Populations & Sustainability

Question 1

Name each of the phases

Answer 1

A = lab phase
B = log phase / exponential
C = stationary phase
D = death

Question 2

What’s happening at a

Answer 2

The lag phase:
Organisms are acclimatising to the new environment
There’s a low rate of reproduction
Population growth is slow

Question 3

What’s happening at b

Answer 3

Log phase / exponential
There are plentiful resources & no competition:
Reproduction&raquo_space;> Mortality
As there a good conditions, there is high population growth

Question 4

What’s happening at c

Answer 4

The stationary phase
This is when reproduction = mortality
- carrying capacity has been reached
Resources / the habitat cannot support a larger population

Question 5

What is carrying capacity

Answer 5

The maximum population size which can be supported & maintained over a particular period by the habitat

Question 6

What happens at d

Answer 6

Death phase
There isn’t enough resources to support the population

Question 7

What are density independent factors and are they linked to abiotic or biotic factors

Answer 7

These are factors that act just as strongly regardless of population size
For example: abiotic (non-living) factors, like light availability, space, soil pH etc

Question 8

Abiotic factors that affect population size

Answer 8

Temperature
Water mineral content
Natural disasters
Light availability
Space
Water supply
Soil pH

Question 9

What are density dependent factors and are they linked to abiotic or biotic factors

Answer 9

As population size increases, the factor is more influential
Therefore more linked to biotic (living!) factors (e.g. interactions between organisms)

Question 10

Examples of factors that affect population size

Answer 10

Predation
Parasitism
Food
Water
Light
Immigration & emigration

Question 11

What’s a K strategist species

Answer 11

A species whose population size is determined by carrying capacity
C.C. Reached -> population growth slows -> limiting factors = more influence

Question 12

Features of K strategists

Answer 12

Low reproductive rates
Late reproductive age
Large body mass
Slow development (longer lifespans)
E.g. large mammals & birds

Question 13

What’s an R strategist

Answer 13

A species that has a rapid increase in population size until they exceed carry capacity & limiting factors begin to have an affect & population growth & level falls

Question 14

Features of R strategists

Answer 14

• faster reproductive growth
  High reproductive rate
  Quick development
  Small body mass
  E.g. mice / insects

Question 15

3 main interactions between populations

Answer 15

Intraspecific competition
Interspecific competition
Competitive exclusion

Question 16

What’s intraspecific competition

Answer 16

Between individuals of the SAME specifies

Question 17

How does intraspecific competition keep the population size relatively stable

Answer 17

Plentiful resources = increased population = more individuals compete for same resources = carrying capacity reached
-> resources become limiting
This keeps the population size relative stable

Question 18

What is interspecific competition

Answer 18

Between individuals of different species
Intensity of competition = no resources = decreases reproduction rate, increases mortality rate

Question 19

What is competitive exclusion

Answer 19

The idea that 2 organisms can’t occupy the same niche

Question 20

What happens in competitive exclusion

Answer 20

2 organisms occupy the same / similar niches
One organism is slightly better adapted
The other organism is outcompeted & dies out in that habitat

This may not always apply in natural ecosystems, as other variables may be acting as limiting factors

Question 21

Explain this predator population graph

Answer 21

Initially predator population size increases, as more prey are available, so more predators can survive & reproduce
More prey are eaten
Less prey survive & reproduce
Prey population size decreases
Less prey avaibke
Predator population size decreases, as less can survive and reproduce
Prey population size increases
& so on

Question 22

What’s the difference between conservation & preservation

Answer 22

Conservation is maintains biodiversity THROUGH sustainable, human activity: its an active process whereas Preservation is a way of protecting the biodiversity of an environmentally sensitive area by restricting human activity

Question 23

What are the reasons for conservation

Answer 23

1. Economic (e.g. ecotourism provides income & resources like medicines, wood & food)
2. Ethical (e.g. all have a right to exist & our responsibility is to ensure that)
3. Social (aesthetic value from which we derive pleasure & relaxation)

Question 24

What are the aims of sustainability (sustainable resource management)

Answer 24

To ensure that there are enough resources for current & future generations
To preserve the environment
To enable development of lower income countries by balancing resource consumption

Question 25

What is the process coppicing

Answer 25

Tree trunk close to ground level
Several new shoots grow from cut surface
Protect young shoots from grasses
Process repeated after certain time / rotational coppicing

Question 26

What is pollarding

Answer 26

Repeatedly cutting tree stems HIGH up
This helps trees avoid being eaten by certain herbivores like deer

Question 27

Aim of coppicing & pollarding

Answer 27

For new shoots to grow out of the stump

Question 28

What’s rotational coppicing

Answer 28

When the stems of each section mature & grow larger before they are recur
-> so more light is let into diff habitats in the woodland
- maintains specifies biodiversity
= basically when trees are cut by section each year

Question 29

Issues with large scale timber production versus how to reduce the issues

Answer 29

Question 30

What are edge habits

Answer 30

Replanting trees @ optimal distance apart
- to avoid competition

Question 31

What is selective cutting

Answer 31

Removing only larger / better trees from the habitat, so the rest are largely unaffected

Question 32

Sustainable fishing methods

Answer 32

Question 33

What is clear felling & how can it be improved

Answer 33

It’s cutting all the trees down in an area
Improved by:
- replant all the trees after
- only do it so often
- limit the area felled

Question 34

Markscheme reasons why something would be conservation

Answer 34

• local people there
• sustainable use e.g. if an areas used for logging or farming
• active measures to maintain biodiversity or the habitat

Question 35

Why can controlled grazing be better than normal

Answer 35

Normal overgrazing can disrupt the food chain

Question 36

Peat bogs need high levels of moisture: what implementations can you do make sure of this

Answer 36

No planting of trees as they’ll remove water from the bog
No ditch as it will drain water from the bog
No ‘controlled burning’ etc - may lead to death in rare species organisms

Question 37

Reasons why something may be preservation (ms)

Answer 37

E.g. no visitors allowed, or restricting human interference e.g. tree planting

Question 38

How to make clear felling SUSTAINABLY

Answer 38

limit the size of the area felled,
Replant the trees that have been felled after
Limit the soil erosion after felling by limiting the area felled too

Question 39

Benefits of coppicing

Answer 39

• fewer large trees = more light for smaller plants
• prevents succession
• provides variety of light levels
• large machinery not needed
• maintains soil quality

Question 40

Other measures of sustainable fishing (ms) and difficulties with implementing them

Answer 40

• fishing quotas (area too large?)
• monitoring & surveillance after implementing restrictions (expensive to monitor & hampered by weather / seasons)
• penalties & sanctions (people could false report their fishing)