S6 Bio Growth And Development Caltec S.6

GROWTH AND DEVELOPMENT Growth is defined as an irreversible or permanent increase in size and dry weight of an organism. It is caused by cell division mainly mitosis. Cell division leads to increase in cell number, also involves cell expansion and cell differentiation in cell differentiation the cells become specialized to perform particular functions i.e. division of labor. They undergo changes both in shape and form and join others of similar kind to form tissues or organs. Such cells do not divide any more therefore growth is usually accompanied by an increase in complexity of an organism called development. What is development? It is the process whereby cells after division differentiate and increase in complexity leading to changes both in shape and form. The process of development is closely linked with growth in that growth and development are commonly used to describe processes which are thought of as growth. In multicellular organisms, growth is divided into 3 phases: Cell division (hyperplasia) which is an increase in cell number as a result of cell division Cell expansion (hypertrophy) which is an irreversible increase in cell size as a result of uptake of water or synthesis of living material Cell differentiation: this is when cells become specialized. This also includes development. All stages of growth involve bio chemical activity. Protein synthesis is important since it is the means by which the DNA message is expressed in terms of enzymes synthesized by the cell. The enzymes control cell activities. The changes at the cell level bring about the changes of the overall form and structure both of individual organs and the organism as a whole. Growth may be positive or negative. Positive growth occurs when anabolism exceeds catabolism whereas negative growth occurs when catabolism exceeds anabolism. E.g. during germination of a seed and …