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Life Sciences > Population Ecology > Flashcards

Population Ecology Flashcards

1
Q

Individual

A

a single organism that forms part of a species

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2
Q

population

A

a group of organisms of the same species that are found in a particular area at the same time and can crossbreed freely

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3
Q

community

A

a group of populations occurring in a particular area

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4
Q

ecosystem

A

a unit of plant and animal communities (biotic/living) in interaction with each other as well as with the non-living (abiotic) factors in a particular area

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5
Q

Factors influencing the size of a population

A
  • natality
  • mortality
  • immigration
  • emigration (exit)
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6
Q

Effects of limiting factors on population growth

A
  • density dependent factors
  • density independent factors
  • environmental resistance
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7
Q

density dependent factors

A

factors that take effect when population numbers increase

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8
Q

density dependent factors

A
  1. decrease in living space, has negative effect on rate of reproduction, due to stress
  2. increase in predation - more food available for predators
  3. greater demand for food and water, causing increased competition, which limits reproduction
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9
Q

density dependent factors 2.0

A
  1. shortage of shelter - increases exposure to adverse weather conditions and predators - leads to decrease in numbers
  2. easier spread of diseases and parasites - as population density is higher
  3. accumulation of waste that may poison the environment
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10
Q

density independent factors 2.0

A

takes place irrespective of the size/density

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11
Q

density independent factors 2.0

A
  • extreme changes in temperature

- natural disasters

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12
Q

environmental resistance

A
  • certain factors that prevent unlimited growth in a population which would exceed its maximum growth rate
  • when no.s of population increase, environmental resistance increases (limiting factors take effect). Due to increase in mortality and/or decrease in natality, population growth decreases
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13
Q

environmental resistance 2.0

A
  • diseases and parasitism
  • accumulation of toxins
  • shortage of food and water
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14
Q

environmental resistance 2.0

A
  • shortage of living space
  • shortage of shelter
  • predation
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15
Q

carrying capacity

A
  • The maximum number of individuals that a specific environment can sustain
  • affected by density independent factors
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16
Q

stable population

A

population where the numbers fluctuate around carrying capacity

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17
Q

unstable population

A
  • when pop numbers far exceed carrying capacity
  • habitat will most likely be damaged
  • this results in a decrease in carrying capacity of environment
  • pop numbers decrease (environment can no longer sustain pop)
  • pop may become extinct
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18
Q

seasonal fluctuation

A

European swallow

-during cold European winter - fly south to southern Arica (food plentiful and ideal conditions for breeding)

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19
Q

direct counting method (census)

A
  • direct contact counting of smaller-sized organisms/humans
  • direct counting (from vehicle /helicopter/plane) of larger organisms
  • counting from aerial photographs taken of larger moving organisms
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20
Q

Indirect counting method (mark-recapture) (counting of only part of the pop)
-method

A
  1. specific area is demarcated
  2. number of individuals are caught, counted and marked (1st sample)
  3. marked individuals are released into environment
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21
Q

Indirect counting method (mark-recapture) (counting of only part of the pop)
-method 2.0

A
  1. sufficient time must be allowed for marked individuals to mix with the rest of the pop
  2. Another group of individuals are caught and counted (2nd sample)
  3. No of marked individuals in 2nd sample are counted
    - data is used to determine the estimated size of the pop (using a specific formula)
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22
Q

Indirect counting method (mark-recapture) (counting of only part of the pop)
-calculation of pop size

A

p=mXs/t
p is the estimated population size
m is the total no of animals captured and marked in 1st sample
s is the total number of animals captured in 2nd sample
t is the number of marked individuals in the 2nd sample

23
Q

Indirect counting method (mark-recapture) (counting of only part of the pop)
-precautions

A
  1. marking methods should not injure/damage the organism
  2. marking methods should not affect the movement/behaviour of organism (chances to be captured should therefore remain the same)
24
Q

Indirect counting method (mark-recapture) (counting of only part of the pop)
-precautions 2.0

A
  1. marks should be clearly visible for duration of investigation
  2. marked organisms should be allowed enough time to mix with the rest of the pop before the next sample is taken
25
Q

Indirect counting method (mark-recapture) (counting of only part of the pop)
-precautions 2.1

A
  1. period between the two samplings should be sufficiently brief (so that no deaths or births occur)
  2. population must be closed
26
Q

Indirect counting method (quadrats) (square frame of …)

-method

A
  1. area where organisms must be counted - is demarcated - surface area determined
  2. quadrat is placed on ground in demarcated area
  3. organisms concerned are counted inside metal frame
27
Q

