Unit 1 Evolution

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How to Explain Evolution Using Darwin's Theory

4 mark Question

1. Variation in (organism named in question) due to mutations

2. Explain how this variation makes organism better adapted to survive

3. Out-compete others of the species without mutation (i.e. survival of the fittest)

4. Survive, breed and pass on genes to offspring

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Evolution Theories

1. CREATIONISM - God created animals and plants

2. LAMARCK'S THEORY - 'Inheritance of Acquired Characteristics'
Characteristics are acquired during an organisms lifetime, then passed onto offspring.
E.g. A giraffe stretches its neck to reach leaves so offspring has stretched neck too

3. DARWIN'S THEORY - 'The Origin of Species by means of Natural Selection'
Populations have genetic variation due to MUTATIONS
Some variations make organism better adapted to environnement
Survival of the Fittest - these best adapted to survive, breed and pass on genes
Better adapted population forms

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Accepting Darwin's Theory

Why Wasn't Darwin's Theory Accepted?

1. Went against belief in CREATIONISM (God made all plants and animals)

2. TOO LITTLE EVIDENCE to convince anyone

3. No way to EXPLAIN HOW INHERITANCE HAPPENED - genetics not discovered for another 50 years

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Plant Adaptations


  • Rounded shape that insulates them, preventing ice crystals forming inside cells
  • Coniferous tree branches allow show to slide off so branches not broken


  • Large leaves for large surface area to absorb light for photosynthesis
  • Dark green leaves have large chlorophyll concentration to absorb light
  • Shinysurfaces and pointed tips allows rain to run off


  • Deep/wide root systems to maximise water collection when rains/ water deep below ground
  • Thick leaves/body for storing water (called SUCCULENTS)
  • No leaves to reduce water loss by transpiration
  • Stomata protected by hairs/ buried in ridges to slow rate of transpiration


  • Sundew plants get extra nutrients by trapping and eating insects
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Animal Adaptations


  • Thick fur to reduce heat loss
  • Hollow hairs containing air for insulation
  • Extra layer of fat/blubber for insulation and energy store when food is scarce
  • Small surface area:volume ratio to slow down rate of heat loss


  • LIve underground, where more constant & cooler temperature
  • Do not need to drink water as they get all their water from food (kidneys excrete little urine)
  • Camels have small sa:v ratio so as not to gain too much heat
  • Pale fur absorbs less heat
  • Large extremities radiate lots of heat to stay cool


  • Camouflage, to improve ability to hunt prey or to hide from predator
  • Hedgehog has spikes to stop being eaten
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