Ecosystems
Biotic factors
The main biotic factors are predation and competition. These include:
Availability of food
All animals require food to live. The availability of food is a major factor in how many animals live
in a ecosystem. Areas like rainforests with rich food supplies have more species of life than other
areas like deserts and the Polar Regions where there is less food.
Food provides animals with energy and raw materials to complete life processes without which
they may die. Because food is so vital, many animals will fight for it.
Animals within a species also compete for mates so they can pass on their genes to their
offspring. Animals have evolved to have a natural drive to reproduce and this often results in
fights. Fights competing for mates leads to serious injury and death but benefits the population
as only the strongest pass on their genes to the next generation.
New predators
The arrival of new predators in an ecosystem has a devastating effect. In balanced ecosystems,
predators and prey evolve together. Predators catch enough food to survive but not so much that
they kill all their food.
Introducing new predators causes a rapid decline in the numbers of prey, which then reduce the
food supply for existing producers.
New pathogens
When organisms inhabit new ecosystems they often bring new pathogens.
Competition
The introduction of a new species results in it out competing another native species.
Abiotic factors
Light intensity
Some plants evolved for optimum growth in bright sunlight, like a cactus houseplant as they
originally grow in the deserts. However, many orchids have evolved for optimum growth in darker
conditions.
An increase in light intensity increases the rate of photosynthesis and increases the production of
glucose so there is less competition, and there is more respiration and more synthesis leading to
more growth
Temperature
Both animals and plants have evolved to grow healthily at their optimum temperatures. Polar bears
could not survive in warmer conditions and cacti houseplants could not survive in cold temperatures.
Optimum – highest rate of photosynthesis
Biotic factors
The main biotic factors are predation and competition. These include:
Availability of food
All animals require food to live. The availability of food is a major factor in how many animals live
in a ecosystem. Areas like rainforests with rich food supplies have more species of life than other
areas like deserts and the Polar Regions where there is less food.
Food provides animals with energy and raw materials to complete life processes without which
they may die. Because food is so vital, many animals will fight for it.
Animals within a species also compete for mates so they can pass on their genes to their
offspring. Animals have evolved to have a natural drive to reproduce and this often results in
fights. Fights competing for mates leads to serious injury and death but benefits the population
as only the strongest pass on their genes to the next generation.
New predators
The arrival of new predators in an ecosystem has a devastating effect. In balanced ecosystems,
predators and prey evolve together. Predators catch enough food to survive but not so much that
they kill all their food.
Introducing new predators causes a rapid decline in the numbers of prey, which then reduce the
food supply for existing producers.
New pathogens
When organisms inhabit new ecosystems they often bring new pathogens.
Competition
The introduction of a new species results in it out competing another native species.
Abiotic factors
Light intensity
Some plants evolved for optimum growth in bright sunlight, like a cactus houseplant as they
originally grow in the deserts. However, many orchids have evolved for optimum growth in darker
conditions.
An increase in light intensity increases the rate of photosynthesis and increases the production of
glucose so there is less competition, and there is more respiration and more synthesis leading to
more growth
Temperature
Both animals and plants have evolved to grow healthily at their optimum temperatures. Polar bears
could not survive in warmer conditions and cacti houseplants could not survive in cold temperatures.
Optimum – highest rate of photosynthesis
