JK Academy Std 7 Science Chapter 2 Plants: Structure and Function answers
Exercise
1. Give examples of 3 plants that have :
(a) spiny fruits: jackfruit, pineapple, litchi
(b) spiny stem: rose, cactus, citrus
(c) red flowers: hibiscus, rose, tulip
(d) yellow flowers: daffodils, sunflower, rose
(e) leaves which close at night: mimosa, acacia, prayer plant
(f) single-seeded fruits: mango, litchi, avocado
(g) many-seeded fruits: watermelon, papaya, custard apple
2. Observe any one flower and its various parts and describe it in your own words.
Flowers may have a long or a short stalk called pedicel. One end of the pedicel is attached to the stem. The other end of the pedicel is expanded and swollen. It is called the receptacle. Petals and other parts of the flower are supported on the receptacle. Calyx, corolla, androecium, gynoecium are different parts of a flower.
Calyx : In the bud condition the petals are covered by leaf-like parts called sepals which are green in colour. They form the calyx.
Corolla : This is made up of colourful parts called petals. Observe the shape, colour and smell of the corolla of various flowers like the rose, chrysanthemum, hibiscus, mogara, kanher, tagar, etc.
Androecium : This is the male reproductive part of the flower. It consists of stamens. Each stamen is made up of anther and filament. Gynoecium : This is the female reproductive part of the flower. This is made up of carpels. A carpel consists of stigma, style and ovary.
3. What are the similarities and differences between?
(a) jowar and moong
Similarities: Both jowar and moong are annual plants
| Jowar | Moong |
| The jowar seed is monocotyledonous. | The moong seed is dicotyledenous. |
| The plant has fibrous root system. | The plant has tap root system. |
| The leaves show parallel venation. | The leaves show reticulate venation. |
(b) onion and coriander
Similarities: Both onion and coriander are annual plants
| Onion | Coriander |
| The onion plant has fibrous root system. | The coriander plant has tap root system. |
| The edible part of the plant is the bulb that grows under the ground and its leaves. | The edible part of the plant is the stem and leaves. |
| The leaves show parallel venation. | The leaves show reticulate venation. |
(c) leaves of banana and mango
Similarities: The leaves of both banana and mango are green in colour and are used in religious customs.
| Leaves of banana | Leaves of mango |
| They are broad and big | They are narrow and small. |
| The leaves show parallel venation. | The leaves show reticulate venation. |
(d) coconut tree and jowar stalk plant
Similarities: They have fibrous root system
| Coconut tree | Jowar stalk plant |
| The tree grows to a height of 25 meters. | The plant grows to a height of 1.5 to 2 meters. |
| The leaves have spiral arrangement. | The leaves grow opposite to each other. |
4. Explain the following images in your own words.
Image A: It is a monocotyledonous seed. Its plant has fibrous root system and its leaves have parallel venation.
Image B: It is dicotyledonous seed. Its plant has tap root system and the leaves have reticulate venation.
5. Describe the functions of various parts of a plant.
Calyx : It protects the petals and the inner parts of the flower in bud condition.
Corolla : It attracts insects with its smell and colourful petals. The insects help in pollination.
Androecium : This is the male reproductive part of the flower. It consists of stamens. Each stamen is made up of anther and filament.
The filaments contains the pollen sacs that have pollen grains.
Gynoecium : This is the female reproductive part of the flower. This is made up of carpels. A carpel consists of stigma, style and ovary.
After fertilization the ovules turn into seeds and the ovary turns into the fruit.
6. Certain properties are mentioned below. Find a leaf corresponding to each property and describe those plants.
leaves with smooth surface: Dogwood family. Cornus florida
The shiny simple smooth-edged leaves are 2.5-5″ long. Flowering dogwoods bloom before being shaded by taller trees. Their blossoms seem to float through the woods in April, before trees have begun to leaf out.
leaves with rough surface: The simple definition for rough leaf texture is anything with an irregular surface – this means the presence of fine hairs, scales, thorns, lumps or any other protuberance. Example: The leaves of the polar bear willow (Salix salicola), is covered with many tiny hairs, resulting in a uniformly fuzzy surface
fleshy leaf: Plants with parts that are thickened, fleshy, and engorged, usually to retain water in arid climates or soil conditions are called succulent plants or succulents.
Example Aloe Vera
spines on leaf: Some plants have spines on their leaves to protect themselves from being eaten up by insects.
Example: Aloe Vera and Pineapple
7. Find the plant parts.
Extra Textual Questions
Use your brain power!
(1) What would have happened if plants like tamarind, banyan and mango had fibrous roots?
Ans. The roots perform two main functions,
(i) to absorb the water and nutrients from the soil and supply it to the plant and
(2) to act as an anchor and give support to the plant.
Plants like tamrind, banyan and mango are big and sturdy trees. If they had fibrous roots, then they would not get enough supply of water and nutrients and the trees would not be able to stand erect and would topple down and eventually die.
(2) What will happen if the root-tip is injured?
The root tip goes deep into the soil; it is very delicate and is supported by a root tip. If it is injured then it will not grow and will not have secondary roots. The plant will not get enough water and nutrients and so will soon wither away and die.
(3) Which types of roots do the fenugreek, spinach and onion plants have?
Fenugreek, spinach and onions have fibrous root.
(4) What could be the use of these prop roots?
The prop roots grow from the branches of huge trees like banyan and go deep into the soil to provide extra support to the branches and the tree.
(5) Why are the underground parts of plants like radish, carrot, beet and sweet potato thick, fleshy and swollen? Which part of the plant are they?
Ans. The underground parts of plants like radish, carrot, beet and sweet potato are thick, fleshy and swollen because they store food in them. The form the roots of the plant.
Do you see stipules in all plants?
No, we do not see stipules in all the plants. They are absent in monocotyledonous plants.