Populations

Question 1

Limiting factors

Answer 1

Limit the growth of a population size
- water
- food
- space
- light
- oxygen
- predators
- disease
- competition

They prevent populations from exceeding the carrying capacity

Question 2

Population growth curve

Answer 2

S shaped curve
- Lag phase
- Log phase / exponential phase
- Stationary phase

Question 3

K strategists

Answer 3

• Believe population size is determined by carrying capacity
• limiting factors exert an increasingly more significant effect as carrying capacity is reached

E.g. larger animals and plants

• Low reproductive rate
• Slow development
• Late reproductive age
• Long life span
• Large body mass

Question 4

R strategists

Answer 4

Population size increases very quickly
Carrying capacity exceeded before limiting factor have an effect
Build up of water can poison the species (boom and bust

E.g. mice, insects, spiders, weeds

• high reproductive rate
• quick development
• young reproductive age
• short life span
• small body mass

Question 5

Boom and bust

Answer 5

Some species exceed their carrying capacity due to a rapid reproductive rate. Once they have exceeded this, there are insufficient resources to maintain the population and some will die. Death can also be caused by the build up of waste products

Question 6

Predator prey relationships

Answer 6

• prey population increases when predator numbers are low, and low environmental resistance with few limiting factors
• more prey = more food for predators
• populations of predator increases after a lag time
• prey eaten by predators = prey numbers decrease
• less food for predators, fewer survive and predator numbers decrease
• cycle repeats

Question 7

Intraspecific competition

Answer 7

Within the species

• as environmental pressures increase (factors become limiting) competition increases
• Those best adapted survive, reproduce and pass on their genes (others die)
• Keeps the stationary phase fairly stable

Question 8

Interspecific competition

Answer 8

Between species

Question 9

Competitive exclusion

Answer 9

Explains why particular species only grow in certain places

Question 10

Conservation

Answer 10

The protection and management of ecosystems so that natural resources in them can be used without running out

Question 11

Preservation

Answer 11

The protection of ecosystems so they’re kept exactly as they are
- nothing is removed from from a preserved ecosystem, and they’re only used for activities that don’t damage then

Question 12

How does increasing human population threaten biodiversity

Answer 12

• over exploitation of wild populations for food
• disrupting habitats with urbanisation and pollution
• introducing non native species which competitively exclude native species

Question 13

In situ

Answer 13

• protected areas, national parks, nature reserves
• Marine Conservation Zones
• Controlling/preventing introduction of species that threaten local biodiversity
• Protecting habitats e.g. coppicing to control water levels to conserve wetlands
• Restoring damaged areas e.g. coastlines polluted by oil
• Promoting particular species e.g. by protecting nesting sites or food sources
• Giving legal protection and endangered species

Question 14

Ex situ

Answer 14

zoos
• Relocating organisms
• Breeding in captivity and reintroducing to the wild
• Botanical gardens- controlled environments
• Seed banks

Question 15

What are SSSI’s

Answer 15

Sites of special scientific interest

Question 16

4 reasons for conservation

Answer 16

• economic
• social
• ethical
• ecological

Question 17

Economic reasons for conservation

Answer 17

Ecosystems provide lots of resources that humans need e.g. rainforests -species providing resources such as drugs, clothes and food.
These are traded at a local and global scale. If not conserved, resources could be lost and there would be less trade in the future

Some species have indirect value e.g. pollinators

Question 18

Social reasons

Answer 18

Recreation and ecotourism give high social and economic value from the aesthetic side of ecosystems e.g. birdwatching and walking

Habitats may be lost if not conserved, so future generations won’t be able to enjoy them

Question 19

Ethical reasons

Answer 19

Some people believe all species have a right to exist and we are obliged to conserve environments

Often ethical arguments are ignored in favour of economic arguments governments - conservation is often driven by economics

