6.3.2 Populations and sustainability

Question 1

What is carrying capacity?

Answer 1

The maximum stable population size of a species that an ecosystem can support.

Question 2

What two types of factors does population size depend on?

Answer 2

Abiotic
Biotic

Question 3

Give some examples of abiotic factors.

Answer 3

Amount of light
Amount of water
Space avaliable
Temperature
Chemical composition of surroundings.

Question 4

When abiotic factors are ideal for a species what happens.

Answer 4

The species can reproduce successfully and population size increases.

Question 5

What is interspecific competition?

Answer 5

Competition between different species.

Question 6

What is intraspecific competition?

Answer 6

Competition within different species.

Question 7

Impact of interspecific competition on population size.

Answer 7

Different species compete with each other for the same resources e.g food and habitats. This can mean that the resources available to both populations are reduced so populations will be limited. As they lack food, they will have less energy for reproduction and growth so the population size will be lower.
If two species are competing but one is better adapted, the less well species is likely to be out-competed and won’t be able to exist alongside the better-adapted species.

Question 8

Impact of intraspecific competition on population size.

Answer 8

The population of a species increases when resources are plentiful. As the population increases there will be more organisms competing for that space and food.
Eventually, resources such as food and space become limiting- there isn’t enough for all the organisms. The population then begins to decline.
A smaller population then means less competition for space and food which is better for growth and reproduction so the population begins to grow again until it reaches carrying capacity.

Question 9

Impact of predation on population size.

Answer 9

As the prey population increases, theres more food for predators so the predator population grows.
As the predator population increases, more prey is eaten so prey population begins to fall. This is an example of negative feedback.
This means theres less food for predators, so their population decreases.
The number of prey increases as there are now fewer predators.
The cycle repeats.

Question 10

What is conservation?

Answer 10

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

Question 11

Give three reasons for conserving ecosystems

Answer 11

Economic
Social
ethical

Question 12

What are the economic reasons for conserving ecosystems?

Answer 12

Ecosystems provide resources for lots of things that humans need e.g rainforests produce things like drugs, clothes and food. These are economically important as they are traded on a local and global scale. If the ecosystems are not conserved, the resources that we use now will be lost, there will be less trade in the future.

Question 13

What are the social reasons for conserving ecosystems?

Answer 13

Many ecosystems bring joy to lots of people because they look attractive and people use them for activities e.g birdwatching and walking. The species and habitats in the ecosystem may be lost if they are not conserved so future generations won’t be able to use them.

Question 14

Give some ethical reasons for conservation.

Answer 14

Some people think we should conserve ecosystems simply because it’s the right thing to do, e.g most people think organisms have a right to exist so they shouldn’t become extinct due to human activity. Some people also think we have a moral responsibility to conserve ecosystems for future generations so that they can use them.

Question 15

What is preservation?

Answer 15

The protection of ecosystems so they are kept exactly as they are. Nothing is removed and they’re only used for activities which will not damage them.

Question 16

How are woodlands conserved?

Answer 16

1) Trees are cleared in strips and patches as woodland rows back quicker in smaller areas between bits of existing woodland than in larger, open areas.

2) The cleared strips or patches arent too long or exposed- lots of soil erosion can occur on large areas of bare ground.

3) Timber is sometimes harvested by coppicing

4) Pollarding- This brings many of the same benefits as coppicing but ensures that herbivores are less likely to be able to reach and consume the new shoots as they grow.

5) Native tree species tend to be planted in preference to non-native species as this is better for biodiversity because native species have long-established interactions with other native species.

6) Planted trees are adapted to posts to provide support and are grown in plastic tubes to stop them from being eaten by grazing animals.

7) Trees are not planted too close together so they are not competing with each other for space or resources.

Question 17

How is fishing done in a sustainable way?

Answer 17

1) Using fishing Quotas- Limits to the amount of certain fish species that fishermen are allowed to catch.

2) International agreements are made that state the amount of fish each country can take and where they can take them from.

3) Banning certain catch practices e.g gillnets (static nets that capture anything that swims).

4) Limiting the mesh size of nets to reduce the number of unwanted and discarded fish that are accidentally caught e.g shrimp as well as cod. Smaller and younger fish will slip through the net allowing them to reach breeding age.

Question 18

What is coppicing?

Answer 18

Cutting down trees in a way that lets them grow back so new trees don’t need to be planted.

Question 19

What is pollarding?

Answer 19

Similar to coppicing- cutting down trees in a way that lets them grow back so new trees don’t need to be planted but they are cut higher up

Question 20

Give some possible causes of extinction.

Answer 20

-Climate change
-Competition
-Hunting by humans
-Mass agriculture
-Degradation and loss of habitats

Question 21

How has climate change led to extinction?

