Evolution
Definition
Evolution is the gradual change in living organisms over many generations.
Species evolve over time through:
- variation
- inheritance
- natural selection
Natural Selection
The Core Idea
Organisms with helpful traits are more likely to survive and reproduce.
Over time:
- beneficial traits become more common
- populations gradually change
Natural Selection Flow
The Natural Selection Process
- Variation exists in a population
- Selection pressure occurs
- Better adapted organisms survive
- Survivors reproduce
- Traits are inherited
- Population changes over generations
Key Terms
| Term | Meaning |
|---|---|
| Evolution | Change in species over time |
| Adaptation | Characteristic improving survival |
| Variation | Differences between organisms |
| Natural Selection | Process where helpful traits survive |
| Species | Organisms able to reproduce together |
| Mutation | Change in DNA |
| Selection Pressure | Environmental factor affecting survival |
| Speciation | Formation of new species |
Adaptations
Structural Adaptations
Physical features helping survival.
Examples:
- thick fur
- camouflage
- sharp claws
Behavioural Adaptations
Actions helping survival.
Examples:
- migration
- nocturnal activity
- hibernation
Physiological Adaptations
Internal body processes.
Examples:
- venom production
- sweating
- water conservation
Adaptation Examples
Evidence for Evolution
Fossils
Fossils show:
- extinct organisms
- changes over time
- transitional species
Examples:
- Archaeopteryx
- horse evolution
Fossil Evidence & Evolution
Comparative Anatomy
Similar body structures suggest common ancestors.
Example:
- human arm
- whale flipper
- bat wing
These are called homologous structures.
Comparative Anatomy Diagram
DNA Evidence
Similar DNA suggests organisms are related.
The more similar the DNA:
→ the closer the evolutionary relationship.
Embryology
Embryos of different animals can look similar in early development.
Darwin’s Theory
Charles Darwin
Developed the theory of evolution by natural selection.
Key observations:
- organisms produce many offspring
- resources are limited
- variation exists
- some survive better than others
Darwin & Galápagos Finches
Speciation
How New Species Form
- Populations become isolated
- Different environments create different pressures
- Mutations and adaptations accumulate
- Populations become too different to interbreed
Result:
→ new species form
Speciation Diagram
Human Influence on Evolution
Artificial Selection
Humans selectively breed organisms for desired traits.
Examples:
- dog breeds
- crop plants
- dairy cattle
Antibiotic Resistance
Some bacteria survive antibiotics because of mutations.
These bacteria reproduce and pass resistance on.
This is evolution happening today.
Antibiotic Resistance Diagram
Fossil Dating
Relative Dating
Older fossils are found deeper underground.
Absolute Dating
Uses radioactive decay to determine exact age.
MUST KNOW EXAMPLES
| Topic | Example |
|---|---|
| Natural Selection | Peppered moth |
| Fossil Evidence | Archaeopteryx |
| Adaptation | Polar bear fur |
| Artificial Selection | Dog breeding |
| Resistance | Antibiotic-resistant bacteria |
Common Exam Questions
Explain Natural Selection
Use:
- variation
- survival
- reproduction
- inheritance
Explain Adaptation
Describe:
- trait
- environmental advantage
- survival benefit
Explain Evidence for Evolution
Use:
- fossils
- anatomy
- DNA
- embryos
Quick Memory Trick
V-S-S-R-I-C
Variation
Selection pressure
Survival
Reproduction
Inheritance
Change
Essential Summary
Evolution occurs because:
- organisms vary
- environments select helpful traits
- survivors reproduce
- traits pass to offspring
- populations change over time
Victorian Curriculum Year 10 Biological Sciences:
- evolution
- biodiversity
- natural selection
- variation
- isolation
- selection
Useful background links to genetics concepts also appear in your uploaded Year 10 genetics notes.