In this piece, Biology Homework Help will be looking the classification system in biology. In other words, Biology Homework Help will be looking at the ways in which the numerous species that share this planet are placed into various groups based on certain criteria which we will be examining later on. From the earliest of times, man has been acquiring and categorising knowledge about the various species of plants, animals and other living organisms in his surroundings in his quest for food, safety and shelter. As civilization progressed and more and more knowledge came to be acquired, scholars soon started to formalize these categories for ease of study.
In Biology Homework Help we see that once again it was the Greeks who laid the basis for the formal classification of the various species. Aristotle, the famous Greek philosopher was the first to classify life. He classified plants on the basis of their structure into shrubs, herbs and trees. He also divided animals into two groups: one containing those with red blood and the other the ones without. Aristotle's system continued to be one of the most used ones until the 18th century when Carl Linnaeus a Swedish botanist introduced the standard hierarchy of class, order, genus and species. Linnaeus was the first to use binomial nomenclature consistently. Moreover he made it possible for naturalists of the time to classify various species with a fair amount of accuracy and ease by providing workable keys. His system continued to be used until the 20th century though it evolved with each new set of information.
In 1969, R.H. Whittaker proposed a Five Kingdom Classification for biology. The kingdoms defined by him were named Monera, Protista, Fungi, Plantae and Animalia. The main criteria for classification included cell structure, thallus organisation, mode of nutrition, reproduction and phylogenetic relationships. Biology Homework Help will now examine these kingdoms in greater detail.
The kingdom Monera consists of prokaryotic organisms such eubacteria and archaebacteria. Prokaryotes lack the definite nucleus and membrane-bound organelles (specialized cellular parts) of eukaryotic organisms. They reproduce mainly by transverse binary fission.
The kingdom Protista contains all the single-celled eukaryotes. Eukaryotes are cellular organisms that possess clearly defined nuclei. Protista includes Chrysophytes, Dianoflagellates, Euglenoids and Protozoans. However its boundaries are rather fluid since this kingdom in biology forms a link with the others dealing with plants, animals and fungi. Members of Protista are primarily aquatic and can reproduce both asexually and sexually by a process involving cell fusion and zygote formation.
The Kingdom Plantae includes all eukaryotic chlorophyll-containing organisms commonly called plants. Biology Homework Help defines the Plantae as organisms which have an almost exclusively photosynthetic mode of nutrition and lack organs of locomotion. The cells contain cellulose in their walls and are therefore fairly rigid and essentially unlimited growth occur at localized regions of cell divisions called meristems. Most of the Plantae lack sensory and nervous systems, and their life histories that show an alteration of haploid and diploid generations.
Biology Homework Help will now look at the Kingdom Animalia. It consists of heterotrophic eukaryotic organisms that are multi-cellular and which depend directly or indirectly on plants for their nutrition. They inject their food which is then digested in a hollow internal cavity. Animalia cells lack cell walls. The organisms follow a definite growth pattern and grow into adults that have a definite shape and size. Higher forms show elaborate sensory and neuromotor mechanisms. Most of them are capable of locomotion. The sexual reproduction is by copulation of male and female followed by embryological development.
