Adaptations and Communities

This lesson covers how organisms are adapted to survive in their environment, the different types of adaptation, and how organisms interact within communities. These are key concepts in the AQA GCSE Combined Science Trilogy specification (8464) — Inheritance, Variation and Evolution, linking closely with Ecology.

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What Are Adaptations?

An adaptation is a feature of an organism that increases its chance of survival and reproduction in its environment. Adaptations develop over many generations through natural selection — they are NOT acquired during an organism's lifetime.

There are three types of adaptation:

Type	Definition	Examples
Structural	Physical features of the body	Thick fur, long roots, streamlined body shape
Behavioural	Actions an organism takes	Migration, hibernation, hunting in packs
Functional	Internal processes and chemistry	Production of venom, antifreeze proteins, enzymes that work at extreme temperatures

Exam Tip: AQA (8464) expects you to identify and explain adaptations of organisms in given scenarios. Always state the adaptation, then explain HOW it helps the organism survive.

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Adaptations to Different Environments

Desert Adaptations (Hot, Dry Environments)

Organism	Adaptation	How It Helps
Camel	Hump stores fat (not water)	Fat can be metabolised to release water; reduces insulating fat elsewhere
Camel	Large, flat feet	Spread weight to prevent sinking in sand
Camel	Long eyelashes and closable nostrils	Keep sand out
Cactus	Leaves reduced to spines	Reduces surface area for water loss by transpiration
Cactus	Thick, fleshy stem	Stores water
Cactus	Extensive shallow root system	Absorbs water quickly from rare rainfall
Cactus	Waxy cuticle	Reduces water loss from the surface

Arctic Adaptations (Cold Environments)

Organism	Adaptation	How It Helps
Polar bear	Thick layer of blubber and fur	Insulation to retain body heat
Polar bear	White fur	Camouflage against snow and ice for hunting
Polar bear	Large feet	Act as snowshoes; spread weight on ice
Arctic fox	Small ears, compact body	Reduced surface area to volume ratio, minimising heat loss
Penguin	Counter-current heat exchange in flippers	Blood flowing to extremities is warmed by returning blood, reducing heat loss
Arctic plants	Small size, ground-hugging growth	Reduces exposure to wind; stays warmer near the ground

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Surface Area to Volume Ratio

The surface area to volume ratio (SA:V) is crucial in understanding adaptations:

• Small SA:V ratio (large, round body) — reduces heat loss; advantageous in cold environments
• Large SA:V ratio (small body, long thin shape) — increases heat loss; advantageous in hot environments

Environment	Ideal Body Shape	SA:V Ratio	Example
Cold	Large, round, compact	Small SA:V	Polar bear, walrus
Hot	Small, thin, elongated	Large SA:V	Fennec fox (large ears), desert hare

Exam Tip: SA:V ratio questions are very common. Remember: organisms in cold environments benefit from a SMALL SA:V ratio (less heat loss), while organisms in hot environments benefit from a LARGE SA:V ratio (more heat loss to cool down).

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Extremophiles

Extremophiles are organisms that live in environments that would be extreme for most living things. Many extremophiles are Archaea (from the three-domain system).

Extreme Environment	Conditions	Example Organism
Deep-sea hydrothermal vents	Very high temperature and pressure	Thermophilic bacteria
Hot springs	Temperatures above 80°C	Thermus aquaticus
Salt lakes	Very high salt concentration	Halophilic archaea
Polar regions	Extremely cold temperatures	Psychrophilic bacteria
Acidic environments	Very low pH	Acidophilic bacteria
Deep underground	No light, high pressure	Chemosynthetic bacteria

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Competition in Communities

A community is all the populations of different species living in a habitat. Within a community, organisms compete for limited resources.

Interspecific Competition

Interspecific competition occurs between organisms of different species competing for the same resources.

Resource	Competed for by
Food	Different herbivore species eating the same plants
Water	Different species in dry environments
Light	Different plant species in a woodland
Space/territory	Different animal species using the same nesting sites

Intraspecific Competition

Intraspecific competition occurs between organisms of the same species. This is often more intense because individuals need exactly the same resources.

Resource	Example
Food	Two robins competing for worms in the same garden
Mates	Male deer competing for access to females
Territory	Male lions defending a pride's territory
Nesting sites	Blue tits competing for nest boxes

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Predator–Prey Relationships

Predator and prey populations are interdependent and show cyclical patterns:

1. When prey numbers increase, there is more food for predators
2. Predator numbers increase because more food is available
3. More predators eat more prey, so prey numbers decrease
4. With less food available, predator numbers decrease
5. With fewer predators, prey numbers increase again
6. The cycle repeats

graph LR
    A["Prey population<br/>increases"] --> B["More food for<br/>predators"]
    B --> C["Predator population<br/>increases"]
    C --> D["More prey eaten"]
    D --> E["Prey population<br/>decreases"]
    E --> F["Less food for<br/>predators"]
    F --> G["Predator population<br/>decreases"]
    G --> H["Fewer prey eaten"]
    H --> A
    style A fill:#c8e6c9,stroke:#2e7d32
    style C fill:#ffccbc,stroke:#d84315
    style E fill:#ef9a9a,stroke:#c62828
    style G fill:#bbdefb,stroke:#1565c0

Exam Tip: AQA (8464) often shows predator-prey graphs and asks you to describe and explain the relationship. Key points: the predator curve follows the prey curve with a TIME LAG; the peaks and troughs of the predator curve occur AFTER those of the prey curve.

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Symbiotic Relationships

Some organisms in a community have closer relationships than just competition or predation: