7.1 Adaptations, interdependence and competition
7.1.1 Communities
Keywords: Ecosystem, competition, interdependence
FSL: GCSE Biology Revision "Competition and interdependence" (sorta)
An ecosystem is the interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment.
There are four different levels within an ecosystem:
- Organisms: Individual living beings, such as a single bird, a tree, or a bacterium. They are the smallest unit of an ecosystem.
- Populations: Groups of individuals of the same species that live in a specific area and interact with one another, like a flock of pigeons in a park.
- Communities: Multiple populations of different species that live in the same area and interact. For example, in a forest, deer, wolves, and various plants form a community.
- Ecosystem: This includes all the living organisms (biotic components) and the non-living factors (abiotic components, like water, air, and soil) in a specific environment. Together, they form an interconnected system.
Competition
From the spec:
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.
Interdependence
From the spec:
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.
For example, if a predator species is removed from an ecosystem, the
population of its prey species will increase, but the population of the
species the prey feeds on will decrease.
7.1.2 Abiotic factors
FSL: GCSE Biology Revision "Biotic & Abiotic factors"
An abiotic factor is a non-living component of an ecosystem. For example:
| Abiotic factor | Description |
|---|---|
| Light intensity | The amount of concentrated light available for photosynthesis. |
| Temperature | Affects the rate of photosynthesis. |
| Moisture levels | Plants and animals need water to survive (obviously). |
| Soil pH and mineral content | Different plants have different needs for pH and mineral content. |
| Wind intensity and direction | Wind speed affects the rate of transpiration, which itself affects photosynthesis (as it makes sure water and minerals are transported to the leaves). |
| Carbon dioxide levels for plants | Carbon dioxide concentration affects the rate of photosynthesis. |
| Oxygen levels for aquatic animals | Some aquatic animals need higher concentrations of oxygen in water than others. |
7.1.3 Biotic factors
FSL: GCSE Biology Revision "Biotic & Abiotic factors" (again)
A biotic factor is a living component of an ecosystem. For example:
| Biotic factor | Description |
|---|---|
| Availability of food | Fluctuations in essential food resources (e.g., seasonal fruiting trees or insect swarms) can influence population sizes and breeding success. |
| New predators arriving | The introduction or migration of predators can disrupt prey populations. For example, the reintroduction of wolves in Yellowstone altered elk behavior and density. |
| New pathogens | Emerging diseases (bacterial, viral, or fungal) can lead to population declines. An example is the chytrid fungus, which has caused significant amphibian losses worldwide. |
| One species outcompeting another so the numbers are no longer sufficient to breed | Competitive exclusion occurs when one species dominates resources, reducing the population of another below sustainable levels. For instance, invasive plants like kudzu can outcompete native vegetation, leading to reduced reproductive populations. |
7.1.4 Adaptations
FSL: GCSE Biology Revision "Adaptations"
Adaptations are the features that enable organisms to survive and thrive in their natural environments. These can be classified into three main types:
Structural Adaptations
Structural adaptations refer to the physical features of an organism that have evolved to suit its environment. For example, the thick fur of a polar bear acts as insulation in frigid Arctic temperatures, while the long neck of a giraffe allows it to browse leaves high up in trees. Another example is the streamlined body shape of fish, which reduces water resistance and aids in swift movement through aquatic environments.
Behavioural Adaptations
Behavioural adaptations are actions or patterns of activity that help an organism survive. These include migration, hibernation, and camouflage. For instance, many bird species migrate thousands of kilometers to exploit seasonal food supplies or more favorable breeding conditions. Similarly, some animals, like certain species of lizards, change their body color or alter their activity patterns during the day to avoid predators.
Functional Adaptations
Functional adaptations are changes in the way an organism's internal systems work. This can include specialised enzymes or metabolic pathways that function efficiently under specific environmental conditions. An example is the way some desert plants have evolved to store water in their tissues, or how certain bacteria produce proteins that remain stable in extreme conditions, ensuring essential biochemical reactions continue even in harsh environments.
Extremophiles
Some organisms have evolved adaptations to survive in extreme environments, where conditions like temperature, pressure, or salt concentration are far from average. These organisms are known as extremophiles. For instance, bacteria living in deep sea vents not only withstand extreme pressures and temperatures but also utilize the chemicals from the vents as an energy source. Similarly, thermophilic microorganisms thrive in hot springs, and halophilic organisms are found in environments with very high salt concentrations.
uhh wait a minute
didn't we...
