Biology 1- Evolution


  • Created by: georgia s
  • Created on: 08-05-12 17:51


Life began as simple organisms from which more complex organisms evolved. 

Species may become extinct because:

  • environment changes more quickly than a species can adapt
  • A new predator or disease kills them all
  • They can't compete with another (new) species for food
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A fossil is any evidence of an animal or plant that lived ages ago.

Fossils form in rocks as minerals replace slowly slowly decaying tissue (or in places where no decay happens) and show features like shells, skeletons, soft tissues, footprints etc. They show what was on Earth millions of years ago. They can also give clues about an organism's habitat and food.

We also know that the layers of rock where fossils are found were made at different times. This means it's possible to tell how long ago a particular species lived.

From studying the similarities and differences between fossils in rocks of different ages, we can see how species have evolved over billions of years

Amber and Ice fossils

  • Amber- yellow stone formed over millions of years from sap of pine trees. Insects trapped in sap as it harden- are preserved.
  • Ice- keeps body preserved- soft parts (e.g. Skin/muscle) as well as hard parts (e.g. bon/teeth)

Fossils can also be found in acid bogs.

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The Evolution of the Horse


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The Evolution of the Horse 2

The fossil record of the horse provides strong evidence for the theory of evolution.

If you stick all the fossil bones in order of age, they seem to show the modern horse evolving gradually from a creature about the size of a dog, with the middle toe slowly getting bigger to form the familiar hoof.

Creationists believe that each species was created seprately by God and will never evolve into new species. They don't think the fossil record is evidence for gradual evolution, but simply shows a lot of different organisms some of which are now extinct.

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Natural Selection

Natural selection is the term used to describe the animals/organisms that are better adapted to their environment are more likely to survive. These genes are then passed onto the next generation. 

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Survival of the Fittest

Survival of the fittest

Some animals differ due to variation. The animals/plants with a species that have better characteristics have an advantage over the rest. Individuals with characteristics adapted to their environment are more likely to survive. These genes are then passed onto the next generation. 

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Charles Darwin

He put forward the theory of survival of the fittest. His evidence: Each island of the Galapagos Islands supported its own form of finch which was closely related but different in important ways. Their beaks were different depending on the food they ate.  His key observations:

  • organisms produces many more offspring than those that each maturity
  • the number of individuals of a species remains roughly constant


  • There must be high mortality rate
  • The individuals of a species are not all the same, they show different characteristics.


  • Some individuals will succeed better than others. These successful individuals will be the parents of the next generation
  • Offspring resemble their parents


  • Later generations will maintain and improve on their adaption by gradual change.
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