Following are Botany Model questions for Intermediate students. Model questions are provided in the categories of very short answers, short answers and long answer type questions.
VERY SHORT ANSWER TYPE QUESTIONS
1. What is meant by heterospory? Mention the two types of spores developed in an angiospermic plant.
Production of two types of spores by a plant is called heterospory.
Microspores, megaspores.
2. How do liver worts reproduce vegetatively?
By production of Gemmae.
3. Why do we refer to an offspring formed by asexual method of reproduction as clones?
The offsprings produced during asexual reproduction are identical to one another and also exact copies of their parent. Hence they are called as clones.
4. Rearrange the following events of sexual reproduction in the sequence in which they occur in a flowering plant:
Embryogenesis, fertilization, gametogenesis, pollination.
Gametogenesis Pollination Fertilization Embryogenesis.
5. Is there a relationship between the size of an organism and its life span?
No.
6. Which of the following are monoecious and dioecious organisms:
a. date palm b. coconut c. Chara d. Marchantia
Date palm – dioecious
Coconut – monoecious
Chara – monoecious
Marchantia – dioecious
7. What do the following parts of a flower develop into after fertilization?
a. ovary b. stamens c. ovules d. calyx
Ovary – fruit
Stamens – fall off
Ovules – seeds
Calyx – falls off ( In plants like Solanum it is persistant after fertilization)
8. Define vivipary with an example.
Vivipary is the germination of the seeds while still attached to the mother plant. Ex: Rhizophora (mangrove).
SHORT ANSWER TYPE QUESTIONS
1) In haploid organisms that undergo sexual reproduction, name the stage in the lifecycle where meiosis occurs. Give reasons for your answer.
In haploid organisms meiosis occurs in the zygote.
This kind of meiosis is known as zygotic meiosis.
As the organism is in haploid phase throughout the life cycle except the zygote the life cycle is called haplontic life cycle.
In these haploid plants zygote is the only diploid phase and hence meiosis is compulsory to produce haploid spores or thallus in these organisms.
As zygote is the connecting link between two generations haploid organisms which reproduce sexually begin life with this single celled zygote.
2) The number of taxa exhibiting asexual reproduction is drastically reduced in higher plants (angiosperms) when compared to the lower groups of plants. Analyze the possible reasons for this situation.
Higher plants exhibit a low frequency of asexual reproduction compared to lower plants because:
Single celled structure or relatively simple organization is necessary for asexual reproduction. But higher plants are complex in their organization.
Asexual reproduction gives rise to offsprings which are identical to one another and also exact copies of their parents. Hence there is no genetic variation or recombination to produce better characters. Hence higher plants limit asexual reproduction to few species.
Due to asexual or vegetative reproduction the clones produced cannot withstand extremities in environmental conditions.
As higher plants show advancement in sexuality being bisexual, unisexual, monoecious and dioecious conditions there is a better chance of sexual reproduction than in lower plants. Hence there is no need for many of them to exhibit asexual reproduction.
3) “Fertilization is not an obligatory event for fruit production in certain plants.” Explain the statement.
In certain plants fertilization is not compulsory for fruit production because:
Fertilization is a chance process which follows pollination.
If in case pollination fails and the ovary does not receive male gametes fertilization does not occur and fruit formation is affected.
Hence some plants have an alternative mechanism where unfertilized female gamete develops into an embryo directly and the fruit is produced by the ovary without fertilization.
This development of an embryo from an unfertilized female gamete is called parthenogenesis and development of fruit from unfertilized ovary is called parthenocarpy.
Generally parthenocarpic fruits are seed less and hence preferred for food industries.
4) Justify the statement “Vegetative reproduction is also a type of asexual reproduction”.
Vegetative reproduction is a kind of reproduction in which multicellular structures become detached from the parent plant and develop into new individuals that are genetically identical to the parent plant.
In asexual reproduction also the offsprings are genetically identical to the parent.
Like asexual reproduction vegetative reproduction also does not involve formation of gametes and fertilization.
LONG ANSWER TYPE QUESTIONS:
1. Describe the post-fertilization changes in a flower.
The changes that occur after fertilization in a flower are called post-fertilization changes.
These changes include formation of zygote, embryogenesis, seed and fruit formation.
In a flower zygote is formed after fertilization of a male gamete with the egg cell or female gamete inside the embryo sac of the ovule.
Zygote is the connecting link between organisms of two different generations.
The zygote undergoes mitotic cell division and cell differentiation to form an embryo.
The process of development of an embryo from the zygote is referred as Embryogenesis.
During this process sepals, petals and stamens of the flower wither and fall off.
Pistil may remain with the plant.
As the zygote develops into embryo, the ovule develops into a seed.
The ovary develops into a fruit. The fruit develops a thick fruit wall called pericarp which is protective in function.
After the seeds and fruit mature the whole fruit or the seeds are dispersed and the seeds germinate under favourable conditions to produce new plants.
Post fertilization changes in a flower may be summed up as:
zygote embryo
PEN (Primary endosperm Nucleus) endosperm
synergids and antipodals degenerate
ovules seeds
integuments seed coat (testa and tegmen)
nucellus used up or sometimes persists as perisperm
ovary fruit
petals, sepals, stamens fall off (sometimes calyx are persistant)