Evidence for evolutionIB MYP Biology: Flashcards

Exam questions on Evidence for evolution

1. Palaeontologists have found fossils in layers of sedimentary rock in Pakistan and Egypt that record the history of whales. The oldest fossils, about 50 million years old, show a wolf-sized animal with four legs that lived partly on land. Younger fossils show animals with shorter back legs and paddle-like front limbs. The youngest fossils show animals with bodies like modern whales and only tiny hind-limb bones.
   Explain why the fossil record is incomplete.2 marks
2. The front limbs of a human, a bat, a whale and a horse look very different and are used for different jobs: grasping, flying, swimming and running. However, when anatomists compare the bones, each limb contains one upper-arm bone, two lower-arm bones, a group of wrist bones and a series of finger bones, arranged in the same basic pattern.
   Explain how the limb bones support the idea that these animals evolved from a common ancestor, even though the limbs have different uses.2 marks
3. Cytochrome c is a protein used in respiration by almost all living organisms. Scientists compared the order of amino acids in cytochrome c from different species with the human protein and counted the positions where the amino acids differ. For the chimpanzee there were 0 differences, for the rhesus monkey 1, for the dog 10, for the chicken 13 and for the tuna 21.
   Describe the pattern in the data and explain what it suggests about how closely related each species is to humans.3 marks