CDS Biology · Biodiversity and Classification
Classification, Plants and Fungi
The ranks from kingdom down to species, the five kingdoms of living things, the main groups of plants from algae to flowering plants, and how fungi grow and feed.
Why this matters
Ten CDS questions from 2019 (I) to 2026 (II). Six are about fungi: three ask about feeding on dead matter (saprophytes), two are about yeast, and one asks what hyphae are. Two ask about the ranks of classification and two about the plant groups.
Concept 1 of 4: The ranks of classification
Classification puts living things into boxes inside boxes. The biggest box, the kingdom, holds a huge variety of organisms that share only a few features. Each smaller box holds fewer organisms that share more. The smallest box, the species, holds organisms so alike that they can breed with each other.
Definition
The taxonomic ranks, from the broadest to the narrowest:
- Kingdom → Phylum → Class → Order → Family → Genus → Species.
- For plants, Division is used in place of Phylum.
- Species is the basic unit: a group of individuals with fundamental similarities that can interbreed (all rose plants of one kind, all human beings).
- A genus is a group of related species; a family is a group of related genera.
- Binomial nomenclature (Carolus Linnaeus): every organism gets a two-word name, the genus first with a capital letter, then the species word in small letters, both in italics, for example Homo sapiens and Mangifera indica (mango).
| Rank | Human being | Mango |
|---|---|---|
| Kingdom | Animalia | Plantae |
| Phylum or Division | Chordata | Angiospermae |
| Class | Mammalia | Dicotyledonae |
| Order | Primata | Sapindales |
| Family | Hominidae | Anacardiaceae |
| Genus | Homo | Mangifera |
| Species | sapiens | indicaQ CDS 2020 (II): all the individuals of one kind, such as rose plants, form a species. |
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
CDS · 2025 · CDS (II) 2025 — General Knowledge · Q41Easy
Example 1 · Biodiversity and Classification · Classification, Plants and Fungi
Which one among the following is the correct scheme followed for classification of animals ?
Order comes before Family
Wrong schemes in the options swap Order and Family, or Genus and Species. The right order is Class, Order, Family, Genus, Species: order is the wider group and species the narrowest.
Species is the basic unit, not genus
All individuals of one kind, such as all rose plants, form a species. A genus is a bigger group that holds several related species.
Concept 2 of 4: The five kingdoms
R. H. Whittaker sorted all living things into five kingdoms by asking three questions. Does the cell have a proper nucleus? Is the body one cell or many? Does it make its own food, or take it from outside? Bacteria have no nucleus, so they stand alone. Single-celled organisms with a nucleus form another kingdom. Fungi, plants and animals are the three kingdoms left.
Definition
Whittaker's five kingdoms (1969):
- Monera: prokaryotes (no true nucleus), single-celled, for example bacteria and blue-green algae.
- Protista: all single-celled eukaryotes, for example Amoeba, Paramecium and Euglena.
- Fungi: a unique kingdom of heterotrophs; cell wall of chitin; most are made of thin threads called hyphae. Yeast is the exception: it is unicellular and reproduces by budding.
- Plantae: many-celled, make their own food by photosynthesis, cell wall of cellulose.
- Animalia: many-celled, heterotrophic, no cell wall.
- Among the fungi, the Ascomycetes (sac fungi) are mostly many-celled, for example Penicillium, and rarely single-celled, for example yeast.
| Kingdom | Cell and body | Nutrition | Examples |
|---|---|---|---|
| Monera | Prokaryotic, single-celled | Varied | Bacteria, blue-green algae |
| Protista | Eukaryotic, single-celled | Varied | Amoeba, Paramecium, Euglena |
| Fungi | Eukaryotic, mostly threads of hyphae; yeast is single-celled | Heterotrophic, mostly saprophytic | Yeast, mushroom, bread mouldQ CDS 2022 (I): the yeast used to make bread is a fungus, not a protist or a moneran. |
| Plantae | Eukaryotic, many-celled, cellulose wall | Autotrophic | Mosses, ferns, flowering plants |
| Animalia | Eukaryotic, many-celled, no cell wall | Heterotrophic | Sponges, insects, human beings |
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
CDS · 2026 · CDS (II) 2026 — General Knowledge · Q119Moderate
Example 2 · Biodiversity and Classification · Classification, Plants and Fungi
Which one of the following statements is NOT correct ?
