Evolution

Evolution

What Is Evolution?

Evolution is the gradual change in species over time. It happens as a result of natural selection, where the best-adapted individuals survive and pass on their genes.

💡 Key Concept: Evolution explains how all living organisms have developed from earlier life forms.

Natural Selection – Darwin’s Theory

Charles Darwin proposed the theory of natural selection after studying species like finches in the Galápagos Islands.

How Natural Selection Works:

1️ Variation exists in a population (due to mutations).
2️ Some individuals have advantageous traits.
3️ They are more likely to survive and reproduce.
4️ These traits are passed to the next generation.
5️ Over time, the population evolves.

What Causes Variation?

✔ Genetic mutations – random changes in DNA.
✔ Sexual reproduction – mixes alleles to create new combinations.

💡 Beneficial mutations increase survival and reproduction chances – these drive evolution.

Evidence for Evolution

Evidence Type

Example

Fossils

Show gradual changes in organisms over time.

DNA similarities

Closely related species have similar DNA.

Antibiotic resistance

Bacteria evolve resistance rapidly – a real-time example of evolution.

Extinction and Evolution

✔ If a species can’t adapt to environmental changes, it may become extinct.
✔ Extinction can be caused by:

  • Rapid climate change
  • Disease
  • New predators
  • Lack of food

Questions 

  1. What is evolution?
  2. Who proposed the theory of natural selection?
  3. What causes variation in a species?
  4. Why is antibiotic resistance an example of evolution?
  5. Name one piece of evidence for evolution.

Summary 

  • Evolution happens through natural selection – survival of the fittest.
  • Variation and mutation are essential to this process.
  • Evidence for evolution includes fossils, DNA similarities, and antibiotic resistance.
  • If species cannot adapt, they may face extinction.