The fundamental unit of life class 9 notes | class 9 science chapter 5 notes скачать в хорошем качестве

The fundamental unit of life class 9 notes | class 9 science chapter 5 notes

The fundamental unit of life class 9 notes | class 9 science chapter 5 notes the fundamental unit of life class 9 notes pdf,the fundamental unit of life class 9 questions and answers Prokaryotes. Eukaryotes. Cells of organism lacks nuclear membrane.Cells of organism have nuclear membrane.Nucleolus is absent.Nucleolus is present.Single chromosomes.Single or multi chromosomesReproduction is always asexual.Reproduction is both sexual and asexual.Always unicellular.Often multicellular.Membrane bound cell organelles are absent.Membrane bound organelles are present like mitochondria.Centriole is absent.Centriole is present only in animals cell.Cell division is by binary fission.Cell division is by mitosis or meiosis.Example: Bacteria, Blue green algae, etc.Example: Fungi, Plant cell, Animal cell Animal Cell. Plant Cell. Cell wall is absent.Cell wall is present.Plastids are absent.Plastids are present.Centrioles are present.Centrioles are absent.Golgi bodies are present.Golgi bodies are present and called dictyosome.Vacuoles are absent. If present, they are small.Vacuoles are present and large in size.Centrosome is present with one or two centrioles.Centrosome is absent Diffusion. • The spontaneous movement of a substance from a region of high concentration to the region of low concentration is called diffusion.. • Some substances like carbon dioxide or oxygen can move across the cell membrane by a process called diffusion. Cell also obtains nutrition from the environment.. Osmosis. • The movement of water molecules through selectively permeable membrane along the concentration gradient is called osmosis.. • Plant cell tend to obtain water through osmosis.. Hypotonic or Hypertonic or Isotonic solution. What happened to cell in sugar or salt solution Plasma membrane or Cell membrane • This is the outermost covering of the cell that separates the contents of the cell from its external environment.. • The plasma membrane allows or permits the entry and exit of some materials in and out of the cell.. • It also prevents movement of some other materials. The cell membrane is called selectively permeable membrane.. • It is made up of lipid and protein.. → Properties of Plasma membrane • It is flexible (made up of organic molecules called lipids and proteins).. • Its flexibility enables cell to engulf in food and other from the external environment. This process is called endocytosis. Amoeba acquire food through this process.. → Functions of Plasma membrane. • It permits the entry and exit of some materials in and out of the cell.. • It prevents movement of some other materials not required for the cell as it acts like selectively permeable membrane.. Cell Wall • Cell wall is another rigid outer covering in addition to the plasma membrane found in plant cell. The cell wall lies outside the plasma membrane.. • The plant cell wall is mainly composed of cellulose. Cellulose is a complex substance which provides structural strength to plants.. → Function of Cell Wall. • Cell walls permit the cells of plants, fungi and bacteria to withstand very dilute (hypotonic) external media without bursting.. • In such media the cells tend to take up water by osmosis. The cell swells, building up pressure against the cell wall. The wall exerts an equal pressure against the swollen cell.. • Because of cell wall, cells can withstand much greater changes in the surrounding medium than animal cells.. Plasmolysis. • When a living plant cell loses water through osmosis there is shrinkage or contraction of the contents of the cell away from the cell wall. This phenomenon is known as plasmolysis.. Nucleus.