Yeast is a single-celled fungus
Yeast is a fungus, not a protist and not a bacterium. It is also unicellular: a statement that calls yeast multicellular is the false one. Most other fungi are made of hyphae.
Protozoa is not one of the five kingdoms
Amoeba and Paramecium are often called protozoa, but the kingdom is Protista. An option offering Protozoa as a kingdom for yeast is a distractor.
Concept 3 of 4: The plant groups
Plants are sorted by three questions. Is the body divided into root, stem and leaf? Does it have tubes (vascular tissue) to carry water? Does it make seeds, and are the seeds inside a fruit? The answers run from the simplest plants, the algae in water, to the flowering plants that cover the land.
Definition
The plant groups, simplest first (NCERT Class 9):
- Thallophyta (algae): body not divided into root, stem and leaf; predominantly aquatic; for example Spirogyra, Ulothrix, Cladophora, Chara.
- Bryophyta: simple plant body, no vascular tissue; the amphibians of the plant kingdom; for example Riccia, Marchantia, Funaria (moss).
- Pteridophyta: true root, stem and leaves with vascular tissue, but no seeds (they reproduce by spores); for example Marsilea, ferns and horse-tails.
- Gymnosperms: seeds are naked (not inside a fruit); for example Pinus, Cycas.
- Angiosperms: seeds inside a fruit; the flowering plants, split into monocots and dicots.
- Thallophytes, bryophytes and pteridophytes have hidden reproductive organs and are called cryptogams; gymnosperms and angiosperms bear seeds and are phanerogams.
| Group | Key feature | Examples |
|---|---|---|
| Algae (Thallophyta) | No root, stem or leaf; mostly in water | Spirogyra, Ulothrix, CharaQ CDS 2020 (II): in Kingdom Plantae, the predominantly aquatic group is the algae. |
| Bryophyta | No vascular tissue; need water to reproduce | Riccia, Marchantia, Funaria |
| Pteridophyta | Vascular tissue but no seeds | Marsilea, ferns, horse-tailsQ CDS 2019 (II): Marsilea, fern and horse-tail are pteridophytes. |
| Gymnosperms | Naked seeds | Pinus, Cycas |
| Angiosperms | Seeds enclosed in a fruit; flowers | Mango, wheat, rose |
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
CDS · 2019 · CDS (II) 2019 — General Knowledge · Q120Moderate
Example 3 · Biodiversity and Classification · Classification, Plants and Fungi
Marsilea, Fern and Horse-tail are examples of which one of the following plant groups ?
Vascular tissue does not mean seeds
Pteridophytes have true roots, stems, leaves and vascular tissue, but they make no seeds. Seeds begin with the gymnosperms.
Bryophytes live on land, algae in water
Bryophytes grow on damp land and need water only to reproduce. The plants that are predominantly aquatic are the algae.
Concept 4 of 4: How fungi grow and feed
A fungus has no chlorophyll, so it cannot make food. Instead it grows thin threads into its food, pours digestive enzymes out onto it, and soaks up what dissolves. When the food is dead matter, such as bread, dung or fallen leaves, the fungus is a saprophyte. Plants and algae with chlorophyll make their own food, and a parasite feeds on a living host.
Definition
The body and food of fungi:
- Hyphae: thin, thread-like filaments; a network of hyphae is a mycelium, the body of most fungi.
- Saprophytic nutrition: food is broken down outside the body by secreted enzymes and the products are absorbed. Yeast, mushrooms (Agaricus) and bread mould (Rhizopus) feed this way.
- Parasitic nutrition: feeding on a living host, for example Cuscuta (amarbel, a plant without chlorophyll), tapeworm, lice.
- Autotrophic nutrition: making food by photosynthesis, for example algae (Spirogyra, Ulothrix, Cladophora), liverworts (Riccia) and grass.
