Topic 5: On the Wild Side
Ecosystems and Energy Transfer
Ecology definitions
You need to be able to understand and define the following keywords which can be used to describe
different groups within the environment:
• Population: all the members of a single species which live in the same area
• Habitat: the area in which an organism lives
• Community: all the populations of different species which interact together in the same habitat
• Ecosystem: a community of organisms and the habitat in which it lives (i.e. both the biotic and
abiotic factors)
Factors which affect population size
The abundance (or population size) is defined as the number of individuals of one species in a
particular area. It depends on both abiotic (non-living) and biotic (living) factors.
• Abiotic factors, such as light intensity and water availability, affect population size because
when these conditions are ideal then organisms can grow and reproduce successfully. When
these conditions fluctuate, for example if the temperature of a habitat is too cold, the organisms in
that habitat cannot grow as efficiently. More energy will be spent maintaining body temperature
which means less energy will be available for growth and reproduction.
• Biotic factors also affect species abundance. These include interspecific competition,
intraspecific competition and predation.
Interspecific competition describes competition
between species for the same resources.
Interspecific competition means that resources
have to be shared between the different species so
there will be less available to both. This means both
species will have less energy for growth and
reproduction, so population numbers of both
species will decrease.
Intraspecific competition describes competition
for the same resources within the same species.
, When resources are abundant, the population size increases. This increases intraspecific competition
since resources will need to be shared between more organisms, which cause population size to
decrease. This pattern causes population numbers to fluctuate around a particular level which is the
maximum stable population size that an ecosystem can support, which is known as its carrying
capacity.
Predation affects the abundance of the prey species and vice versa. Whenever the population size of
prey increases, this causes the population size of the predator species to increase because more
food is available. The increase in the predator population causes a decrease in the prey population
because there are more predators to feed on the prey. This causes a drop in the prey population size,
which reduces the food availability for the predators, which in turn leads to a reduction in the predator
population.
Ecosystems and Energy Transfer
Ecology definitions
You need to be able to understand and define the following keywords which can be used to describe
different groups within the environment:
• Population: all the members of a single species which live in the same area
• Habitat: the area in which an organism lives
• Community: all the populations of different species which interact together in the same habitat
• Ecosystem: a community of organisms and the habitat in which it lives (i.e. both the biotic and
abiotic factors)
Factors which affect population size
The abundance (or population size) is defined as the number of individuals of one species in a
particular area. It depends on both abiotic (non-living) and biotic (living) factors.
• Abiotic factors, such as light intensity and water availability, affect population size because
when these conditions are ideal then organisms can grow and reproduce successfully. When
these conditions fluctuate, for example if the temperature of a habitat is too cold, the organisms in
that habitat cannot grow as efficiently. More energy will be spent maintaining body temperature
which means less energy will be available for growth and reproduction.
• Biotic factors also affect species abundance. These include interspecific competition,
intraspecific competition and predation.
Interspecific competition describes competition
between species for the same resources.
Interspecific competition means that resources
have to be shared between the different species so
there will be less available to both. This means both
species will have less energy for growth and
reproduction, so population numbers of both
species will decrease.
Intraspecific competition describes competition
for the same resources within the same species.
, When resources are abundant, the population size increases. This increases intraspecific competition
since resources will need to be shared between more organisms, which cause population size to
decrease. This pattern causes population numbers to fluctuate around a particular level which is the
maximum stable population size that an ecosystem can support, which is known as its carrying
capacity.
Predation affects the abundance of the prey species and vice versa. Whenever the population size of
prey increases, this causes the population size of the predator species to increase because more
food is available. The increase in the predator population causes a decrease in the prey population
because there are more predators to feed on the prey. This causes a drop in the prey population size,
which reduces the food availability for the predators, which in turn leads to a reduction in the predator
population.
