Lesson Notes By Weeks and Term v3 - Senior Secondary 1
Micro-organisms around us
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Micro-organisms around us
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Subject: Biology
Class: Senior Secondary 1
Term: 3rd Term
Week: 2
Theme: The Organism And Its Environment
This page supports the lesson note with a companion video and a short classroom-ready summary.
For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.
Identify some micro-or ganisms present in airand water. State the characteristics(colour, pattern of growth,appearance) of colonies of microorganisms. Identify microorganismsthat can be found on and inside human bodies e.g.under the fingernail,mouth cavity and expiredair. Describe the effects(beneficial and harmful) of microorganisms on humanbody
and fibres that human enzymes cannot digest, thereby enhancing nutrient absorption. They also synthesize essential vitamins like Vitamin K and B vitamins (e.g., E. coli in the large intestine).
Immune System Development: Exposure to a diverse range of microorganisms, especially in early life, helps to "train" the immune system, making it more robust and less prone to allergies and autoimmune diseases.
Protection Against Pathogens: The normal flora (beneficial microbes) compete with harmful pathogens for space and nutrients, preventing the colonization and growth of disease-causing microbes.
Food Production: Many traditional Nigerian fermented foods rely on beneficial microorganisms.
Examples include: Garri: Fermentation of cassava by lactic acid bacteria and yeasts.
Ogi (pap): Fermentation of maize, sorghum, or millet. Iru (fermented locust beans) and ogiri (fermented melon seeds): These use bacteria and fungi to break down proteins, enhancing flavour and nutrient availability.
Fura da nono: Fermented milk product involving lactic acid bacteria.
Harmful Effects (Pathogens): Diseases (Infections): Pathogenic microorganisms cause a wide range of infectious diseases.
Bacteria: Typhoid fever (Salmonella typhi), cholera (Vibrio cholerae), tuberculosis (Mycobacterium tuberculosis), whooping cough (Bordetella pertussis), bacterial meningitis.
Viruses: Measles, chickenpox, HIV/AIDS, Lassa fever, yellow fever, common cold, influenza.
Protozoa: Malaria (Plasmodium species), amoebiasis (Entamoeba histolytica), giardiasis (Giardia lamblia).
Fungi: Ringworm, athlete's foot, candidiasis (thrush).
Food Spoilage: Microorganisms cause food to rot, ferment undesirably, or become toxic. Examples include mould growth on bread (Rhizopus stolonifer), souring of milk, and spoilage of cooked foods left unrefrigerated. This is a significant economic loss in Nigeria.
Toxin Production: Some bacteria (e.g., Clostridium botulinum, Staphylococcus aureus) produce potent toxins that can cause severe illness or death even if the bacteria themselves are no longer present in the food. 2.
1. Definition of Microorganisms Microorganisms, often simply called microbes, are minute living organisms that are too small to be seen individually with the naked eye. Their observation typically requires a microscope. They include a diverse group of organisms such as bacteria, fungi (e.g., yeasts, moulds), viruses, protozoa, and microscopic algae. 2.
2. Habitats of Microorganisms Microorganisms are ubiquitous, meaning they are found almost everywhere.
In Air: Microbes are not airborne themselves but are typically carried on dust particles, water droplets (from sneezes/coughs), pollen, and fungal spores. For example, mould spores are abundant in the air, leading to mould growth on forgotten bread or clothes in humid environments in Nigeria. Similarly, bacteria and viruses responsible for respiratory infections (e.g., common cold, tuberculosis) can be found in expelled air droplets.
In Water: Water bodies are teeming with microorganisms. This includes fresh water (rivers, streams, boreholes, tap water, stagnant puddles) and salt water (oceans). Some are harmless (e.g., photosynthetic algae), while others are pathogenic, causing waterborne diseases. For instance, consuming contaminated water (common in areas with poor sanitation in Nigeria) can lead to infections by bacteria like Vibrio cholerae (causing cholera) or protozoa like Entamoeba histolytica (causing amoebiasis).
On and Inside Human Bodies: The human body is a complex ecosystem for many microorganisms, collectively known as the microbiome or normal flora.
Skin: The surface of the skin, especially moist areas like armpits and groin, harbours various bacteria and fungi.
Under Fingernails: This area is a common trapping point for dirt, food particles, and a multitude of microorganisms from various sources, making it a significant site for pathogen transmission if not cleaned regularly.
Mouth Cavity: The mouth is rich in bacteria, yeasts, and protozoa due to its warm, moist environment and constant supply of food debris. These microorganisms contribute to dental plaque formation and, if unchecked, tooth decay.
Expired Air: When humans breathe out, they expel microscopic droplets of moisture, saliva, and mucus that contain microorganisms (bacteria, viruses) from the respiratory tract. This is a primary mode of transmission for airborne diseases.
Intestinal Tract: The gut contains a vast and diverse community of bacteria and other microbes that play crucial roles in digestion, vitamin synthesis (e.g., Vitamin K), and immune system development. For example, Escherichia coli (E. coli) is a common bacterium found in the human gut. 2.
