Chapter 15: Evidence For Evolution

Question 1

• Using an example, explain how the study of DNA in different species has added to the evidence for evolution.
• What are the 3 biotechnological techniques, used to facilitate DNA sequencing for the purpose of providing evidence for evolution.
• Describe how mtDNA has been used to provide evidence for evolutionary relationships between species.
• Describe how scientist can use comparative protein analysis to discover evolutionary relationships between organisms.
• What role has comparative genomics played in the study of evolutionary changes among organisms?
• How does a study of embryology assist in supporting the theory of evolution? Give examples to illustrate your answer.

Answer 1

• All species have the same DNA code, suggesting all species evolved from a common ancestor. Species that are more distantly related have more differences in their DNA and vice verser. Eg chimpanzee genomes share 98% of human DNA whereas orang-utans share 97.5%. Therefor chimpanzees are closer related.
• PCR (to amplify minute amounts of DNA), bacterial enzymes and gel electrophoresis (to facilitate DNA sequencing of genomes).
• mtDNA is inherited from mothers. It mutates more than nuclear DNA and amount of mutation is proportional to time passed. Similarities and differences in mtDNA of species thus show evolutionary relationships.
• Every protein has a specific number of amino acids which are arranged in a particular sequence. Similarity of amino acid sequence is evidence of close evolutionary relationship.
• By comparing regions of genomes of species, similarity and differences can be identified to determine relationships between them
• By comparing the early embryonic stages in species, there are noticeable similarities eg gill patches, gill arcs and others. This indicates that they all diverged from a common aquatic ancestor.

Question 2

• What are homologous organs?
• Using an example, describe how homologous structures provides evidence for evolution.
• Explain how vestigial organs could provide evidence for evolution.
• List 5 vestigial organs in humans.
• Explain how geographical distribution provides evidence for evolution.
• Describe how Polymerase chain reaction has facilitated DNA sequencing.
• Describe how Gel electrophoresis has facilitated DNA sequencing.

Answer 2

• Organs that posses similar structure, though may differ in function.
• Species with organs of similar structure are likely to have evolved from a common ancestor. Eg forearms of vertebrates - whales and humans,indicating they diverged from a common ancestor.
• They are structures of reduced size with no function due to natural selection pressures, so that the body doesn’t waste energy maintaining them. This suggest ancestral relationship with organisms that have functional forms of the same organs.
• Ear muscles, wisdom tooth, body hair, coccyx and appendix.
• It shows groups were separated and evolved independently, resulting in related species having different characteristics.
• Produces large amounts of small amounts of DNA so that it can be used in the sequencing of a genome.
• Establishes a DNA profile to be compared with other profiles to trace relationships between individuals and groups.

Question 3

• Describe how Bacterial enzymes has facilitated DNA sequencing.
• Describe how Darwin explained the way different populations of finches became established as separate species on the Galápagos Islands.
• How has information from DNA been used to speculate on the relationship between species?
• Why would scientists use a comparative study of haemoglobin in different species in a search for data to support their theories of primate evolution?
• What are ubiquitous proteins?
• Why is bioinformatics used?

Answer 3

• Restriction enzymes cut DNA into small fragments to be sequenced.
• The 1st finches to reach the islands from the mainland would have shown variation in beaks. With different survival pressures, different beak on different Islands was naturally selected independently. This resulted in each island developing its own species with distinctive characteristics.
• By comparing similarities in DNA base sequences, similar DNA sequences = earlier common ancestor.
• mtDNA has only 37 genes so species not closely related have too many mutations that relationships would be difficult to determine.
• Proteins that appear to be in all species. They carry out the same functions regardless of the species in which they are found in.
• Provides the database for the information provided by genomics.

Question 4

• What are endogenous retroviruses?
• How do retroviruses become endogenous?
• What is the value of endogenous retroviruses in a study of evolution?
• Why has cytochrome C been so valuable in providing evidence for evolution?
• Explain why mtDNA is only of use when looking at the relationships within species or between closely related species.

Answer 4

• Viral sequences that’s become part of an organism’s genome.
• Retrovirus copies its RNA into DNA (reverse transcription) and inserts it into host cell. Only endogenous if the host cell is inherited by next generation- gametes.
• Offsprings of infected individuals will have copies of the ERV in the same place in the same chromosome. If different species are found to have exactly the same ERV on the same place of their chromosomes, the species must of had a common ancestor. More same ERVs = closer related.
• Cytochrome C is a ubiquitous protein that’s changed very little over time. The more similarity there is between the cytochrome C from different species, the more closely related they are.
• Haemoglobin is common to all primates, so all primates would have started with the same haemoglobin and as they formed separate species, there have been gradual changes in the haemoglobin. Comparing differences demonstrates relationships.