Fossil Evidence for Evolution PDF

Evidence for evolution Learning intention: Be able to explain how fossils provide evidence to support the theory of evolution Success criteria List types of fossils Explain the 5 ways that fossils provide evidence for the theory of evolution  What are Fossils? Preserved re...

Evidence for evolution Learning intention: Be able to explain how fossils provide evidence to support the theory of evolution Success criteria List types of fossils Explain the 5 ways that fossils provide evidence for the theory of evolution  What are Fossils? Preserved remains and traces of organisms (over 10 000 years old) Types of fossils Trace- footprint, trail, burrow, coprolite Mould- impression left by an organism Cast- formed when mould is filled with mineral rock (mineralisation) Trueform- shells, teeth, bones  How do cast fossils form? Not many plants and animals are lucky enough be turned into fossils. They usually decompose. Very rarely when the conditions are just right, its remains can be buried quickly, it may be fossilised. There are several different ways fossils are formed. 1. An animal dies, its skeleton settles (organic matter decomposes) on the sea floor and is buried by sediment. 2. The sediment surrounding the skeleton thickens and begins to turn to stone. 3. The skeleton is dissolved by groundwater and a mould is formed. 4. Minerals from the groundwater crystallise inside the mould and a cast is formed. 5. The fossil is exposed on the Earth's surface by erosion  What conditions are required for fossilisation? Absence of decomposers Absence of O2 and H2O Low temperatures Fossil evidence is like a making a puzzle but you are missing 9/10 of the pieces, becoming a fossil is highly unlikely! What things might prevent an organism being fossilised? What things might prevent a fossil being found? How does the fossil record provide evidence for evolution? 1. Shows changes in structure over time  2. Organisms in the fossil record have become more complex over time e.g. unicellular→invertebrates→vertebrates. More recent (younger) fossils are more similar to organisms living today 3. The variety of fossils increases in the upper more recent layers of rock 4. No fossil record exists of any modern living plants or animals Have they avoided being fossilised or evolved? Why do only extinct organisms get fossilised? This suggests that the organisms that are found as fossils either became extinct or evolved into species currently living. 5. Missing links – the common ancestors e.g. Archaeopteryx. Feathers like a bird Teeth like a reptile 3 clawed digits with one opposable toe Lacks keel on breastbone Archaeopteryx is thought to be an intermediate ancestor between reptiles and birds  Principle of superposition layers at the top are younger than the one beneath them Youngest Oldest  Correlation of Rock Strata Matching layers of rock from different areas Rocks containing the same type of fossils can be assumed to be the same age