Answer 21

The large-scale burning of fossil fuels by humans has led to an increase in the levels of carbon dioxide in the atmosphere creating the greenhouse effect. This increased carbon dioxide concentration in the atmosphere has had several knock-on effects e.g ice caps melting, sea levels rising, increase in mean global temperature. These effects have massively changed the habitats of some species so much so that they cannot survive in the new conditions.

Question 22

Explain how conservation has led to extinction.

Answer 22

When there is limited supply of resources within an area, organisms begin to compete for resources e.g food, water, habitat, reproductive mates.
Competition reduces population size.

Question 23

Explain how the introduction of species has led to extinction.

Answer 23

When humans colonised new land they would often exchange animal and plant species between their home and the new land. These are non-native species. These can be highly problematic as they often have no natural competitors, predators of pathogens in the new areas and so without these they can massively increase in number and negatively affect the native species.

Question 24

Explain how hunting by humans has led to extinction.

Answer 24

Nowadays the meat that humans consume comes from domesticated live stock like cattle, sheep and chicken. The hunting of wild animals is still common and has become a sport for some individuals. The rarer and more vulnerable species are often more desirable.

Question 25

Explain how degredgation and loss of habitats has led to extinction.

Answer 25

Over recent years humans have aggressively destroyed animals habitats by cutting down forests, draining wetlands and polluting water, soil and air.
This is highly problematic as species are adapted to survive within their specific habitat and without this they will not get the resources they need to survive.

Question 26

Give 4 examples of environmentally sensitive ecosystems

Answer 26

Galapagos islands
Antarctica
Snowdonia national park
The lake district

Question 27

What are the problems in snowdonia national park in wales?

Answer 27

Lots of rain falls on the snowdonia hills which leads to be erosion of the paths. Walkers often trample the surrounding vegetation as they try to walk around the flooding.

Question 28

How is conservation in snowdonia done?

Answer 28

Volunteers have dug drains next to the paths to prevent flooding.

Question 29

What are the problems in the Terai Arc.

Answer 29

Nearly 7 million also live in this area and may of them depend on the forests resources to survive.
Areas of the forest are being destroyed to make room for more housing and other development. This creates conflict between animals and humans so the animals are more likely to be shot.

Question 30

How is conservation done in the terai arc?

Answer 30

Conservation charity WWF has worked with the local people to help balance their needs with conserving the wildlife. E.g provided solar cookers and biogas generators so they do not need to use wood from the forest as fuel. Farmers are encouraged to plant mint hedges and mint repels animals away.

Question 31

Problems in the masai mara regions.

Answer 31

Its large area of grassland is home to huge populations of wildebeest and zebra as well as lions and cheetahs. It is also home to the Masai people who traditionally earn a living by raising livestock. This can bring them into conflict with conservationists e.g overgrazing by livestock can destroy grass for wildlife.

Question 32

How is the masai maria conserved?

Answer 32

Conservation tourists are working with the Masai people to help them to make money from their land through conservation and ecotourism projects rather than farming. This means their economic needs are met and the wildlife is conserved.

Question 33

Problems with UK peat bogs.

Answer 33

Peat bogs store water and carbon dioxide and are home to lots of different plants and animals.
Farmers use peat bogs to graze sheep and deer however this leads to conflict with conservationists as overgrazing causes loss of moss species, soil compaction and general peat bog erosion.

Question 34

How are peat bogs conserved?

Answer 34

Recent government funded programmes like the Environmental Sterwardship scheme have given farmers money to use peat bogs in a sustainable way e.g carry out measures to reduce water runoff, to lower the number of livestock and remove livestock over winter

Question 35

Problems with the galapagos islands.

Answer 35

Non-native animals have been introduced to the islands. These compete with native plant species causing a decrease in their populations. E.g goats.
Non-native plants have also been introduced to the island and these compete with native plant species causing a population decrease. E.g Quinine trees are taller than some native plants and block out light for other plants which struggle to survive.

Question 36

How is the galapagos islands conserved?

Answer 36

Eradication programmes have removed wild goats from some of the smaller islands and wild dogs from the larger islands. Quinine trees are kept in check using chemical herbicides.
When people visit the park, they are required to follow a list of rules e.g not bringing any live plants or animals and being with a guide at all times.

Question 37

What are the problems with antarctica?

Answer 37

Unique icy landscape with plants and animals which have adapted to its harsh conditions.
Visitors have caused pollution in the past by dumping sewage into the sea and leaving rubbish. Shipping accidents lead to oil spills.
hunting, whaling and fishing have all reduced wildlife populations.

Question 38

How is conservation done in Antarctica?

Answer 38

All waste apart from food waste and sewage must be taken away by ship for disposal in other countries.
Ships that use thick oil as fuel are banned from antarctic waters,
Tourist restrictions e.g only allowed on land in certain locations at certain times.
Hunting and whaling banned.

Question 39

List some advantages of coppicing

Answer 39

• Takes up less time for trees to grow back.
• Lifespan of trees extended.
• Provides habitats
• Prevents succession
• Prevents soil erosion
• Large machinery not needed.