 Fossils D. Crowley, 2008

Fossils To know how fossils are formed and how they provide evidence for evolution

How are fossils formed?  How do you think the following fossils were formed?  What types of rock do you think they are found in?

Making Fossils  Use a shell to make an imprint into a lump of plasticine.  Fill the mould with plaster of paris and leave to dry.  At the end of the lesson you can peel the plasticine away from the plaster and you will have your own fossilised imprint!

Fossils What are fossils?  As soon as plants and animals die they begin to rot away – however, sometimes the dead plants and animals can be turned into fossils (rock copies of the original plant or animal)  Fossils forms when dead plants or animals become covered in a layer of sediment which initially protects them…

Fossils  An organism dies, and settles on the sea floor  Gradually it is covered with sediment which protects it, and over time the layers build up  As the layers build up the pressure increases, causing sedimentary rock to form  The dead organism undergoes a series of chemical changes resulting in rock-like minerals taking the place of the original chemicals  Over millions of years the original organism is replaced with minerals, and a rock-like copy of the organism is left

Fossil Formation Fossils can be formed in a couple of ways…  Some are stone copies of the organism, formed as the organism become petrified (turned to rock) by the deposition of minerals in the tissues as they decompose  Other fossils consist of impressions of the organism's shape, left behind in the surrounding stone as the tissues decompose  Most dead organisms decay very rapidly and their tissues are recycled, leaving no trace of their existence, but certain environmental conditions drastically slow down the decay process, thus helping to preserve the tissues, for example: -  Insufficient oxygen (organism trapped in resin, e.g. amber)  Low temperatures (organism frozen in glacier)  High soil acidity (organism in peat bog)

Design a cartoon strip to explain how fossils are formed  Everyone must produce a unique piece of work  A cartoon in five panels describing the stages in fossil formation (L4)  A conclusion explaining where you are most likely to find fossils (L5/6)  An evaluation of why the formation of fossils is rare/but why fossils are quite common in some rocks (L6/7)

Dating Where would we find the earliest fossils? The earliest fossils are found in the deepest parts of the rock (over time more and more sediment is laid down, meaning organisms which dies the longest time ago are found in the deepest parts) What does this provide evidence for?

Evolution  How has our understanding of fossils over the past few hundred years led to a better understanding of evolution?  Most of the evidence for evolution comes from rocks and fossils – fossil remains have been found in rocks of all ages: -  Fossils of the simplest organisms are found in the oldest rocks  Fossils of more complex organisms are found in the newest rocks,  This supports the evolutionary theory that simple life forms gradually evolved into more complex ones, and that all animals have gradually evolved from a common ancestor

Evidence for evolution  esource&template=vid&resourceID= esource&template=vid&resourceID=2524

Evolution  Is it that simple?! What problems can you identify with fossil evidence being used solely as evidence for evolution?  Rocks move around, so you don't always find the newest rocks near the surface, or the oldest rocks deep down  Evolution is not always an orderly progression from simple to evermore complex organisms - it goes in fits and starts  Building up the story of evolution of any one species is difficult, as in most cases there are big gaps in fossil records (it can be like putting together a jigsaw puzzle with half the pieces missing)

Human Evolution  Humans evolved from apes, however evidence for this transition is not abundant when we look to fossil records  The evolution from ape to modern man was by no means instantaneous, yet fossil evidence of how man gradually changed is still vastly incomplete – we are still in search of the ‘missing link’…  *Humans did not evolve from chimpanzees or any other modern ape – they are instead closely related organisms, probably all sharing a common ancestor

Using fossil evidence to find out about “the hobbit” The Hobbit people  Remains of small humans were discovered in 2003 on the island of Flores in Indonesia.  Scientists think Homo floresiensis is a possible human species, now extinct  Partial skeletons of nine individuals have been recovered, including one complete skull. Artist’s reconstruction

Write about hobbits using dig evidence. Complete for your homework. Here are some questions to help with your writing. What sort of things might hobbits have eaten? Why? (L5) How long did hobbits live on the island of Flores? (L5/6) What tools did hobbits use? (L5) What might have caused the extinction of hobbits? (L5/6) What did hobbits use for shelter? (L6) What evidence is missing? Why? (L6) How certain are you of your explanations? Why? (L7) Mammoth tooth Mammoth bone with cut marks

Human Evolution?

Fact Opinion or Speculation?  “Dinosaur Fossils found in South America”.  147 fossils have been found.  “Scientists think the discovered fossils may be from a dinosaur related to the Stegosaurus as the bones are similar”.  Scientists have dated them 200 million years old using carbon dating techniques.  Scientists think there could be up to another 100 fossils in the area  Mr Robinson says they ate turtles.  Three German scientists disagree with Mr Robinson and think they were vegetarians.  They were probably land animals not water based on the bones they have.