Notes
Diversity in Plants and Animals Around Us :
- Biodiversity refers to the wide variety of plants and animals found in a particular region.
- This diversity is shaped by similarities and differences among organisms and by varying environmental conditions.
- Each organism plays a distinct role in its ecosystem, demonstrating interdependence, such as trees providing food and shelter or animals aiding in seed dispersal.
How to Group Plants and Animals?
To study the huge variety of living organisms, scientists classify them into groups based on their similarities and differences. This classification makes it easier to understand and compare different living beings.
How to group plants? :
Grouping Plants :
Plants are classified by observing differences in their visible features, such as:
- Stem (thin or thick)
- Leaves (shape and size)
- Flowers (color and number of petals)
- Roots (tap root or fibrous root)
- Seeds (with or without cotyledons)
These characteristics help us identify and group plants easily.
Detailed Classification of Plants :
Plants can be classified into different groups by observing their physical features such as the type of stem, leaves, roots, and seeds. One of the most common ways of classification is based on stem type.
(i) Classification by Stem Type :
The stem is the above-ground part of a plant that supports branches, leaves, flowers, buds, and fruits. Based on the height, strength, and nature of the stem, plants are grouped into three major categories, along with two special types.
Main Categories of Plants Based on Stem :
| Category | Stem Characteristics | Branching Pattern | Examples |
| Herbs | Small plants with green, soft, and tender stems | Usually do not have many branches | Mint, tomato, wheat, grass |
| Shrubs | Larger than herbs; stems are hard but not very thick | Branches arise from the base of the stem | Rose, tulsi, hibiscus, lemon |
| Trees | Very tall plants with hard, thick, woody stems | Branches are found on the upper part of the stem | Neem, mango, peepal, oak, banyan |
Special Types of Plants :
Creepers :
- Have thin, long, and weak stems.
- Cannot stand upright; spread along the ground.
- Examples: Strawberry, pumpkin, watermelon
Climbers :
- Have soft, green, weak stems similar to creepers.
- Climb upwards by taking support from nearby objects.
- Some climbers have tendrils to help them grip support.
- Examples: Bitter gourd, grapevines, bean stalk
(ii) Classification by Leaf Anatomy and Venation :
- A leaf is a flat, thin, green part of the plant that plays an important role in making food through photosynthesis.
- If a leaf does not have a petiole (leaf stalk) and is attached directly to the stem, it is called a sessile leaf.
Parts of a Leaf :
(1) Petiole (Leaf Stalk) :
- A thin stalk that attaches the leaf to the stem.
- Helps hold the leaf in a position to receive sunlight.
(2) Lamina (Leaf Blade) :
- The broad, flat, green part of the leaf.
- The main surface where photosynthesis takes place.
(3) Veins :
- A network of thin lines spread throughout the lamina.
- Help in the transport of water, minerals, and food.
(4) Midrib :
- The thick, central, prominent vein running through the middle of the leaf.
- Provides support to the leaf and branches into smaller veins.
Types of Venation (Pattern of Veins) :
- Reticulate Venation :
- Veins form a net-like pattern on both sides of the midrib.
- Common in most dicot plants.
- Examples: Hibiscus, neem, periwinkle (sadabahar), tulsi, mustard, sunflower, orange, guava, rose, pea, mango.
- Parallel Venation :
- Veins run parallel to each other along the length of the leaf.
- Common in monocot plants.
- Examples: Wheat, maize, onion, garlic, banana, lily, grass.
(iii) Classification by Root System :
- The root is the underground, non-green part of the plant that remains below the soil.
- It helps in anchoring the plant, absorbing water and minerals, and sometimes storing food.
Based on their structure, roots are classified into two main types.
Types of Root Systems :
Plants mainly have two types of root systems: Tap Root System and Fibrous Root System.
(i) Tap Root System :
- Some plants have one thick main root called the tap root.
- From this main root, many smaller roots called lateral roots arise.
- The tap root grows vertically downward into the soil, while the lateral roots spread in different directions.
- Generally, plants with tap roots also show reticulate venation in their leaves.
- Examples: Chickpea, radish, carrot, neem, hibiscus, mango, tulsi, mustard, balsam.
(ii) Fibrous Root System :
- In some plants, there is no single main root.
- All roots are thin, hair-like, and similar in size, arising from the base of the stem, giving a bushy appearance. This is called a fibrous root system.
- Generally, plants with fibrous roots have parallel venation in their leaves.
- Examples: Onion, lily, lemongrass, wheat, maize, grass, millet.
Classification by Seed Structure :
One important way to classify flowering plants is by the number of cotyledons (seed leaves) present in their seeds. Cotyledons provide nourishment to the young developing plant.
Parts of a Seed :
Seed Coat :
- The outermost protective covering of the seed.
- Shields the inner parts from injury, drying, and infection.
- Cotyledons (Seed Leaves) :
- Located just inside the seed coat.
- Store food for the developing embryo.
- The number of cotyledons is used to classify plants.
Embryo :
- The young plant inside the seed.
- Develops into the root, stem, and leaves of the new plant.
Types of Plants Based on Cotyledons :
Dicotyledons (Dicots) :
- Seeds contain two cotyledons.
- Usually show features like tap root and reticulate venation (not always needed, but common).
- Examples: Chickpea, pea, black bean, bean, mustard, neem, hibiscus.
Monocotyledons (Monocots) :
- Seeds contain one cotyledon.
