Biology Lesson Notes For JSS1 – SS3

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 […]

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

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

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

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,

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

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 impression

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 the same species. This

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 blending with the

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.