Topic 7C - Populations in ecosystems

Question 1

Define succession

Answer 1

Succession is the process by which an ecosystem changes over time (the biotic conditions such as plant and animal communities, change as the abiotic conditions, such as water availability, change)

Question 2

Define the 2 types of succession

Answer 2

1- Primary succession

2- Secondary succession

Question 3

Define primary succession

Answer 3

This is the type of succession that happens on land that’s been newly formed or exposed, e.g. where a volcano has erupted to form a new rock surface , or where sea levels have dropped, exposing a new area of land.
- There’s no soil or organic material to start with, just bare rock.

Question 4

Define secondary succession

Answer 4

This is the type of succession that happens on land that’s been cleared of all plants, but where the soil remains e.g. after a forest fire or where a forest has been cut down by humans.

Question 5

Define the term ‘pioneer species’ and explain their importance

Answer 5

Pioneer species: the first species to colonise a new land surface.

Question 6

Describe how pioneer species are important in an ecosystem

Answer 6

THEY ARE IMPORTANT AS:
1- Abiotic conditions are hostile e.g. no soil to retain water. Only pioneer species grow since they’re specially adapted to cope with harsh conditions. e.g. marram grass can grow on sand dunes due to its deep roots to get water and ability to tolerate salty environment.

2. Pioneer species change abiotic conditions - they die and microorganisms decompose the dead organic material (humus). This forms basic soil
3. This makes conditions less hostile. (e.g. basic soil helps retain water, which means new organisms with different adaptations can move in and grow. These then die and are decomposed, adding more organic material, making the soil deeper and richer in minerals. This means larger plants like shrubs can start to grow in the deeper soil, which retains even more water.

Question 7

State the effect that organisms like sand sedge may have on previous organisms like marram grass.

Answer 7

Sand sedge stabilises the sand through the growth of rhizomes (underground stems). This makes the conditions less suitable for marram grass, which needs constant reburial by sand in order to grow healthily.

Question 8

Why are the pioneer species in secondary succession much larger?

Answer 8

The pioneer species in secondary succession are much larger as there’s already a soil layer.

Question 9

At each stage of succession…

Answer 9

Organisms that are better adapted for the improved conditions move in, out-compete the plants/animals that are already there and become the dominant species in the ecosystem.
- as succession goes on, ecosystem becomes more complex. New species move in alongside existing species, increasing biodiversity.

Question 10

What is the final stage of succession?

Answer 10

Climax community - the ecosystem is supporting the largest and most complex community of plants that it can. It is in a steady state.

Question 11

Describe how primary succession causes bare rock to turn into woodland.

Answer 11

1. Pioneer species colonise rocks e.g. lichen grow on and break down rocks, releasing minerals.
2. The lichens die and are decomposed, helping to form a thin soil which thickens as more organic material is formed. This allows other species like mosses to grow.
3. As soil deepens, larger plants that need more water move in, e.g. grasses and small flowering plants. Soil continues to deepen as larger plants die and are decomposed.
4. Shrubs/ferns/small trees start to grow, out-competing grasses and smaller plants to become dominant species. Diversity increases.
5. Soil is deep/rich enough in nutrients to support large trees. These become dominant species and climax community is formed.

Question 12

Read up on how succession happens in sand dunes/salt marshes/lakes

Answer 12

own research

Question 13

Define climatic climax

Answer 13

the climax community for a particular climate

Question 14

What would the climatic climax be in a temperate climate?

Answer 14

Temperate climate: Plenty of water available, mild temperatures, and not much change between seasons. Hence, there’d be loads of trees as they can grow in these conditions once deep soils have been developed.

Question 15

What would the climatic climax be in a polar climate?

Answer 15

Polar climate: There wouldn’t be much water available, temps are low and there are massive changes between seasons. Hence, large trees wouldn’t ever be able to grow in these conditions, so climatic climax only contains herbs or shrubs, but it’s still the climax community.

Question 16

Define plagioclimax. (give an example)

Answer 16

This is the climax community when succession is prevented from developing due to human activity.

Question 17

Why does the moorland need to be conserved.

Answer 17

It is a habitat to many plants/ animals and if left to natural processes, succession would lead to climax community of spruce forest. This could mean the loss of habitats for many plants and animals = death.

Question 18

Name 2 ways to manage succession to conserve the moorlands ecosystem.

Answer 18

1. Animals are allowed to graze on land: Animals eat growing points of shrubs/trees, stopping them from establishing themselves and helping to keep vegetation low.
2. Managed fires are lit: after fires, secondary succession occurs on moorland - pioneer species will be conserved. Larger species will take longer to growl back and will be removed again the next time the moor is burnt. ***(why burn a forest when your trying to conserve habitats of plants and animals?)

Question 19

Define conservation.

Answer 19

Conservation: The protection and management of ecosystems in a sustainable way

Question 20

Define sustainability

Answer 20

Sustainability: the use of resources to meet the needs of people today, without reducing the ability of people in the future to meet their own needs

Question 21

Why doesn’t everyone agree with conservation?

