Introduction:
– The world is the home of millions of living organisms.
– Major characteristics of living organisms are Reproduction, Growth and development, Respiration, Excretion,
Movement etc.
– Biology is the branch of science where we discussed about the living organisms. It has two sub-branches- Botany (discussed about plants) and Zoology (discussed about animals).
Organisation of living body:
– Cell is the basic unit of life. All the living organisms are composed of cells.
– Unicellular organisms have only a single cell which performs all the biological functions.
– Multicellular organisms have millions of cell and these cells aggregate and form tissues or organs, which are responsible for biological functions.
– In 1665, robert Hooke discovered cell for the first time using microscope.
– Important facts about cells
| 1. Amoeba, Yeast (fungus), Paramecium etc. are example of unicellular organism. |
| 2. Plants, animals, algae, fungi etc. are example of multicellular organism. |
| 3. All the cells are classified as Prokaryotic cell and Eukaryotic cell. |
| 4. The shape of cells may be fixed or spherical, round,oval, elongated or branched. |
Prokaryotic cell vs Eukaryotic cell:
| Prokaryotic cell | Eukaryotic cell |
| They have no nucleous and membrane bound cell organelles. | They have nucleous and membrane bound cell organelles. |
| They are found in some lower organisms. | They are found in higher and multicellular organisms. |
| Additional circular plasmid DNA are found. | No plasmid DNAs are found. |
Various parts of cell:
1. Cell Membrane:
– It is also called plasma membrane. Cell membrane is composed of lipids, proteins and carbohydrates. Among those lipids are found in high amount followed by proteins and carbohydrates.
– Cell membrane is semi-permeable which allows exchange of substances.
– It also provides shape to the cell.
2. Cell wall:
– Cell wall is only found in plant cells. It’s the outer covering of plant cells.
– Cell wall is made up of cellulose.
– It protects the plant cell and also provides shape to the plant cell.
3. Cytoplasm or Protoplasm:
– It is semi-liquid substance found inside the plasma membrane.
– Various cell organelles are found in the cytioplasm.
4. cell organelles:
– Mitochondria is double membrane bound structure found in eukaryotic cell. It is called the power house of cell. Major function is to synthesis ATP or energy. Altmann in 1890 discovered mitochondria.
– Golgi complex Camillo Golgi in 1898 discovered golgi complex. Function is secretion, protein storage and formation of lysosome and cell membrane.
– Endoplasmic reticulum is discovered by Porter in 1945. It provides mechanical support to the cell. Rough E.R. has ribosomes on the surface but in case of Smooth E.R. no ribosomoes are present on the surface.
– Ribosomes are discovered by Palade in 1955. These are the smallest organelle and have no membrane. They help in protein synthesis.
– Lysosome discovered by de Duve in 1949. Single membrane bound cell organelle. It contains hydrolytic enzymes which digests antigens. These are called suicidal bags.
– Plastids are found in plant cell and double membrane bound cell organelle. Their main function is photosynthesis. It contains various types of chlorophyl molecules.
– Nucleus is discovered by Robert Brown in 1831. It is the largest cell organelle. It is double membrane bound cell organelle. It contains heriditary material or DNA. Small pherical body called nucleolus is found inside the nuclous. The thread like structures found are called chromatin network, which form chromosomes during the time of cell division. it is the control centre of all cellular activities.
Classification of organisms:
– Carrolus Linnaeus first divided all the organisms into two kingdoms e.g. Plant kingdom or Plantae and Animal kingdom or Animalia. phothosynthetic organisms are kept in plant kingdom and non photosynthetic organisms are kept in animal kingdom.
– Ernst Haeckel forwarded the three kingdom system of classification.
– Copeland classified whole living beings into four kingdoms- Monera, Protista, Plantae and Animalia.
– R H Whittaker divided the whole living beings into five kingdoms- Monera, Protista, Fungi, Plantae and Animalia.
| Monera | Protista | Fungi | Plantae | Animalia |
| They are prkaryotes and simplest organism. | They are eukaryotic having nucleous and other cell organelles. | These are eukaryotic and multicellular organisms. | This includes all the multicellular, eukaryotic and photosynthetic plants. | This includes all the multicellular, eukaryotic animals. |
| Their cell has no nucleous. | They are autotrophic or heterotrophic. | Nutrition is heterotrophic. | Nutrition is autotrophic. | Nutrition is heterotrophic. |
| Examples- bacteria, blue green algae. | Examples- Euglena, Paramecium, Amoeba, Chlamydomonous etc. | Examples- Various types of fungi (Yeast), Agaricus. | Examples – All the herbs, shrubs, tall plants, grasses etc. | Examples- All the multicellular higher organisms. |
Plant kingdom:
– Whole plant kingdom is classified as- Cryptogamae (Non flowering and non seed plants) and Phanerogamae (flowering and seed).
– Cryptogamae means thallophyta whose body is not divided into root. stem and leaves. Examples are algae, bryophyta and pteridophyta.
– Algae may be unicellular or multicellular. Unicellular algae may be motile (Chlamydomonus) or non motile (Diatoms). Multicellular algae are various types eg. filamentous, branched, colonial, etc.
– The branch of biology dealing with the study of algae is called phycology or Algology.
– Some algae possess flagella which helps in swimming.
– various types of algae are found like green algae, brown algae and red algae.
– Bryophytes are called amphibians of plant kingdom because they live in soil but require water for sexual reproduction.
– In case of bryophytes true roots, stems and leaves are absent.
– Root like structures in bryophytes are called rhyzoids.
– There is no vascular system in bryophtes.
– Examples Riccia, mosses, marchantia etc.
– In case of pteridophytes vascular system (xylem and phloem) is present.
– Pteridophytes are called snakes or botanical snakes of plant kingdom.
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