Thursday, December 29, 2011

CBSE VII REPRODUCTION IN PLANTS (Science Solved Questions) CORE ASSIGNMENT

REPRODUCTION IN PLANTS CLASS7th CORE ASSIGNMENT
Q1. Describe the different methods of asexual reproduction . Give examples.
A.There are different methods by which plants reproduce asexually. They are vegetative propagation, budding,fragmentation and spore formation. The vegetative parts of a plant are the roots, stems and leaves. When new plants are produced from these parts, the process is called vegetative propagation.
1. Budding- A bulb like projection grows on the parent organism. It grows and may eventually break away from the parent. E.g. yeast, hydra, corals, sponges.
2. Fragmentation- The organism breaks up into two or more fragments after maturation. These fragments grow into new individuals. E.g. spirogyra, hydra
3. Spore formation- A spore is a tiny, spherical and unicellular body protected by a thick wall. Under favourable conditions, a spore germinates and develops into a new individual. E.g. mosses, ferns, moulds
Q2. Describe the various ways by which seeds are dispersed.
A. Seeds and fruits are dispersed by agents like wind, water, animals and humans.
The pods present in these seeds dry up in the sun. This causes the pod to split with great force, thereby dispersing the seeds away from the parent plant.
Some seeds are dispersed by a special method called explosion. Examples are mustard, ladies finger, peas, bean, pod and castor.
Q3. How is fertilization brought about in a flower?
A. The zygote is formed by the fusion of the male and female gametes. This process is called fertilisation. After fertilisation, the ovary changes into a fruit. It may be either fleshy or dry.
Q4. Write 4 advantages of vegetative propagation.
A.The advantages are- 1. New plants can be produced quickly.
2. The plants so produced are exact copies of parent plants
3. Seedless plants can be easily propagated.
Q5. Differentiate between:-
1. unisexual flowers and bisexual flowers-
Bisexual flowers contain both – the stamens and the pistil. For example, mustard and rose.
Unisexual flowers have either the stamens or the pistil. For example, cucumber, maize and watermelon
2. sexual and asexual reproduction
In sexual reproduction, the male and the female gametes fuse to form seeds that eventually develop into new plants.
The seeds are formed inside the fruit. On the other hand, in asexual reproduction, a new plant is grown from any part of a plant other than the seeds.
3. cross pollination and self pollination
The transfer of pollen grains from the anther of one flower, to the stigma of another flower on another plant of  the same type, is known as cross-pollination.
The transfer of pollen grains from the anther to the stigma of the same flower or to the stigma of another flower on the same plant, it is termed self-pollination.
Q6. Why are flowers known as reproductive parts of a plant?
A.flowers are known as reproductive parts of a plant as flowers contain both male and female reproductive structures as  stamen and pistil respectively.
Q7. What is the significance of dispersal of seeds and fruits?
A. A plant produces a large number of seeds. They are required to be dispersed properly to get enough space, water and minerals and sunlight to grow healthy.
Q8. Why do spores can survive for a long time?
A. Spores are protected within a thick wall that makes it withstand unfavourable and extreme climate.
Q9. Which take less time to grow and bear flowers and fruits, plants produced by vegetative propagation or from seeds? Why?
Ans: A plant produced by vegetative propagation takes less time to develop and bear fruits and flowers. Plants grown from seeds require more attention and take good time to germinate and grow.
Q10. Write a short note on pollination.
A. It is the transfer of pollen grains from an anther to the stigma. Insects, birds and other animals help in cross pollination of flowers. Insects are attracted by the colour and scent of petals. Winds can also blow pollen grains. Such flowers such plants have flowers with small petals or with no petals at all.
Q11. Describe the process of seed formation.
A. After fertilization, petals, sepals and stamen wither away and fall off. Style and stigma also fall off. The ovule walls develop hard layers and seed develop. Each seed contains embryo enclosed in a protective seed coat.
Q12. Explain the process of fruit formation.
A. The ovary begins to swell. In time it becomes a fruit. So, a fruit is actually a developed ovary. Some fruits, like mangoes and apples are sweet and juicy. Sometimes, they become hard and woody forming the shells of nuts.
Q13. What are characteristics of seeds dispersed by water.
A. Seeds develop floating ability in the form of spongy or fibrous outer coat. E.g. coconut seeds have a thick coat of fiber that enables it to float in water. Lotus fruit has a spongy part that enables it to float.
Q 14.Define reproduction.
Ans:Reproduction is life process of producing new individuals from their parents of its own kinds. Q.15. What do you understand by the term 'leaf venetion'? What are the two types of leaf venetion?
Ans: The arrangement of veins in a leaf is called the leaf venation.
Reticulate Venation :In this the veins form a network like structure
Parallel venation : In this the veinsrun paralell to each other

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