Biology – Key Topic 7
4.7 Ecology
4.7.1 Adaptations, interdependence and competition
4.7.1.1 Communities
An ecosystem is the interaction of a community of living organisms (biotic) with the
non-living (abiotic) parts of their environment
To survive and reproduce, organisms require a supply of materials from their
surroundings and from the other living organisms there.
Plants in a community or habitat often compete with each other for light and space,
and for water and mineral ions from the soil. Animals often compete with each other
for food, mates and territory.
Within a community each species depends on other species for food, shelter,
pollination, seed dispersal etc. If one species is removed it can affect the whole
community. This is called interdependence. A stable community is one where all the
species and environmental factors are in balance so that population sizes remain
fairly constant
- Organisms in an ecosystem depend on each other and compete for: food, shelter,
animals that carry out pollination and seed dispersal for plants and recycling of
nutrients/decomposers and microorganisms – interdependence
- The interdependence of all the living things in an ecosystem means that any
change in the ecosystem can have far-reaching effects
- Animals compete for food, predator-prey relationships, space, nesting sites and
mates
- Plants compete for light for photosynthesis, space, availability of mineral ions and
water
- If a disease or lack of food affects one population, this also affects other
populations in the food web
A community is a group of organisms of different species/2 populations or more in a
habitat
A biome is a geographical region on earth that has distinct biological communities
that have formed as a result of their physical climate e.g. desert
A habitat is a place where an organism lives – where there can be microhabitats. A
microhabitat is a smaller habitat within a main habitat e.g. the bark of spruce trees in
a coniferous forest
- species in the same habitat will compete for the same resources
A niche is the role of an organism in the ecosystem
A population is a group of organisms of the same species (in a habitat at a given time)
, 4.7.1.2 Abiotic factors
Abiotic (non-living) factors which can affect a community are:
- Light intensity
- Temperature
- Moisture levels
- Soil pH and mineral content
- Wind intensity and direction
- Carbon dioxide levels for plants
- Oxygen levels for aquatic animals
A change in the environment could be an increase or decrease in an abiotic factor.
This can also affect the sizes of populations in a community. This means they can
affect the population sizes of other organisms that depend on them as well.
- a decrease in light intensity, temperature or level of carbon dioxide could decrease
the rate of photosynthesis in a plant species. This could affect plant growth and
causes a decrease In population size
- a decrease in the mineral content of the soil could cause nutrient deficiencies. This
could also affect plant growth and cause a decrease in the population size
4.7.1.3 Biotic factors
Biotic (living) factors which can affect a community are:
- Availability of food
- New predators arriving
- New pathogens
- One species outcompeting another so the numbers are no longer sufficient to
breed
A change in the environment could be the introduction of a new biotic factor e.g. a
new predator or pathogen
These changes can affect the sizes of populations in communities which can have
knock on effects because of interdependence
4.7.1.4 Adaptations
Organisms have features (adaptations) that enable them to survive in the conditions
in which they normally live. These adaptations may be structural, behavioural or
functional. Different factors affect different biomes
- Structural – features of an organisms body structure such as shape or colour. E.g.
arctic animals have white fur to camouflage and animals like whales that live in
cold places have a thick layer of blubber to help them retain heat
- Behavioural – the ways the organisms behave – many species migrate to warmer
climates during the winter to avoid cold conditions
4.7 Ecology
4.7.1 Adaptations, interdependence and competition
4.7.1.1 Communities
An ecosystem is the interaction of a community of living organisms (biotic) with the
non-living (abiotic) parts of their environment
To survive and reproduce, organisms require a supply of materials from their
surroundings and from the other living organisms there.
Plants in a community or habitat often compete with each other for light and space,
and for water and mineral ions from the soil. Animals often compete with each other
for food, mates and territory.
Within a community each species depends on other species for food, shelter,
pollination, seed dispersal etc. If one species is removed it can affect the whole
community. This is called interdependence. A stable community is one where all the
species and environmental factors are in balance so that population sizes remain
fairly constant
- Organisms in an ecosystem depend on each other and compete for: food, shelter,
animals that carry out pollination and seed dispersal for plants and recycling of
nutrients/decomposers and microorganisms – interdependence
- The interdependence of all the living things in an ecosystem means that any
change in the ecosystem can have far-reaching effects
- Animals compete for food, predator-prey relationships, space, nesting sites and
mates
- Plants compete for light for photosynthesis, space, availability of mineral ions and
water
- If a disease or lack of food affects one population, this also affects other
populations in the food web
A community is a group of organisms of different species/2 populations or more in a
habitat
A biome is a geographical region on earth that has distinct biological communities
that have formed as a result of their physical climate e.g. desert
A habitat is a place where an organism lives – where there can be microhabitats. A
microhabitat is a smaller habitat within a main habitat e.g. the bark of spruce trees in
a coniferous forest
- species in the same habitat will compete for the same resources
A niche is the role of an organism in the ecosystem
A population is a group of organisms of the same species (in a habitat at a given time)
, 4.7.1.2 Abiotic factors
Abiotic (non-living) factors which can affect a community are:
- Light intensity
- Temperature
- Moisture levels
- Soil pH and mineral content
- Wind intensity and direction
- Carbon dioxide levels for plants
- Oxygen levels for aquatic animals
A change in the environment could be an increase or decrease in an abiotic factor.
This can also affect the sizes of populations in a community. This means they can
affect the population sizes of other organisms that depend on them as well.
- a decrease in light intensity, temperature or level of carbon dioxide could decrease
the rate of photosynthesis in a plant species. This could affect plant growth and
causes a decrease In population size
- a decrease in the mineral content of the soil could cause nutrient deficiencies. This
could also affect plant growth and cause a decrease in the population size
4.7.1.3 Biotic factors
Biotic (living) factors which can affect a community are:
- Availability of food
- New predators arriving
- New pathogens
- One species outcompeting another so the numbers are no longer sufficient to
breed
A change in the environment could be the introduction of a new biotic factor e.g. a
new predator or pathogen
These changes can affect the sizes of populations in communities which can have
knock on effects because of interdependence
4.7.1.4 Adaptations
Organisms have features (adaptations) that enable them to survive in the conditions
in which they normally live. These adaptations may be structural, behavioural or
functional. Different factors affect different biomes
- Structural – features of an organisms body structure such as shape or colour. E.g.
arctic animals have white fur to camouflage and animals like whales that live in
cold places have a thick layer of blubber to help them retain heat
- Behavioural – the ways the organisms behave – many species migrate to warmer
climates during the winter to avoid cold conditions
