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Population Ecology > Population growth and limitation > Flashcards

Population growth and limitation Flashcards

1
Q

What is ecosystem regulation ?

A

Maintaining species numbers in equilibrium with available resources.

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2
Q

Who proposed that populations are regulated by density dependant factors ?

A

A J Nicholson, 1933

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3
Q

State the argument of Birch, 1954 in opposition to A J Nicholson.

A

Little empirical evidence for density dependant factors

Instead density independent factors regulated populations

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4
Q

Describe a Geometric population growth and give a species example.

A

Pulsed,
Will occur If reproduction is seasonal
Red deer

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5
Q

Describe a Exponential population growth and give a species example

A

Continuous
Will occur if reproduction at any time
Humans

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6
Q

Describe the population growth of all populations when placed in a new environment

A

Logistic curve
Exponential growth
Until resources begin to deplete.
Population will slow and eventually stop

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7
Q

Where is the fastest rate of growth in a logistic curve ?

A

In the middle of the curve

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8
Q

Where does population growth stop in a population ?

A

At the ecosystems carrying capacity

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9
Q

Define the carrying capacity (K) of a population ?

A

The number of individuals an ecosystem can support.

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10
Q

When a population reaches carrying capacity, what will happen to the growth rate ?

A

It will equal zero.
The population will no longer grow
Birth rate = Death rate

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11
Q

Carrying capacity of a population is constant.

True or False ?

A

False

It is a moving target, Due to variations in the environment r

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12
Q

Year by year, populations will over shoot and under shoot the carrying capacity
True or False ?

A

True

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13
Q

The size of the population oscillation depends on..

A

How rapidly the organism reproduces

How rapidly the environmental conditions change

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14
Q

Density dependant factors are usually Abiotic or Biotic factors ?

A

Biotic factors

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15
Q

Density independent factors are usually Abiotic or biotic ?

A

Abiotic factors

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16
Q

What factors interact to affect species populations ?

A

Density dependant (B) and Density independent (A) factors.

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17
Q

Define density dependant factors.

A

Where the size & growth of the population is depedant on the density of the population

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18
Q

Define density independent factors

A

Where the size or the growth of the population is not dependant on the density of the population.

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19
Q

Give an example of a density dependant factor

A

Nesting sites on a cliff

If there is too large a population, there will be no sites left and birds will be unable to nest.

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20
Q

Limited availability of a resource will have a density dependant impact on a population.
How ?

A

There is only a finite supply of resources such as prey and nutrients in an ecosystm.
The larger the population, the harder they are to find.

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21
Q

What impact can disease, competition and predation have on a population?

A

Negative or a positive impact

in some cases more resources available

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22
Q

Do density dependant factors effect every individual equally ?

A

No

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23
Q

Describe how red squirrels show that not all individuals are affected by density dependant factors.

A

Food availability and density limit RS reproduction rates

When high density of squirrels, weaker females will be relegated to poor quality territories = Poor reproductive. success

When density high, an increased no will be relegated.

However females remaining in good territories are not impacted.

NB- if low density of RS, All will inhabit high quality habitats

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24
Q

How will the overall red squirrel population be impacted by density dependant factors ?

A

There will be a decrease in birth rate and population growth

(Remember females in high quality habitats not impacted)

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25
Q

In the red deer population, are juveniles or adults most impacted by density ?

A

Juveniles

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26
Q

Why will there be a decrease in red deer males as density increases ?

A

Males are larger and have greater energy demands.
Density will impact males more
Sex ratio will shift to favour females (more likely to survive)

Less males will enter the population as already completion for resources

Increased no. of males will emigrate to find better resources

27
Q

When will systems begin to regulate population growth ?

A

When the population is at 60% carrying capacity

28
Q

What does the example of the red deer tell us about density dependant factors ?

A

They can impact male and females differently

They can influence immigration and emigration

29
Q

Define Negative density dependence

A

A situation in which population growth is curtailed by crowding, predators and competition

30
Q

Define Positive density dependence, or the Allee effect

A

A situation in which population growth is facilitated (made easier) by increased population density.

31
Q

Define the alee effect

A

A correlation between population size and the individual fitness of a population

32
Q

List the 2 positive density dependant factors.

