notes of fundamental unit of life Class9
Answers
Answer:
The theory that all the plants and animals are composed of cells and the cell is the basic unit of life, was presented by two biologists, Schleiden and Schwann. The cell theory was further expanded by Virchow by suggesting that all cells arise from pre-existing cells.
Answer:
Introduction...
•The fundamental unite of is cell.
• Cell was first discovered by Robert Hooke in 1665 in a simple microscope.
• In 1674 , Leeuwenhoek, with the help of developed microscope, discovered the free living cells in pond water.
• In 1839, Purkinje used the term 'protoplasm' for the fluid substance found in the cell.
• In 1831, Robert Brown had discovered the nucleus in the cell.
• The cell theory was proposed by Schleiden (1838) and Schwann (1839).
.• According to the cell theory, all the plants and animals are composed of cell and that the cell is the basic unit of life.
• In 1855, Virchow further expanded the cell theory and suggest that all cell arise from pre-existing cells.
• In 1940 , the discovery of electron microscope made possible to observe and understand the complex structure of the cell.
Unicellular Organisms-
• The single cellular organisms, such as Amoeba, Chlamydomonas, Paramecium, and bacteria, are known as unicellular Organisms.
Multicellular organisms-
• The organisms consisting of many cells are known as multicellular organisms. eg.human being, animals, birds, etc.
Significant characteristics of cells---
• Each living cells has the aptitude to perform certain basic functions that are characteristics of all living forms.
• Each such cell has certain specific components within it known as cell organelles.
• These organelles collectively constitute the basic unit of life known as cell.
Plasma Membrane/ Cell Membrane--
• Plasma membrane is the outermost covering layer of the cell.
• Plasma membrane allows certain material to enter inside the cell and come out from the cell; therefore, it is known as selectively permeable membrane.
Nucleus--
The nucleus has a double layered covering, which is known as nucleus membrane.
• The nucleus membrane has some pores, which allows certain material come inside and go outside.
• The most significant features of nucleus is-. it contains chromosome.
• chromosome are rod shaped structure and it is visible only when the cell is about to divide.
• Chromosome are composed of DNA and protein.
Cytoplasm---
• Cells consist of cytoplasm inside the cell membrane, which contains many biomolecules including protein and nucleic acid.
• There are many structure found in the cytoplasm known as cell organelles.
Cell Organelles--
• Following are the major cell organelles that play a major role in the functioning of cell-
• Nucleus
• Endoplasmic Reticulum
• Ribosome
• Golgi apparatus
• Lysosome
• Mitochondria
• Plastids
•Vacuoles