(GIVE AN EXAMPLE OF:

• A group that doesnt agree with conservation
• How conservationists are combatting this issue)

Answer 21

Because it oftens comes into conflict with human needs

MAASAI

• Maasai people earn living by raising livestock, such as cattle. But conservationists dont like this as it could ruin grassland (as cattle eat grass)
• Conservationists are working with Maasai to help them make money through conservation/ecotourism projects rather than farming (So needs of both groups are met).

Question 22

Give 4 examples of conservation techniques

Answer 22

1. Seedbanks: Stores of lots of seeds from lots of different plant species. If plant becomes extinct in wild, stored seeds can be used to grow new plants.
2. Fishing quotas: limits to amount of certain fish species that fisherman can catch. They help to conserve fish species by reducing numbers that are caught and killed.
3. Protected areas (national parks/nature reserves): They protect habitats and species in them by restricting urban development, industrial development, and farming.
4. Captive breeding programmes: To increase numbers of species, before returning them to wildlife.

Question 23

evaluate supporting and conflicting data on conservation issues

Answer 23

page 190-191

Question 24

Define these words:

• Habitat?
• Population?
• Community?

Answer 24

• Habitat - the place where an organism lives
• Population: All the organisms of 1 species living in a habitat
• Community:Populations of different species in a habitat

Question 25

Define these words:

• Ecosystem?
• Abiotic conditions?
• Biotic conditions?

Answer 25

• Ecosystem: A community, plus all the non-living conditions living together in a habitat
• Abiotic conditions: Non-living conditions
• Biotic conditions: Living conditions

Question 26

Define these words:

• Niche?

- Adaptation?

Answer 26

• Niche: The role of a species in a habitat

- Adaptation: A feature that members of a species have that increases their chance of survival and reproduction

Question 27

What is the most important rule about niches?

Answer 27

Every species has its own unique niche - no 2 species can occupy the same niche
- If 2 species try and occupy the same niche, they will compete with each other until 1 species out-competes the other

Question 28

Give 3 examples showing how organisms can be adapted to ABIOTIC conditions

Answer 28

1. Otters have webbed paws - this means they can walk on land and swim effectively. (Increases chances of survival as they can live and hunt both in land & water).
2. Seals have a thick layer of blubber (fat) - keeps them warm in coldest seas. (Increases chances of survival as they can live in places where food is plentiful).
3. Hedgehogs hibernate - This lower their metabolism rate over winter. (Increases chances of survival as they can conserve energy during coldest months)

Question 29

Give 3 examples showing how organisms can be adapted to BIOTIC conditions

Answer 29

1. Sea otters use rocks to open shellfish and clams (increases their chance of survival as it gives them access to another source of food)
2. Male frogs produce mating calls to attract females - This makes sure they attract mate of same species. (Increases chances of reproduction by making successful mating more likely)
3. Some bacteria produce antibiotics - This kill other species of bacteria in same area. (Increases chances of survival as there would be less competition)

Question 30

Define carrying capacity

Answer 30

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

Question 31

Population sizes can vary because of…

Answer 31

abiotic and biotic factors

Question 32

Explain how population sizes can vary because of an abiotic temperature like temperature

Answer 32

When temp of a mammals surroundings is the ideal temp for metabolic reactions to take place, mammals don’t have to use up more energy trying to maintain internal body temp. This means more energy can be used for growth and reproduction so pop. size increases

Question 33

What biotic factors can affect population sizes?

Answer 33

1. Interspecific Competition
2. Intraspecific Competition
3. Predation

Question 34

What is INTERspecific competition?

Answer 34

COMPETITION BETWEEN DIFFERENT SPECIES

1. Organisms compete for same resources.
2. This can lead to reduction in resources available to both species so they’ll be less energy for growth and reproduction in both species, and both their pop. sizes would fall.
3. Species that is better adapted will out-compete the other one, and so their pop. size increases whilst other one decreases.

Question 35

What is INTRAspecific competition?

Answer 35

COMPETITION WITHIN A SPECIES

1. Population increases when food is plentiful. As pop. increases, there’ll be more organisms competing for same amount of space and food.
2. This causes environmental resistance - not enough food and space so pop. begins to decline
3. Smaller pop. means less competition for space and food, which is better for growth and reproduction - so pop. starts to grow again.

Question 36

How are predator and prey population sizes linked)

Answer 36

1. When the prey increases, predator pop. increases as more food for predators
2. As predator pop. increases, prey pop. decreases as more of them are being eaten.
3. If the prey pop. decreases, predator pop. also decreases as there is less food for the predator

Question 37

Are predator/prey relationships always that simple?

Answer 37

No - it is often thought that other factors are involved in the cycle such as availability of food (e.g. it is thought that the pop. of snowshoe hare initially begins to decline as there’s too many of them for the amount of food that is available).
- This is then accelerated by predation from lynx.

Question 38

What do niches consist of?

Answer 38

1. Biotic features e.g. What an organism eats/is eaten by

2. Abiotic features e.g. The O2 it breathes in, the CO2 is breathes out

Question 39

Why may animals have broader ecological niches in some areas than others?

Answer 39

Animals may have broader ecological niches in areas with less competition.