Classification of Plants
ICSE Class 7 · Biology · Chapter 2
What this chapter covers
- Meaning and need of classification
- Advantages of classification
- Five-kingdom classification
- Kingdom Monera
- Kingdom Protista
- Kingdom Fungi
- Kingdom Plantae
Key points
- Classification is the grouping of organisms by their shared and differing features; it is needed because the living world has millions of kinds of organisms.
- The old two-kingdom system (Plantae and Animalia) could not place bacteria, fungi and single-celled organisms properly.
- Classification makes study easier, helps identify organisms, shows relationships and shows how complex life developed from simple life.
- The five-kingdom classification (1969) has Monera, Protista, Fungi, Plantae and Animalia, based on cell type, number of cells and mode of nutrition.
- Monera are prokaryotic, single-celled organisms such as bacteria, which are round (cocci), rod-shaped (bacilli), spiral (spirilla) or comma-shaped (vibrio).
- Useful bacteria make curd, fix nitrogen, decompose waste and give some antibiotics; harmful bacteria cause cholera, typhoid, tuberculosis and food spoilage.
- Protista are single-celled eukaryotes; Amoeba moves and feeds with pseudopodia, breathes and excretes by diffusion, removes extra water with a contractile vacuole and reproduces by binary or multiple fission.
- Fungi lack chlorophyll and are mostly saprophytes; bread mould has hyphae forming a mycelium, rhizoids that absorb food, and sporangia full of spores.
- Useful fungi give food, make bread rise and provide penicillin; harmful fungi cause ringworm, crop rust and food spoilage.
- Plantae are multicellular, eukaryotic autotrophs with cellulose cell walls and chlorophyll, such as moss, fern, pine, mango and rice.
Questions answered
Define classification.
Classification is the arrangement of living organisms into groups on the basis of the features they share and the features in which they differ.
Give two reasons why the two-kingdom classification was found inadequate.
Bacteria have no proper nucleus and did not fit with plants or animals; fungi are fixed like plants but cannot make their own food, so they did not fit either group.
State three advantages of classification.
It makes the study of living things easier, helps in identifying new organisms, and shows relationships between organisms (any three of the advantages listed).
Name the five kingdoms and state the year in which this system was proposed.
Monera, Protista, Fungi, Plantae and Animalia; it was proposed in 1969.
What is the main difference between a prokaryotic cell and a eukaryotic cell?
A prokaryotic cell has no well-defined nucleus enclosed by a membrane, while a eukaryotic cell has a proper nucleus with a nuclear membrane.
Name the four common shapes of bacteria, with one example of each where you can.
Coccus (round), bacillus (rod-shaped, for example Lactobacillus), spirillum (spiral) and vibrio (comma-shaped, for example the cholera bacterium).
Explain why farmers grow pulses such as gram and moong to restore tired soil.
Rhizobium bacteria in the root nodules of pulses take nitrogen from the air and turn it into a form plants can use, so the soil becomes richer in nitrogen for the next crop.
How does Amoeba get rid of the extra water that keeps entering its body?
The contractile vacuole collects the extra water and then bursts at the surface, pushing the water out of the cell.