BIOLOGY 2 Marks Questions

The types of classification of plants are as follows:
1. Artificial Classification
2. Natural Classification
3. Phylogenetic Classification
Natural Classification: This classification were based on natural affinities among the organisms and consider, not only the external features, but also internal features, like ultra-structure, anatomy, embryology and phytochemistry. Such a classification for flowering plants was given by George Bentham and Joseph Dalton Hooker.

These are usually occur in damp, humid and shaded localities. Bryophytes are also called amphibians of the plant kingdom. They grow on land, but depend on water for sexual reproduction. The liverworts grow usually in moist, shady habitats such as banks of streams, marshy ground, damp soil, bark of trees and deep in the woods.

Bryophytes in general are of little economic importance but some mosses provide food for herbaceous mammals, birds and other animals. Species of Sphagnum, a moss, provide peat that have long been used as fuel, and as packing material for trans-shipment of living material because of their capacity to hold water. Mosses along with lichens are the first organisms to colonise rocks and hence, are of great ecological importance. They decompose rocks making the substrate suitable for the growth of higher plants. Since mosses form dense mats on the soil, they reduce the impact of falling rain and prevent soil erosion.

In these, vegetative reproduction usually takes place by fragmentation or by formation of different types of spores. Asexual reproduction is by flagellated zoospores produced in zoosporangia. The sexual reproduction shows considerable variation in the type and formation of sex cells and it may be isogamous, anisogamous or oogamous.

These are brown algae. There is a vacuole and nucleus in the centre of the protoplast of the cell. The cell wall is made of cellulose which has a gelatinous lining of algin on the outside. These contain chlorophyll carotenoids and xanthophyll. Their brown colour is due to the high amount of xanthophyll pigment, fucoxanthin. The food stored in these is in the form of laminarin or mannitol.

In these, vegetative reproduction occurs through fragmentation, asexual reproduction occurs through non- motile spores and sexual reproduction occurs through non- motile gametes. Sexual reproduction is oogamous and accompanied by complex post fertilisation developments.

Gymnosperms are plants in which the ovules are not enclosed by any ovary wall and remain exposed, both before and after fertilisation. The seeds that develop post- fertilisation, are not covered, i.e., are naked.