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Flashcards in Populations and Sustainability Deck (43)
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1
Q

What is population dynamics?

A

The study of population growth and the factors responsible for influencing their growth rate.

2
Q

What is population density?

A

The number of individuals per unit area/volume.

3
Q

What is the name of the shape of the curve delineated by a natural population increase?

A

Sigmoid curve

4
Q

What are the three main stages of the natural growth of a population?

A

Lag phase
Log phase
Stationary phase

5
Q

Describe the lag phase of natural population growth.

A

Few individuals, still acclimatising to the habitat.

Reproductive rate is low so the population growth is slow.

6
Q

Describe the log phase of natural population growth.

A

Conditions are favourable, so reproductive rate far exceeds mortality rate, resulting in exponential population increase.

7
Q

Describe the stationary phase of natural population growth.

A

The population size has stabilised at the carrying capacity of the habitat, but still fluctuates around an equilibrium value.
The reproductive rate is roughly equal to the mortality rate.

8
Q

What are limiting factors for population growth?

A

Factors that prevent exponential growth in natural populations.
Factors become limiting, providing environmental resistance to exponential growth.

9
Q

What are some examples of abiotic limiting factors?

A

Temperature, light intensity, pH of soil, availability of water, oxygen.

10
Q

What are some examples of biotic limiting factors?

A

Predation, disease, competition (interspecific and intraspecific)

11
Q

What is carrying capacity?

A

The maximum population size that can be maintained over a period of time in a particular habitat.
The population still fluctuates around an equilibrium level.

12
Q

What are the two types of factors influencing mortality rates?

A

Density dependent.

Density independent.

13
Q

What are density dependent factors?

A

Limit the growth of the population in proportion to the size of the population (population density). Mainly biotic factors.

14
Q

What are density independent factors?

A

Limit the growth of the population independently of population density. Mainly abiotic factors (natural disasters such as earthquakes or floods)

15
Q

What are the two types of migration?

A

Immigration

Emigration

16
Q

Describe immigration and give an example.

A

Movement of organisms into an area, increasing population size.
Christmas island red crabs (from forest to coastal areas)

17
Q

Describe emigration and give an example.

A
Movement of organisms out of an area, decreasing population size.
Norway lemmings (away from high population density)
18
Q

What are the two types of competition?

A

Interspecific and intraspecific

19
Q

What is interspecific competition?

A

Competition between different species for the same resource.

20
Q

What is the competitive exclusion principle and when does it apply?

A

Interspecific competition.
If one species is less well adapted (uses the limited resource less effectively), it is outcompeted and will eventually be eliminated.
This is called competitive exclusion, where species have overlapping niches.

21
Q

What is an example of interspecific competition?

A

Red and grey squirrels in the UK.

22
Q

What is intraspecific competition?

A

Competition between members of the same species due to limiting factors.

23
Q

What is the relationship between predator and prey populations?

A

Predation can act as a limiting factor on a population of prey, which can in turn affect the predators population size (interdependence).

24
Q

Describe the 4 stages of a predator-prey relationship.

A
  1. When the predator population increases, more prey are eaten.
  2. Prey population decreases, meaning less food for predators.
  3. Predator population decreases.
  4. Prey population increases due to decrease in predation.

Cycle repeats

25
Q

What is conservation?

A

The maintenance of biodiversity through the active management of an ecosystem.
Conservation is a dynamic process involving management and reclamation.

26
Q

What is preservation?

A

A form of conservation, but leaves ecosystems undisturbed, attempting to keep things the way they are.

27
Q

What are some conservation/preservation techniques?

A
Provide extra food (raise carrying capacity).
Restrict dispersal by fencing.
Control predators and poachers.
Vaccinate individuals against disease.
Prevent pollution/disruption of habitats.
Increase habitat size.
Remove non-indigenous species.
Irrigate/drain dry/swamp land.
28
Q

Why is sustainable management so important?

A

The increase of the human population results in the need to intensely exploit the environment for resources. This leads to the destruction of habitats, reduced biodiversity and the eventual complete depletion of resources.

29
Q

What are 3 sustainable management techniques for small scale timber harvest?

A

Coppicing, Pollarding, Rotational coppicing

30
Q

What is coppicing?

A

Cutting deciduous tree trunks close to the ground to encourage new growth from the merismatic tissue.

31
Q

Why is coppicing good?

A

The tree recovers much more quickly than a newly planted tree.
The root system is still intact, so the soil is not disrupted.

32
Q

What is pollarding and why is it useful?

A

Similar to coppicing, but the tree is cut higher up.

Pollarding prevents herbivory by animals such as deer.

33
Q

What is rotational coppicing?

A

Foresters divide a wood into sections and only cut one section each year, rotating once all have been cut.

34
Q

In rotational coppicing, what determines the period of the rotation?

A

The species of tree.

The dimensions of the wood required.

35
Q

Why is rotational coppicing good?

A

Maintains biodiversity, as the trees do not block out all the light, so succession cannot occur and more species can survive.

36
Q

What are the dangers of large scale timber harvest?

A

Often involves clear-felling of all the trees in an area, so:
destroys habitats.
leads to water pollution due to the destruction of root networks.
reduces soil nutrient levels.

37
Q

What is reforestation?

A

Areas of destroyed forest can be replanted.

38
Q

What is afforestation?

A

New forest planted in areas where there previously was no forest.

39
Q

What are some sustainable planting strategies (large scale).

A

Trees not planted too closely together (limits competition).
Young trees protected from grazing.
Only native plant species planted.
Fast-growing trees planted (e.g: conifers).
Control pests and pathogens.

40
Q

What are some sustainable felling strategies? (2)

A
Selective felling (only mature trees removed).
Strip felling (trees cut in strips to maintain biodiversity).
41
Q

What are 5 sustainable fishing practices?

A

EU common fisheries policy (quota and species allowed for fishing).
Minimum netting mesh size (allows juvenile fish to escape).
Fishing seasons (helps allow time for repopulation).
Fishing licences.
Dedicated fish farms.

42
Q

What are the problems with fish farms?

A

Ethical issues.
Easy spread of disease.
Can harm biodiversity in the area.

43
Q

Why is it important to maintain ‘wild types’ of crop species?

A

Can be a source of useful alleles.
Can be cross bred with crops to increase genetic variation.
Allow the introduction of different traits that may be required in future, particularly due to changing climates.
Promotion of hybrid vigour.
Source of replacement of crop populations if the cultivated population is in danger.