- Often show fibrous roots and parallel venation.
- Examples: Wheat, maize, rice, onion, lily, lemongrass, grass, millet.
How to group animals?
Animals can also be grouped based on a variety of features, including their habitat, diet, and physical characteristics.
Grouping Animals :
Animals are grouped based on:
- Habitat (place where they live – land, water, air)
- Food habits (herbivores, carnivores, omnivores)
- Movement (walking, flying, swimming)
- Body parts used for movement (legs, wings, fins)
For example, pigeons, bats, and butterflies can be grouped together because all of them can fly, even though they look different.
A primary method discussed is classification by movement.
- Modes of Movement: Animals exhibit diverse movements, including flying, running, crawling, walking, hopping, and swimming.
- Body Parts for Movement: Different body parts are used for locomotion, such as wings, legs, and fins.
| Animal | Type of Movement | Body Parts Used |
| Ant | (Walks) | Legs |
| Goat | Walks and jumps | Legs |
| Pigeon | Walks and flies | Legs and wings |
| Housefly | Walks and flies | Legs and wings |
| Fish | (Swims) | Fins |
Plants and Animals in Different Surroundings
Habitats and Adaptations :
An organism's survival is intrinsically linked to its environment, or habitat.
- Habitat: The place where an organism lives and grows, which provides food, water, shelter, and favorable climatic conditions.
- Adaptation: The special features that plants and animals develop to survive and thrive in their particular habitat.
Types of Habitats:
- Terrestrial Habitats: Habitats on land. Examples include forests, grasslands, deserts, and mountain regions.
- Aquatic Habitats: Habitats in water. Examples include ponds, lakes, rivers, and oceans.
- Amphibians: Animals, such as frogs, that can live both in water and on land.
Case Studies in Adaptation :
Organisms exhibit a wide range of adaptations tailored to their specific environmental challenges.
- Cactus (Desert Habitat):
- Found in the hot, dry deserts of Rajasthan.
- Possesses thick and fleshy stems to store water, which is limited in its environment. Globally, there are around 1,750 different species of cacti found in both arid and semi-arid habitats.
- Deodar Trees (Mountain Habitat):
- Found in the Himalayas of Himachal Pradesh, where temperatures are extremely low and snowfall is frequent.
- They are conical in shape with flexible and sloping branches, which allows snow to slide off easily, preventing damage.
- Rhododendrons (Varying Mountain Habitats):
- This plant shows different adaptations in different regions.
- In the Shola Forest of Nilgiris, they are shorter in height and have smaller leaves to withstand heavy winds.
- In the mountains of Sikkim, they are taller. This variation demonstrates adaptation to localized environmental conditions like water availability, light intensity, and climate.
- Fish (Aquatic Habitat):
- They have a streamlined shape to help them move inside water.
- Their bodies are covered with slippery scales, which protect the fish and aid in easy movement.
- They possess flat fins and tails to help change directions and maintain balance.
- Camels (Desert Habitats):
Camels exhibit different adaptations depending on whether they live in a hot or cold desert.
| Feature | Camel in Hot Desert (e.g., Rajasthan) | Camel in Cold Desert (e.g., Ladakh) |
| Body Size | Taller with long legs. | Shorter height and legs to walk easily in mountainous regions. |
| Hooves | Wide hooves to walk on sand without sinking. | Strong hooves to help grip on mountainous terrain. |
| Hump(s) | A single large hump to store fat for energy during food scarcity. | Two humps, which shrink in late winter due to food scarcity. |
| Fur/Hair | Less fur. | Grow long hair from head to neck to protect from the cold. |
| Other Adaptations | Excretes a small amount of urine and has dry dung to conserve water. Does not sweat. Can live for many days without water. | - |
Biodiversity Conservation :
The preservation of biodiversity is crucial, as ecosystems are under threat from human activities.
(1) Threats to Biodiversity :
- The primary threat identified is the damage and loss of natural habitats caused by human activities.
- When a habitat is destroyed, plants and animals lose their homes, food sources, and other essential resources, leading to a decline in their populations and an overall loss of biodiversity.
(2) Impacted Species in India :
The several species whose populations have declined in India due to habitat loss:
- Bengal Tiger
- Cheetah
- Great Indian Bustard
(3) Conservation Initiatives :
A multi-pronged approach involving government, communities, and scientists is necessary for conservation.
Government Projects:
- Project Tiger (1973): Initiated to protect the declining Bengal Tiger population.
- Cheetah Reintroduction Project (2022): Aimed at restoring the cheetah population.
- Protected Areas: Habitats of the Great Indian Bustard in Gujarat, Rajasthan, and Maharashtra have been declared as protected.
Community-Led Conservation:
- Save Silent Valley Movement: A successful 10-year public movement that protected a moist evergreen forest in Kerala from the construction of a hydroelectric dam.
- Sacred Groves: Undisturbed patches of forest protected by local communities. In these groves, it is forbidden to harm animals or cut trees, making them community-protected "treasures of biodiversity."
Key Figures in Indian Conservation :
- Janaki Ammal (1897–1984): An Indian botanist who documented India's plant biodiversity, headed the Botanical Survey of India, and played a key role in the 'Save Silent Valley' movement.
- Salim Ali (1896–1987): Known as the "Birdman of India," he extensively documented bird diversity, habitats, and migration routes. His work led to the conservation of important bird regions, including Keoladeo National Park. He was awarded the Padma Vibhushan in 1976.
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