(i) Classification helps us in exploring the diversity of life forms.
(ii) It simplifies to study them for scientific research.
(iii) It helps in cross breeding and modification for commercial purpose.
(iv) It helps in interpretening the interrelation of humans with other entities.
(v) It helps in studying their dependence and interactions.
The basis of the start of the hierarchy will be formed by the Gross character while the basis of steps further will be taken care of by the fine character.
For eg: 1.Human beings are categorized under vertebrates as they possess the vertebral column 2. For categorization of tetrapods, the existence of four limbs is taken into consideration.
3. In the case of mammals, the mammary gland is the required part.
The major characteristics considered for classifying all organisms into five major kingdoms are:
(a) Whether they are made of prokaryotic or eukaryotic cells.
(b) Whether the cells are living singly or organised into multicellular and thus complex organisms.
(c) Whether the cells have a cell-wall.
(d) Whether they prepare their own food.
Plants are classified on the basis of morphological characteristics such as Thallophytes and Bryophytes is the basic cell structure and gymnosperms and angiosperms are classified on the basis of visibility of seeds whereas in animal classification cytology is considered primarily as more minute structural variations are taken into account such as the cell layers and the presence and absence of various features like coelom, four legs, etc. decide the classification.
Vertebrata has two main subclasses namely, pisces(have a streamlined body with tails and fins which help them in swimming) and tetrapod(have four limbs for their movement.)
The tetrapod animals are further classified into:
1. Amphibia: The animals belonging to this group are adapted to live in both land and water. They can breathe underwater through their skin and through lungs when on land.
2. Reptilia: The animals belonging to this group crawls for their movement. Their skin is very thick and withstands extreme temperatures.
3. Aves: The forelimbs of these organisms are modified into wings which help them in their flight. They have a beak, and feathers that cover up their body.
4. Mammalia: The animals belonging to this group show nurturing skills as they contain mammary glands to support them. Their skin is covered with hair and most of them are viviparous in nature.
When we classify different organism on the basis of their similarities, it is easier and more convenient to study their characteristics and hence study the group as a whole.
(i) Small ant to big elephant.
(ii) Black crow to white swan.
(iii) Grass to rewood tree.
A eukaryotic cell has membrane-bound organelles, including a nucleus, which allow cellular processes to be carried out efficiently in isolation from each other. Therefore, organisms which do not have a clearly demarcated nucleus and other organelles would need to have their biochemical pathways organised in very different ways. This would have an effect on every aspect of cell design. Further, nucleated cells would have the capacity to participate in making a multicellular organism because they can take up specialised functions. Therefore, this is a basic characteristic of classification.
The primary characteristic on which the broad division of organisms is made is nature of cell and its broadly classified as prokaryotic cells and eukaryotic cells.
Plants and animals are put into different categories o the basis of presece and absece of cell wall and mode of nutrition, as plants make their own food and animals acquires their food.
Groups of organisms which have a very simple and basic cell arrangement, mechanism and structure and no division of labour is observed.
Advanced organisms, are the organisms possessing millions of cells that are grouped into various organs performing different functionality such as mammals.
Yes, advanced organisms are the same as complex organisms as advanced organisms means more evolution which leads to more complex organisms. The consequence of advancement leads to multiple cell arrangements that operate uniquely.
The criterion for classification of organisms as belonging to kingdom Monera or Protista is the presence or absence of well defined nucleus, as Monera have no nuclear membrane whereas Protista have well defined nuclei walls.
Since organism is single-celled, eukaryotic and photosynthetic it will be placed in Protista kingdom as for photosynthetic it must have a well-defined nucleus wall.
In the hierarchy of classification, Monera will have the smallest number of organisms with maximum common characteristics and Animalia will have the largest number of organisms.
Algae or Thallophyta has the simplest organisms among the plants.
(i) Pteridophytes possess a naked embryo whereas Phanero possess a covered embryo. (ii) Pteridophytes eexhibit unclear reproductive organ whereas Phanero exhibit well-defined reproductive organ.
Gymnosperms and angiosperms differ from each other on the basis that seed is covered or not. In gymnosperms, the seeds are naked while in angiosperms the seeds are covered.