CHROMOSOME: THE BASIS OF HEREDITARY – FULL EXPLANATION LOCATION AND STRUCTURE OF CHROMOSOMES Chromatin granules (thread – like structures) found in the nucleus of eucaryotic cells are the precursors or raw materials of chromosomes. Chromosomes occur in pairs known as homologous chromosomes. Each chromosome is made up of two threads called chromatids joined […]
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SEX-LINKED TRAITS Sex–linked traits are characteristics whose genes are carried on the X chromosome of the sex chromosomes instead of autosomes. Such genes are inherited along with such X chromosomes. They are all controlled by a recessive gene. Examples of Sex-linked traits are: colour blindness, haemophilia, baldness, sickle cell anaemia and albinism. Colour blindness: A
DIHYBRID INHERITANCE Gregor Mendel crossed plants which differ in two pairs of contrasting characteristics e.g. seed shape (round or wrinkled seeds) and seed colour (yellow or green seeds). He crossed plants having round and yellow seeds with these having wrinkled and green seeds. The F1 seeds were having round and yellow seeds. Self-pollinating F1 plants
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DETERMINATION OF THE GENOTYPE OF A DOMINANT PHENOTYPE A dominant phenotype has the genotypic patterns RR, Rr. The genotype is determined using test cross or back cross Test cross is the crossing of an organisms with an homologous recessive organism Back cross is the crossing of an organism with an homologous recessive organism from the
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BIOLOGY OF HEREDITARY AND VARIATION (GENETICS) DEFINITIONS OF GENETIC TERMS What is Genetics? Genetics is the scientific study of heredity and variation in all living things. The word genetics was coined by Dilliam Bateson (1906). What is hereditary?: Hereditary/Inheritance is the transmission and expression of characters or traits from parents to offspring. It accounts for
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HEREDITARY VARIATION AND CAUSES What is Hereditary? Hereditary variation is the differences among individuals which can be passed from the parents to their offspring (progenies). NOTE: No two offspring inherit exactly the same set of characteristics from parents except in identical twins. Hereditary variation arises because of Genetic reshuffling during meiosis due to independent assortment
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MENDELS WORK IN GENETICS In the study of genetics, Gregor Mendel (1866) worked with the garden pea. (Pisumsativum) because of three unique properties present in it. These are Peas are self-pollinating They have a very short lifespan They have several unique genetic characteristics e.g. round or wrinkled seeds, tallness or shortness, seeds /pods/ flowers colouration,
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SOCIAL ANIMALS – MEANING, CHARACTERISTICS, IMPORTANCE & LIFE HISTORY Social animals are those in which individuals of the same species live together cooperatively in organized communities known as societies (colonies). Examples of social animals are: social insects (like termites, honey bees or wasps, ants etc), wolves, foxes, baboons etc. Characteristics of Social Insects
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THEORIES OF EVOLUTION ORGANIC EVOLUTION Organic evolution is the sum total of adaptive changes from pre–existing or old forms that has taken place over a long time resulting in diversity of forms, structures and functions among organism. The basis of evolution is that all organisms have pre–existing ancestors. Evidences of evolution Fossil record: A
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VARIATION IN POPULATION Population is a group of organisms of the same specie living in a specified area within a given period of time. Variation refers to the differences which exist between individuals of the same species Types of variations Morphological variation Physiological variation. Morphological variation is the noticeable physical appearance of individuals of
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ADAPTIVE COLOURATION AND BEHAVIOURAL ADAPTATION ADAPTIVE COLOURATION This is the possession by an organism of a colour which enables it to catch its prey, avoid its predators or enemies, secure mates and ensure their survival. Adaptive colouration may be grouped into Concealing (cryptic) colouration to help organisms blend with their background and remain unnoticed
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ADAPTATION FOR SURVIVAL COMPETITION Competition is the process by which living organisms in the habitat struggle with one another for limited essential needs in the environment. Such scarce resources in plants include; light, space, nutrient and water while animals complete for food, space or mate. Competition finally results in survival of the fittest and elimination
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What is a fruit? A fruit is a matured fertilized ovary of a flower containing one or more seeds. Contrary to this, some plants do not undergo fertilization for the formation of their fruit.
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BIOLOGY PRACTICAL ACTIVITIES – WELL EXPLAINED To observe prepared slides of transverse section of stems of herbaceous and woody plants. Permanent slides of transverse sections of: Herbaceous plant and Woody plant are obtained. The permanent slide of an herbaceous plant is placed onto the stage of the microscope. Observations under the low power and medium
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JOINTS AND MOVEMENT What is a joint? A joint is a connection between two or more bones. Joints provide articulation between bones making movement possible.. However some joints do not allow any movement e.g. the joints, between bones of the skull. Movable joints are of three main types: Gliding joint g., joints which occur
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There are three types of muscles, located at various parts of the body. In order to function all use energy in form of ATP. These include smooth, skeletal and cardiac muscles.
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The mammalian skeleton is divided into two:
Axial and appendicular.
Axial skeleton is made up of the skull and the vertebral column.
Appendicular skeleton is made up of the pelvic and pectoral girdles and limbs (hind limb and forelimbs).
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SUPPORT AND MOVEMENT IN PLANTS Necessity for support and movement Movement is a characteristic of all living organisms. It enables animals and plants to adjust to their environment. Most animals move from place to place but some are sessile (i.e. fixed to the substratum). Majority of plants move only certain parts. However, though not easily
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SUPPORT AND MOVEMENT IN ANIMALS Necessity for support and movement in animals. Animals move from place to place: In search of food. To escape from predators. To escape from hostile environment. To look for mates and breeding grounds. The skeleton, which is a support structure, helps to maintain the shape of the body. Movement is
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HUMAN EAR – STRUCTURE, FUNCTIONS AND PARTS The Mammalian Ear The mammalian ear performs two major functions: Hearing and detecting changes in the positions of the body to bring about balance and posture. The ear is divided into three sections. The Outer Ear This consists of: An outer flap, the pinna which is made up
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