High density = Increased growth rate

A

Aggregations

Co-operative hunting

33
Q

What is the benefit of aggregations to a population ?

A

Increase survival by

Safety in numbers
Too many organisms for a predator to consume

Protection against extreme weather conditons

34
Q

What is the benefit of co-operative hunting ?

Give a species example

A

Increase survival
Can obtain more prey

Wild dogs

35
Q

Give examples of species which use aggregations

A

Nesting birds
Fish shoals
Forests of trees (protection)
Plants (overproduction of seed)

36
Q

How do aggregations impact fertilisation of plants ?

A

Clumping attracts insects who will ignore sparse patches

Increasing chance of fertilisation

37
Q

What do negative density dependant factors such as Predation and Resource competition affect ?

A

Negatively impact survivorship, growth rates and birth rates

38
Q

What do positive density dependant factors such as Allee effect, Aggregation and Co-operation affect ?

A

Increase survivorship, growth rates and fertility.

39
Q

What have density dependant factors led to in some species ?

A

Stage specific differences in
survivorship, growth and fertility

(Different effects on organisms throughout life cycle)

40
Q

Give examples of stage specific differences in species

A

Bird nestlings
Young- will keep each other warm
Older- Larger nestlings will supress weaker siblings

Diff impacts on survivorship at diff stages.

41
Q

What is fecundity ?

A

Ability to produce offspring

Stage specific difference.
Will vary depending on density and age of organism.

42
Q

What happens to the rate of mortality as population density increases ?

A

The rate of mortality will increase.

43
Q

What is K value analysis in a population ?

A

A measurement of the killing power (mortality rate)

44
Q

Can populations be maintained at their carrying capacity ?

A

No, impossible to achieve

45
Q

What is under compensation in a population ?

A

Will be more births than deaths

Just in case conditions improve

46
Q

What is over compensation in a population ?

A

Rapid and dramatic fluctuations in size

Overshoot and undershoot

47
Q

Populations are controlled by exploitation of other species.
Give examples of this.

A

Predation and herbivory

48
Q

How many functional Reponses are there in changes to food availability ?

A

3

49
Q

Describe the type 1 response to changes in food availability

A

assumes linear increase in intake rate with food density.

Time needed by consumer to process food is negligible
I.e. whale eating plankton

50
Q

Describe the type 2 response to changes in food availability

A

Decelerating intake rate, saturation occurs at high density

Consumer limited by capacity to process food
i.e Wolves hunting caribou, will reach a plateau as only so many caribou that can be caught and consumed in a given time.

51
Q

Describe the type 3 response to changes in food availability

A

Saturation occurs at high densitys
But at low densities will struggle to find prey as require tranfer of learning
i.e Deer mice and cocoons

52
Q

What is a numerical response ?

A

A change in predator density as a function of prey density

53
Q

What is a demographic response ?

A

Changes in rates of predator reproduction or survival

result of prey availability

54
Q

What is an aggregational response ?

A

Changes in predator number due to immigration into an area with higher numbers of prey

55
Q

Other than the density of the population what else will effect population growth ?

A

Density independent factors, Often Abiotic

56
Q

List some density independant factors

A

Food, nutrient limitation, pollutants, climate extremes, seasonal cycles, Catastrophic factors

57
Q

Give 2 catastrophic factors which impact population growth

A

Fires and hurricanes

58
Q

Give a species example where light is the density independent factor, affecting populations

A

Early purple orchid
Have a higher reproductive rate in light
Light impacts fecundity, thus impacting population

59
Q

Give a species example where heat is the density independent factor, affecting populations

A

Thrips

Cool weather limits rate of development and fecundity

60
Q

How do nutrients affect organisms ?

A

Can affect the ability of an organism to survive, grow and reproduce

61
Q

What is the impact of pollutants on a population ?

A

Can cause;
Direct increase in mortality
Imitations in growth and fecundity
Increased deformities

62
Q

What group of organisms is particularly at risk to pollutants ?

A

Amphibians, irrespective of their population size

63
Q

Which 2 population factors interact in complex ways ?

A

Density-dependant and density-independent factors.

64
Q

Why do scientists need to understand the factors that affect population growth rates ?

A

Important for management and applied conservation

Population Ecology (6 decks)

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