3. Characteristics of Microbial Colonies When microorganisms are cultured on a solid nutrient medium (like agar in a Petri dish), individual cells multiply to form visible masses called colonies. Observing these characteristics helps in initial identification and differentiation.
Colour: Colonies can display a range of colours, including white, cream, yellow, orange, pink, red, green, or even black, depending on the pigment produced by the microorganism. For example, Staphylococcus aureus often forms golden-yellow colonies.
Pattern of Growth/Shape: The overall form of the colony can vary.
Common shapes include: Circular: Round, smooth edges.
Irregular: Asymmetrical, non-uniform shape.
Punctiform: Very small, pinpoint colonies.
Rhizoid: Root-like, spreading extensions.
Filamentous: Thread-like, often seen with fungi or some bacteria.
Appearance/Texture: This refers to the surface and consistency of the colony: Smooth/Rough: Referring to the surface texture.
Shiny/Dull (Matte): Indicating reflectivity.
Mucoid: Slimy or gummy appearance, often due to capsule production.
Dry/Butyrous: Dry and brittle, or butter-like consistency.
Raised/Flat/Umbilicate: Describing the elevation of the colony from the agar surface. 2.
4. Effects of Microorganisms on Human Body Microorganisms have both beneficial and harmful effects on human health and well-being.
Beneficial Effects: Digestion and Nutrient Absorption: Gut bacteria aid in breaking down complex carbohydrates and fibres that human enzymes cannot digest, thereby enhancing nutrient absorption. They also synthesize essential vitamins like Vitamin K and B vitamins (e.g., E. coli in the large intestine).
Immune System Development: Exposure to a diverse range of microorganisms, especially in early life, helps to "train" the immune system, making it more robust and less prone to allergies and autoimmune diseases.
Protection Against Pathogens: The normal flora (beneficial microbes) compete with harmful pathogens for space and nutrients, preventing the colonization and growth of disease-causing microbes.
Food Production: Many traditional 3.
1. Engagement/Introduction (10 minutes)
Teacher Activity: Begin by asking students what they understand by "living things." Guide them to recall organisms they can see (plants, animals). Then, pose a question: "Are there living things that are so tiny we cannot see them with our eyes, but they can still affect us?" Facilitate a brief brainstorming session on common experiences related to unseen agents (e.g., getting sick, food spoiling, 'fever').
Student Activity: Students share their ideas and experiences, contributing to the brainstorming session. 3.
2. Activity 1: Where Microorganisms Live (20 minutes)
Teacher Activity: Introduce the concept of microorganisms as "invisible inhabitants." Guide a class discussion on potential habitats: ask students where they think these "invisible things" could be. Prompt with questions like "What happens if you leave food open for too long?", "What makes stagnant water smell?", "Why do doctors ask us to wash our hands?" Categorize student responses into "Air," "Water," and "Human Body." Present visual aids (pictures or short video clips, if available) showing dust particles under a microscope, pond water teeming with microbes, or diagrams of bacteria on skin. Explain how microbes are carried in air (dust, droplets) and found in various water sources (drinking water, stagnant water).
Student Activity: Students actively participate in the discussion, suggesting places where they believe microbes might be found. They take notes on key habitats of microorganisms. 3.
3. Activity 2: Observing Microbial Colonies (Practical/Simulation) (30 minutes)
Teacher Activity: Option A (Practical - if resources available): Prior to the lesson, the teacher should prepare agar plates (e.g., nutrient agar or potato dextrose agar) and demonstrate a simple swab technique.
Examples: Swab a dusty surface, a finger, or expose a plate to air for 10-15 minutes. Incubate at room temperature for 2-3 days. On the day of the lesson, bring the incubated plates. Guide students to observe the various "spots" or "patches" growing on the agar. Explain that each spot originated from a single microorganism and is called a "colony." Direct students to look closely at different colonies and describe what they see in terms of: Colour: (e.g., white, yellow, off-white, black, green)
Shape/Pattern of growth: (e.g., circular, irregular, spreading, pinpoint)
Appearance/Texture: (e.g., shiny, dull, smooth, rough, slimy/mucoid)
Option B (Simulation - no lab resources): Display large diagrams or projected images of different types of microbial colonies (e.g., E. coli, Staphylococcus, Rhizopus mould). Describe the characteristics of each type using the terms (colour, shape, texture).
Student Activity: Option A: Observe the incubated agar plates, sketching different colonies and noting their characteristics. Engage in discussions about the observed differences.
Option B: Study the diagrams/images, listening attentively to the teacher's descriptions of colony characteristics. Ask questions for clarification. 3.
4. Activity 3: Microbes on and in the Human Body (20 minutes)
Teacher Activity: Elaborate on specific locations on and inside the human body where microorganisms are found (fingernails, mouth, expired air, skin, gut). Use the context of local hygiene practices: "Why is it important to trim nails?", "Why brush teeth?", "Why cover mouth when coughing/sneezing?" Explain the concept of "normal flora" – beneficial microbes that naturally live on/in us without causing harm.
