Ecosystems Flashcards
Define ecosystem
All the living organisms in one area and the non-living aspects of their environments.
Can range in size
Dynamic and are influenced by biotic and abiotic factors
Define biotic and abiotic factors and give examples
Biotic - living features of an ecosystem e.g predators, disease
Abiotic - non-living features of an ecosystem e.g light, temperature
What is biomass and how is it transferred?
The total weight of living matter in a certain area
Biomass is transferred up trophic levels through consumption
How is biomass measured?
Mass of carbon
Dry mass of tissues
Give the formula for efficiency of biomass transfer
Biomass transferred
= —————————— x 100
Biomass intake
How can human activity affect biomass transfer?
Light, water, temperature maximised
Increased nutrients in soil
Pests and weeds removed
growth rates boosted through steroids and selective breeding
Outline the roles of microorganisms in the nitrogen cycle?
Nitrogen fixing bacteria e.g Rhizobium in the roots and Azotobacter in the soil - convert nitrogen to ammonia
Nitrifying bacteria e.g Nitrosomonas convert ammonium compounds to nitrites
Nitrobacter converts nitrites to nitrates
Outline the role of organisms in the carbon cycle
Respirarion adds CO2 to the atmosphere
Photosynthesis removes CO2 from the atmosphere
Decomposers decay plant and animal matter to release CO2
What is primary succession?
Where an area of newly exposed land is colonised by a community of organisms
What is the process of primary succession?
Pioneer plants colonise the area because they can survive harsh conditions.
They die, decompose and add nutrients to the ground
Overtime this allows more complex organisms to survive
What is the climax community?
The final stage of succession, where the ecosystem is balanced and stable
How is the climax community reached?
Soil is rich enough to support large trees or shrubs and the environment is no longer changing
What is deflected succession?
Where succession is interrupted, usually by human interference
What is sampling
Selecting a group of individuals that will represent the whole target population.
Give methods of sampling and explain how they are used?
Quadrats - used in small areas. Randomly or regularly placed across habitit. Frequency or % cover calculated
Transects - used in larger area. Sample taken along a line that crosses habitat. Can be combined with quadrats to form a belt tansect
Define carrying capacity?
The maximum population that a habitat can support, defined by the presence of limiting factors
What factors limit carrying capacity?
Food
Water
Light
Oxygen
Nesting sites
Shelter
Parasites
Predators
Describe the pattern of a typical predator-prey relationship
Prey is eaten by predator
Predator population increases
Prey population decreases
Fewer prey means increased competition for food
Predator population decreases
Fewer predators means more prey survive
What is intraspecific and interspecific competition?
Intraspecific - competition between organisms of the same species
Interspecific - competition between organisms of different species
Difference between conservation and preservation?
Conservation - maintains biodiversity of a habitat by allowing sustainable use of the resources there
Preservation - maintains biodiversity by minimising human impact
Why do we conserve and preserve habitats?
Economic - food source, natural pest control, boosts tourism
Social - organisms can be used in medicine, aesthetics
Ethical - responsibility to maintain habitats for future generations
Define sustainability
Using resources in a way that maintains them for future generations
What methods allow sustainable use of an ecosystem’s resources?
Timber production - coppicing to encourage growth, replacing felled trees, selective cutting
Fishing - stocks not depleted, no overfishing, can continue indefinitely
