Biology

GENETIC: HEREDITARY, TERMINOLOGY, MENDEL’S WORK, GENOTYPE & PRINCIPLES OF HEREDITARY

Biology, SS 3 Biology (1st, 2nd & 3rd Term)

GENETIC TERMINOLOGY Genetics, the scientific study of heredity and variation in all living organisms, was termed by Dilliam Bateson in 1906. Heredity/Inheritance pertains to the passage and manifestation of traits from parents to offspring, accounting for the common resemblances between them. Variation encompasses the dissimilarities existing among parents, offspring, and siblings. Genes are hereditary units […]

GENETIC: HEREDITARY, TERMINOLOGY, MENDEL’S WORK, GENOTYPE & PRINCIPLES OF HEREDITARY Read More »

MALE AND FEMALE REPRODUCTIVE STRUCTURES

SS 2 Biology (1st, 2nd & 3rd Term), Biology

REPRODUCTIVE SYSTEM Most multicellular animals and plants undergo a complex form of sexual reproduction in which especially differentiated male and female reproductive cells (gametes) unite to form a single cell, known as a zygote, which later undergoes successive divisions to form a new organism. The process takes place with the help of the system known

MALE AND FEMALE REPRODUCTIVE STRUCTURES Read More »

POLLINATION

SS 2 Biology (1st, 2nd & 3rd Term), Biology

This is the transfer of mature pollen grains from the anther of one flower to the mature stigma of the same or another flower of the same plant or another plant of closely related species. Pollination usually precedes fertilization. There are two types of pollination namely, self-pollination and cross-pollination. SELF POLLINATION This is the transfer

POLLINATION Read More »

CIRCULATORY SYSTEM | CLOTTING, VESSELS, ARTERY, VEIN, HEART & ORGANS

SS 2 Biology (1st, 2nd & 3rd Term), Biology

PROTECTIVE FUNCTION OF BLOOD The blood performs two basic functions in mammals and these are: (1) Transportation of various substances and (2) Protection of the body against diseases The blood defends the body in major ways Antibody production (Clumping): The lymphocytes produce antibodies which are any of a large variety of proteins normally present in

CIRCULATORY SYSTEM | CLOTTING, VESSELS, ARTERY, VEIN, HEART & ORGANS Read More »

DIGESTIVE SYSTEM | HYDRA, EARTHWORM, INSECTS, BIRD, MAN

SS 2 Biology (1st, 2nd & 3rd Term), Biology

INVERTEBRATES Feeding in Hydra Digestion in Planaria Digestion in Earthworms Digestion in insects (Grasshopper) VERTEBRATES Digestion in Birds Digestion in Rabbits FEEDING IN HYDRA Hydra feeds on small aquatic organisms e.g. crustaceans. It captures its food through its structure called nematocysts found on its tentacles. The food is then passed into the mouth while the

DIGESTIVE SYSTEM | HYDRA, EARTHWORM, INSECTS, BIRD, MAN Read More »

CHROMOSOMES – STRUCTURE, FUNCTIONS AND PROPERTIES

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

CHROMOSOMES – STRUCTURE, FUNCTIONS AND PROPERTIES Read More »

SEED GERMINATION: DEFINITION, TYPES, FACTORS

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.

SEED GERMINATION: DEFINITION, TYPES, FACTORS Read More »

PRIMARY AND SECONDARY GROWTH

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

PRIMARY AND SECONDARY GROWTH Read More »

PLANT GROWTH & HORMONES

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

PLANT GROWTH & HORMONES Read More »

Animal Growth and Development

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

Animal Growth and Development Read More »

GENETICS

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

GENETICS Read More »

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 the same species. This

VARIATION IN POPULATION Read More »

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 DNA? DNA is made

STRUCTURE OF DNA Read More »

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 all normal but have

COMPLETE AND INCOMPLETE DOMINANCE Read More »

LINKAGE

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.

LINKAGE Read More »

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 if

MUTATIONS Read More »

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 e.g. Alph-Anti-Trypsin

GENETIC ENGINEERING Read More »

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 fossil is an impression

THEORIES OF EVOLUTION Read More »

BIOLOGY PRACTICAL ACTIVITIES

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 power objective are made. A plan

BIOLOGY PRACTICAL ACTIVITIES Read More »

BIOLOGY PRACTICAL ACTIVITIES

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

BIOLOGY PRACTICAL ACTIVITIES Read More »