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 at a point called centromere. Each human somatic cell […]
SS 3 Biology (2nd Term)
Genetics is the scientific study of heredity and variation in all living things. The word genetics was coined by Dilliam Bateson (1906
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 fossil is an
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 by predators Colour blendingwith the environment
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 of the unfit.
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
STRUCTURE OF 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. Such fruits are called parthenocarpic fruits e.g. banana and pineapple. Such fruits are seedless. A typical fruit has the following parts