Biology arose in a twofold manner - firstly, as a practicing art towards exploring and improving a variety of usable plant and animal products as well as towards maintaining good health; secondly, as an academic pursuit out of curiosity to know about humans and other living beings and to understand their position on the planet Earth.
The diseases that are transmitted through sexual contact are known as sexually transmitted diseases. Sexually transmitted diseases are those diseases that are transmitted via the mucous membrane and secretions of the sexual organ, throat and the rectum. Syphilis, gonorrhoea, and AIDS are some sexually transmitted diseases.
Any malfunctioning process which interferes with the normal functioning of the body is called a disease. Disease may be defined as a disorder in the physical, physiological, psychological or social state of a person caused due to nutritional deficiency, physiological disorder, genetic disorder, pathogen or any other reason.
The body needs energy to carry on various activities of life. This energy is obtained by eating food. The energy requirement of an individual depends on various factors like age, sex, amount of work done (occupation), special needs like pregnancy and lactation.
Minerals are micronutrients required in varying amounts for proper functioning, normal growth and keeping good health of body. They are inorganic elements, occurring in the form of their salts like calcium, potassium, sodium, phosphorus, iron, etc. They do not supply energy to our body but are essential for protection against diseases and also have role in body functions.
Vitamins are complex chemical substances required by the body in very small amounts. They do not yield energy but act as biocatalysts in the body. They are essential for good health and protect the body from various diseases. They are essential for the utilization of other nutrients that we take in the diet.
Nutrition is the sum of the processes by which an organism takes in, metabolizes and utilizes food substance for its various biochemical activities. Nutrients are the organic or inorganic substances which help in survival and in maintaining proper health. A nutrient supplies energy to the body, builds and repairs body tissues and regulates the body metabolism.
DNA (Deoxyribonucleic acid) is a polynucleotide, a macromolecule made of units called nucleotides. Each nucleotide consists of three sub units:
In the last over hundred years, genetics and molecular biology have gone far ahead and the progress has been very rapid. Today there is hope for cure of genetic disorders through gene therapy. This is because in 2003, most of the genes on human chromosomes have been mapped or located on the 23(n) chromosomes.
Human karyotype is the arrangement of human chromosomes in seven groups according to the types of chromosomes and their size. It is prepared by arranging chromosomes seen at mitotic metaphase in descending order with the longest pair of chromosomes drawn first, and the sex chromosomes are drawn the last.
Sex of the unborn individuals is determined in different ways in different kinds of organisms. In some diploid organisms, specific chromosomes have a role in sex determination. Such chromosomes are called sex chromosomes and the rest of the chromosomes of a set are called autosomes.
Bateson and Punnett performed a dihybrid cross with true breeding varieties of sweet pea (Lathyrus sativus) and instead of 9:3:3:1 ratio in F2 generation they got the ratio 7:1:1:7. It means that the characters controlled by the two genes chosen for the experiment do not follow the principle of independent assortment as postulated by Mendel. Instead they tend to be inherited together or are linked together. Thus genes present on the same chromosome tend to be inherited together and are said to be linked. This phenomenon is called linkage.
Sutton and Boveri in 1902 observed that chromosomes from two parents come together in the zygote as a result of the fusion of two gametes and again separate out during meiosis at the time of formation of gametes. Chromosomes are filamentous bodies present in the nucleus and seen only during cell division. Gametes have half (n) number of chromosomes or are haploid and zygote is diploid or has (2n) or double the number of chromosomes when compared to chromosome number in the gametes.
Sir Gregor Johann Mendel (1822 to 1884) was Austrian monk who used garden pea (Pisum sativum) for his experiments on plant breeding and published his results in 1865. However, his work was independently rediscovered in 1900, long after Mendel’s death, by Tschermak, Correns and DeVries. But since Mendel was the first to suggest principles underlying inheritance he is regarded as the founder or father of genetics.
Whenever an infant is born in a family, the relatives begin to wonder about the resemblance of the infant’s eyes, facial features, complexion, colour of hair with those of the parents, siblings and grand parents. The source of such resemblances and differences are in the genes that are passed down form parents to children and so on generation after generation. This inheritance of genes is termed heredity the study of reasons of heredity is Genetics.
Spermatoza remain viable in the female genital tract from 24 to 72 hours. For fertilization, sperms are introduced into the female body. One sperm fuses with the ovum in the fallopian tube.
Movements of plants are completely different from body movement. Except some unicellular plants, all other higher plants cannot move from place to place as their roots are fixed in the soil. Still they show movement by folding the buds, opening and closing the flowers, and bending towards sun light. These movements in plants are very slow and you have to wait and observe them carefully and patiently to notice these movements.
Like animals, plants also have fixed life span and after completing that perioid, they die. Before death several degradation processes occur in their body like yellowing of leaves and fading of flower colour. It is due to loss in structure and function of an organ or the whole plant. The deteriorative processes which ultimately lead to complete loss of organization and functioning of the plant or its parts is known as Senescence.
The temperature affects growth and development of plants. For flowering in some plants, a particular temperature is required. Studies show that if temperature is reduced to a particular point then flowering occurs at an early stage. For example by applying a temperature ranging between 1-10°C to certain variety of wheat, rice and cotton, growth of seedlings is accelerated and flowering occurs earlier. This method of inducing early flowering in plants at low temperature is called vernalisation.
Some plants like spinach and wheat produce flowers in summer while others like and dahlia and cosmos flower in winter. Plants that flower in summer require longer duration of light per day than those flowering in winter. The duration of light plays an important role in flowering of plants. This effect of duration of light on the growth of plants is known as photoperiodism.
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