Student Activity: Students identify and discuss these specific locations. They relate the presence of microbes to personal hygiene habits and public health. 3.
5. Activity 4: Effects of Microorganisms (30 minutes)
Teacher Activity: Divide students into small groups. Assign each group either "Beneficial Effects" or "Harmful Effects" of microorganisms.
Provide guiding questions: Beneficial: "How are microbes useful in making Nigerian foods?", "How do microbes help our bodies?" Harmful: "What diseases do microbes cause?", "How do microbes spoil food?" Facilitate a class discussion after group work, consolidating information and providing examples relevant to Nigerian context (e.g., garri fermentation, fufu preparation, malaria, typhoid, food spoilage).
Student Activity: In groups, students brainstorm and list examples for their assigned category. Groups present their findings, and other groups contribute to the discussion. Students take comprehensive notes on both beneficial and harmful effects.
Question 1: List three common places in the immediate environment where microorganisms can be found.
Solution: Air: Carried on dust particles, pollen, or water droplets.
Water: In ponds, rivers, stagnant puddles, and even tap water (though treated, some persist).
Soil: Abundantly present, playing roles in nutrient cycling. (Also acceptable: Food, on surfaces, on plants/animals.)
Commentary: This question assesses the students' understanding of the pervasive nature of microorganisms and their ability to identify common habitats as per Performance Objective
1. Question 2: Imagine you observed two different microbial colonies on an agar plate. Colony A was white, circular, and smooth, while Colony B was yellow, irregular, and rough. Describe two distinct characteristics for each colony that differentiate them.
Solution: Colony A: Colour: White Pattern of growth/Shape: Circular Appearance/Texture: Smooth Colony B: Colour: Yellow Pattern of growth/Shape: Irregular Appearance/Texture: Rough
Commentary: This question directly targets Performance Objective 2, requiring students to state specific observable characteristics of microbial colonies. The example uses contrasting features to emphasize differentiation.
Question 3: Give two examples of microorganisms that can be found inside the human body and state their common location.
Solution: Bacteria (e.g., Escherichia coli): Commonly found in the large intestine/gut. Bacteria/Fungi (e.g., various species of Streptococcus, Candida yeast): Commonly found in the mouth cavity. (Also acceptable: Bacteria on skin, under fingernails, viruses in respiratory tract via expired air.)
Commentary: This question addresses Performance Objective 3, focusing on the presence of microorganisms within the human body. It requires students to recall specific locations and types of microbes.
Question 4: Differentiate between a beneficial and a harmful effect of microorganisms on humans, providing one Nigerian example for each.
Solution: Beneficial Effect: Microorganisms aid in the fermentation of local food products, improving their flavour, preservation, and nutritional value. Nigerian
Example: Lactic acid bacteria and yeasts are used in the fermentation of cassava to produce garri, transforming it into a digestible staple food.
Harmful Effect: Pathogenic microorganisms cause infectious diseases that can lead to illness or death in humans. Nigerian
Example: The bacterium Vibrio cholerae causes cholera, a severe diarrheal disease prevalent in areas with poor sanitation and contaminated water supplies. (Other beneficial examples: Digestion of food in gut, vitamin synthesis.
Other harmful examples: Malaria, typhoid, food spoilage.)
Commentary: This question evaluates Performance Objective 4, requiring students to distinguish between the two major impacts of microorganisms and provide context-specific examples relevant to Nigeria.
Public Health and Hygiene: Application: Understanding the presence of microorganisms in water and on bodies emphasizes the importance of basic hygiene. Students can relate this to regular hand washing, especially before eating and after using the toilet, to prevent the spread of diseases like cholera and typhoid, which are prevalent in many Nigerian communities due to contaminated water or poor sanitation.
Local Context: The lesson can be integrated with community health campaigns on safe drinking water (e.g., boiling water, using water filters, proper storage of sachet water) and proper waste disposal to minimize microbial contamination. The importance of trimming fingernails for school children to reduce germ carriage can be highlighted.
Food Science and Preservation: Application: Students learn about both beneficial microbes in food production and harmful ones causing spoilage. This knowledge is directly applicable to traditional Nigerian food processing and preservation methods.
Local Context: The role of microorganisms in fermenting indigenous foods like garri, ogi, iru, ogiri, and fufu can be discussed, showing how microbes enhance flavor and extend shelf life. Conversely, understanding harmful microbes reinforces why foods like amala or cooked rice spoil quickly if left unrefrigerated in the Nigerian heat, leading to food poisoning. This connects to proper food storage techniques.
Environmental Management: Application: Microorganisms are crucial in natural decomposition and waste treatment.
Local Context: This can be linked to the decomposition of organic waste in local communities, turning it into compost (manure) for farming. Teachers can discuss how microorganisms are used in sewage treatment plants (if any nearby) or in the bioremediation of polluted sites (e.g., oil spills in the Niger Delta), demonstrating their environmental utility beyond just disease.