December 9, 2013

Junior Inter Botany 4 Marks Questions and Answers - AP Board

4 Marks Questions
Q: What is meant by identification and nomenclature? How is a key helpful in the identification and classification of an organism?
A: Identification means to determine whether a collected organism is entirely new or
already known.
- Nomenclature means providing a scientific name to an identified organism.
- A taxonomic key is based on contrasting characters in pairs (couplet).
- It refers to a choice between two opposite options out of which one is accepted and the other rejected. Thus plants or animals may be classified using keys based on similarities and differences. Each taxonomic category requires separate taxonomic keys.
Ex: Couplet in a key:
Reticulate venation - Parallel venation
Flower pentamerous - Trimerous
Tap root - Fibrous root
Two cotyledons in seed - One cotyledon in seed
By comparing the characters of a plant with the above options one can classify a plant into dicotyledonae / monocotyledonae.

Q: Give the salient features and importance of Chrysophytes.
A: Salient features of Chrysophytes:
- Chrysophytes are single-celled eukaryotes which belong to the kingdom Protista.
- They include microscopic photosynthetic plankton like diatoms and desmids (golden
- They are aquatic which may be marine or fresh water.
- They are surrounded by a soap box like cell wall which is composed of two overlapping
halves the epitheca and the hypotheca.
- The cell wall is made up of hard and indestructible silica.
- Based on the symmetry the diatoms may be classified into Centrales (radial symmetry)
and Pennales (bilateral symmetry).
- They reproduce by binary fission and formation of auxospores.

Importance of diatoms:

- Diatoms are photosynthetic and chief producers (phytoplankton) of seas and oceans.
- The diatom cell walls accumulated in the sea form diatomaceous earth or kieselguhr.
- It is used in polishing, filtration of oils and syrups.

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