Class 6 Science Notes Chapter 7 (Getting to Know Plants) – Science Book
Detailed Notes with MCQs of Chapter 7, 'Getting to Know Plants'. This is a fundamental chapter, and understanding plants is crucial not just for biology but also forms a base for many questions in competitive exams. Pay close attention to the details.
Chapter 7: Getting to Know Plants - Detailed Notes for Exam Preparation
1. Introduction to Plants:
- Plants are living organisms, essential for life on Earth. They produce oxygen and are the primary source of food for most living beings.
- They exhibit great diversity in shape, size, and habitat.
2. Classification Based on Size and Stem:
Plants are broadly categorized based on their height, stem nature, and branching pattern:
-
Herbs:
- Short plants with green, tender (soft) stems.
- Usually have few or no branches.
- Examples: Tomato, Wheat, Paddy (Rice), Grass, Coriander, Mint.
-
Shrubs:
- Medium-sized plants.
- Stem is hard but not very thick.
- Branches arise from the base of the stem, giving a bushy appearance.
- Examples: Lemon, Rose, Jasmine, China rose (Hibiscus), Tulsi.
-
Trees:
- Very tall and large plants.
- Have a hard, thick, brown main stem called the trunk.
- Branches arise from the upper part of the stem, much above the ground.
- Examples: Mango, Neem, Banyan, Peepal, Coconut.
-
Creepers: Plants with weak stems that cannot stand upright and spread on the ground. Examples: Pumpkin, Watermelon, Sweet Potato.
-
Climbers: Plants with weak stems that take support from neighbouring structures (like walls, trees, sticks) to climb up. Examples: Pea plant, Grapevine, Money plant, Bean plant.
3. Parts of a Plant:
A typical plant consists of two main systems:
- Root System: Usually the underground part (Roots).
- Shoot System: The part above the ground (Stem, Branches, Leaves, Flowers, Fruits).
4. The Stem:
- Structure: The main axis of the shoot system, bears leaves, branches, buds, flowers, and fruits. Can be soft (herbs) or woody (shrubs, trees).
- Functions:
- Support: Holds the plant upright and supports branches, leaves, etc.
- Conduction:
- Conducts water and minerals absorbed by the roots upwards to the leaves and other parts (through xylem tissue - extra info, may not be in Class 6 text but useful).
- Conducts food prepared by the leaves downwards/upwards to other parts including roots (through phloem tissue - extra info).
- Food Storage: Some stems store food (e.g., Potato, Ginger - these are modified stems).
5. The Leaf:
- Structure: Usually a flat, green structure attached to the stem or branch.
- Petiole: The stalk by which a leaf is attached to the stem.
- Lamina (Leaf Blade): The broad, green, flat part of the leaf.
- Veins: Lines on the lamina. They provide support and transport water, minerals, and food.
- Midrib: The prominent vein running through the middle of the lamina.
- Veinlets: Smaller veins branching out from the midrib and other veins.
- Leaf Venation: The pattern or arrangement of veins on the lamina.
- Reticulate Venation: Veins form a net-like pattern on both sides of the midrib. (Common in dicot plants). Examples: Mango, Rose, Peepal, Neem.
- Parallel Venation: Veins run parallel to each other from the base to the tip of the lamina, or parallel to the midrib. (Common in monocot plants). Examples: Grass, Wheat, Maize, Banana, Bamboo.
- Functions:
- Photosynthesis: The process by which green leaves prepare food for the plant using carbon dioxide (from air), water (from soil), sunlight, and chlorophyll (the green pigment).
- Equation Simplified: Carbon Dioxide + Water ---(Sunlight + Chlorophyll)---> Food (Glucose/Starch) + Oxygen
- Food is stored primarily as starch.
- Oxygen is released as a byproduct, essential for respiration in animals.
- Stomata: Tiny pores, usually on the underside of leaves, through which exchange of gases (CO2 in, O2 out) occurs.
- Transpiration: The process by which plants release excess water in the form of water vapour through stomata.
- Helps in cooling the plant.
- Creates a 'suction pull' which helps in the absorption and upward movement of water from the roots.
- Photosynthesis: The process by which green leaves prepare food for the plant using carbon dioxide (from air), water (from soil), sunlight, and chlorophyll (the green pigment).