Indirect counting method (quadrats)

-method 2.0

A
  1. this is the no of individuals per unit area

5. process repeated a few times in diff areas of demarcated area - how? - by placing quadrant randomly on ground

28
Q

Indirect counting method (quadrats)

-method 2.1

A
  1. average no of individuals is calculated

7. total no of individuals in pop is determined using a specific formula

29
Q

Indirect counting method (quadrats)

-calculation of pop size

A

pop size = average no of individuals per quadrant X

surface area of area/ surface area of quadrant

30
Q

Indirect counting method (quadrats)

  • precautions
  • more quadrants - more accurate estimation
A
  1. exact no of organims in each quadrant must be known
  2. surface area of quadrant must be known
  3. surface area of demarcated area must be known
  4. quadrant must be placed randomly in demarcated area (same shape, fair chance, excludes bias)
31
Q

random sampling

A

Each member of pop has an equal and independent chance of being included (fair chance of being counted)

32
Q

quadrant method

A
  1. data must be collected from same shaped quadrants in order to be comparable
  2. size of quadrant will depend on type of organism concerned
  3. this method is particularly suited to plant populations and sessile / slow-moving invertebrates
33
Q

predator-prey relationship

predation is density-dependent factor

A

the biological interaction between the organism that hunts and kills for food (predator) and the organism that serves as its source of food (prey)

34
Q

predator-prey graph

A
  1. graph line of prey pop always peaks first
  2. peaks of two graph lines never overlap - predator graph follows prey graph after short delay in time
  3. X axis - time
  4. Y axis- population size
35
Q

intraspecific competition
a for family mantra
(density-dependent factor)

A
  • takes place between individuals of the same species

- live in same habitat and use same resources

36
Q 
interspecific competition
(density-dependent factor)
A
  • takes places between individuals of different species

- similar habitats and ecological niches

37
Q

niche

A
  • each species has a specific role to play in a community

- this role is known as its ecological niche

38
Q

niche

A
  • within the roles - each species needs a particular set of environmental conditions and resources to survive and reproduce in its habitat
  • survival of species depends on how successfully the organisms use their available resources
39
Q

resource partitioning

A

when the same resources are used differently and co-existence is possible

40
Q

resource partitioning 2.0

A
  • using resources at diff times
  • using diff parts of resource
  • using resource in diff habitats (two diff species of monkey feed on same species of tree but in diff parts of the forest)
41
Q

ecological succession

A

series of events where one community replaces another over time resulting in long-term changes in ecosystem

42
Q

pioneers / pioneer communities

A

the first organisms (plants and animals) that become established in a new habitat

43
Q

climax community

A

when ecological succession continues until a complex, stable ecosystem develops

44
Q

primary succession

A
  • takes place when plants and animals settle for the first time in a new habitat where there was previously no life
  • usually occurs in areas where initially there was no soil
45
Q

secondary succession

occurs in established community where a disturbance has occurred

A
  • takes place when plants and animals settle in a new habitat disrupted by human activities or by natural disasters
  • occurs faster than primary succession - area already has soil, organic nutrients and seeds from previous growth
46
Q

benefits of herds/flocks to avoid predators

A
  • protection against predators

- the larger a group - the better the chances of survival of individuals

47
Q

cooperative hunting using
wild dogs as an example
(group members work together to hunt and kill their prey)
-advantages

A
  • quicker and easier to catch prey
  • less threat from competing predators for same prey
  • potential predators of wild dogs will not confront pack, rather target individual
48
Q

cooperative hunting using
wild dogs as an example
-advantages 2.0

A
  • ensures sufficient resources for all
  • many ears and ears for detection of prey
  • females and young cubs not exposed to dangers of predators (don’t leave security of den to look for food)
49
Q

dominant breeding pair

A
  • when animals have one pair or a limited no of reproductive individuals in colony
  • non-reproductive members of pack take care of pups
  • dominant queen prevents other females from reproducing by releasing pheromones that inhibit their reproductive cycles
50
Q

eusocial animals

A
  • animals that reach the highest level of social organisation in a community
  • live together in highly organised colonies
51
Q

eusocial animals

A
  • have diff groups/castes that perform specialized functions in colonies
  • functions include finding food, cleaning, protecting, building etc
52
Q

reason for exponential growth

A

advances in medical field:

  • improved methods for treating diseases
  • development of vaccinations against infectious diseases
53
Q

reason for exponential growth 2.0

A

massive increase in agricultural productivity due to:

  • cultivation of new disease-resistant food crops
  • use of fertilizers
  • use of more effective farming methods

Life Sciences (6 decks)

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