| A | B |
|---|
| Fossil | Any preserved trace left by a previously living organism |
| Types of fossils | Bones, teeth, footprints, faeces |
| How fossils occur | Burial by drifting sanf, mud deposited by rivers, volcanic ash or othe members of the species |
| Conditions for fossilisation | Alkaline soil, no oxygen |
| Why is it unusual for animals to be preserved near volcanic eruptions | Heat from volcanic material destroys organism, whereas ash preseves |
| Why is fossilisation rare | Normally, dead organisms are decayed by microorganisms and no trace of their existence is left |
| Artefact | Any object made by humans, such as tools and weapons |
| Absolute dating | Age of the fossil in years is found |
| Relative dating | Scientist is determining whether a fossil is older or younger than another fossil |
| Statigraphy | Dating depends on knowledge of how sediments are laid down to form strata. Sedimentation occurs and eventually a rock is formed. The differnet layers form and the principle of superposition is put in action |
| Sedimentation | Process where sediments such as clay, silt and rock particles are deposited on the bottom of lakes, rivers and oceans. |
| Principle of superposition | Lowest stratum in an area will be the oldest |
| Index fossils rely on what assumptions? | Species only lived during a particular time in the past, and died out about the same time everywhere |
| Flourine analysis | Measure the amount of flourine in fossil bones. Longer the bone is in the ground, the more flourine it absorbs (bones absorb flourin from groundwater). Can only compare ages of fossils from the same place as ground water varies in different locations |
| Potassium argon | Potassium 40 decays at a constant rate to form argon gas. Rock traps the argon as it forms and so by measuring the amount of k40, can determine age. Half life 1300 million years |
| How and what factors affect the rate of K40? | None - not heat, pressure or chemicals |
| What is K40 useful for and why? | Useful for volcanic rocks as they contain lots of potassium-rich minerals, argon produced by the decay of K40 before the eruption is released before the eruption because it is a gas and the solidified lava traps all the argon that forms after the eruption |
| Radiocarbon dating | Based on decay C14. When cosmic rays from space act on nitrogen atoms in the upper atmosphere they convert some to C14. Plants absorb C14 during photosynthesis. Passes along food chain as organisms feed so when organism dies their intake ceases, but decay of C14 continues. Half life is 5568 yrs |
| Uses of radiocarbon dating | Determining the age of anything containing organic carbon and due to short half life, only useful up to 50 000 yrs (as then not enough C14) |
| Limitations of carbon dating | Rise in CO2 since industrial evolution |
| Isotope | Same elemnt with different number of neutrons |
| Tree ring dating | Each ring represents one year's growth and rings differ in width according to how favourable growing season was |
| Geological time scale | Consists of eras, subdivided into periods, subdivided into epochs |
| Heterotrophic | Feeding on the organic compounds of the sea |
| Autotrophic | making their own organic compounds |
| Culture | Skills and ways of life that are passed on from generation to generation by communication and tradition |
| Cultural evolution VS biological evolution | Cultural evolution involves change in culture and skilss, whereas biological is the change in physical characteristics |
| Kitchen midden | Accumlation of seeds, shells etc as evidence of an ancient living site |
| Cultural isolation | Religious and social factors prevent interbreeding |
| Uses of fire for early humans | Cooking, protection, warmth, light and splitting stones |
