classification/taxomy

Question 1

7 groups

Answer 1

Kingdom, Phylum, Class, Order, Family, Genus, Species

Question 2

Describe the principles on which the system of classification of living organisms is based. (4)

Answer 2

Hierarchy of 7 taxonomic groups (KPCOFGS);
no overlap between groups;
organisms placed in groups due to common structures / similar characteristics;
reflecting evolutionary history (phylogeny) of organisms within a group;
binominal nomenclature / example;
definition of a species;

Question 3

Phylogenetics

Answer 3

The study of the evolutionary history of groups of organisms, telling us who is related to whom and how close this relationship is compared to a common evolutionary ancestor.
It is closely related to classification because grouping needs to reflect evolutionary relationship
Members of one genus must be more closely related to each other than they are to organisms in a different genus.

Question 4

How does a phylogenic system differ to a simple hierarchy?

Answer 4

Hierarchical classification, large groups are divided into smaller groups
Process starts with species grouped into genus then grouped into family, order, class, phylum. As the groups get larger there is a more distant common ancestory
Initially this was based on shared easily observable characteristics
(phylogenetic) based on evolutionary history;
shows ancestry of groups / points of divergence;
members of a group have features in common; based on anatomy/fossils/embryology/DNA/specific aspect of cell biology or homologous structures, reflecting evolutionary history; phylogeny.

Question 5

Explain the principles biologists use to classify organisms into groups compared to older models.

Answer 5

Consider phylogeny
Look at evolutionary lineage/history
Find the point of divergence from a common ancestor
Consider, genetic, biochemical, embryology, homology of anatomy
Organisms are arranged in a hierarchy where large taxa (groups) are subdivided into smaller taxa
(K, P, C, O, F, G,S)
As groups get smaller the similarities between the species increase
Each species is given a binomial name using the genus and species
Older models of classification used observable features to group organisms

Question 6

Problems with classification

Answer 6

Defining a species is difficult when, reproductive behaviour cannot be observed because….
They organisms are extinct
Reproduce asexually
Practical and ethical issues involved when trying to cross breed certain different species

Question 7

DNA sequencing

Answer 7

Directly compare DNA by looking at the order of bases (A, T, C and G). Closely related species will have a higher percentage of similarity

Question 8

DNA Hybridisation

Answer 8

DNA from 2 species is collected, heated and separated into single strands (heating breaks H-bonds between the DNA bases)
The 2 separates species DNA is mixed and allowed to cool, this allows H-bonds to reform between complementary base pairs. The more similar the base sequences the more H-bonds that will form.
The similarity is measure by heating the hybrid strands and recording the temperature required to separate the strands. The higher the temperature required the more H-bonds that existed and the more closely related the DNA.

Question 9

Comparing amino acids sequences

Answer 9

Proteins are made up of amino acids. The sequence of amino acids is coded for by DNA. The closer the DNA sequences the more closely related the proteins.

Question 10

Immunological comparisons

Answer 10

Uses antibody specificity to see how similar proteins are

Question 11

Biologists can also use protein structure to investigate the relationship between different species of crane. Explain why.

Answer 11

1. More closely related (species) have more similarities in amino acid sequence/primary structure;
2. In same protein / named protein e.g. albumin;
3. Amino acid sequence is related to (DNA) base/triplet sequence;
   OR
4. Similar species have a similar immune response to a protein/named protein;
5. More closely related (species) produce more ‘precipitate’ / antibody-antigen (complexes) / agglutination;