6.3.1 / 6.3.2 Ecosystems, Populations and Sustainibilty

Question 1

Define ecosystem

Answer 1

*All the living organisms found in one area, and the non-living aspects of their environment.
*Can greatly range in size e.g. rock pool to tree to field
*Referred to as ‘dynamic’ as they depend on interactions between biotic and abiotic factors.

Question 2

Describe biotic and abiotic factors of an ecosystem

Answer 2

*Biotic - living features of am ecosystem e.g. predators and disease
*Abiotic - non-living features of an ecosystem e.g. light and temperature.

Question 3

What is biomass and how is it transferred ?

Answer 3

The total weight of living matter in a certain area, transferred up trophic levels through consumption

Question 4

How can we measure transfer of biomass ?

Answer 4

Measured in terms of mass of carbon in each trophic level, or dry mass of tissue.

Question 5

Give the formula for efficiency of biomass transfer

Answer 5

Efficiency = (biomass transferred / biomass intake) x 100

Question 6

How can human activities maximise
biomass transfer ?

Answer 6

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

Question 7

Outline the roles of microorganisms in the nitrogen cycle

Answer 7

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

Question 8

What is meant by primary succession ?

Answer 8

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

Question 9

Summarise the process of primary succession

Answer 9

•Pioneer species that are able to survive harsh areas colonise the area
•When they die, they 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 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 11

What is deflated succession ?

Answer 11

Where succession is interrupted - typically by human interference

Question 12

What is sampling ?

Answer 12

•Selecting a group of individuals that will represent a whole target population
•This 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 -

Question 14

Define carrying capacity

Answer 14

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

Question 15

Give factors that limit the maximum size of a population

Answer 15

•Food
•Water
•Light
•O2
•Nesting sites
•Predators

Question 16

Describe the pattern of a typical predator-prey relationship in terms of a 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 survive, and cycle repeats.

Question 17

What is intraspecific variation vs interspecific variation ?

Answer 17

Intraspecific - competition within a species
Interspecific - competition between species.

Question 18

What is the difference between conservation and preservation ?

Answer 18

Conservation - maintains biodiversity of a habitat by allowing the sustainable use of recourses
Preservation - maintains biodiversity of a habitat by minimising human impact.

Question 19

Give reasons why we conserve and preserve habitats

Answer 19

•Economic - food sources, natural pest control, tourism
•Social - many organisms can be used in medicine
•Ethical - sustainability for future generations

Question 20

Define sustainability

Answer 20

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

Question 21

What are sustainable uses of an ecosystem’s recourses ?

Answer 21

*Timber 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 in Nepal, it was over exploited for fuel
•Locals ensure there are migration paths and habitats for wildlife.

Question 23

Give an example of how human action effects sensitive ecosystems

Answer 23

•Galapagos islands
•Many species are endangered due to hunting and tourism
•New species have been introduced and are invasive