Topic 10.1 The nature of ecosystems Flashcards
Define ecosystem
an environment including all the living organisms interacting within it, the cycling of nutrients and the physical and chemical environment in which the organisms are living
Define habitat
the place where an organism lives e.g. a stream, tropical rainforest or sand dune
Define population
a group of organisms of the same species, living and breeding together in a habitat
Define microhabitat
a small area of a habitat e.g. a fig on a tree may be home to a fig wasp
Define community
all the populations of all the different species of organisms living in a habitat at any one time
Define niche
the role of an organism in the community
Define abiotic factors
non-living elements of the habitat of an organism
Give examples of abiotic factors
- sunlight
- temperature
- rainfall
- drainage and pH of soil
- oxygen availability
Define biotic factors
living elements of a habitat that affect the ability of a group of organisms to survive there
Give examples of biotic factors
- predators
- suitable prey
- disease
Define biosphere
all of the areas of the surface of the earth where living organisms survive
Define biomes
the major ecosystems of the world
Define succession
the process by which the communities of organisms colonising an area change over time
Define climax community
a self-sustaining community with relatively constant biodiversity and species range. it is the most productive group of organisms that a given environment can support long term
What does primary succession start with?
an empty inorganic surface such as bare rock or a sand dune
Describe the stages of succession
1) Colonisation: species grow that are capable or surviving difficult conditions e.g. bare rock. they begin to break down rock and add organic matter
2) Pioneer species: these are able to grow when the colonisers have made conditions more hospital
3) Pioneer species produce soil as dead material accumulates which allows large herbaceous plants to outcompete pioneers
4) Shrubs and bushes can be supported when soil becomes deep enough
5) A climax community forms when the largest plants are able to grow . no further succession
Define succression
series of changes that occur to the composition of species in the community of organisms present in an area over a period of time
Define plagioclimax
a climax community which is partly the result of human intervention e.g. humans changing the landscape by adding grazing animals that prevent the growth of larger plant species
Define edaphic factors
relate to the structure of the soil
Define leaching
the loss of minerals from soil as water passes through rapidly
How does light affect population size?
- plants dependent on light for photosynthesis
- animals affected indirectly as a result of plant distribution
- seasonal light changes also affect reproductive patterns due to circadian rhythms
What does secondary succession start with?
begins on existing soil that is clear of vegetation e.g. after fires and floods
How are plants adapted to cope with low levels of light?
- reproduce early to avoid shade from larger plants
- extra chlorophyll
- different ratio of photosynthetic pigments that are sensitive to lower levels of light
- having very large leaves
How does temperature affect populations?
- affects enzyme-controlled reactions
- most organisms have a limited range in which they can reproduce successfully
What abiotic factors affect populations?
- temperature
- light
- wind and water currents
- water availability
- oxygen availability
- edaphic factors (soil structure and mineral content)
What is the affect of wind and water currents on organisms in a habitat?
- direct effect
- increases water loss from the body
- can destroy habitats
- organisms must flow with the current, be strong swimmers or attach to a surface
What affects water availability on land?
- amount of precipitation
- rate of evaporation
- edaphic factors e.g. drainage through soil
What is the effect of a decrease or increase in water availability on populations?
decrease: organisms die unless specially adapted
increase: increase in population size
Give examples of where water availability may be low
- if temp of water rises or it becomes stagnant
- waterlogged soil (no longer aerated)
What biotic factors effect populations?
- predation
- finding a mate
- territory
- parasitism and disease
Define intraspecific competition
competition between members of the same species for a limited resource
Define interspecific competition
occurs when different species within a community compete for the same resources
