4.7.2 Organisation of an ecosystem Flashcards
define population
A species that occupy the same habitat.
Define habitat
The place in which an organism lives.
Define community
Populations of different species
interacting.
Define ecosystem
The interactions between the biotic and
abiotic factors in an area
Define biomass
The total mass of living material
Describe a simple food chain
producer → primary consumer →
secondary consumer → tertiary consumer.
What is a producer?
An organism that makes its own food
What types of organisms are primary
producers?
Photosynthetic organisms like green
plants and algae that trap energy from
the sun.
What is a primary consumer?
An organism that feeds on producers.
What is a secondary consumer?
An organism that feeds on primary
consumers.
What is a tertiary consumer?
An organism that feeds on secondary
consumers.
What is a predator?
A consumer that kills and eats other
animals.
What is prey?
An animal that is killed and eaten by
another animal.
Describe the pattern of predators and prey in a
stable community
The numbers of predators and prey rise
and fall in cycles.
Why are producers the first trophic level?
● Producers provide all biomass for the food
chain (production of glucose via
photosynthesis).
● The rest of the food chain involves the transfer
of this biomass.
What piece of apparatus is used to
measure the abundance and distribution
of organisms in an area?
quadrat
Describe how materials cycle through
the living and non-living components of
an ecosystem
● Organisms take in elements from their surroundings e.g. soil, air.
● Elements converted to complex molecules which become biomass.
● Elements transferred along food chains.
● Elements returned to environment during excretion and
decomposition of dead organisms.
Give 3 molecules which are cycled through
ecosystems
Oxygen, carbon dioxide and water.
Describe the carbon cycle
- Plants fix carbon dioxide into organic molecules during
photosynthesis. - The organic carbon-containing molecules are passed onto organisms
that eat the plants. - Carbon dioxide is released back into the atmosphere by respiration
from animals and plants. - Burning fossil fuels also releases carbon dioxide into the atmosphere.
Why is the carbon cycle important?
Carbon-containing molecules such as
glucose are important for living
organisms to grow and provide energy
for vital functions within cells.
Describe the water cycle
- Water from lakes and oceans evaporates.
- The evaporated water condenses into clouds and returns
to earth as precipitation. - The water from precipitation is useful for life on land.
- The water then returns to rivers and oceans through
surface runoff
Why is the water cycle important?
Living organisms require water and the
water cycle provides organisms on land
with a continuous supply of water
Why are microorganisms important for
the cycling of materials through an
ecosystem?
Microorganisms (bacteria and fungi) return carbon to the
environment by releasing carbon dioxide through
respiration while they decompose dead matter. The
decomposition of dead matter in soil returns mineral ions to
the environment for other organisms to use e.g. plants use
mineral ions for growth.
What is meant by decomposition?
The breakdown of dead materials into
simpler organic matter
How do decomposers break down dead matter?
Decomposers release enzymes which
catalyse the breakdown of dead material
into smaller molecules.
What are the two types of
decomposition?
Aerobic decomposition (with oxygen)
Anaerobic decomposition (without oxygen)
What factors affect the rate of decomposition?
● Oxygen availability
● Temperature
● Water content
Why is oxygen required for decomposition?
Most decomposers require oxygen for
aerobic respiration.
How does the availability of oxygen
affect the rate of decomposition?
● As oxygen levels increase, the rate of
decomposition increases.
● As oxygen levels decrease, the rate of
decomposition decreases.
Why can decomposition still occur in the absence of
oxygen?
Some decomposers respire anaerobically.*
*However, the rate of decomposition is slower as
anaerobic respiration produces less energy.
How does soil water content affect the
rate of decomposition?
Decomposers require water to survive:
● In moist conditions the rate of decomposition is high.
● In waterlogged soils there is little oxygen for
respiration so the rate of decomposition decreases
Why does decomposition require water?
Water is required for the secretion of
enzymes and absorption of dissolved
molecules
How does temperature affect the rate of
decomposition?
Decomposers release enzymes:
● Rate highest at 50°C (optimum temperature for enzymes).
● Lower temperatures, enzymes work too slowly, rate decreases.
● High temperatures, enzymes denature, decomposition stops.
How is the rate of change calculated
when considering the decay of biological
material?
Rate of change =
Change in value / Change in time
Where value is a measurable variable associated with
the decay of the material
What is compost?
The nutrient-rich product of the rapid
decay of waste biological material (dead
plants and animal waste) in optimum
conditions set by gardeners and farmers.
How is compost used?
Used as natural fertiliser to promote
growth of crops or garden plants.
Describe how biogas generators work
Biogas generators provide methane gas
for fuel through anaerobic decomposition
that occurs in animal waste.
Name 5 greenhouse gases
- Water vapour
- Carbon dioxide
- Nitrous oxide
- Methane
- CFCs
Give 3 human activities that contribute to
greenhouse gases
- Burning fossil fuels
- Deforestation
- Large scale livestock farming
How do greenhouse gases lead to global
warming?
- Greenhouse gases allow heat from the
sun to enter the atmosphere. - The gases act as a ‘blanket’ and trap
the heat in the atmosphere.
State 3 negative consequences of global warming
- Sea level rise caused by melting icebergs.
- Disrupted farming and agriculture.
- Increased spread of diseases in warmer
climates
