Evidence For Relationships Between Organisms Flashcards
Why would similar species have similar DNA?
- when 1 species evolves into new species, DNA of both species will be very similar
- over time more mutations occur, making DNA more different
- more similar species, less mutations, more genetically alike
Describe process of DNA hybridisation
- DNA from 2 species is extracted and cut into short pieces
- DNA from 1 is labelled radioactively and mixed with DNA from other
- DNA mixture is heated to separate strands
- Mixture is cooled; complementary bases pair up, hybrid strands will be 50% labelled
- Temp is increased in stages, higher temp needed to separate, more H bonds, more comp pairs, more closely related
Why can sequences of amino acids be used to show similarity between species?
DNA codes for amino acids, therefore comparison of amino acids is comparison of DNA
What is the principle behind immunological comparison of proteins?
The antibodies of 1 species will react to specific antigens on proteins in blood serum of another species
Outline process of immunological comparison of proteins
- Serum from A is injected into B
- B produces antibodies specific to antigens from serum of A
- Serum is removed from B, containing antibodies and injected into C
- Antibodies respond to antigens from C, higher number of antibody-antigen reactions, more precipitate formed
- More precipitate formed, closer relationship between A and C
What does courtship behaviour enable individuals to do?
- recognise members of own species; to produce fertile offspring
- make pair bond; leads to successful mating
- identify a mate capable of breeding
- synchronise breeding
Why is courtship carried out by male?
To determine if female is receptive. In many species females can only conceive during a short period
Why is courtship behaviours decribed as a ‘stimulus-reaction chain’?
Behaviour of male is stimuli for behaviour of female. If 1 fails to respond correctly, courtship ends
