6.5 - C - Ecosystems Flashcards
What is an ecosystem?
Any group of living organisms and non‐living things occurring
together and the interrelationships between them.
What is a habitat?
The place where an organism lives.
What is a population?
All of the organisms of one species who live in the same place, at the same time and breed together.
What is a community?
All the populations of different species who live in the same place at the same time and can interact with each other.
What is a niche?
The role of an organism in the ecosystem.
What is a biotic factor?
Living organisms in an ecosystem that can affect each other.
What is an abiotic factor?
Non‐living things in an ecosystem that can affect the living organisms.
Ecosystems are dynamic.
What does this mean?
How are ecosystems dynamic?
This means they are constantly changing.
As abiotic/biotic factors change they can have an affect on other factors:
Cyclic changes and repeat in a regular pattern.
Directional changes do not repeat, tend to be long lasting and go in one direction e.g. erosion.
Erratic changes cannot be predicted and are neither cyclic or
directional e.g. effects of lightning.
What is a producer?
Start of food chains (plants and some photosynthetic bacteria), that convert energy from sunlight into chemical energy (glucose) in photosynthesis. They supply the chemical energy to the rest of the food chain.
What are the different consumers?
Define them.
Primary consumers are herbivores, which feed on plants, and which are eaten by:
Secondary consumers. These in turn are eaten by carnivorous:
Tertiary consumers.
What are decomposers?
Give examples.
They feed on waste material or dead organisms.
They include bacteria, fungi and some animals.
Bacteria, fungi and some animals.
State the 3 types of change in ecosystems that affect population size
Cyclic changes.
Directional changes.
Unpredictable/erratic changes.
Explain cyclic changes.
Give examples.
These are changes that repeat themselves in a rhythm.
Eg: tide movements, changes in day length, the way in which predator and prey species fluctuate.
Explain directional changes
These changes are not cyclic. They go in one direction, and tend to last longer than the lifetime of organisms within the ecosystem. Within such change, particular variables continue to increase or decrease.
Eg: deposition of silt in an estuary, or the erosion of the coastline.
Explain unpredictable/erratic changes.
Give examples.
These have no rhythm and no constant direction.
Eg: the effects of lighting or hurricanes.
What is a trophic level?
The level at which an organism feeds
Define biomass.
Define biomass transfer.
Explain biomass.
The dry mass of the organic material in an organism.
Transfer of biomass from one trophic level to another.
Biomass flows through food chains and food webs ‐ it can give an
indication of the energy flow through the food chains too.
Why are food webs useful?
Food webs more accurately describe the relationships in an ecosystem.
There is a loss of biomass (and energy) from food chains at each trophic level.
Why?
Some food not eaten e.g. bones.
Respiration releases energy from organic molecules e.g. glucose and materials e.g. CO2 are lost & energy is also released as heat.
Waste products and dead organisms contains biomass which will only be available to decomposers.
Explain pyramids of numbers
They reflect numbers in a food chain.
The area of the bar is proportional to numbers of individuals.
Compare pyramids of numbers vs pyramids of biomass
Pyramids of biomass are more useful to scientists because they take into account the size of organisms and the mass of material at each level. They give an indication of the energy contained at each trophic level.
What might the problems be with constructing pyramids of biomass?
To measure biomass:
Organisms have to be heated in an oven to evaporate all water.
Weighed periodically until all water evaporated and mass doesn’t
reduce any more.
This is very destructive (organism dies) ‐ instead, wet mass is
measured and dry mass is estimated using old published data.
Define productivity.
Why is this important?
The rate of production of new biomass/the rate of energy flow
through each trophic level.
Reflects how much biomass/energy is available to organisms of a trophic
level, per m^2 (usually) per year (usually).
e.g. Units: kg/MJ m^-2 yr^-1.
Define primary productivity.
Define gross primary productivity.
Total amount of energy fixed by photosynthesis.
The rate at which plants convert light energy into chemical energy through photosynthesis.
Define NPP.
What does it stand for?
Give the equation for it.
The rate of production of new biomass available for heterotrophic
consumption and therefore the amount of energy available to them.
Net primary productivity.
NPP = gross primary productivity ‐ respiration (R)
Why is about 90% of the sunlight not converted into biomass (net primary productivity)?
Reflected off plant/only certain wavelengths of light can be absorbed.
Absorbed by non‐photosynthetic parts e.g. bark.
Misses chlorophyll/chloroplasts.
Some energy is ‘lost’ as heat that is used in respiration.
What must be done to improve NPP?
Why would farmers want to do this?
Make energy conversion more efficient, reduce energy losses.
Increases crop yield.
Explain how you would ensure max rate of photosynthesis by ensuring limiting factors are controlled in order to improve NPP
Light levels ‐ grow with light banks/plant early to give longer growing season.
Temperature ‐ greenhouses.
CO2 conc. ‐ levels increased in greenhouses.
water ‐ irrigation techniques and drought resistant plants.
Nutrients ‐ fertilisers, crop rotation with legumes (nitrogen fixing).
Reduced yield from pests ‐ use of pesticides, pest‐resistant plants containing Bt gene.
Competition from weeds ‐ herbicides.
Define improving secondary productivity.
Why is this necessary for farmers?
How might they go about doing this?
Improving the rate of generation of biomass in heterotrophs.
i.e. making sure animals grow as large as possible to increase mass of meat production.
Necessary because energy transfer from producers to consumers is very
inefficient. A lot of energy is lost from food chains as the producers can’t digest everything they eat (cellulose), they don’t eat all of the plant, heat loss in respiration, egestion losses.
Growth steroid treatment ‐ illegal.
Selective breeding.
Antibiotics ‐ less energy lost fighting pathogens.
Battery farming ‐ reduce movement so less energy used in respiration for
energy; warm stable temperatures so less energy used in maintaining body temp.
