Three and four kingdom classification, Biology

Assignment Help:

Three and Four Kingdom Classification

The two-kingdom classification, while solving many of the problems of classification, failed to establish clear-cut distinction between plants and animals. It also could not indicate correct relationships among organisms. Difficulty was particularly felt at the unicellular level. There are forms like Euglena and Volvox which possess both plant and animal like characters. On the one had like plants they contain chlorophyll and manufacture their food by photosynthesis.

On the other Kind the" actively swim like animals. Due to this reason zoologists classified them with animals under phylum protozoa while botanists included them as plants under Thallophyta. In addition to this, there are some other organisms like Peranema which closely resemble Euglena in structure but lack chlorophyll. These are not included among plants but were always classified under Protozoa. In order to overcome such difficulties, Haeckel (1866) proposed setting up of a third kingdom under the name Protista (meaning the very first) to include all thallophytes and protozoans. This kingdom also included bacteria and blue-green algae. According to this system the old kingdom Plantae included only the members of Embryophyta while Animalia was left only with Parazoa and Metazoa. However, many forms such as blue-green algae and bacteria of Protista lack membrane- bound nuclei. So, a fourth kingdom, Monera, was later established by Whittaker in order to accommodate these forms. From the evolutionary point of view the kingdom Monera is regarded as the most primitive.


Related Discussions:- Three and four kingdom classification

Autumn (fall) overturn, Autumn (fall) overturn In autumn or early wint...

Autumn (fall) overturn In autumn or early winter the air temperature falls, resulting in the cooling of the surface waters. When the surface water cools to 4°C it becomes dens

Food borne infections, Q. Food borne infections? Food borne infections,...

Q. Food borne infections? Food borne infections, as you may recall reading earlier, are caused by the ingestion of pathogenic microorganisms that penetrate the intestinal muco

What is waterston shunt in palliative operations, What is Waterston Shunt i...

What is Waterston Shunt in palliative operations? In this, direct anastomosis between the posterior aspect of ascending aorta and anterior aspect right pulmonary artery is done

Explain risk factors for cad, Explain Risk Factors For CAD? As has been...

Explain Risk Factors For CAD? As has been noted, CAD is very common among the Indians and many studies have been undertaken to find out the reasons behind this predilection. Wh

Define the axon of a neuron, Consider an axon of a neuron. At time=t1, its ...

Consider an axon of a neuron. At time=t1, its voltage is at threshold for an action potential; at time=t2, its voltage is at 0 millivolts prior to the peak of that action potential

Explain the term trans fatty acids, Explain the term Trans fatty acids? ...

Explain the term Trans fatty acids? Plant derived fats and oils contain cis-fatty acids. You may recall reading about the cis and trans isomers in the Nutritional Biochemistry

Main constituents of the earth''s atmosphere in our time, What are the main...

What are the main constituents of the earth's atmosphere in our time? The present atmosphere of the earth is constituted essentially of molecular nitrogen (N2) and molecular ox

Evolution of human kind, The evolution of human kind can be regarded as the...

The evolution of human kind can be regarded as the climax of phylogenic history of organisms. In the previous units of this block as well as the previous block we have detailed for

What is the evolutionary origin of the internal membranous, What is the evo...

What is the evolutionary origin of the internal membranous organelles of the cell? It is accepted that the internal membranous organelles of the eukaryotic, like the Golgi app

Availability of adp, Availability of ADP When  the ADP  levels increase...

Availability of ADP When  the ADP  levels increase due to hydrolysis ofATP  in various biosynthetic reactions,  the  rate of reaction to generate ATP  is accelerated and this i

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd