size

12

B + I = D + E

Stable population size

13

Two main approaches to finding the population size

  • direct counting / census
  • estimating / indirect methods

14

A tool often used for direct counting of organisms

Aerial photography

15

Two indirect methods of estimating population size

  • Mark-recapture
  • Quadrats

16

Population estimation technique for stationary or slow moving populations

  • Quadrats
  • direct methods

17

Quadrats are used for estimating...

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

18

Mark-recapture methods are used for estimating...

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

19

Population estimation formula for Mark-recapture

N = (M x C) / R

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

20

Population estimation formula for Quadrats

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

21

Precautions required when using Mark-recapture method

  • 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

22

Example ways of marking organisms in the Mark-recapture method

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

23

Types of interactions in a community

  • Predation
  • Competition
  • Parasitism
  • Mutualism

24

Predator

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

25

The environment benefits from predation

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

26

Five examples of predators

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

27

Population cycles

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

28

Cyclical fluctuations between predator and prey

  • 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.

29

Individuals in a prey population most likely to be killed

Old, young or sick

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

30

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

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