Detailed Notes 3 – Chapter2-Biological Classification

2.4 KINGDOM PLANTAE

1. Characteristics:

   • Kingdom Plantae includes all eukaryotic chlorophyll-containing organisms, commonly referred to as plants.
   • While most plants are autotrophic, a few members are partially heterotrophic, such as insectivorous plants or parasites.
   • Plant cells have a eukaryotic structure with prominent chloroplasts and cell walls mainly composed of cellulose.

2. Examples:

   • Examples of partially heterotrophic plants include bladderwort and Venus flytrap (insectivorous plants), and Cuscuta (a parasite).

3. Taxonomic Groups:

   • Kingdom Plantae encompasses various taxonomic groups, including algae, bryophytes, pteridophytes, gymnosperms, and angiosperms.

4. Life Cycle:

   • The life cycle of plants involves two distinct phases: the diploid sporophytic phase and the haploid gametophytic phase.
   • These phases alternate with each other, and the lengths of the haploid and diploid phases vary among different plant groups.
   • This phenomenon is known as alternation of generations.

2.5 KINGDOM ANIMALIA

1. Characteristics:

   • Kingdom Animalia is characterized by heterotrophic eukaryotic organisms that are multicellular.
   • Unlike plants, animal cells lack cell walls.
   • Animals directly or indirectly depend on plants for food.
   • They digest their food in an internal cavity and store food reserves as glycogen or fat.
   • The mode of nutrition in animals is holozoic, which involves the ingestion of food.
   • Animals follow a definite growth pattern and grow into adults with a specific shape and size.
   • Higher forms of animals exhibit elaborate sensory and neuromotor mechanisms.
   • Most animals are capable of locomotion.

2. Reproduction:

   • Sexual reproduction in animals typically involves copulation between male and female individuals, followed by embryological development.

3. Further Details:

   • Salient features of various animal phyla are described in Chapter 4, providing more detailed information about the diversity and characteristics of different groups within Kingdom Animalia.

2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS

1. Viruses:

   • Viruses are acellular organisms characterized by having an inert crystalline structure outside the living cell.
   • They are considered obligate parasites as they require a host cell to replicate.
   • Viruses contain genetic material, which can be either RNA or DNA, but not both.
   • Bacterial viruses, or bacteriophages, are usually double-stranded DNA viruses.
   • Viruses cause various diseases in both plants and animals, such as mumps, smallpox, herpes, influenza, and AIDS.

2. Viroids:

   • Viroids are infectious agents smaller than viruses.
   • They consist of free RNA and lack the protein coat found in viruses.
   • Viroids were discovered in 1971 and are known to cause diseases like potato spindle tuber disease.

3. Prions:

   • Prions are infectious agents consisting of abnormally folded proteins.
   • They are similar in size to viruses and are associated with certain neurological diseases in animals and humans, such as bovine spongiform encephalopathy (BSE) and Creutzfeldt-Jakob disease (CJD).

4. Lichens:

   • Lichens are symbiotic associations between algae and fungi.
   • The algal component, known as the phycobiont, is autotrophic, while the fungal component, the mycobiont, is heterotrophic.
   • Algae produce food for fungi, while fungi provide shelter and absorb mineral nutrients and water for algae.
   • Lichens are excellent pollution indicators, as they do not grow in polluted areas.