NCERT/CBSE Notes/ Class 9/Chapter 7/ Diversity in Living Organisms
NCERT/CBSE Notes/ Class 9/Chapter 7/ Diversity in Living Organisms
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Chapter 7/ Diversity in living organisms: Notes
There are about 10 million species of organisms on the earth, but only one-third of them are have been identified so far. if we attempt to study such a vast variety of organisms, it will be convenient if we group them and give each of them a biological name.
Classification
Classification means identifying similarities and dissimilarities between different kinds of organisms and then placing them in groups is called classification. This type of classification is called phylogenetic classification. this type of classification was first given by Swedish Naturalist Carl Linnaeus in 1735.
Basis of Classification
1. presence or absence of membrane-bound nucleus:
This is the basic characteristic of classification. All Eukaryotic cells have membrane-bound organelles such as the nucleus, which Prokaryotes do not have.
2. Occurrence of cells singly or in groups:
This is another characteristic that is lewd while classifying living organisms.
Cells are classified depending on their number, i.e., They live singly (Single-cell organisms) and live as individual groups.
Mode of Food Procurement
This means organisms produce their own food through photosynthesis (Autotrophs) and depend on food manufacturers by others (Hetrotrops).
Importance of classification
- Classification makes it easy to study a wide variety of organisms on this earth.
- Classification projects a picture of all life forms at a glance.
- It helps us understand the relationship between different groups of organisms.
- it serves as a base for the development of the other biological, Ecological, and Behavioral Sciences, Bio-geography, Evolution, e.t.c.
- It helps us in the identification and classification of different organisms such as agricultural pests, pathogens, and other organisms of the ecosystem.
Classification and Evolution
- Evolution is a change in time most life forms that we see today have arisen by an accumulation of changes in a body design over a period of time for better survival.
- The idea of evolution was described by Charles Darwin in the year 1859, in his book ” The Origin Species ”.
Older Organisms
Organisms with a primitive body design that has not changed much over a period of time are called older organisms.
Younger Organisms
There are organisms that have acquired their peculiar body design quite recently. They may be considered advanced or younger organisms.
Biodiversity
The diversity of life forms or a variety of life forms in a particular region on the classics of rough estimation there is about 10 million species of plants and animals, out of which only 2 million are known.
Regions of Rich Biodiversity
The Tropical region between the tropic of cancer and the topic of Capricorn are rich in biodiversity of plants and animal life. this is because afterward and humid climate the region is called the humid climate this region is called as the mega biodiversity region. More than .5% of biodiversity on the earth is concentrated in a few countries like Greek, Colombia, Mexico, Australia, China, Indonesia,e.t.c.
The Hierarchy in Classification of Groups
The largest group of organisms recognized by biologists is the Kingdom till recently there were only 2 kingdoms of classification are there. Namely, plants and animals. This however had caused problems in classifying fungi, Bacteria, and unicellular organisms which do not fit into either kingdom.
Five Kingdom Classification
R.H Whittaker suggested the 5 kingdom classification in 1969 on the basis of:
- Presence or absence of the nucleus.
- Unicellular or multicellular organisms.
- Mode of nutrition.
- Kingdoms that were recognized are:
- Monera
- Protista
- Fungi
- Plantae
- Animalia
Scheme of Classification
Five Kingdoms
Kingdom- Monera
- Monera is the simplest, oldest, and the most rigorous microorganisms.
- They are prokaryotes.
- They are mostly unicellular but maybe in the form of colonies or filaments of the independent cells.
- Some of them have a cell wall while some of them do not have a cell wall.
- Their mode of nutrition is mainly autotrophic but may be heterotrophic.
- They are usually non-volatile, but some may have flagellum and gliding movements. Celia is absent.
- Their reproduction is asexual by fusion, like Bacteria, Blue-green algae, Cyanobacteria, and Mithoplasma.
- Examples:
2.
Kingdom: Protista
- They are the first Eukaryotes to have a well-organized nucleus and complex membranous organelles.
- They are unicellular, without distinct divisions of labor.
- their mode of nutrition may be autotropic or heterotrophic.
- They have their lived cilia.
- examples: Amoeba, Algae, dictyosomes, Protozoans e.t.c.
- Diagram of one of its examples:
Kingdom: Fungi
- Fungi grow in dark, damp, and moist places and use dead organic matter as food and are therefore called saprophytes.
- Many of them have the capacity to become multicellular organisms at certain stages in their lives.
- They have a definite cell wall made up of tough sugar called chitin.
- They do not have chlorophyll, hence are heterotrophic.
- They are usually non-motile.
- They reproduce mostly by spore formation. However sexual reproduction may also take place.
- Some fungi live in mutual relationships with blue-green algae. Such a relationship is called a symbiotic relationship.
- These symbiotic forms are called lichens. They are usually found growing on the bark of trees.
- Example: Yeast, Agaricus (mushroom).
