CELL THEORY

Cell theory was proposed by Schleiden and Schwann in 1855 to explain the concept of the cellular nature of living organism. But they did not explain how new cells are formed. Rudolf Virchow in 1858 made a generalization “omnis cellula e cellula” i.e., all cells comes from pre-existing cells. The three fundamental facts of the […]

DEFINITIONS OF IMPORTANT TERMS OF GENETICS

1. Alleles – Alleles are the different alternate form of a particular gene. (OR) Alleles are the genes that govern variations of the same characteristic and that occupy corresponding loci on homologous chromosomes. 2. Back Cross – When a plant is crossed with any of its parents, it is known as Back Cross. 3. Cross […]

METHODS OF CONTRACEPTION

Contraceptive devices are the devices which prevents fertilisation and hence control birth rate. These also prevents unwanted pregnancy. Broadly contraceptive methods are classifieds into two types: Temporary method Permanent methods TEMPORARY METHODS: These methods are used to control fertilisation for a short interval of time. Temporary methods are further classified into four. 1. Natural method. […]

RESPIRATION

Respiration is a complex process that includes the combination of breathing and cellular respiration. Breathing: Breathing is exchange of gases i.e intake of oxygen from the atmosphere and release of carbon dioxide. Cellular respiration: It is the complex catabolic process, in which the biochemical oxidation of nutrients takes place for the production of energy in […]

ASEXUAL REPRODUCTION

Asexual reproduction is a mode of reproduction by which offspring arises from single parent without fusion of gametes. This method is mainly adapted by single celled organisms and plants. Offsprings produced by this method are identical to each other and to its parent. Morphologically and genetically identical individuals are termed as clones. Type of asexual […]

NUTRITION IN GREEN PLANTS

Green plants prepare their own organic food (starch) from inorganic sources by the process of photosynthesis. They are autotrophic in nature Photosynthesis: photo – light; synthesis = putting together. It is the process of conversion light energy into chemical energy in which the inorganic components like carbon dioxide and water (CO2 and H2O) are utilised […]

DIGESTIVE SYSTEM IN HUMAN BEINGS

Human beings are heterotrophic omnivorous organisms. They obtain food from plants and animals by holozoic mode of nutrition. The human diet includes · Carbohydrates · Fats · Proteins · Vitamins · Minerals · Water The human digestive system consists of alimentary canal and digestive glands. Alimentary canal: [Digestive tract] The alimentary canal is a long […]

NUTRITION IN AMOEBA

Amoeba is a unicellular protozoan and the mode of nutrition is holozoic. It is omnivorous in nature i.e, it can take both plants and animals as food source. Amoeba feeds on unicellular plants or animals such as paramoecium. The various steps of nutrition are ingestion, digestion, assimilation and egestion. Amoeba sends out finger like pseudopodia […]