Topic 3, Biology

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  • Created by: Hannah
  • Created on: 17-08-12 07:54

Fossil is the reamains of a organism which lived a long time ago.

Sedimetary rock is where the fossil are founded in

Common ancestors are animals which are closely related to one another.

Charlie Darwin was the biologist who suggested evolution.

Decomposition is when the animal decompose into fossils

Fossil recors is a way of keeping track of the different fossils.

Fossils are preserved in sedimentary rock over a period of time which are a record of all life on Earth; by studying the different layer, it is concluded that vetebrates did not exsist until 600 million years ago, Fish were the first to be on Earth 510 million years ago and Reptiles did not appear on Earth until 300 million years ago.

Fossil can be formed in three ways

  • Feature like teeth, shells and bones don't decay as easily as other features of the body therefore they can last ages whilst being buried. This means that the fossil could be formed by the replacement of minerals inside the features which forms a rock-like structure shaped like the original feature. This is a gradual process and  the fossil stays prominent in the rock until it is dug up to be analyse.
  • Casts and impression are made when organisms are buried in a soft material such as clay. The clay hardens around the organism and the organism decays leaving a cast or impression of itself.
  • Preservation are made when the conditions in the habitat are too extreme to actually allow decay to happen as the conditions aren't suitable for the microbes to work in e.g. glaciers which are too cold, peat bogs which are too acidic and amber where there is no oxygen or moisture.

Fossil found in sedimentary rocks tells us:

  • What the creature or plant look like
  • How long ago they exsisted
  • How they evolve. When scientist study the simalarities and differences between fossils in different aged rocks, you can study how organisms have changed through out the years and evolved into what they are now.

However fossil records are incomplete because:

  • Most organisms decompose to quickly to become fossils.
  • Most just decay away.
  • Some have not been found yet.
  • Body parts such as tissue tend to decay away completely.

Evolution is not always a gradual change, sometimes is can be for a short period o time.

A pendactyl limb is a limb in which has five digits. The evidence of a pendactyl limb is seen is many species, but has different uses. For example a humans hand and a bats wing. This gives scienctist the evidence that all the species have evolved from a common ancestor that have the pendactyl limb.

The measure of growth is established by:

  • Size
  • Length
  • Wet Mass
  • Dry Mass

Wet Mass is when organism contain a lot of water. The mass of the organism may depend on how much water is gained or lost. This includes all water in the body and can very from day to day.

Dry mass is when an organism has…


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