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Population Ecology > Population Growth and regulation > Flashcards

Population Growth and regulation Flashcards

1
Q

What is a regulating factor ?

A

A factor affecting a population, usually density dependant which helps keep a population at equilibrium.

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2
Q

Give an example of a regulating factor.

A

Food supply,
As a population increases food availability will decrease, leading to more deaths and decreased fecundity
As organisms decline, food availability increases.

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3
Q

What are limiting factors ?

A

Factors affecting population size and and growth

Usually density dependant

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4
Q

What is the difference between a regulating and limiting factor ?

A

Both may limit population size

But a limiting factor does not regulate the population like a regulating factor.

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5
Q

Give an example of how regulating and limiting factors interact

A

Disease
Limits population size (LF)
However animals in a poorer condition may be more vulnerable to disease
Higher prevalence in a low density population. (becomes RF)

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6
Q

Give 3 examples of disease affecting population size.

A

Rabies- Foxes
Myxomatosis- Rabbits
Canine distemper- Lions

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7
Q

Describe the outbreak of rabies in foxes.

A

Disease eradication
High numbers of casualties-
2000 rabid foxes per year.
Limited population size

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8
Q

How did the introduction of a rabies vaccine affect fox population size ?

A

Caused a huge increase in population numbers

Rabies no longer limiting population size

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9
Q

Describe the use of Myxomatosis as a means of population control

A

Introduced in 1953 as biocontrol
Severely impacted population size in the UK
Population remains lower than pre myxo introduction.

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10
Q

Describe the impact of canine distemper on lions In the Ngorongoro crater,

A

Originally limited by food supply- enough for 100.
But had 3 outbreaks of CD in rapid succession
Should see ^ in pop. no as habitat now able to provide for 100+
However pop. are unusually susceptible to CD due to inbreeding (closed population)

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11
Q

Describe the processes acting on the population of lions in the Ngorongoro crater

A

Originally regulated by bottom up (food supply only for 100)

Now regulated by top down (disease- reg, factor)

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12
Q

What is the maximum sustainable yield ?

A

the largest yield that can be taken from a species’ stock over an indefinite period.

(Half the carrying capacity of a population- where largest no. of reproducing offspring found)

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13
Q

What is carrying capacity ?

A

The maximum population size of a species which can sustain the environment indefinitely

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14
Q

What is the population growth at carrying capacity ?

A

Zero, Birth rate= Death rate

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15
Q

Birth and death rate are density dependant- True or false ?

A

True

If the population is above carrying capacity, birth rate will decrease and death rate will increase.

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16
Q

Carrying capacity, K remains constant over time - True or false ?

A

False, carrying capacity changes over time.

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17
Q

What does carrying capacity, K depend on ?

A

Population size
Amount of resources in ecosystem
Amount of resources each individual is consuming
Number of competitors

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18
Q

Why are most populations held below the carrying capacity, K ?

A

Due to competitors.

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19
Q

What is human carrying capacity dependant on ?

A

OIL, Makes up 60% of humanity’s primary energy

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20
Q

Give the uses of oil.

A

Agriculture

pesticides, fertilisers, mechanisation, genetic engineering.

21
Q

Describe the population growth of a K species.

A

Reach a stable level and sustain their population for an indefinite period
Oscillating around K

22
Q

Describe the population growth of a R species

A

The population grows to a peak and then collapses

23
Q

How can the human population regain balance with the carrying capacity of its environment.

A

Decrease in the population size

Decrease in consumption

24
Q

Why is the Irish population at a lower carrying capacity since the 1840’s ?

A

Potato famine
Potato was staple of the diet, 90% of diet. Potato blight struck
Irish population finally crashed due to death and emigration.

25
Q

What is an overshoot ?

A

Occurs when a populations consumption exceeds the carrying capacity of its environment.

26
Q

What happens to a population when an overshoot occurs ?

A

The environment can no longer support the population
Will be reduced birth rates and increased mortality
Population will decline rapidly.

27
Q

What does the rapidity of decline in a population after an overshoot depend on ?

A

The degree of the overshoot

Whether carrying capacity continues to be eroded during decline.

28
Q

Why will the population after an overshoot tend to decline rapidly and to a lower level than was sustainable before ?

A

As the overshoot has degraded the carrying capacity of the environment,
Decline can be long lived

29
Q

Describe the population size of the introduced reindeer population on St Matthews island between 1944-1980

A

29 reindeer introduced
(no emigration or predation)
increased to 6000, 1963
Completely died out by 1980

30
Q

Why did the overshoot of the St Matthews reindeer population occur ?

A

No migration
Overgrazing of lichen
Massive pop. ^ meant excessive no. all competing for limited forage.
Led to population crash.

31
Q

What is the aim of maximum sustainable yield ?

A

to maintain population size at point of maximum growth by harvesting individuals which are being added to the population.
= Population will be productive indefinitely.

32
Q

Above maximum sustainable yield (half carrying capacity) what will occur ?

A

Density dependant factors will limit breeding until the population reaches carrying capacity,
Above MSY there are no surplus individuals to harvest

33
Q

List the problems with using maximum sustainable yield as a way to harvest organisms.

A 
Impossible to estimate population size
Carrying capacity continually changes 
Ignores several key demographic factors
Mating systems are often unknown
Irresponsibly used.
34
Q

It is not economically beneficial to overharvest a long lived species-
True or False ?

A

False
Driving extinction means the no. will decrease
Increasing rarity and price.

35
Q

Describe an industry where maximum sustainable yield is irresponsibly used

A

Fishing industry
Ignore size, age and reproductive status- Pop, crash
Ignore ecosystem damage, species interaction
Bycatch- Unintentional catching of other species

36
Q

What is maximum economic yield ?

A

The harvesting of organisms that provides the best economic gain.

37
Q

Describe maximum economic yield using elephants.

A

Meat- 6% can be harvested per year
Ivory- 2% can be harvested per year
MEY- gained from ivory.

38
Q

Which yields do we want to balance In population ecology ?

A

Maximum sustainable yield

Maximum Economic yield

39
Q

What is Optimum sustainable yield ?

A

The level of effort that maximises the difference between total revenue and total cost
(lower effort level than MSY)

40
Q

Which is safer fixed effort management or fixed quota management ?

A

Fixed effort management

If population low, less will be found and killed.

Self regulating system.

41
Q

What is fixed effort management ?

A

Specify the number of hunters or length of hunting season

42
Q

What is fixed quota management ?

A

Specify the number that can be killed.

43
Q

What does Fixed effort management rely on ?

A

Adaptive harvest management
Constant flow of information from hunters on no. & sex killed

Use data to know when to close the season.

44
Q

What does maximum sustainable yield rely on ?

A

Careful observation of the managed population.

45
Q

What is one way that MSY can have a lower impact on populations ?

A

Compensatory mortality

Targeting of age groups, (older) with naturally high rate of mortality.

46
Q

What is additive mortality ?

A

Reducing the population by more than its natural mortality.

The excess= Additive

47
Q

When applying a population dynamics model to the harvesting of a species
What is important ?

A

An in-depth knowledge of ecology and the species under management.

48
Q

What does ecologically safe harvest management require ?

A

Adjustment of age of animal harvested (compensatory mortality)

Population Ecology (6 decks)

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