HUMAN EYE – STRUCTURE, FUNCTIONS AND PARTS Structure The human eye is spherical in shape and situated within a socket or orbit in the skull. It is attached to the skull by three pairs of muscle, which also control its movement. It is made up of three main layers; sclerotic layer, choroid and the light […]
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DRUGS ABUSE – EFFECTS ON THE HUMAN HEALTH Drug abuse can be defined as misuse of drugs. Drugs are chemical compounds that affect the working of body or kill disease causing microorganisms. Prescription drugs There are drugs prescribed by a doctor. Prescribed drugs can be abused through taking overdose which may cause death. Over the
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ENDOCRINE SYSTEM – ROLES IN HUMAN BEINGS WHAT IS ENDOCRINE? Endocrine system consists of glands that secrete hormones. The glands have no ducts and are known as endocrine glands. Other glands are known as exocrine glands because they have ducts. The pancreas has an outer exocrine portion and an inner endocrine portion. Hormones are
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SPINAL CORD – SIMPLE AND CONDITIONED REFLEX ACTIONS The spinal cord is located within the vertebral column and consist of the following: The grey matter forms the central part of the spinal cord. It consists of nerve¬cell bodies and intermediate nerve fibres. The white matter of the spinal cord carries sensory nerve fibers while
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HUMAN BRAIN – FUNCTIONS AND MAJOR PARTS OF THE HUMAN BARIN The Central Nervous System (CNS) consists of the brain and the spinal cord. The CNS co-ordinates body activities by receiving impulses from sensory cells from different parts of the body. It then sends the impulses to the appropriate effectors. The brain is enclosed
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What is the nervous system? The nervous system is a complex network of nerves and cells that carry messages to and from the brain and spinal cord to various parts of the body
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ANIMALS – RECEPTION, RESPONSES AND CO¬ORDINATION The nervous and endocrine systems (together known as the neuro-endocrine system) act as a co-coordinating system. They linking the receptors to the effectors and regulating their activities. Receptors Receptors are cells that detect or receive stimuli. They may be scattered more uniformly all over the body surface e.g.
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PLANTS – RECEPTION, RESPONSE AND CO-ORDINATION Introduction The structures involved in detecting the changes may be located far away from the ones that respond. There is need for a communication system within the body. The nervous system and the endocrine system perform this function, i.e. linking the parts of the body that detect changes
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PRODUCTION OF AUXINS AND THEIR EFFECTS ON PLANT GROWTH 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
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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
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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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GENETIC ENGINEERING 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
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PRACTICAL APPLICATIONS OF GENETICS 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
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MUTATIONS 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
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 AND INCOMPLETE DOMINANCE 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
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STRUCTURE OF DNA 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
STRUCTURE. FUNCTIONS AND PROPERTIES OF CHROMOSOMES 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
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GENETICS Introduction 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