Auxins are produced by plant apices, i.e. root apex and shoot apex. They bring about cell elongation resulting in growth. They are diffusible substances which effect growth when in very small amounts. Roots require lower concentrations than shoots. The effect of auxins on the growth of roots and shoots has already been discussed. Auxins also […]
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EVOLUTION Meaning of Evolution and Current Concepts Evolution is the development of organisms from pre-existing simple organisms over a long period of time. It is based on the similarities in structure and function that is observed in all organisms. All are made up of cells, and similar chemical compounds are present. This indicates that all
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BIOLOGY PRACTICAL ACTIVITIES Comparison of Vertebrate Limbs Limbs of various vertebrates are provided: e.g. fish- Tilapia, amphibian-frog reptiles, lizard; bird – domestic fowl (chicken), mammal- rabbit. Their anatomy can be studied. The following can be noted: That all limbs have five sets of bones; A single upper bone- the femur in hind limb and the
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Height of students Students should work in pairs, use chalk and metre rule to mark level of top of head onto the wall. Or door as one student stands straight without shoes, next to the wall or door. The height for each student is recorded on chalk board. The frequency distribution of height is recording
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This is a technology that involves the manipulation of the genotype of an organism to get the desired trait. It also involves the transfer of gene coding for the desired trait from one organism to another. Application of Genetic Engineering Pharmaceutical industries: Making of hormones e.g. Human insulin and human growth hormone. Enzymes e.g. Alph-Anti-Trypsin
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Study of genetics has been put into a wide variety of uses encompassing plants and animals and in particular humans. Blood transfusion. Blood groups are genetically determined. As discussed earlier a person of blood group A can only get blood from another one of A or O. In case of emergencies and unavailability of blood,
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What is mutations? Mutations are sudden changes in the genotype that are inherited. Mutations are rare in nature and mutated genes are usually recessive to the normal (wild type) genes. Most mutations are generally harmful and some are lethal. A somatic mutation is a genetic change in somatic cells. Somatic mutations are only inherited if
LINKAGE.
The term linkage describes the situation where genes or certain characters are located on the same chromosome.
Offspring produced by sexual reproduction show only the parental characteristics and only sometimes few new recombinants.
e. offspring with combinations of characteristics not found in either of the parents due to crossing over in first prophase of meiosis.
Genes are said to be linked when they are located close together on the same chromosome such that they are always inherited together.
Complete Dominance Mendel happened to choose characters that showed complete dominance, the dominant trait completely masked the recessive one in the F1 generation. In man, certain characters are inherited in the same way e.g. colour of the skin; normal colour is dominant to albinism (lack of skin pigment). The children are all normal but have
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What is structure of DNA? The structure of DNA was first explained in 1953 by Watson and Crick. DNA was shown to be a double helix that coils around itself. The two strands are parallel and the distance between the two is constant. Components of DNA What are the components of DNA? DNA is made
What are chromosomes? These are thread-like structures found in the nucleus. They are normally very thin and coiled and are not easily visible unless the cell is dividing. When a cell is about to divide, the chromosomes uncoil and thicken. Their structure, number and behaviour is clearly observed during the process of cell division. The
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What is genetics? Genetics is the study of inheritance. The fact that the offspring of any species resemble the parents indicates that the characters in the parents are passed on to the offspring. Factors that determine characters (genes) are passed on from parent to offspring through gametes or sex cells. In fertilization the nucleus of
In higher animals, most cells with the exception of the nerve cells retain their power of division. Thus, there is a continued breakdown and replacement of cells. Animal cells undergo rapid cell division and cell differentiation but, unlike plant cells, they undergo very little cell enlargement. In most animals growth occurs throughout their life till
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What is plant hornmones? Plant hormones are chemicals produced in very small amounts within the plant body, and play a very important part in regulating plant growth and development. Most growth hormones are produced at the tip of a shoot and transported downwards to the root. The root tip produces very small quantities of the
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The region of growth in plants is found in localized areas called meristems. A meristem is a group of undifferentiated cells in plants which are capable of continuous mitotic cell division. The main meristems in flowering plants are found at the tips of shoots and roots, in young leaves, at the bases of the inter-nodes. Zone
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SEED GERMINATION: DEFINITION, TYPES, FACTORS & PROCESS What are the types of germination? The nature of germination varies in different seeds. During germination the cotyledons may be brought above the soil surface. This type of germination is called epigeal germination. If during germination the cotyledons remain underground the type of germination is known as hypogeal.
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What are the conditions necessary for seed germination? Seeds can easily be destroyed by unfavourable conditions such as excessive heat, cold or animals. Seeds need certain conditions to germinate and grow. Some of these conditions are external, for example water, oxygen and suitable temperature while others are internal such as enzymes, hormones and viability of
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What is the seed structure? A typical seed structure consists of a seed coat enclosing an embryo. The seed coat is the outer covering which, in most seeds, is made up of the two layers, an outer testa and inner one, the legmen. The testa is thick; the tegmen is a transparent membrane tissue. The
Requirements Small plots/boxes, meter rule and seeds of beans (or green grams, peas, maize), Procedure Place some soil in the box or prepare a small plot outside the laboratory. Plant some seeds in the box and place it in a suitable place outside the laboratory (or plant the seeds in your plot). Water the seeds
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Concept of Growth and Development Growth is a characteristic feature of all living organisms. Most multicellular organisms start life as a single cell and gradually grow into complex organisms with many cells. This involves multiplication of cells through the process of cell division. This quantitative permanent increase in size of an organism is referred to
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