Question

How various biochemical approaches are helpful in the process of classification of plants and animals? Give examples. should be long answer​

Answer 1

Answer:

Plantae is the plant kingdom which includes all plants on the earth. They are multi-cellular eukaryotes. They consist of cell walls and chlorophyll. Plants are photosynthetic. Hence, they have an autotrophic mode of nutrition. The plant kingdom is a vast group; therefore, the kingdom is further classified into subgroups. Level of classification is based on the following three criteria:

1.Plant body– whether the body has well-differentiated structures or not.

2 Vascular system-whether the plant has vascular system for transportation of substances or not.

3.Seed formation– whether the plant bears flowers and seeds or not; if it does, then whether it is enclosed within fruits or not.

Considering all these factors, the plant kingdom has been divided into two groups and five subgroups.

The two subgroups are:-

Cryptogams- reproduction through spores and no seed formation. They include subgroups Thallophyta, Bryophyta and Pteridophyta

Phanerogams-they have specialised reproductive organs and they produce seeds. Gymnosperms and Angiosperms belong to this group.

The 5 subgroups are as follows:

A)Thallophyta- body not differentiated into roots and stem,no vascular system,no seed formation

B)Bryophyta-body differentiated but lack vascular system,no seed formation

C)Pteridophyta- well- differentiated body, vascular system present, no seeds formation

D)Gymnosperms- well-differentiated body with vascular system, seeds are naked(not enclosed in a fruit)

E)Angiosperms- well-differentiated body with vascular system, seeds are covered(enclosed in a fruit)

Answer 2

Answer:

Biochemical Approach:

Biochemical approach has been extensively studied in plants than in animals. Animals contain a large number of complex compounds like hormones, enzymes and protein molecules comprising of peptides, nucleic acids, amino acids etc.

The primary work of a biochemical taxonomist is concerned with the comparison and contrasting of compounds of the same class and performance of similar functions in different animal species, in respect to their properties as well as their distribution in dif­ferent body organs.

Based on the above, taxonomy can be:

1. Protein Taxonomy:

Protein taxo­nomy was coined by Crick (1958), as species can be differentiated based on the sequence of amino acids in the proteins of an organisms. Thus, species differ in the differences of their amino acid sequences.

2. Molecular Taxonomy:

Molecular taxonomy, the term coined by Lahni (1964), was primarily based on the nucleotide sequences of polynucleotides. When trying to measure degrees of genetic relationship it is very important to look for the genetic material they are composed of and this is when molecular taxonomy comes into play. It is also believed that the changes in the enzyme structure can help in the discovery of new species.

Turner in 1966 divided mole­cular taxonomy into –

(i) Micro-molecular taxonomy:

It lays stress upon the distribution and biosynthetic interrelationships of small molecular weight compounds like free amino acids, alkacids, terpenes, flavonoids etc. These are common­ly referred to as secondary compounds. This type of approach is particularly useful in resolving systematic problems where hybri­dization has been a factor.

(ii) Macromolecular taxonomy:

Macro molecular taxonomy is concerned with the polymeric molecules. It is more or less close to the core of hereditary information that is the DNA sequence, RNA, polysaccharides and proteins. This approach is useful in solving some of the more intractable syste­matic problems, especially those involving relationships among higher categories. Biochemical characters have been found to be extremely useful in solving various taxonomic problems.

A few examples are:

1. Phylogenetic relationship among vari­ous orders of birds have been demonstrated by Basu Chaudhary and Chatterjee (1969), based on the quantative analysis of ascorbic acid. Ascorbic acid is produced by some birds (Anseriformes, Columbiformes etc.) in the kidney; in some (piciformes) it is pro­duced in the liver; while in some in both liver and kidney, and in some of the more evolved passerine birds, it is completely lost.

2. Using the biochemical characters of the unique venoms of fire ants, Brand (1972) were able to establish the phylogeny of a group of fire ants. Although the biochemical approach is helpful in solving many taxonomical prob­lems, yet in many cases they are not useful.

Moreover, such studies are not possible in extinct organisms and, therefore, it is difficult to trace the course of evolutionary history through this process. However, proteins and nucleic acids provide a much reliable esti­mate of the degree of genetic homology among animals.

The distribution of free amino acids in different organs of insects is of greater taxonomic value. Similarly, in mam­mals, the classification of species, based on the amino acid sequences, are in accordance to the accepted one based on the morpho­logical data. Such biochemical studies are conducted in five ways — immunological, chromatographic, electrophoresis, infra-red spectrophotometry and histochemical studies.