Diatoms do not decay easily because
1. they have siliceous walls
2. their body is impervious to water
3. they are chitinous
4. they are abundant in saline soil
Group of organisms in which cell wall forms two thin overlapping shells are
1. Responsible for bioluminescence.
2. Chief producers of ocean.
3. Prokaryotes.
4. Heterotrophs.
The cell wall is impregnated with silica to form transparent siliceous shell in
1. Dinoflagellates
2. Euglenoids
3. Diatoms
4. Slime moulds
Diatoms have left behind large amounts of cell wall deposits in their habitat because:
1. They are most abundant in that habitat
2. Their life span is long
3. Their wall is indestructible
4. The statement is not true
Select the wrong statement.
(1) The walls of diatoms are easily destructible
(2) 'Diatomaceous earth' is formed by the cell walls of diatoms
(3) Diatoms are chief producers in the oceans
(4) Diatoms are microscopic and float passively in water
Assertion(A): |
Diatomaceous earth is used in polishing, filtration of oil and syrups. |
Reason(R): | Diatomaceous earth is gritty due to presence of silica. |
1. | Both (A) and (R) are True, and (R) correctly explains (A) |
2. | Both (A) and (R) are True, but (R) does not correctly explain (A) |
3. | (A) is True, but (R) is False |
4. | Both (A) and (R) are False |
Which of the following features does not go with characteristics of chrysophytes
(1) Diatoms + Desmids
(2) Rarely photosynthetic
(3) Plankton
(4) Found in both type of aquatic habitat ie marine and fresh water
In which group of organisms the cell walls form two thin overlapping shells which fit
together?
1. Chrysophytes
2. Euglenoids
3. Dinoflagellates
4. Slime moulds
Which of the following feature is not associated with diatoms?
(1) Chief producers of Earth
(2) Form diatomaceous earth which has gritty soil
(3) Gritty soil is used in filtration
(4) Gritty soil is used in polishing