Module 7
Adaptation & inheritance
Quick-reference revision notes for parents.
7.1 Competition
Organisms compete for resources they need to survive:
- Plants: light, water, space, soil minerals.
- Animals: food, water, mates, shelter, territory.
The best-adapted individuals get more resources, survive and reproduce.
7.2 Adapting to change
An adaptation is a feature that helps an organism survive in its environment.
| Habitat | Example adaptation |
|---|---|
| Hot desert (camel) | Stores fat in hump; thick eyelashes; wide feet |
| Arctic (polar bear) | Thick fur, layers of fat, white camouflage |
| Cactus (dry climate) | Spines (instead of leaves), thick waxy stem stores water |
7.3 Variation
Differences between individuals.
- Genetic: inherited from parents (eye colour, blood type).
- Environmental: caused by surroundings (scars, language spoken, fitness).
- Most variation has both genetic and environmental causes (height, weight).
7.4 Continuous and discontinuous variation
| Continuous | Discontinuous | |
|---|---|---|
| Values | Any value within a range | Only certain categories |
| Examples | Height, weight, hand span | Blood type, eye colour, attached/free earlobes |
| Best graph | Histogram or line graph | Bar chart |
7.5 Inheritance
- Inside cell nuclei are chromosomes (humans have 23 pairs).
- Chromosomes contain genes — sections of DNA that code for features.
- You inherit one of each chromosome from each parent — half your DNA from mum, half from dad.
7.6 Natural selection
Charles Darwin's theory — explains how species evolve over time.
- Individuals in a species show variation.
- More offspring are produced than the environment can support.
- Those best adapted are more likely to survive (survival of the fittest).
- Survivors reproduce, passing their helpful features to offspring.
- Over many generations, the species changes — evolution.
Before the Industrial Revolution, light-coloured moths were camouflaged on light tree bark. Soot from factories darkened the trees, so dark moths now had the advantage. Within decades, the population was mostly dark.
7.7 Extinction
A species is extinct when no individuals remain. Causes include:
- Climate change
- Habitat destruction
- New predators or competitors (often introduced)
- Disease
- Catastrophes (e.g. asteroid impact ended the dinosaurs)
Biodiversity is the variety of species in an ecosystem. We protect it via national parks, breeding programmes, and gene/seed banks.
Quick reference
- Adaptation: feature that helps an organism survive
- Genetic vs environmental variation (often both)
- Continuous = any value (height); discontinuous = categories (blood type)
- DNA → genes → chromosomes → nucleus
- Natural selection: variation → competition → fittest survive → pass on traits → species evolves