Topic 10 - Ecosystems Flashcards
Ecosystem?
A life-supporting environment that includes both living and non-living elements. Vary in size;
- Biosphere (all life-supporting environments on the earth’s surface)
- Biome (major ecosystems)
- Habitat
- Microhabitat
What are trophic levels (& examples)?
Describes feeding relationships with other organisms/ position in a food chain/web.
- Producer
- Primary consumer
- Secondary consumer
- Tertiary consumer
- Decomposer
Methods of measuring distribution?
- Line transect (line is placed down across habitat and species that come in contact are recorded)
- Quadrat (square frame of given size randomly placed in sampled area and species within are recorded, counted/percentage cover)
- Belt transect (combination of line transect and quadrat)
Net Primary Productivity (NPP)
The rate at which energy is transferred into the organic molecules that make up new plant biomass
Gross Primary Productivity (GPP)
The energy transferred to primary producers
NPP= …
NPP = GPP - R
R (respiration losses)
Why is some energy lost at each trophic level?
- Undigested matter (e.g. bones & hair)
- Respiration (exothermic, transfers thermal energy to the surroundings)
- Metabolic waste products like urea
Describe the carbon cycle
- Carbon dioxide in the atmosphere
- Used in photosynthesis to produce carbohydrates & other biological molecules
- Some of these plants will die and fossilise as well as animals in specific conditions
- Carbon is stored in fossil fuels (coal & oil)
- Carbon is released into the atmosphere when fossil fuels are burned (combustion)
- Some of the plants may be eaten by animals
- Then this could either be released back into the atmosphere during respiration of plants, animals and decomposers
- Or the carbon dioxide is put back into the soil in decaying matter and waste
- Or carbon in dead and decaying matter is broken down by decomposers (which is released back into the atmosphere through respiration of the decomposers)
Describe the nitrogen cycle
- Atmospheric nitrogen
- Nitrogen-fixing bacteria in root nodules of legumes and in soil male ammonium compounds
- By nitrifying bacteria, converts ammonium compounds to nitrates in soil
- Denitrifying bacteria turns these nitrates back into nitrogen (nitrogen is made into nitrates in soil through lightning)
- Nitrates in soil are taken up through roots to make protein in plants
- These plants either die to make nitrogen compounds in dead organic matter which are then decomposed to ammonium compounds
- Or they are eaten to make protein in animals which either die (same process as plants) or urea and faeces have nitrogen compounds in which are decomposed to make ammonium compounds
Spearman’s Rank Correlation Coefficient
- Measures correlation
- Closer the answer is to 1, closer to a linear positive correlation
- Closer the answer is to -1, closer to a linear negative correlation
T-test
- Used to determine if the means of two sets of data are significantly different from one another
Succession
The colonisation of an area by organisms and the gradual replacement of those organisms by other, more varied and productive species
Primary succession
Occurs when an area previously devoid of life is colonised by communities of organisms e.g. after the eruption of a volcano which led to formation of a rock surface
Secondary succession
Occurs with exisiting soil that is clear of vegetation, may occur after an event such as forest fire
How does succession occur
- Area is colonised by pioneer species e.g. lichens which are adapted to survive in harsh conditions
- They penetrate rock surface and break it down into grains
- As organisms die, they are decomposed by microorganisms, adding humus (the organic component of soil)
- This leads to formation of soil, makes it more suitable environment for more complex organisms
- More organisms decomposed over time, soil becomes richer in minerals to enable larger, more varied & more productive plants and shrubs to survive
- Eventually, climax community is established (the most productive, self-sustaining & stable community of organisms the environment can support)
