Chapter 1 Classification of humans Revision Question 1 Identify technological advances and resulting new information that have changed scientists' opinions about the classification of primates. Hint Identify means recognise and name Answer DNA-DNA hybridisation, haemoglobin comparison, DNA sequencing and the study of mitochondrial DNA are all technological advances in biochemistry which have led to changing information and hence changing scientists' views on primate classification. Prior to these technological advances scientists' opinions only revolved around fossil evidence and comparative anatomy, usually indicating a separate evolutionary line for humans compared to apes. Now scientists have reached different conclusions from new technologies that indicate that chimpanzees and gorillas are more closely related to humans than orangutans and gibbons. Scientists also suggest that a possible common ancestor for apes and humans may have lived between 5-10 million years ago.

Marking criteria Links two or more technological advances to changing information and scientists' opinions 3 Names two technological advances and gives an indication of changing information or changing scientists' opinions 2 Names one technological advance 1 Stephanie HOLLIS BIOLOGY OPTIONS the human story Worked Example Chapter 2 Biological evidence and interpretation Revision question 2 Using examples, describe and distinguish between relative and absolute dating techniques for fossils. Hint Describe means provide characteristics and features Distinguish means recognise or note / indicate as being distinct or different from; to note differences between Answer Relative dating techniques provide accurate information about the sequence in which fossils appear in the fossil record. Examples of techniques are: 1 The use of the principle of superposition where a sequence of rock layers (strata) can be dated as the youngest layer at the top compared to the oldest layer at the bottom. 2 Stratigraphic correlation is where strata containing similar fossils around the world are presumed to have been laid down together, and are of the same age. Index fossils are commonly used to date other organisms found in the same layer of rock. 3 Fluoride-nitrogen dating uses the comparison of the amount of nitrogen lost to fluoride absorbed to determine age.

All these techniques provide estimates of age. However, absolute dating provides a more accurate method. Absolute dating is used to determine a numerical value of the age of a material. It uses techniques such as radiometric dating to calculate the age through the half-life (or rate of breakdown or decay) of radioactive elements into other elements (for example, uranium, carbon-14 and potassium). Another technique used is electron-spin resonance which dates an object by measuring the accumulation of higher-energy electrons from natural radiation in the soil over time. Thermoluminescence also dates materials by measuring the amount of electrons trapped from radioactive elements.