This article brings you the CBSE Class 9 Science notes on chapter 7 ‘Diversity in Living Organisms’ (Part-I). These chapter notes are prepared by the subject experts and cover every important topic from the chapter. At the end of the notes you can try the questions asked from the discussed set of topics. These questions will help you to track your preparation level and get a hold on the subject.
Main topics covered in this part of CBSE Class 9 Science, Diversity in Living Organisms: Chapter Notes, are:
- Definition of Biodiversity
- Classification: It’s Importance and Basis
- Hierarchy of classification
- Classification System
- Robert H. Whittaker’s Five Kingdom Classification
Key notes for Chapter- Diversity in Living Organisms, are:
Biodiversity or Biological Diversity
Biodiversity refers to the variety of living organisms present on a particular region. Eastern Ghats, Western Ghats, Tropical rain forests, Nilgiri mountain range and Himalayas are Biodiversity rich regions of India.
It is a branch of biology which deals with identification, nomenclature, and classification of organisms. Carolus Linnaeus is called the father of taxonomy.
The method of arranging organisms into groups or sets on the basis of similarities and differences is called classification.
Classification and Evolution:
It is a well established fact that all the life forms have evolved from a common ancestor. Scientists have proved that the life begun on the earth in the form of simple life forms. During the course of time, complex organism evolved from them. So, classification is also based on evolution.
Importance of classification:
- It makes the study of wide variety of organisms easy and in systematic manner.
- It helps to understand how the different organisms have evolved with time.
- It helps to understand the relationships between different groups of organisms.
- It forms a base for the study of other biological sciences, like biogeography.
Basis of classification:
There are the certain features or properties used for the classification of living organisms which are known as characteristics. Organisms with same characteristics are placed in same groups.
Some important characteristics used for hierarchical classification are
- Presence and absence of nucleus in the cell.
- Body composed of single cell or group of cells.
- Autotrophs (producing own food) and heterotrophs (getting food from outside).
- Development and organisation of different body parts.
Hierarchy of classification
Linnaeus proposed a classification system by arranging organisms into taxonomic groups at different levels according to the characteristics they have. The groups or the levels from top to bottom are:
Species is the basic unit of classification. A species is a group of living beings which can reproduce among themselves and keep their population alive.
1. Two kingdom classifications: Carolus Linnaeus in 1758 classified the living organisms into two groups as plants and animals.
2. Five kingdom classification: H. Whittaker in 1959 further classified the organisms into five kingdoms as Kingdom Monera, Kingdom Protista, Kingdom Fungi, Kingdom Plantae, and kingdom Animalia.
The five kingdoms and their key characteristics are given below:
- These are prokaryotes; which means nuclear materials are not membrane bound in them.
- They may or may not have cell wall.
- They can be autotrophic or heterotrophic.
- All organisms of this kingdom are unicellular.
- Examples: Bacteria, blue green algae (cyanobacteria) and mycoplasma.
- These are eukaryotes and unicellular.
- Some organisms use cilia or flagella for locomotion.
- They can be autotrophic or heterotrophic.
- Examples: Plants like unicellular algae, diatoms; animals like protozoans (Amoeba, Paramecium, Euglena)
- These are eukaryotic organisms with cell wall, made up of Chitin. They do not perform Photosynthesis (Heterotrophs).
- They may be unicellular (yeast) or filamentous (most fungi).
- They feed on decaying organic materials. Such a mode of nutrition is called saprophytic. Some fungi live in symbiotic relationship with other organisms (Lichens), while some are parasites as well.
- Examples: Mushrooms(Agaricus), green mold(Penicillium), smut(Aspergilus).
- These are multicellular and autotrophs.
- Presence of chlorophyll is a distinct characteristic of plants, because of which they are capable of taking out photosynthesis.
- Cell wall is present.
- These are eukaryotic, multicellular and heterotrophic organisms.
- Cell wall is absent.
Try the following questions:
Q 1. Name one basic characteristic for classifying organisms.
Q 2. Why is it difficult to classify bacteria? Give two reasons.
Q 3. Why is it difficult to classify bacteria? Give two reasons.
Q 4. Explain the basis for grouping organisms into five kingdoms?
Q 5. What is symbiotic relationship?