The menstrual cycle (Latin: mensis means a lunar month) is a characteristic of primates (monkeys, apes, and humans). Menstruation is defined as the cyclic discharge of blood carrying broken tissue materials through the vagina. In a human female, the fertility period extends from the age of puberty, i.e. about 11-13 years up to menopause, i.e. 45-50 years. The […]
In this article we shall study about movements and locomotion. Movements: The act of changing position or place by one or more of its parts is called a movement. Movement is one of the significant features of living beings. Animals and plants exhibit a wide range of movements. The study of movements is called kinesiology […]
Muscle is a specialized tissue of mesodermal origin. About 40-50 percent of the body weight of a human adult is contributed by muscles. They are formed by specialized elongated cells called muscle fibres or myofilaments. They have special properties like electric excitability, contractility, extensibility, and elasticity. Contractility is due to the presence of myofibrils formed by highly […]
Typhoid is a bacterial infection that can lead to high fever, diarrhea, and vomiting. If typhoid is diagnosed early, it can be successfully treated with antibiotics; if it is not treated, typhoid can be fatal. The name typhoid is given to the disease by Louis in 1829, as a derivative from typhus. Typhoid fever has received […]
In this article, we shall study the female reproductive system in humans. Human Reproductive System: Puberty means the changes that occur in boys and girls as they grow up. In this period the maturity of human sex organs begins. Most of these changes occur between the ages of 10 to 14 years. These changes are brought about by […]
In this article, we shall study sexual reproduction and the male reproductive system in humans. The process of formation of life from pre-existing life is called reproduction. In animals two types of reproduction are observed a) asexual reproduction and b) sexual reproduction. Asexual Reproduction: A mode of reproduction in which the offspring comes from a single […]
The process in which a DNA molecule produces exact copy or replica of itself is known as replication of DNA. In eukaryotes, replication of DNA takes place inside the nucleus. In DNA replication, the double helix (parent strand) unzips forming two separate strands called templates. These templates provide the base sequences used to synthesize new DNA (daughter) strands. […]
In this article, we shall study the difference between DNA and RNA, and also the structure of RNA. Differences between RNA molecules and DNA molecule: RNA contains ribose sugar units while DNA contains deoxyribose sugar unit. RNA contains the base uracil while DNA contains thymine. RNA is single-stranded, except in some viruses while DNA is […]
In this article, we shall study the structure of DNA. Each cell in a particular living organism contains the exact same DNA. The size of the DNA polymer is directly related to the complexity of the organism; more complex organisms tend to have larger molecules of DNA, while less complex organisms have smaller DNA. For e.g. […]
Karl Landsteiner in 1900 discovered that blood in all persons is not alike and hence clumping or agglutination occurs on the mixing of blood of certain persons. Blood group is determined by the antigens present on the surface of RBC’s. An antigen is a molecule (in this case a carbohydrate) that acts as a signal, […]