Adaptations, Interdependence and Competition (B7.1)

Communities and ecosystems

• Population: all organisms of the same species in an area.
• Community: all populations of different species in an area.
• Ecosystem: a community plus its non-living (abiotic) environment.

Interdependence

Species within a community are interdependent — they rely on each other. If one species changes in number, others are affected through food chains, competition and mutualism.

Stable community: species populations are roughly constant over time because of balanced predator-prey, competition and abiotic factors.

Abiotic and biotic factors

Abiotic (non-living):

• Temperature, light intensity, moisture/water availability, CO₂ concentration, wind, pH of soil, salinity

Biotic (living):

• Food availability, predation, disease, competition (inter- and intra-specific)

Adaptations

An adaptation is a feature that increases an organism's chance of survival and reproduction in its environment. Adaptations are inherited — they arose by natural selection.

Types:

• Structural: body shape, colour, size (e.g. polar bear thick fur, cactus thick stem)
• Behavioural: actions (e.g. migration, nocturnal activity, hibernation)
• Physiological: internal processes (e.g. camel — concentrated urine, reduced sweating; Arctic animals — antifreeze proteins in blood)

Desert adaptations (camels, cacti)

Camels:

• Fat stored in hump (not insulation) — provides water and energy when metabolised
• Oval red blood cells — flow even when dehydrated; can drink 100 L rapidly without haemolysing
• Concentrated urine, dry faeces — reduce water loss
• Wide feet — spread load on sand

Cacti:

• Thick waxy cuticle — reduces water loss
• Spines instead of leaves — reduce SA; deter herbivores
• Wide, shallow root system — absorbs rain quickly over large area
• CAM photosynthesis — stomata open at night

Arctic adaptations (polar bears, Arctic foxes)

• Thick layer of fat (blubber) — insulation
• White fur — camouflage; hollow hair — traps air for insulation
• Small ears — reduce SA for heat loss
• Large hairy feet — distribute weight on ice; grip

Competition

Intraspecific: between same species (for food, mates, territory).
Interspecific: between different species (often for food or space).

Common exam errors

1. Confusing abiotic and biotic factors — abiotic = non-living.
2. Saying "adaptations are developed during life" — they are inherited genetic features, produced by natural selection over generations.
3. Confusing population (one species) with community (all species).