Introduction
Q. What is Kingdom Plantae?
Ans: These are multicellular eukaryotes with cell walls mainly made of cellulose. They are autotrophs and use chlorophyll for photosynthesis. A few members are partially heterotrophic such as the insectivorous plants or parasites. Bladderwort and Venus fly trap are examples of insectivorous plants and Cuscuta is a parasite.
Key Points
- Plantae includes algae, bryophytes, pteridophytes, gymnosperms, and angiosperms.
- The Lifecycle of plants has two distinct phases - the diploid sporophytic and the haploid gametophytic - that alternate with each other.
- The lengths of the haploid and diploid phases, and whether these phases are free-living or dependent on others, vary among different groups of plants. This phenomenon is called alternation of generation.
Animalia
- .These include all organisms which are multicellular eukaryotes without cell walls. They are heterotrophs.
- They directly or indirectly depend on plants for food. They digest their food in an internal cavity and store food reserves as glycogen or fat {Carbohydrates, Fats - Healthy Fats and Unhealthy Fats}.
- Their mode of nutrition is holozoic - by ingestion of food.
- They follow a definite growth pattern and grow into adults that have a definite shape and size.
- Higher forms show elaborate sensory and neuromotor mechanism. Most of them are capable of locomotion.
- The sexual reproduction is by copulation of male and female followed by embryological development.
- In the five-kingdom classification of Whittaker {Biological Classification} there is no mention of some acellular organisms like viruses and viroids, and lichens. These are briefly introduced here.
- Viruses did not find a place in classification since they are not truly ‘living’ if we understand living as those organisms that have a cell structure.
- The viruses are non-cellular organisms that are characterized by having an inert crystalline structure outside the living cell.
- Viruses are obligate parasites. Once they infect a cell they take over the machinery of the host cell to replicate themselves, killing the host.
- The name virus that means venom or poisonous fluid was given by Pasteur.
- In addition to proteins, viruses also contain genetic material, that could be either RNA or DNA . No virus contains both RNA and DNA.
- In general, viruses that infect plants have single-stranded RNA and viruses that infect animals have either single or double-stranded RNA or double-stranded DNA.
- Bacterial viruses or bacteriophages (viruses that infect the bacteria) are usually double-stranded DNA viruses
- The protein coat called capsid made of small subunits called capsomeres protects the nucleic acid. These capsomeres are arranged in helical or polyhedral geometric forms.
- Viruses cause diseases like mumps , smallpox , herpes , and influenza . AIDS in humans is also caused by a virus.
- In plants, the symptoms can be mosaic formation, leaf rolling and curling, yellowing and vein clearing, dwarfing and stunted growth.
- Viroids are infectious agents that are smaller than viruses. A viroid was found to be a free RNA, it lacked the protein coat that is found in viruses, hence the name viroid.
- The RNA of the viroid was of low molecular weight. Viroids caused potato spindle tuber disease.
- Lichens are symbiotic associations i.e. mutually useful associations, between algae and fungi .
- The algal component is known as phycobiont and fungal component as mycobiont, which is autotrophic and heterotrophic, respectively.
- Algae prepare food for fungi and fungi provide shelter and absorb mineral nutrients and water for its partner.
- So close is their association that if one saw a lichen in nature one would never imagine that they had two different organisms within them.
- Lichens are very good pollution indicators - they do not grow in polluted areas.
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