NCERT Class 12 Biology: Chapter –1 Reproduction in Organisms Part 3

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Question 5:

Rearrange the following events of sexual reproduction in the sequence in which they occur in a flowering plant:

Embryogenesis, fertilisation, gametogenesis, pollination.

Answer:

Gametogenesis Pollination Fertilisation Embryogenesis

Question 6:

The probability of fruit set in a self-pollinated bisexual flower of a plant is far greater than a dioecious plant. Explain.

Answer:

A bisexual flower has both male and female flowers in the same plant so, the transfer of the pollen to stigma is easier as compared to dioecious plant which are unisexual and requires an agent for the transfer of pollens like birds, insects, wind or water so, and the probability of fruit set formation decreases as external help is required.

Question 7:

Is the presence of large number of chromosomes in an organism a hindrance to sexual reproduction? Justify your answer by giving suitable reasons.

Answer:

The basis of sexual reproduction is the generation of haploid gamete only so, the presence of a greater number of gametes do not affect the reproduction. For example: Fern plant has 1260 chromosomes but still it reproduces sexually.

Question 8:

Is there a relationship between the size of an organism and its life span? Give two examples in support of your answer.

Answer:

There is no relationship between the size of an organism and its life span this can be justified by giving two examples:

1. The size of birds like crow and parrot is similar but the life span of crow is 15 years and the life span of parrot is 140 years this shows there is no such relation between the size and age.

2. Both Mango and Banyan tree have same size, but their life spans are different.

Question 9:

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.

Chapter-1- Question - 9- Image of The Plant Bears Two Differ …

The Plant Bears Two Different Types of Flowers

Answer:

‘A’ shows Chasmogamous flowers with exposed anthers and stigma and cross pollination will happen in them. ‘B’ shows flowers which do not open at all. These are bisexual flowers and self-pollination will happen in them. On the other hand, agents of pollination can easily work in flower ‘A’ as its anthers and stigma are exposed.

Question 10:

Give reasons as to why cell division cannot be a type of reproduction in multicellular organisms.

Answer:

Cell division takes place in unicellular organisms because each of the parent body forms a daughter cell, but in multicellular organisms no such differentiation occurs. Cell division would be an impractical method.

Question 11:

In the figure given below, mark the ovule and pericarp.

Mark the ovule and pericarp.

Mark the Ovule and Pericarp

Answer:

Mark the ovule and pericarp.

Mark the Ovule and Pericarp

1. After fertilization takes place, the zygote develops to form an embryo. The ovule develops into seeds.

2. The pericarp develops from the wall of the ovary. It protects the seed.

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