B23 - Ecosystems Flashcards
1
Q
What is ecology?
A
- study of relationships between organisms and the environment
- can help to understand the interdependence of living organisms
2
Q
What is an ecosystem?
A
- made up of all the living organisms that interact with one another in a defined area (also includes the physical factors in that region)
- boundaries of a particular ecosystem being studied are defined by the person/team carrying out the study
3
Q
What factors affect ecosystems?
A
- biotic:
- living factors
- e.g. presence of shrews, hedgehogs, size of population
- competition between two animal populations
- abiotic:
- non-living/physical factors
- e.g. amount of rainfall, yearly temperature range of the ecosystem
4
Q
What are biotic factors?
A
- interactions between organisms that are living
- involves competition (within/between) for food, territory, breeding partners
5
Q
What are abiotic factors?
A
- light:
- needed for photosynthesis
- the greater the light availability, the greater the success of a plant species
- adaptations include larger leaves in areas with low light intensity
- temperature:
- it’s greatest effect is on the enzymes of controlling metabolic reactions
- plants develop more rapidly in warmer temps.
- changing temp. of an ecosystem can trigger migration in some animal species and hibernation in others
- water availability:
- lack of water can lead to water stress which will lead to death
- it will also cause most plants to wilt as water is required for turgidity and photosynthesis
- oxygen availability:
- aquatic ecosystems = beneficial to have fast-flowing cold water as it contains high concentrations of oxygen
- warm water will have a slower flow rate and a drop in O2 conc will cause the organisms to suffocate
- waterlogged soil, spaces between soil particles are filled with water
- edaphic (soil) factors:
- clay = fine particles, easily waterlogged, forms clumps when wet
- loam = different-sized particles, retains water but does not become waterlogged
- sandy = coarse, well-separated particles that allow free draining (does not retain water and is easily eroded)
6
Q
What is biomass transfer?
A
-
7
Q
What are trophic levels?
A
- each stage in a food chain is a trophic level
- the first trophic level is always a producer
- converts light energy into chemical energy by photosynthesis
- the next one is always consumers
- they obtain energy by feeding on other organisms
- the following trophic levels are labelled successively
- they usually go up to quaternary consumer as there is not enough biomass to support the following organisms
8
Q
What are decomposers?
A
- they break down dead organisms releasing nutrients back into the ecosystem
9
Q
What is biomass?
A
- mass of living material present in a particular/organisms
- biomass = biomass of each organisms x total no. of organisms
- this represents biomass at a particular moment in time (does not take into account seasonal changes)
- easiest method = fresh material present
- most accurate = dry mass (killing organisms and placing them in the oven at 80 degrees C)
- to minimise destruction of organisms, only a small sample is taken
- units = g m -2 / g m -3
10
Q
What is the efficiency of biomass and energy transfer between trophic levels?
A
- biomass in each trophic level is almost always less than the one below
- when animals eat, only a small proportion of the food is converted into new tissue
- energy available for each trophic level is kJ m-2 yr-1
- efficiency with which biomass is transferred from one trophic level to another is ecological efficiency
11
Q
What is efficiency at producer level?
A
- producers only convert 1-3% of the sunlight into chemical energy (biomass)
- not all of the solar energy available is used for photosynthesis (90%)
- water availability may limit photosynthesis
- proportion of energy is lost as it is used for photosynthetic reactions
- net production = gross production - respiratory losses
- producer = primary production
- consumer = secondary production