Question 20

Ecological reasons

Answer 20

Helps to prevent climate change e.g. when trees are burnt, CO₂ is released which contributes to global warming. Conservation of trees slows this

Disrupting food chains also has a knock on effect on other organisms

Question 21

Large scale timber production

Answer 21

• clear felling is completely cutting down all of the trees in an area. It is for large scale timber production
• Trees take up water from the soil which stops the soil being washed away (soil erosion) and polluting rivers. Keep nutrient levels in balance in the carbon and nitrogen cycle. Clear felling leads to the opposite
• If trees are felled on a rotation of 50-100 years then biodiversity can be increased but this isn’t cost effective

Question 22

Sustainable production

Answer 22

Harvesting in amounts which leaves sufficient organisms to grow and replenish what has been harvested
- it can be carried on indefinitely via replanting, coppicing…

Question 23

Sustainable forestry- large timbers

Answer 23

• replant a tree for each one harvested
• whole woodland must maintain its ecological function of biodiversity, climate, mineral and water cycles
• local people should benefit from the forest

Balance needed between making money and maintaining biodiversity

Question 24

How to ensure max. yield

Answer 24

• control pests and pathogens
• only plant tree species that will grow well in the area
• plant trees optimal distances apart to prevent too much competition for light, water, minerals

Question 25

Coppicing- smaller timber

Answer 25

Cutting a tree trunk close to the ground to encourage several new, thinner stems to grow

• once they have grown, the new stems will be cut
• all this thin wood can be used for furniture, firewood… but the trees don’t die and so no replanting is needed

Question 26

Rotational coppicing - smaller timber

Answer 26

Woodlands are divided up and different sections are coppiced on different years.
• This means each section is at a different stage and coppicing can be done to provide a continuous supply of wood each year.
• By the time they are ready to coppice the first section again, the shoots should have regrown and be ready to be re‐cut.

‘Standards’ are trees left uncoppiced and cut to produce larger timber for planks etc. ‐ these have more value

Question 27

2 methods of managing fish stocks

Answer 27

1. Fisheries
2. Aquaculture

Question 28

Aquaculture

Answer 28

Breeding, rearing and hare eating of plants and animals in all types of water environments including ponds, rivers, lakes and ocean

• restricts impact on oceanic fish stocks
• expected to feed more people than traditional fishing in future

Question 29

Fisheries

Answer 29

• high economic value (sales and jobs)

Marine Stewardship Council has 3 main principles for sustainable management:
1. Over fishing must be avoided to stop extinction of species
2. No permanent damage to local habitats
3. Always comply with local, national and global regulations

Question 30

What are the advantages and disadvantages of aquaculture, rather than ‘capture fisheries’?

Answer 30

Advantages
- restricts the impact of fishing on oceanic fish stocks
- is a cheap and plentiful protein source for an increasing human population

Disadvantages
- populations susceptible to pests and pathogens
- possible cause of pollution.

Question 31

State 2 reasons the forests in the Terai region has been under pressure

Answer 31

1. Expansion of agriculture into forested areas, grazing from farm animals, over exploitation of forest resources
2. replacement of traditional agricultural crop varieties with modern ones

Question 32

State 1 reason the forests in the Terai region are important to local communities

Answer 32

The forests provide people with a sustainable source of fuel, animal feed, food building materials, agricultural and household tools and medicines

Question 33

State 2 of the community forestry initiates introduced by the WWF and Nepalese gov.

Answer 33

1. Conservation of the forest landscape. To ensure conservation with development, they introduced community forestry initiatives in which local people had rights to exploit the forest as well as responsibility to look after it.
2. Scheme also introduced biogas plants and wood efficient sticks to reduce demand for firewood

Question 34

1 advantage of a partnership between conservancies and tourism in the Maasai Mara

Answer 34

Use money from tourism for conservation

Question 35

1 disadvantage of a partnership between conservancies and tourism in the Maasai Mara

Answer 35

Tourism may destroy the land