Ecosystems, Populations And Sustainability

Question 1

Define ecosystems

Answer 1

All the living organisms found in one area and the non living aspects of their environment
Can range in size from rock pool to African savannah
Known as ‘dynamic’ as they depend on interactions between biotic and abiotic factors

Question 2

Describe biotic factors with examples

Answer 2

The living features of an ecosystem
Any from
Predators
Disease
Symbiosis
Parasitism
Mutualism
Competition

Question 3

Describe abiotic factors and give examples

Answer 3

Non living features of an ecosystem
Any from
Light
Soil
Water availability
Water movement
Oxygen concentration
pH
Wind
Salinity
Temperature
Humidity

Question 4

What is biomass and how is it transferred?

Answer 4

Total weight of living matter in a certain area, transferred up trophic levels through consumption. Can be measured in terms of mass of carbon or dry mass of tissue

Question 5

Give the formula for the efficiency for a biomass transfer

Answer 5

Efficiency = ( Biomass transferred / Biomass intake ) x100

Question 6

How can human activities affect biomass transfer

Answer 6

• Light, water, temperature maximised
• Increased nutrients in soil
• Pests and weeds removed
• Growth rates boosted through steroids, selective breeding etc

Question 7

Outline the role of microorganisms in the nitrogen cycle

Answer 7

Nitrogen-fixing bacteria e.g. Rhizobium in roots and Azotobacter in soil convert gaseous nitrogen into ammonia
Nitrifying bacteria e.g. Nitrosomonas convert ammonium compounds into nitrites
Nitrobacter then converts nitrites to nitrates

Question 8

Outline the role of organisms in the carbon cycle

Answer 8

• Respiration of plants and animals add carbon dioxide into the atmosphere
• Photosynthesis of plants removes carbon dioxide from the atmosphere
• Decomposers (microorganisms) decay plant and animal material into carbon dioxide

Question 9

What is meant by primary succession

Answer 9

Where an area previously devoid of life is colonised by a community of organisms

Question 10

Summarise the process of primary succession

Answer 10

• Pioneer species, able to survive harsh conditions, colonise the area
• They die, decompose and add nutrients to the ground
• Over time, this allows more complex organisms to milestone

Question 11

What is the climax community and how is it reached?

Answer 11

The final stage of succession, where the ecosystem is balanced and stable. It is reached when the soil is rich enough to support large trees or shrubs, and the environment is no longer changing

Question 12

What is deflected succession

Answer 12

Where succession is interrupted, usually by human interference

Question 13

What is sampling

Answer 13

Selecting a group of individuals that will represent the whole target population
Allows us to measure the distribution and abundance of organisms

Question 14

Give methods of sampling and explain how they are used

Answer 14

Quadrats = used in small areas. Randomly or regularly placed across habitat. Frequency or % cover calculated
Transects = used in larger areas. Sample taken along a line that crosses the habitat. Can be combined with quadrats in the form of a belt transect

Question 15

Define carrying capacity

Answer 15

The maximum population size that a habitat can support, defined by the presence of limiting factors

Question 16

Give factors that limit the maximum size of a population

Answer 16

Food
Water
Light
Oxygen
Nesting sites
Shelter
Parasites
Predators

Question 17

Describe the pattern of a typical predator-prey relationship in terms of population change

Answer 17

Prey is eaten by predator, resulting in predator population increasing and prey population decreasing
Fewer prey means greater competition for food, so predator population decreases
Fewer predators means more prey survives, and the cycle begins again

Question 18

What is meant by intraspecific and interspecific competition

Answer 18

Intraspecific= competition between organisms of the same species
Interspecific= competition between organisms of different species

Question 19

Differentiate between conservation and preservation

Answer 19

Conservation= maintains biodiversity of a habitat by allowing the sustainable use of the resources there
Preservation= maintains biodiversity of a habitat by minimising human impact

Question 20

Give reasons why we conserve and preserve habitats

Answer 20

Economic= Food source, natural pest control, boosts tourism
Social= many organisms can be used in medicine, aesthetics
Ethical= we have a responsibility to maintain habitats for future generations

Question 21

Define sustainability

Answer 21

Using resources in a way that also maintains them for future generations

Question 22

What methods allow sustainable use of an ecosystems resources

Answer 22

Timber production= coppicing to encourage growth, replacing felled trees, selective cutting
Fishing= stocks not depleted, no overfishing, can continue indefinitely

Question 23

Give an example of how the conflict between conservation and human needs can be balanced

Answer 23

Terai region (Nepal). Over-exploited for use in fuel. Locals now have a responsibility to look after the forest. ‘Corridors’ placed to enable migration

Question 24

Give an example of how human effects are controlled in sensitive ecosystems

Answer 24

Galapagos islands. Many species endangered due to hunting and tourism. New species introduced, but caused damage to native species. Trying to find a balance