Module 7- Populations in ecosystems Flashcards
4 marks
Succession occurs in natural ecosystems. Describe and explain how succession occurs
- Colonisation by pioneer species
- Pioneers species change the environment conditions e.g. produces thin layer of soil called humus
- Environment becomes less hostile for other/new species, which enable other species to colonise
- Increase in biodiversity
- To climax community
1 mark
Explain why it would be more appropriate to use a transect rather than random quadrats when investigating this succession.
Ensures sampling of each community
3 marks
Many species in the pioneer community are xerophytes. Suggest and explain how having sunken stomata is an advantage to these plants.
- Sand has a low water retention
- Sunken stomata reduce transpiration
- as pocket pf saturated air trapped near stomatal pore
- This reduces diffusion / water potential gradient
Define succession
The change in an ecological community overtime
Define pioneer species
The first species that colonise bare rock. Can withstand hostile abiotic factors
e.g. lichen
Define primary succession
Starts with a pioneer species colonising bare rock or sand
Define secondary succession
Succession is disrupted and plants are destroyed.
Succession starts again, but soil is already created (doesnt start from bare rock)
Define climax community
The final stage of succession. The animals/ plants/ species remain constant and exist in balance with the environment
2 marks
Algae are green protoctists. Lichens consist of a fungus and an alga living together in a relationship where both organisms benefit. Suggest how the relationship between the alga and the fungus allows the lichen to survive on an inorganic surface such as a wall.
- Algae photosynthesise and produce carbohydrates
- Funus absorbs water and mineral ions which is available to the algae
4 marks
Explain colonisation
- Lichens able to survive hostile environment
- Death of lichen makes the habitat less hostile
- E.g. Produces thin layer of soil called humus
- Slow growth limits spread of lichen, other plants grow faster
5 marks
Explain what limits the size of populations in a climax community
- Number of producers providing energy
- Light intensity affecting the rate of photosynthesis
- Space for niches
- Birth rate balancing death rate
- Competition for limited resources e.g. food
- Predation
Reasons for conserving woodlands
- Conserving / protecting habitats / niches
- Conserving / protecting endangered species / increases biodiversity
- Reduces global warming
- Source of medicines / chemicals / wood
- Reduces erosion / eutrophication
Describe how you would investigate the distribution of marram grass from one side of the dune to the other
Line transects from one side of the dune to the other
Place quadrats at regular intervals along the line
Work out % cover of marram grass for each quadrat
Define community
Populations of different species
4 marks
Describe how ecologists could use the mark-release-recapture method to estimate the number of one species of fish in the lake
- Capture sample, mark, and release
- Mark fish with a fluorescent/marker in a non harmful way
3.. Leave sufficient time for lizards to randomly distribute before collecting a second sample - Collect a second sample and count number of marked fish
- Population = (number of fish in sample 1 x number of fish in sample 2) / number of marked in sample 2
2 marks
Define succession
- Change in community over time
- Either due to change environmental factors or change is due to species present
1 mark
Define climax community
Stable community / no further succession
Interspecific competition
This is competition for the same resources between individuals from different species
e.g. food, shelter, light
Intraspecific competition
This is competition for the same resources between individuals from the same species
e.g. food, shelter, light
3 marks
Heather plant mean % cover decreased over years due to a dire and other plant species present increased
Reasons on why the rate of a heather plant producing new biomass measured in g per kg of plant per year decreased as the heather plant aged.
- Fewer leaves so less photosynthesis to produce new biomass / glucose / growth
- Competition with other species for nitrates so reduced synthesis of protein
- Ratio of leaves to woody parts and roots decreases so higher respiration relative to photosynthesis
