Adaptations and CompetitionAQA GCSE Biology: Revision notes

Adaptations are characteristics that help organisms survive and reproduce in their environment. There are three main types:

Structural adaptations are physical features of an organism's body:

• Examples include thick fur for insulation, sharp teeth for catching prey, or waxy leaves to reduce water loss
• These are inherited traits that develop during an organism's lifetime or are present from birth

Behavioural adaptations are actions and responses that improve survival:

• Examples include migration, hibernation, hunting in packs, or building nests
• These are learned or instinctive patterns of behaviour

Functional (physiological) adaptations are internal processes that help organisms cope with their environment:

• Examples include the ability to produce toxins, efficient kidney function in desert animals to conserve water, or the ability to digest plant material using special enzymes
• These involve metabolic and biochemical processes

All three types work together to allow an organism to thrive in its specific habitat.

Extremophiles are organisms that live in extreme environmental conditions where most other life cannot survive. Examples include:

These adaptations are often highly specialised, meaning extremophiles are uniquely suited to their extreme habitat but cannot survive elsewhere.

Competition occurs when organisms in an environment require the same limited resources. The outcome of competition affects survival, reproduction, and population size.

Animals compete for:

• Food – the source of energy and nutrients needed for growth and metabolic processes
• Mates – essential for sexual reproduction and passing on genes to the next generation
• Territory – an area of land or space that provides food, shelter, and access to mates

Plants compete for:

• Light – needed for photosynthesis to produce glucose for energy and growth; taller plants may shade shorter plants
• Water – required for photosynthesis, maintaining turgor pressure, and nutrient transport from the roots
• Mineral ions – particularly nitrogen (for amino acids and proteins), phosphorus (for ATP and nucleic acids), and potassium (for enzyme function and stomatal opening)

Intraspecific competition occurs between members of the same species (e.g. two lions hunting in the same territory). This is often more intense than interspecific competition because individuals have identical resource requirements.

Interspecific competition occurs between members of different species (e.g. a lion and a leopard both hunting antelope). Different species may have slightly different requirements, making this competition less direct.

A niche is the specific role or position a species occupies in its environment. It includes:

• The habitat (where the organism lives)
• The food sources the organism uses
• The environmental conditions it requires (temperature, pH, light intensity, etc.)
• The time of activity (nocturnal, diurnal, etc.)
• The interactions with other species (predation, symbiosis, etc.)

Each species has a unique niche—no two species can occupy exactly the same niche indefinitely because they would compete directly for all resources. This is called the Principle of Competitive Exclusion.

How niches reduce competition:

When species occupy different niches, they avoid direct competition by:

• Feeding at different times (e.g. owls hunt at night, hawks hunt during the day)
• Feeding in different locations (e.g. woodpeckers feed on tree bark, thrushes feed on the ground)
• Feeding on different food sources (e.g. zebras eat grass, giraffes eat leaves from higher branches)
• Using different resources (e.g. some plants have deep roots for water from deep soil, others have shallow roots for surface water)

When species occupy similar niches, they must compete for overlapping resources. The species that is most efficient at obtaining those resources will outcompete the other, potentially leading to local extinction of the weaker competitor.

Species can coexist in the same habitat by avoiding direct competition through several strategies:

1. Spatial separation (using different areas of the habitat):

• Lions and hyaenas may hunt in different parts of the savanna
• Ground-feeding and canopy-feeding birds in a forest
• Plants with roots at different soil depths

2. Temporal separation (being active at different times):

• Diurnal hunters (hawks) and nocturnal hunters (owls) hunt the same prey but at different times
• Some plants flower at different seasons, reducing competition for pollinators

3. Dietary specialisation (eating different foods):

• Different bird species in a forest eat seeds of different sizes
• Carnivores, herbivores, and omnivores in the same ecosystem feed on different trophic levels

4. Morphological specialisation (having different body structures):

• Different beak shapes in Darwin's finches allow them to exploit different food sources (seeds, insects, cactus)
• Leaves and root systems of different plant species are adapted to capture different resources

When species do occupy similar niches, the outcome of competition depends on:

• Competitive ability – which species is more efficient at obtaining the limiting resource
• Resource availability – if resources are abundant, both may coexist; if scarce, one will outcompete the other
• Environmental stability – fluctuations may favour different species at different times

The species with the greatest competitive advantage will exclude competitors or force them to shift their niche.