Life Science is the branch of science that deals with the study of living organisms and their interactions with one another and with their environment. This unit helps the teacher trainee understand the basic characteristics of living things, the structure and function of cells, the major systems in the human body, plant structures, and common diseases affecting humans. Knowledge gained from this unit is essential for teaching science at the Primary and Junior High School levels and for answering application-based questions in the Ghana Teacher Licensure Examination.

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MODULE 2.1: LIVING AND NON-LIVING THINGS

Introduction

All objects around us can be classified as either living or non-living. Living things possess certain characteristics that distinguish them from non-living things. These characteristics are commonly summarized using the acronym MRS GREN.

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Characteristics of Living Things (MRS GREN)

Living things share seven basic characteristics:

1. Movement (M)

Movement refers to the ability of living things to change position or move parts of their body. Animals move from one place to another, while plants show movement through growth responses such as bending towards light (phototropism).

2. Respiration (R)

Respiration is the process by which living organisms release energy from food. This energy is needed for growth, movement, repair, and other life processes. Respiration may be aerobic (using oxygen) or anaerobic (without oxygen).

3. Sensitivity or Response (S)

Sensitivity is the ability of living organisms to respond to stimuli in their environment. For example, humans feel pain when injured, and plants respond to touch or light.

4. Growth (G)

Growth is a permanent increase in size, mass, or number of cells. Living things grow through cell division and cell enlargement. Non-living things may increase in size, but this is not growth; it is only an increase by addition.

5. Reproduction (R)

Reproduction is the ability of living organisms to produce new individuals of the same kind. This ensures the continuity of life. Reproduction may be sexual or asexual.

6. Excretion (E)

Excretion is the removal of metabolic waste products such as carbon dioxide, urea, and excess water from the body. Accumulation of waste can be harmful to living organisms.

7. Nutrition (N)

Nutrition is the process by which living organisms obtain and use food for energy, growth, and repair. Plants manufacture their own food through photosynthesis, while animals obtain food by feeding on plants or other animals.

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Differences Between Living and Non-Living Things

Living Things	Non-Living Things
Show all characteristics of MRS GREN	Do not show MRS GREN
Grow from within	Do not grow naturally
Reproduce	Cannot reproduce
Respire	Do not respire
Respond to stimuli	Do not respond

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Learning Outcomes Achieved

At the end of this module, the learner should be able to:

• Identify the characteristics of living things

• Clearly differentiate between living and non-living things

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MODULE 2.2: CELL STRUCTURE AND FUNCTION

Definition of a Cell

A cell is the smallest structural and functional unit of a living organism. All living things are made up of one or more cells. Some organisms are unicellular (made of one cell), while others are multicellular (made of many cells).

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Types of Cells

There are two main types of cells commonly studied:

• Plant cells

• Animal cells

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Structure of Plant and Animal Cells

Similarities

Both plant and animal cells have:

• Cell membrane

• Cytoplasm

• Nucleus

• Mitochondria

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Cell Organelles and Their Functions

1. Cell Membrane

The cell membrane surrounds the cell and controls what enters and leaves the cell. It protects the cell and maintains its shape.

2. Cytoplasm

The cytoplasm is a jelly-like substance that contains all the cell organelles. It is the site of most chemical reactions in the cell.

3. Nucleus

The nucleus controls all activities of the cell. It contains genetic material that determines the characteristics of the organism.

4. Mitochondria

Mitochondria are the sites of respiration. They release energy required for life activities and are often referred to as the “powerhouse” of the cell.

5. Cell Wall (Plant Cell Only)

The cell wall provides support and protection to the plant cell. It gives the cell a definite shape.

6. Chloroplast (Plant Cell Only)

Chloroplasts contain chlorophyll and are the site of photosynthesis.

7. Vacuole

The vacuole stores food, water, and waste materials. In plant cells, it also helps maintain turgidity.

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GTLE Examination Focus

• Labeling diagrams of plant and animal cells

• Identifying functions of organelles

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MODULE 2.3: HUMAN ORGAN SYSTEMS

Introduction

An organ system is a group of organs that work together to perform a specific function in the body. The human body has several organ systems that ensure survival.

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1. Digestive System

The digestive system breaks down food into simpler substances that can be absorbed and used by the body.

Main organs: Mouth, oesophagus, stomach, small intestine, large intestine

Functions:

• Digestion of food

• Absorption of nutrients

• Elimination of undigested food

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2. Respiratory System

The respiratory system enables breathing and gaseous exchange.

Main organs: Nose, trachea, lungs

Functions:

• Intake of oxygen

• Removal of carbon dioxide

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3. Circulatory System

The circulatory system transports substances around the body.

Main organs: Heart, blood, blood vessels

Functions:

• Transport oxygen and nutrients

• Remove waste products

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4. Excretory System

The excretory system removes metabolic waste products from the body.

Main organs: Kidneys, lungs, skin

Functions:

• Removal of urea, water, and salts

• Regulation of body fluids

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5. Reproductive System

The reproductive system enables humans to produce offspring.

Functions:

• Production of sex cells

• Continuity of the human species

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MODULE 2.4: PLANT STRUCTURE AND FUNCTIONS

Roots

Roots anchor the plant in the soil and absorb water and mineral salts.

Stems

Stems support the plant and transport water and food between roots and leaves.

Leaves

Leaves manufacture food through photosynthesis and allow gaseous exchange.

Flowers and Fruits

Flowers are reproductive organs of plants, while fruits protect seeds and aid in seed dispersal.

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MODULE 2.5: DISEASES AND HEALTH

Communicable Diseases

These are diseases that can be transmitted from one person to another.

Examples: Malaria, Cholera, Tuberculosis

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Non-Communicable Diseases

These are diseases that cannot be transmitted.

Examples: Diabetes, Hypertension

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Modes of Transmission

• Air

• Water

• Vectors (mosquitoes)

• Direct contact

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Prevention and Control

• Good sanitation

• Immunization

• Use of insecticide-treated nets

• Safe drinking water

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GTLE Focus

• Identifying diseases and their modes of transmission

• Preventive health measures

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