6. The Root:
- Structure: The non-green, underground part of the plant (usually).
- Functions:
- Anchorage: Holds the plant firmly in the soil.
- Absorption: Absorbs water and dissolved mineral nutrients from the soil.
- Prevention of Soil Erosion: Roots bind the soil particles together.
- Food Storage: Some roots store food (e.g., Carrot, Radish, Turnip, Sweet Potato - Note: Sweet Potato is a modified root, Potato is a modified stem).
- Types of Root Systems:
- Taproot System: Consists of a main, thick primary root (the taproot) growing vertically downwards, from which smaller lateral roots arise. Found in plants with reticulate venation. Examples: Carrot, Radish, Mango, Neem, Rose, Pea.
- Fibrous Root System: Consists of a cluster of thin, fibre-like roots arising from the base of the stem. There is no main root. Found in plants with parallel venation. Examples: Grass, Wheat, Maize, Rice, Onion.
Relationship between Leaf Venation and Root Type:
- Plants with Reticulate Venation in leaves usually have a Taproot System.
- Plants with Parallel Venation in leaves usually have a Fibrous Root System. (This is a very important correlation for exams).
7. The Flower:
-
Function: The reproductive part of the plant. Develops into fruit and seeds.
-
Structure: Usually colourful and attractive to insects/birds for pollination. Attached to the stem by a stalk called a pedicel.
-
Main Parts (Whorls):
- Sepals (Calyx): The outermost whorl, usually green, leaf-like structures. Protect the flower in the bud stage.
- Petals (Corolla): Usually brightly coloured, leaf-like structures inside the sepals. Attract insects/pollinators.
- Stamens (Androecium): The male reproductive part, located inside the petals. Each stamen consists of:
- Anther: Swollen tip that produces pollen grains (containing male gametes).
- Filament: Stalk that supports the anther.
- Pistil or Carpel (Gynoecium): The female reproductive part, located in the centre of the flower. Consists of:
- Stigma: Sticky tip that receives pollen grains.
- Style: Tube-like structure connecting the stigma to the ovary.
- Ovary: Swollen base containing ovules. Ovules contain the female gamete (egg cell).
-
Post-Fertilization: After pollination and fertilization, the ovary develops into the fruit, and the ovules develop into seeds.
8. Fruit and Seed:
- Fruit: Develops from the ovary, protects the seed(s). Can be fleshy (mango) or dry (pea pod).
- Seed: Develops from the ovule, contains the embryo (baby plant) and stored food. Can germinate under suitable conditions (water, air, warmth) to grow into a new plant.
Multiple Choice Questions (MCQs)
-
Which of the following is an example of a shrub?
(a) Tomato
(b) Mango
(c) Lemon
(d) Grass -
The part of the leaf that attaches it to the stem is called:
(a) Lamina
(b) Midrib
(c) Petiole
(d) Veinlet -
Plants release excess water into the atmosphere through the process of:
(a) Photosynthesis
(b) Respiration
(c) Absorption
(d) Transpiration -
Which type of root system is typically found in plants with parallel venation in their leaves?
(a) Taproot system
(b) Fibrous root system
(c) Prop root system
(d) Stilt root system -
The primary function of the flower is:
(a) Food storage
(b) Absorption of water
(c) Reproduction
(d) Support -
Which part of the flower develops into the fruit after fertilization?
(a) Petal
(b) Sepal
(c) Ovary
(d) Stamen -
Photosynthesis requires carbon dioxide, water, chlorophyll, and:
(a) Oxygen
(b) Nitrogen
(c) Sunlight
(d) Soil -
Potato is a modified:
(a) Root
(b) Stem
(c) Leaf
(d) Flower -
The male reproductive part of a flower is the:
(a) Pistil
(b) Sepal
(c) Petal
(d) Stamen -
Which of these has a taproot system?
(a) Wheat
(b) Maize
(c) Grass
(d) Pea plant
Answer Key for MCQs:
- (c) Lemon
- (c) Petiole
- (d) Transpiration
- (b) Fibrous root system
- (c) Reproduction
- (c) Ovary
- (c) Sunlight
- (b) Stem
- (d) Stamen
- (d) Pea plant
Make sure you revise these notes thoroughly. Understanding the structure and function of each plant part, along with the key processes like photosynthesis and transpiration, is essential. Good luck with your preparation!