Topic 2: Polygentic Trees

Question 1

PHYLOGENTETIC TREES

• A phylogenetic Tree is a diagram that represents evolutionary relationships among organisms
• The pattern of branching in a phylogenetic tree reflects how species or other groups evolved from a series at common ancestors

Answer 1

MAKING PHYLOGENETIC TREES

• In trees, two species are more related if they have a more recent common ancestor
• Each branch point represents a divergence event, or splitting apart of a single group into two descendent groups
• To generate a phylogenetic tree, scientists often compare and analyse many characteristics of the species of other groups involved
• These characteristics can include external morphology, internal anatomy, behaviours, biochemical pathways, DNA and protein sequences and even characteristics of fossils
• A large number of differences corresponds to less related species, s smaller number of differences corresponds to more related species

Question 2

DNA

• DNA hybridisation is a technique used to determine the similarity of DNA from different species
• In this technique
• DNA is extracted from different species and cut into pieces using special enzymes; the DNA is heated to seperate the double strands into single strands of DNA from different species are mixed together and then cooled so that the double helix strands of hybrid DNA form
• Hybrid DNA consists of one strand from each of the two different species. Heat is then used to test how well the strands have joined. The DNS nucleotides must match more closely in hybrid DNA strands that seperate at higher temperatures than in hybrid DNA strands that seperate at a lower temperature.

Answer 2

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