Diversity in Living World – WBBSE Class 10 Life Science Notes & Guide

Life on Earth shows an astonishing variety of forms. To study this variety scientists group organisms into hierarchical categories based on shared features. Understanding these groups, the way they are named, and why preserving them matters forms the backbone of the "Diversity in Living World" chapter.

Key concepts

Five‑Kingdom Classification

The five‑kingdom system, proposed by Robert Whittaker, arranges all living organisms into Monera, Protista, Fungi, Plantae and Animalia. The kingdoms differ mainly in cell type (prokaryotic vs eukaryotic), mode of nutrition (autotrophic, heterotrophic, saprophytic), level of organization (unicellular vs multicellular) and presence of cell walls.

Characteristics of Monera

• Prokaryotic cells (no true nucleus)
• Cell wall contains peptidoglycan
• Mostly unicellular; some form filaments
• Reproduce mainly by binary fission
• Nutrition: autotrophic (photosynthetic cyanobacteria) or heterotrophic (chemo‑heterotrophs)
• Example: Escherichia coli, Streptococcus spp.

Characteristics of Protista

• Eukaryotic cells, usually unicellular or colonial
• May have cell walls (algae) or lack them (amoeba)
• Diverse modes of nutrition: photosynthetic (algae), heterotrophic (protozoa), mixotrophic
• Reproduction: asexual (binary fission, budding) and sexual (spores)
• Example: Amoeba proteus, Paramecium caudatum, Chlamydomonas spp.

Characteristics of Fungi

• Eukaryotic, mostly multicellular (except yeasts)
• Cell wall composed of chitin
• Heterotrophic by absorption; secrete enzymes to break down organic matter
• Reproduce by spores (sexual & asexual)
• Important roles: decomposers, symbionts, pathogens
• Example: Mushroom (Agaricus), Penicillium spp.

Characteristics of Plantae

• Eukaryotic, multicellular, autotrophic (photosynthesis)
• Cell wall made of cellulose
• Possess chloroplasts with chlorophyll a & b
• Life cycle shows alternation of generations (sporophyte & gametophyte)
• Example: Rosa spp., Mango (Mangifera indica)

Characteristics of Animalia

• Eukaryotic, multicellular, heterotrophic (ingestion)
• No cell walls; tissues organized into organs & systems
• Development from a blastula (embryonic stage)
• Mostly sexual reproduction, though a few show asexual methods
• Example: Homo sapiens, Felis catus, Butterfly (Danaus chrysippus)

Binomial Nomenclature and Taxonomic Hierarchy

• Binomial nomenclature: each species gets a two‑part Latin name – Genus (capitalised) + specific epithet (lowercase). Example: Homo sapiens.
• Taxonomic hierarchy (from broad to specific): Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species.
• The hierarchy reflects evolutionary relationships; organisms placed in the same lower rank share more traits.

Importance of Biodiversity

• Ecological stability: diverse ecosystems recover faster from disturbances.
• Genetic resources: provide raw material for food, medicine, and industry.
• Cultural and aesthetic value: many societies derive identity and recreation from natural diversity.
• Ecosystem services: pollination, nutrient cycling, climate regulation.

Endangered Species and Conservation

• Species become endangered due to habitat loss, over‑exploitation, pollution, invasive species, and climate change.
• Conservation strategies:

1. In‑situ conservation – protected areas, wildlife sanctuaries.
2. Ex‑situ conservation – zoos, seed banks, gene banks.
3. Legal measures – Wildlife Protection Act, CITES.
4. Community participation – eco‑tourism, awareness programmes.

Important definitions and formulas

Solved examples

Example 1 – Classifying an organism Problem: A microscopic organism has a nucleus, moves using pseudopodia, and ingests food particles. Into which kingdom does it belong? Solution:

1. Presence of nucleus → eukaryote.
2. Unicellular, motile by pseudopodia → typical of Amoeba.
3. Ingests particles (phagocytosis) → heterotrophic.
4. These features match the kingdom Protista.

Answer: The organism belongs to the kingdom Protista.

Example 2 – Writing a binomial name Problem: The common mushroom belongs to the genus Agaricus and its species name is bisporus. Write its correct scientific name. Solution:

1. Write the genus name with initial capital: Agaricus.
2. Write the specific epithet in lower case: bisporus.
3. Italicise both words (or underline if handwriting).

Answer: Agaricus bisporus.

Example 3 – Calculating percentage of endangered species in a habitat Problem: In a forest reserve, 120 species of birds are recorded. 18 of them are listed as endangered. What percentage of the bird species are endangered? Solution:

1. Percentage = (Number of endangered species ÷ Total species) × 100.
2. = (18 ÷ 120) × 100.
3. = 0.15 × 100 = 15 %.

Answer: 15 % of the bird species are endangered.

Common mistakes to avoid

• Confusing prokaryotes with unicellular; many unicellular organisms (e.g., algae) are eukaryotes.
• Writing binomial names without italics or with both words capitalised.
• Forgetting that the taxonomic hierarchy includes Domain above Kingdom.
• Assuming all fungi are multicellular; yeasts are unicellular fungi.
• Mixing up endemic (restricted to a region) with endangered (at risk of extinction).

Exam tips

• Memorise the key characteristics of each kingdom in a tabular form – it helps quick recall.
• Practice writing scientific names correctly; the exam often checks italics and capitalization.
• For biodiversity questions, link concepts: why does a diverse ecosystem resist pests better?
• Use flow‑charts for the taxonomic hierarchy; they earn marks for clear presentation.
• In conservation questions, mention at least one in‑situ and one ex‑situ method.

Frequently asked questions

1. How is the five‑kingdom system different from the three‑domain system?

The five‑kingdom system groups organisms based on cell type, nutrition and organization, whereas the three‑domain system (Bacteria, Archaea, Eukarya) separates life primarily on differences in ribosomal RNA and fundamental cellular chemistry.

2. Why do scientists use Latin for scientific names?

Latin is a dead language; its words do not change over time, providing a stable, universal naming system that transcends regional languages.

3. Can a species belong to more than one kingdom?

No. Each species is placed in a single kingdom based on its overall characteristics. However, re‑classification may occur when new data (e.g., molecular studies) suggest a different placement.

4. What is the role of seed banks in ex‑situ conservation?

Seed banks store seeds under controlled conditions, preserving genetic material of plants for future restoration, research and breeding programmes, thereby safeguarding plant biodiversity outside their natural habitats.