BSc 1st Year Botany Bacillariophyta Diatom Sample Model Practice Question Answer Papers
BSc 1st Year Botany Bacillariophyta Diatom Sample Model Practice Question Answer Papers: BSc is a three-year program in most universities. Some of the universities also offer BSc Honours. After getting enrolled for BSc, there are certain things you require the most to get better grades/marks in BSc. Out of those, there are BSc Study Material, BSc Sample Model Practice Mock Question Answer Papers along with BSc Previous Year Papers. At gurujistudy.com you can easily get all these study materials and notes for free. Here in this post, we are happy to provide you with BSc 1st Year Botany Bacillariophta Diatom Sample Model Practice Question Answer Papers.
Index for BSc 1st Year Botany Bacillariophyta Diatom Sample Model Practice Question Answer Papers
Distinguished features of Bacillariophyceae: Page 1
Economic importance of diatoms: Page 2
Navicula: Page 3
Q.1. Give the distinguished features of Bacillariophyceae.
Ans.1. The forms of Bacillariophyceae are popularly called diatoms which may be a unicellular or colonial. Their highly sculptured and symmetrically ornamented cell wall makes this group separate from rest of the algae. The group contains about 190 genera classified into 5,500 species, majority of which are living and a few are fossil.
The class Bacillariophyceae are characterised by the following features:
1. The forms may be unicellular or colonial.
2. The vegetative cells of the thallus are diploid.
3. The plant body consists of two overlapping halves called valves.
4. The cell walls are silicified.
5. Chromatophores are characteristic with the presence of chlorophyll-e together with fucoxanthin, diatoxanthin and diadinoxanthin and therefore give brown colouration. There may be one to many chromatophores in each cell.
6. The reserve food material is oil and chrysolaminarin.
7. Quite interestingly there occurs reduction in size of cells during vegetative multiplication. However, auxospores are larger in size than the cells producing them.
Occurrence: Forms are cosmopolitan and grow in all kinds of aquatic habitats, both in fresh and salt waters and on damp surface to planktonic conditions. They can be frequently seen as a yellow scum on the surface of mud in ponds and ditches. They are quite important as primary producers in the food wave of aquatic ecosystem
The most common fresh water forms are Asterionella, Navicula, Nizchia, Melosira, Synendra, etc. The epiphytic forms growing under similar habitat are Cocconeis, Gomphonema, and Euntia. They grow on fresh water algae such as Cladophora, Oedogonium, Pithophora, etc. Triceratium and Hyalodicus are marine forms which grow as epiphytes on sea weeds.
Fossil diatom: Abundant fossils of diatoms from Silurian are abundantly known and about 70 genera have been so far reported. Majority of such fossils are centric. A diatom, Pynidicula is supposed to be oldest one from Jurassic. Quite many fossil forms are reported from India, especially from Laradura, Kashmir. Their deposits are popularly called Kieslguhr.
BSc 1st Year Botany Bacillariophyta Diatom Sample Model Practice Question Answer Papers