The Three Domains System || CH # 02 || Biodiversity || Grade 9 || Biology || Federal Board Islamabad

Описание: The Three Domains System || CH # 02 || Biodiversity || Grade 9 || Biology || Federal Board Islamabad


2.4 CLASSIFICATION- THE THREE DOMAINS SYSTEM

In biology, a domain means the largest of all groups in the classification of life. Domain is group of kingdoms or taxonomic category above the kingdom.in 1990 Carl Woese introduced a three domains system of classification. The three domains of life are Archaea, Bacteria and Eukarya.

Classification into three domains is based on difference in the sequence of nucleotides in the rRNA (ribosomal Ribonucleic acid) of the cell, the cell's membrane lipid structure and its sensitivity to antibiotics.

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Archaea

Bacteria

Eukarya

Fig. 2.2 The three domains of life

Chapter 2: Biodiversity

1. The Domain Archaea

The domain Archaea have the following characteristics:

a. Archaea are prokaryotic cells.

b. The cell walls of Archaea contain no peptidoglycan.

c. The rRNA (ribosomal RNA) are not found in Bacteria and Eukarya.

d. Archaea are not sensitive to some antibiotics that affect bacteria. They are sensitive to some antibiotics that affect the Eukarya.

e. Archaea often live in extreme environmnet.

f. Archae membrane can withstand higher temperature and stronger acid concentration.

g. Archaeal creatures include: Methanogens, Halophiles, Thermoacidophiles.

2. The Domain Bacteria

The domain bacteria have the following characteristics:

a. Bacteria are prokaryotic cells.

b. The cell walls of bacteria contain peptidoglycan.

c. They contain rRNA that is unique to bacteria.

d. Bacteria are sensitive to traditional antibacterial antibiotics but are resistant to most antibiotics that affect eukarya.

3. The Domain Eukarya

The domain Eukarya (also spelled Eucarya) have the following characteristics:

a. Eukarya have eukaryotic cells.

b. Not all Eukarya have cells with a cell wall. Their cell wall contains no peptidoglycan.

c. Eukarya contains rRNA that is unique to Eukarya.

d. Eukarya are resistant to traditional antibacterial antibiotics but are sensitive to most

antibiotics that affect eukaryotic cells.

Domain Eukary

Animalia

Peptidoglycan or murein is a polysaccharide, consisting of sugar and amino acids that form a layer outside the rig Animalia id cell wall.

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Protista

Fungi

Plantae

The domain Eukarya are divided into four kingdoms: Protista, Fungi, Plantae and Animalia.

1. Protista: Protists include eukaryotic organisms with unicellular or colonial organization.

These are mostly aquatic. It is a diverse group of organisms. It includes: Animal like protists

called protozoa e.g., Amoeba. Plant like protists called algae e.g., Euglena. Fungi like

protists e.g., slime molds.

S= Sugar AA-Amino Acid

Founda

1. Microorganisms that produce methane as a metabolic byproduct methanogens. is called

2. Microorganisms that live in high salt concentration are called halophiles.

3. The microorganisms that can live in high temperature and high acidity are called thermoacidophiles.

2. Fungi: Fungi are eukaryotic organisms which have chitin in their cell wall. Fungi are saprotrophic decomposers. Mostly fungi are multicellular. Some fungi are unicellular. The examples of fungi are black bread mold, yeast, mushroom, etc.

3. Plantae: The members of kingdom plantae are eukaryotic multicellular and autotrophic with chloroplasts containing chlorophyll. Their cell wall is made up of cellulose e.g., moss, mustard.

4. Animalia: Animals are multicellular heterotrophic eukaryotes. Animals lack cell wall and chlorophyll. They can generally move from place to place. This kingdom includes invertebrates e.g., insects, starfish and vertebrates e.g., fish, frogs and man.