CG Board Class 9 Science Chapter 1 Solutions: Biodiversity and Classification (जैव विविधता एवं वर्गीकरण) – 2026-27

(i) (b) Members of a class share maximum similarities
Reason: Organisms placed in the same taxonomic group share the greatest number of fundamental body features and evolutionary traits.

(ii) (d) Mustard
Reason: Mustard seeds have two cotyledons (dicotyledons), along with taproot systems and reticulate leaf venation. Onion, grass, and banana are monocots.

(iii) (d) Presence of wings
Reason: Birds have wings modified from forelimbs for flying, whereas fishes possess fins rather than wings. Both birds and fishes lay eggs and have a vertebral column.

Answers:

1. It is important to select a basis for grouping and classification.
2. Prokaryotic organisms are included in Monera kingdom.
3. Robert H. Whittaker gave the 5 kingdom classification (in 1969).

Two distinguishing features of Kingdom Fungi:

1. Heterotrophic Mode of Nutrition: Fungi lack chlorophyll and cannot synthesize their own food by photosynthesis. They absorb dissolved organic matter from decaying matter (saprophytes) or live on other organisms (parasites).
2. Cell Wall Made of Chitin: Unlike plants whose cell walls contain cellulose, fungal cell walls consist of chitin, a tough nitrogen-containing polysaccharide.

Examples: Amphibians include frog, toad, and salamander. Reptiles include lizard, snake, and tortoise.

Organisms of kingdom Fungi are excluded from the plant kingdom for two decisive biological reasons:

1. Absence of Chlorophyll and Autotrophic Nutrition: Plants contain chlorophyll and manufacture food through photosynthesis (autotrophic). Fungi lack chlorophyll entirely and obtain nutrients by absorbing organic compounds from external sources (heterotrophic saprophytes or parasites).
2. Different Cell Wall Composition: Plant cell walls are made of cellulose, whereas fungal cell walls are made of chitin.

Snakes and tortoises are classified together in the Class Reptilia based on these shared anatomical and physiological characters:

1. Mode of Locomotion: Both crawl or creep along the ground.
2. Dry, Scaly Skin: Both possess dry, cornified skin covered with epidermal scales or scutes that prevent moisture loss.
3. Cold-Blooded (Poikilothermic): Both cannot regulate their internal body temperature and depend on environmental warmth.
4. Respiration: Both breathe through lungs throughout their life cycle.
5. Reproduction: Both lay leathery-shelled eggs on land (oviparous).

Five common dicotyledonous (dicot) plants are:

1. Gram / Chickpea (चना)
2. Mustard (सरसों)
3. Pea (मटर)
4. Mango (आम)
5. Neem (नीम)

Key Feature: When soaked in water, their seed coat splits easily into two equal halves (cotyledons), and their leaves display reticulate venation.

We need classification for the following key scientific reasons:

1. Systematic Study: Millions of plant and animal species exist on Earth. Studying each organism individually is impossible, but classification allows us to study representative organisms from each group.
2. Understanding Diversity: It helps us comprehend the vast biodiversity around us in an organized, orderly manner.
3. Revealing Relationships: It highlights evolutionary links, anatomical similarities, and common ancestry among different living groups.
4. Standardized Identification: It creates a universal scientific framework for accurately identifying newly discovered organisms without ambiguity.

Meaning: Binomial nomenclature is a universally accepted scientific method introduced by Carolus Linnaeus for naming organisms using a two-word Latinized name.

Rules for Writing Scientific Names:

1. The first word denotes the Genus (generic name) and starts with a capital letter.
2. The second word denotes the Species (specific epithet) and starts with a lowercase letter.
3. Both words are written in Latin or Latinized, printed in italics, or underlined separately when handwritten.

Examples:

• Human: Homo sapiens (Genus: Homo, Species: sapiens)
• Frog: Rana tigrina (Genus: Rana, Species: tigrina)
• Mango: Mangifera indica (Genus: Mangifera, Species: indica)

Although bats fly in the air and rats run on land, both belong to the Class Mammalia because they share these definitive mammalian features:

1. Mammary Glands: Females of both species possess mammary glands that produce milk to nourish their young.
2. Viviparity: Both give birth to live young rather than laying eggs.
3. Body Hair: Both possess hair or fur covering their body surfaces.
4. External Ears (Pinnae): Both have visible external ear flaps (pinnae).
5. Warm-Blooded (Homeothermic): Both maintain a constant internal body temperature regardless of the outside environment.
6. Four-Chambered Heart and Lungs: Both have a four-chambered heart and breathe air through lungs.

Bases of Whittaker’s Five Kingdom Classification:

1. Complexity of Cell Structure: Prokaryotic (primitive, lack nuclear membrane) vs Eukaryotic (well-defined nucleus with organelles).
2. Body Complexity: Unicellular (single cell) vs Multicellular (tissue/organ level).
3. Mode of Nutrition: Autotrophic (photosynthesis) vs Heterotrophic (absorptive saprophytes or ingestive holozoic).

The Five Kingdoms in Detail:

1. Kingdom Monera: Unicellular, prokaryotic organisms without membrane-bound organelles. They have peptidoglycan cell walls. Nutrition is autotrophic or heterotrophic. Examples: Bacteria, Cyanobacteria (Blue-green algae), Anabaena.
2. Kingdom Protista: Unicellular, eukaryotic organisms. Many have cilia or flagella for locomotion. Nutrition can be photosynthetic or heterotrophic. Examples: Amoeba, Paramecium, Euglena.
3. Kingdom Fungi: Multicellular (except unicellular yeast), eukaryotic organisms with chitin cell walls. They lack chlorophyll and feed saprophytically on decaying matter. Examples: Mucor, Agaricus (Mushroom), Yeast, Penicillium.
4. Kingdom Plantae: Multicellular, eukaryotic autotrophs with cellulose cell walls. They contain chlorophyll to perform photosynthesis. Examples: Algae, Bryophytes, Ferns, Gymnosperms (Pinus), Angiosperms (Neem, Mango).
5. Kingdom Animalia: Multicellular, eukaryotic heterotrophs without cell walls or chloroplasts. Most show active locomotion and ingestive nutrition. Examples: Insects, Fish, Frogs, Birds, Mammals.

This statement is fully justified because classification is not fixed; it directly depends on the scientific criteria and observational tools available at the time:

1. Habitat-Based Criteria (Aristotle): Aristotle initially classified living organisms based on habitat into land-dwellers, water-dwellers, and air-dwellers. However, placing fish, whales, and crabs in the same group ignored their fundamental anatomical differences.
2. Gross Morphology (Linnaeus): Linnaeus used external visible characteristics and reproductive morphology to divide organisms into two kingdoms (Plants and Animals). However, this placed unicellular bacteria alongside trees, and fungi alongside photosynthetic plants.
3. Cellular and Evolutionary Criteria (Whittaker): When electron microscopes revealed cellular ultrastructure, Whittaker shifted the basis to cell architecture (prokaryotic vs eukaryotic), cellularity, and nutrition mode, giving rise to the five-kingdom system.

Thus, as scientific knowledge and observational technology advance, the classification criteria shift, and the whole organizational system adapts accordingly.