- Animals such as Amoeba and Paramecium take food inside and digest it there (holozoic nutrition).
| Organism | Group | Mode of nutrition |
|---|---|---|
| Agaricus (mushroom) | Fungus | SaprophyticQ CDS 2019 (I): Agaricus is the saprophyte; Ulothrix, Riccia and Cladophora make their own food. |
| Rhizopus (bread mould) | Fungus | SaprophyticQ CDS 2023 (II): the saprophyte among Cuscuta, Rhizopus, Spirogyra and grass is Rhizopus. |
| Yeast | Fungus | SaprophyticQ CDS 2021 (II): yeast, mushroom and bread mould break food down outside the body and absorb it. |
| Cuscuta | Flowering plant | Parasitic |
| Spirogyra | Alga | Autotrophic |
| Amoeba | Protist | Holozoic (takes food in) |
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
CDS · 2022 · CDS (I) 2022 — General Knowledge · Q30Easy
Example 4 · Biodiversity and Classification · Classification, Plants and Fungi
Hyphae are :
A plant without chlorophyll is not a saprophyte by default
Cuscuta has no chlorophyll, but it feeds on a living host plant, so it is a parasite. A saprophyte feeds on dead matter, like Rhizopus on bread.
Hyphae are threads, not spores
Hyphae are the thin threads that make up a fungus's body. They are not reproductive cells, and a mass of them together is the mycelium.
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (4)
The ranks of classification7 rows
| Rank | Human being | Mango |
|---|---|---|
| Kingdom | Animalia | Plantae |
| Phylum or Division | Chordata | Angiospermae |
| Class | Mammalia | Dicotyledonae |
| Order | Primata | Sapindales |
| Family | Hominidae | Anacardiaceae |
| Genus | Homo | Mangifera |
| Species | sapiens | indicaQ CDS 2020 (II): all the individuals of one kind, such as rose plants, form a species. |
The five kingdoms5 rows
| Kingdom | Cell and body | Nutrition | Examples |
|---|---|---|---|
| Monera | Prokaryotic, single-celled | Varied | Bacteria, blue-green algae |
| Protista | Eukaryotic, single-celled | Varied | Amoeba, Paramecium, Euglena |
| Fungi | Eukaryotic, mostly threads of hyphae; yeast is single-celled | Heterotrophic, mostly saprophytic | Yeast, mushroom, bread mouldQ CDS 2022 (I): the yeast used to make bread is a fungus, not a protist or a moneran. |
| Plantae | Eukaryotic, many-celled, cellulose wall | Autotrophic | Mosses, ferns, flowering plants |
| Animalia | Eukaryotic, many-celled, no cell wall | Heterotrophic | Sponges, insects, human beings |
The plant groups5 rows
| Group | Key feature | Examples |
|---|---|---|
| Algae (Thallophyta) | No root, stem or leaf; mostly in water | Spirogyra, Ulothrix, CharaQ CDS 2020 (II): in Kingdom Plantae, the predominantly aquatic group is the algae. |
| Bryophyta | No vascular tissue; need water to reproduce | Riccia, Marchantia, Funaria |
| Pteridophyta | Vascular tissue but no seeds | Marsilea, ferns, horse-tailsQ CDS 2019 (II): Marsilea, fern and horse-tail are pteridophytes. |
| Gymnosperms | Naked seeds | Pinus, Cycas |
| Angiosperms | Seeds enclosed in a fruit; flowers | Mango, wheat, rose |
How fungi grow and feed6 rows
| Organism | Group | Mode of nutrition |
|---|---|---|
| Agaricus (mushroom) | Fungus | SaprophyticQ CDS 2019 (I): Agaricus is the saprophyte; Ulothrix, Riccia and Cladophora make their own food. |
| Rhizopus (bread mould) | Fungus | SaprophyticQ CDS 2023 (II): the saprophyte among Cuscuta, Rhizopus, Spirogyra and grass is Rhizopus. |
| Yeast | Fungus | SaprophyticQ CDS 2021 (II): yeast, mushroom and bread mould break food down outside the body and absorb it. |
| Cuscuta | Flowering plant | Parasitic |
| Spirogyra | Alga | Autotrophic |
| Amoeba | Protist | Holozoic (takes food in) |
Watch out for (8)
- Order comes before Family→ The ranks of classification
- Species is the basic unit, not genus→ The ranks of classification
- Yeast is a single-celled fungus→ The five kingdoms
- Protozoa is not one of the five kingdoms→ The five kingdoms
- Vascular tissue does not mean seeds→ The plant groups
- Bryophytes live on land, algae in water→ The plant groups
- A plant without chlorophyll is not a saprophyte by default→ How fungi grow and feed
- Hyphae are threads, not spores→ How fungi grow and feed
Test yourself on Biodiversity and Classification
10 past CDS questions from this chapter, timed at 10 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.