BIOLOGY – SS2

OBJECTIVES: At the end of the lesson students should be able to:

1. list five sense organs highlighting their respective locations.
2. describe the organ of smell and taste.
3. identify the different parts of the tongue associated with sweetness, bitterness, salty taste and sour taste.
4. draw the skin showing the different receptors present.
5. state two ways to care for the skin.

SENSE ORGANS

A sense organ is a group of specialized cells or tissues and receptors which are able to receive or collect perceive and detect stimulus and transmit the information; and message to the central nervous system. The human body has five sense organs they are all found in a person, each function in perceiving various sensation they includes;

• Eye for vision
• Ear for hearing and balance
• Nose for smelling
• Tongue for tasting
• Skin to receive sensation of temperature, pain touch and pressure (feelings)

In each sense organ, sensory nerve endings are close to the body surface they receive and relay those to the brain or spinal cord

THE SKIN AS A SENSE ORGAN

The skin is the toughest in the body apart from the bones.

OBJECTIVES: At the end of the lesson students should be able to:

• describe the development of the toad
• describe the life history of a cockroach
• describe the life history of a housefly
• state three adaptive features in a developing animal
• state three functions of the placenta and three functions of the umbilical cord to the foetus.

DEVELOPMENT OF NEW ORGANISMS

During reproduction, the sperm fuses with the ovum to form zygote. The zygotes then develop into a new individual.

In multi-cellular organisms, the development involves division, differentiation and organization of cell to form tissue, organs and system.

DEVELOPMENT OF THE TOAD

During the life cycle of an organism, there  is a rapid and major change in the appearance of the organism’s body, this is  called METAMORPHOSIS. There are two types of metamorphosis namely complete metamorphosis e g. butterflies, bees, ants, mosquito, houseflies and tsetse flies, in-complete metamorphosis e.g bugs, locusts, termites, cockroaches and grasshoppers.

At the beginning of the rainy season, adult female toads are swollen with eggs and gather in large numbers.

OBJECTIVES: At the end of the lesson students should be able to:

• give the meaning of pollination.
• state two types of pollination.
• explain the two types of pollination.
• mention five agents of pollination.
• outline the features of a cross pollinated flowers.
• state two advantages and two disadvantages of self-pollination.
• mention five features of a wind pollinated flower.
• highlight five features of an insect pollinated flower.

POLLINATION IN PLANTS

Pollination is the process by which mature pollen grains are transferred from a mature stigma of a flower.

It may be to the same flower or another flower of the same or related species. Pollination is the first phase in sexual reproduction of flowering plants.

TYPES OF POLLINATION

1. Self pollination
2. Cross pollination
3. SELF POLLINATION: Is the process in which mature pollen grains are transferred from the anther of a flower to the stigma of the same flower or a flower on the same plant.
4. CROSS POLLINATION: Is the transferred of mature pollen grain from the anther to the stigma of another flower of the same or closely related species e g.