6.3.1 / 6.3.2 Ecosystems, Populations and Sustainibilty Flashcards
Define ecosystem
*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.
Describe biotic and abiotic factors of an ecosystem
*Biotic - living features of am ecosystem e.g. predators and disease
*Abiotic - non-living features of an ecosystem e.g. light and temperature.
What is biomass and how is it transferred ?
The total weight of living matter in a certain area, transferred up trophic levels through consumption
How can we measure transfer of biomass ?
Measured in terms of mass of carbon in each trophic level, or dry mass of tissue.
Give the formula for efficiency of biomass transfer
Efficiency = (biomass transferred / biomass intake) x 100
How can human activities maximise
biomass transfer ?
*Light, water, temperature maximised
*Increased nutrients in soil
*Pests and weeds removed
*Growth rates boosted through steroids, elective breeding etc.
Outline the roles of microorganisms in the nitrogen cycle
*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.
What is meant by primary succession ?
Where an area that is previously devoid of life is colonised by a community of organisms
Summarise the process of primary succession
•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.
What is the climax community and how is it reached ?
•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.
What is deflated succession ?
Where succession is interrupted - typically by human interference
What is sampling ?
•Selecting a group of individuals that will represent a whole target population
•This allows us to measure the distribution and abundance of organisms.
Give methods of sampling and explain how they are used
Quadrats -
Define carrying capacity
The maximum population size that a habitat can support, defined by the presence of its limiting factors
Give factors that limit the maximum size of a population
•Food
•Water
•Light
•O2
•Nesting sites
•Predators
Describe the pattern of a typical predator-prey relationship in terms of a population change
•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.
What is intraspecific variation vs interspecific variation ?
Intraspecific - competition within a species
Interspecific - competition between species.
What is the difference between conservation and preservation ?
Conservation - maintains biodiversity of a habitat by allowing the sustainable use of recourses
Preservation - maintains biodiversity of a habitat by minimising human impact.
Give reasons why we conserve and preserve habitats
•Economic - food sources, natural pest control, tourism
•Social - many organisms can be used in medicine
•Ethical - sustainability for future generations
Define sustainability
Using recourses in a way that also maintains them for future generations
What are sustainable uses of an ecosystem’s recourses ?
*Timber production - coppicing to encourage growth, replacing felled trees, selective cutting
*Fishing - stocks not depleted, no overfishing, can continue indefinitely.
Give an example of how the conflict between conservation and human needs can be balanced
•Terai region in Nepal, it was over exploited for fuel
•Locals ensure there are migration paths and habitats for wildlife.
Give an example of how human action effects sensitive ecosystems
•Galapagos islands
•Many species are endangered due to hunting and tourism
•New species have been introduced and are invasive
