Is there a relationship between the size of an organism and its life span? Give two examples in support of your answer.
There is no relationship between the size and life span of an organism. e.g.,
(i) The mango tree has a shorter life span as compared to a peepal tree though both are of the same size.
(ii) The size of crow and parrot is almost same but the life span is 15 years and 150 years respectively.
In the figure given below the plant bears two different types of flowers marked ' $A$ ' and ' $B$ '. Identify the types of flowers and state the type of pollination that will occur in them.
$$ \text { In the figure given below the plant bears folllowing two types of flowers } $$
A-Chasmogamous flower (the flowers remain open, exposing anthers and stigmas).
B-Cleistogamous flowers (the flowers remain closed, so that anthers and stigmas are never exposed) following are the types of pollination that will occur in these flowers.
(i) Autogamy (within same flower)
(ii) Geitonogamy (different flowers of same plant)
(iii) Xenogamy (different plants)
It is a case of cleistogamy (a type of autogamy) in which some plants, like, Commelina bengalensis possess both chasmogamous and cleistogamous flowers.
In chasmogamous flowers, the flowers may undergo self-pollination or cross-pollination, while in cleistogamous flowers, the flowers undergo only self-pollination.
Give reasons as to why cell division cannot be a type of reproduction in multicellular organisms.
In unicellular animals, cell division is the means of reproduction to increase their number while, in case of multicellular organisms, they have well developed reproductive organs which help in reproduction.
Their whole body does not participate in reproduction like unicellular organisms.
$$ \text { In the figure given below, mark the ovule and pericarp. } $$
In flowering plants, the zygote is formed inside the ovule. After fertilisation the sepals, petals and stamens of the flower wither and fall off. The pistil however, remains attached to the plant.
The zygote develops into the embryo and the ovules develop into the seed. The ovary develops into the fruit which develops a thick wall called pericarp that is protective in function.
Why do gametes produced in large numbers in organisms exhibit external fertilisation?
Organisms that take part in such process produce large number of gametes because
(i) In external fertilisation, there is a great chance that the sperm and the eggs released by the organisms can be affected by factors present in the environment like dessication, predators, etc. So, to make up for the high fatality rate of the gametes, the organism produces a lot of gametes.
(ii) Producing large number of gametes increase the chance for at least some eggs and sperms to meet in the environment ensuring that atleast a stable number of offspring are able to survive and carry on.