10.4 - Investigating diversity Flashcards
1
Q
How do we investigate diversity when comparing observable characteristics
A
- old method — form of artificial classification (looking at anatomical features)
- based on the fact that each observable characteristic is determined by a gene(s) (with environmental influences)
- the variety within a characteristic depends on the number and variety of alleles of that gene (plus environmental influences)
2
Q
What are the limitations with comparison of observable characteristics
A
- large number of characteristics are coded for by more than one gene. Instead the characteristics are phylogenic (means they’re not discrete from one another but rather vary continuously)
- often difficult to distinguish 1 from another, and characteristics may be modified by the environment
- therefore differences may be due to the environmental conditions and not the different alleles
- e.g. height being affected by genes, but also environmental factors like diet
3
Q
Because inferring DNA differences by comparing observable characteristics has its limitations, what has replaced it
A
- inferring DNA differences by DIRECTLY OBSERVING DNA SEQUENCES
- this has been made possible through advances in gene technology made over recent years
4
Q
Describe how comparison of DNA base sequences is done
A
- computerised systems will tag each nucleotide with a different colour fluorescent dye
- green = A, red = T, blue = C, yellow = G
- through sampling a member of a species’s DNA, we can sequence it to produce a pattern of coloured bands
- by analysing these patterns with scans via lasers, and interpreting these scans with computers, we are able to compare one species with another in order to determine how diverse they are
—> this technique can also be used to determine the evolutionary relationships between species (phylogenetic evidence)
5
Q
Why is DNA sequencing able to tell us about a species’ evolutionary relationships
A
- when 1 species gives rise to another during evolution, the DNA of the new species will initially be very similar to that of the species that gave rise to it
- due to mutations, the sequences of nucleotide bases in the DNA of the new species will change
- over time, the new species will acquire more and more over time —> more differences in DNA
- therefore we expect that the more closely related = the more similarity in their DNA
6
Q
Describe comparison of the base sequences of mRNA
A
- mRNA is coded for by DNA
- the base sequences on mRNA are complementary to those of the strand of DNA from which they were made
- we can therefore measure DNA diversity and therefore genetic diversity by comparing the base sequence of mRNA
7
Q
Describe comparison of amino acid sequence in proteins
A
- sequence of amino acids is determined by mRNA, which is determined by DNA
- therefore we can measure genetic diversity by comparing the amino acid sequence of their proteins
- the degree of similarity will in turn reflect the degree to how closely related they are
8
Q
A
Chimpanzee, gorilla, orang-utan, lemur, gibbon
9
Q
A
The chimpanzee and the gorilla because they both show the same % precipitation (95%)
10
Q
A
- The gibbon because it shows only a 3% difference (85-82) in precipitation between itself and the orang-utan
- all other primates show a greater difference
11
Q
A
- these data suggest that the gibbon is much more closely related to humans than the lemur
- the haemoglobin study suggested the lemur was a closer relative
- the chimpanzee is shown to be most closely related to humans in the haemoglobin study, while in the gene bases study it is the gorilla
12
Q
A
- there are fewer differences between the bases in the gene of a human and that of an orangutan 🦧 (29) then there are between the genes of a human and a lemur (48)
- this suggests that the evolution of humans and lemurs diverged earlier than that of humans and orangutans, giving more time for the amino acid differences to occur
13
Q
A
- No
- the study suggests that gorillas (with fewer base differences) are more closely related to humans than chimpanzees
- the other studies suggest chimpanzees are more closely related to humans
- the position of the orangutan is the same in all 3 studies
- the position of the lemur is the same as in the immunological study but different from that in the haemoglobin study
14
Q
What are Analogous characteristics
A
- arise from convergent evolutions
- when unrelated organisms develop similar structures which perform the same job
- these species are different in anatomical structure because they all have different evolutionary origin
- e.g. wings of a butterfly and wings of a pterodactyl
15
Q
What are homologous characteristics
A
- arise from divergent evolutions
- they come from similar evolutionary origins and so will share the same basic anatomical structure
- e.g. ribs of snake and the ribs of a fish (both have similar evolutionary origin)
