Short answer questions.
Define fertilization in the case of plants.
Answer: Fertilization in plants is defined as the process of fusion of the male gamete produced in the pollen tube and the female gametes or eggs present in the ovule to form zygote.
When a seed has two cotyledons, why are they thick and fleshy?
Answer: when a seed has two cotyledons, they are thick and fleshy because it is the sole part of seed to store food.
What do you understand by the germination of a seed?
Answer: Seeds alone cannot transform into a plant. It needs proper conditions (oxygen, water, light etc)for its growth to form plants. The whole process of development of a seed into a baby plant is called germination.
Why do all seeds not grow into new plants?
Answer: all seeds do not grow into new plants as some are eaten by the animals, some get destroyed by rain or wind, while some do not get proper warmth, air or water for proper growth.
Define seed dispersal. Mention different ways in which seed dispersal takes place.
Answer: The process by which the seeds are moved away from the parent plant is called seed dispersal.
Different ways in which seed dispersal takes place are:
- By wind: Dandelion seeds, Maple seeds
- By water: Coconut, Lotus.
- By animals: papaya, mango
- By explosion: pea plant, mustard
What are the conditions necessary for germination?
Answer: Conditions necessary for germination of seeds are enough water, air, sunlight, and good quality soil .
Why is dispersal of seeds necessary?
Answer: Dispersal of seeds is necessary to avoid the overcrowding and competition between existing plants for various essential components. This will ensure proper growth and survival of the parent plant as well as the new plant.
Name three agents of dispersal. In each case, give an example of a plant whose seeds are
dispersed by the agent.
Answer: The three agents of dispersal are:
- Wind: wind scatter the light weight seeds of cotton plants and Dandelion
- Water: seeds of the plant that grow in or near water bodies like lotus, coconut are dispersed through the water.
- Animal: seeds of fruits like papaya, mango,apple are scattered by animals.
Some seeds have hooks and spines on them. Why?
Answer: Some seeds have hooks and spines on them because it helps them to be dispersed to long distances by attaching themselves to the furs or coats of animals .
Why are crops important to us?
Answer: crops are important to us because they provide us with food and various other useful things like fiber, oils etc.
Long answer questions.
How does formation of fruits and seeds take place after fertilization?
Answer: After fertilization the zygote develops into an embryo, the ovule changes into a seed. The ovary surrounding the ovule turns into a fruit that contains one or more seeds. The rest of the parts of the flower dry up and then fall away. Under favorable conditions the seeds grow and develop into new plants.
Describe the structure of a bean seed.
Answer: The bean seed has following parts:
- Seed Coat: thick outer covering which protects seeds from any damage. It also prevents the seed from drying out. It has a tiny opening through which water can enter the seed.
- Cotyledons : inside the seed coat it has seed leaves that cover and store food for the baby plant. These are cotyledons.
- Embryo : A tiny baby plant inside the seed is called the embryo. It has two parts: radicle and plumule.
What is the need for seed dispersal?
Answer: Dispersal of seeds is important because:
- to avoid the overcrowding of plants in a particular area.
- To avoid competition between existing plants for various essential components.
- It ensures proper growth and survival of the parent plant as well as the new plant.
- Seeds will get fairly equal chances for survival.
Explain with examples, how dispersal of seeds by wind takes place.
Answer: Seeds which are of light weight and have wing-like structures are scattered by wind. These seeds are carried away easily to farther places by wind. Such seeds float on air and when landed on ground grow into a new plant under favorable conditions.
Examples: a) Maple seeds have wing-like structures which are easily carried away by the wind.
b) Dandelion flowers have hair-like seeds that are dispersed by wind easily.
What is a seed coat? What is the role of the tiny hole that is present on the
seed coat?
Answer: Seed coat is the thick outer covering which protects seeds from any damage and prevents the seed from drying out.
the tiny hole that is present on the seed coat is called as microphyle. It allows water, oxygen, minerals to enter the seed.
Which part of the rose plant can be used to grow new plants?
Answer: The stem of the rose plant can be used to grow new plants. Planting a cutting of a stem of a rose plant in soil will reproduce new plants.
List three ways by which plants reproduce.
Answer: Plants can reproduce through:
- Stems: Stem of plants like potato, onion, ginger can grow into new plants.
- Roots: Roots of some plants like sweet potato ,turnip develop adventitious buds on them. These buds under favorable conditions and become a new plant.
- Seeds: When seeds fall on the soil and given favorable conditions they grow into new plants.
