341: A small weight put on the pressure cooker increases the pressure of steam because:
(a) It is air tight
(b) Area of contact is very small
(c) Density of metal is very high
(d) Pressure builds up irrespective of the weight placed
342: Among living organisms, which one of the following is the most responsible factor for bringing about the origin of a new species?
(a) Isolation
(b) Mutation
(c) Natural Selection
(d) Sexual Reproduction
Explanation:
Mutation is the most important factor for bringing about the origin of a new species. Mutation is the sudden heritable change and is the seat of all variations of the ultimate source of variation. Evolution is a change in the genetic composition of the population brought about when natural selection acts on the variability of population.
343: Epiphytes are plants which depend on other plants for
(a) food
(b) mechanical support
(c) shade
(d) water
Explanation:
Epiphytes are small plants of orchidaceae family which take shelter on the branches of other trees to obtain more sunlight in ever green forests and also for mechanical support with the help of clinging roots. Example : Vanda.
344: Consider the following techniques/phenomena:
1. Budding and grafting in fruit plants
2. Cytoplasmic male sterility
3. Gene silencing
Which of the above is/are used to create transgenic crops?
(a) 1 only
(b) 2 and 3
(c) 1 and 3
(d) None
345: The rich source of iron is:
(a) Eggs
(b) Green vegetables
(c) Pulses
(d) Milk