Ecosystems & Population And Sustainability

Question 1

Define Ecosystem

Answer 1

• ALl living organisms found in an area (Biotic), and the non-living aspects of their environment (Abiotic). Can range in size e.g. rock pool,tree, field.
• Known as dynamic as they’d penned on interactions between biotic and abiotic factors

Question 2

Describe biotic and abiotic factors, giving examples

Answer 2

• Biotic: Livig features of an ecosystem e.g. predators, disease
• Abiotic: Non-living features of an ecosystem e.g. light, temperature

Question 3

What is a biomass and how is it transferred? How can we measure this ?

Answer 3

• The total weight of living matter in certain area, transferred up tropic levels through consumption, can be measured as mass of carbon, or dry mass of tissue

Question 4

What is the formula for efficiency of biomass transfer ?

Answer 4

Efficiency = Biomass transferred ÷ Biomass intake x 100

Question 5

How can human activities affect biomass transfer ?

Answer 5

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

Question 6

Outline the roles of microorganisms in the nitrogen cycle

Answer 6

• 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 convert nitrites to nitrates

Question 7

Outline the Role of organisms in the carbon cycle

Answer 7

• 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 8

What is meant by primary succession ?

Answer 8

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

Question 9

Summarise the process of primary succession

Answer 9

• 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 survive

Question 10

What is the climax community and how is it reached ?

Answer 10

• The final stage of Succession, where the ecosystems becomes balanced and stable
• Is reached when the soil is rich enough to support large trees or shrubs, and the environment is no longer changing

Question 11

What is deflected succession ?

Answer 11

• Where succession is interrupted, usually by human interference

Question 12

What is sampling ?

Answer 12

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

Question 13

Give methods of sampling and explain how they are used

Answer 13

• Quadrats = used in small areas randomly or regularly placed across habitats. 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 14

Define carrying capacity

Answer 14

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

Question 15

Give factors that limit the maximum size of a population

Answer 15

• Food
• Water
• Light
• Oxygen
• Nesting sites
• Shelter
• Parasites
• Predator

Question 16

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

Answer 16

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

Question 17

What is meant by intraspecific and interspecific competition ?

Answer 17

• Intraspecific: Competition between organism of the same species
• Interspecific: Competition between organisms of different species

Question 18

Differentiate between conservation and preservation

Answer 18

• Conservation: Maintains biodiversity of a habitat by allowing sustainable use of resources there
• Preservation: Maintains biodiversity of a habitat by minimising human impact

Question 19

Give reasons why we conserve an persevere habitats

Answer 19

• Economic: Food source, Natural pest control, boosts tourism
• Social: Many organism can be used in medicine, aesthetics
• Ethical: We have a responsibility to maintain habitats for future generations

Question 20

Define sustainability

Answer 20

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

Question 21

What methods allow sustainable use of an ecosystems resources ?

Answer 21

• The Production: Coppicing to encourage growth, replacing felled trees, selective cutting
• Fishing: Stocks not depleted, no overfishing, can continue indefinitely

Question 22

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

Answer 22

• 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 23

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

Answer 23

• Galápagos Islands. Many species endangered due to hunting and tourism, New species introduced, but caused damage to native species