Lesson Notes By Weeks and Term v4 - SHS 2
BIOLOGY AS THE SCIENCE OF LIFE
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BIOLOGY AS THE SCIENCE OF LIFE
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Subject: Biology
Class: SHS 2
Term: 1st Term
Week: 2
Grade code: 2.1.1.LI.2
Strand code: 1
Sub-strand code: 1
Content standard code: 2.1.1.CS.1
Indicator code: 2.1.1.LI.2
Theme: EXPLORING BIOLOGY IN SOCIETY
Subtheme: BIOLOGY AS THE SCIENCE OF LIFE
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Welcome, future scientists! Today, we are moving beyond just identifying living things to understanding their direct impact on our lives, particularly on our economy. We often see mould on old bread, moss growing on damp walls, and ferns decorating our gardens. Have you ever considered that these simple organisms can create jobs, clean our environment, and also cause significant financial loss? This lesson explores the hidden economic power of three common simple organisms: *Rhizopus* (bread mould), Moss, and Ferns. Understanding their roles helps us appreciate biodiversity and make informed decisions in agriculture, industry, and environmental management right here in Ghana.
This lesson focuses on economic importance, which means how an organism affects human wealth and well-being. This can be positive (benefits that make or save money) or negative (harms that cost money). A. Rhizopus (The Black Bread Mould) What is it? *Rhizopus* is a common type of fungus, a saprophyte that feeds on dead organic matter. You see it as a fuzzy, black or greyish growth on stale bread, fruits, and other decaying food items. It consists of thread-like structures called hyphae. Positive Economic Importance (Benefits) Industrial Fermentation: *Rhizopus* species are used in biotechnology to produce valuable chemicals. For example, *Rhizopus oryzae* is used to produce lactic acid (used in food preservation, plastics) and fumaric acid (a food additive). This creates an industry and jobs. Enzyme Production: Industries use *Rhizopus* to produce enzymes like amylase, which breaks down starch into sugar. This is crucial in the baking and brewing industries, as well as in the production of high-fructose corn syrup. Food Production: In some parts of the world (especially Southeast Asia), a related fungus is used to make tempeh, a fermented soybean cake that is a rich source of protein. This shows its potential in food processing. Decomposition: As decomposers, fungi like *Rhizopus* are essential for nutrient cycling in the ecosystem. They break down dead organic matter, returning vital nutrients to the soil, which indirectly supports agriculture, saving farmers money on fertilisers. Negative Economic Importance (Harmful Effects) Food Spoilage: This is the most significant negative impact. *Rhizopus* causes spoilage of bread, fruits (like pawpaw and mangoes), and vegetables. This leads to massive financial losses for bakeries, market women at Agbogbloshie or Kejetia, food processing companies, and households across Ghana. Plant Diseases: Some species of *Rhizopus* cause diseases in crops. For instance, it can cause soft rot in sweet potatoes, yams, and cassava during storage, reducing the harvest yield and income for farmers. Human Infections (Rare): In individuals with weakened immune systems (e.g., HIV/AIDS patients, diabetics), *Rhizopus* can cause a serious and often fatal infection called zygomycosis. Treating this disease is very expensive, creating a high cost for the healthcare system and families. B. Mosses What are they? Mosses are small, non-vascular plants (bryophytes) that lack true roots, stems, and leaves. They thrive in damp, shady environments like on rocks, tree trunks, and moist soil. A common example is *Sphagnum* moss. Positive Economic Importance (Benefits) Horticulture and Floristry: Dried *Sphagnum* moss is processed and sold as peat moss. It has an amazing ability to hold water and is therefore mixed with soil to improve its quality for gardening. This is a multi-million dollar global industry. In Ghana, florists use mosses for decorative purposes in bouquets and wreaths, adding value to their products. Soil Formation and Erosion Control: Mosses are pioneer species – they are among the first organisms to colonise bare rock. They slowly break down the rock surface and trap dust and organic matter, creating the first layer of soil for other plants to grow. On hillsides, their dense mats help to bind the soil, preventing soil erosion during heavy rains, which is a valuable, free service protecting farmlands and infrastructure. Fuel Source: In some countries (like Ireland and Finland), compacted, decayed peat moss from bogs is harvested and used as a source of fuel for heating and electricity generation. Historical Medical Use: *Sphagnum* moss was used as a sterile, highly absorbent wound dressing during wars because it has mild antiseptic properties. Negative Economic Importance (Harmful Effects) Nuisance on Structures: Mosses can grow on rooftops, pavements, and building walls. This can be unsightly and can damage the materials over time by trapping moisture, leading to decay. Homeowners and institutions spend money on chemicals and labour to remove them. Weed in Lawns: Moss can invade lawns, competing with grass for nutrients and water, making the lawn look patchy. People spend money on special fertilisers or moss killers to control it. Clogging Gutters and Drains: Moss can grow in and clog drainage systems, which can lead to water damage in buildings, requiring costly repairs. C. Ferns What are they? Ferns are vascular plants that have true roots, stems (often underground, called rhizomes), and leaves (called fronds). Unlike flowering plants, they reproduce using spores, which are usually found in clusters (sori) on the underside of their fronds. Positive Economic Importance (Benefits) Ornamental Plants (Horticulture): This is the biggest economic benefit. Many species of ferns are cultivated and sold as ornamental plants for homes, offices, and landscaping. Think of the beautiful ferns sold at the Aburi Botanical Gardens or by roadside plant sellers. This is a source of income for many Ghanaians. Source of Fossil Fuels: Ancient ferns that lived millions of years ago were buried and compressed under layers of sediment. Over time, heat and pressure transformed them into coal, a major fossil fuel used for generating electricity and in industries worldwide. Phytoremediation (Environmental Clean-up): Some ferns have the remarkable ability to absorb and store heavy metals from contaminated soil. For example, the Brake fern (*Pteris vittata*) can absorb large amounts of arsenic. This is a low-cost, environmentally friendly way to clean up soils polluted by mining activities (like "galamsey"), which is a major issue in parts of Ghana. Food and Medicine: The young, coiled fronds of some fern species (called fiddleheads) are harvested and eaten as a vegetable in some cultures. Additionally, extracts from certain ferns have been used in traditional medicine to treat ailments like worms and skin conditions. Negative Economic Importance (Harmful Effects) Invasive Species: Some fern species, when introduced to a new environment, can become invasive. They can grow aggressively and outcompete native plants or crops, reducing biodiversity and agricultural productivity. Controlling them costs money. Toxicity to Livestock: Certain ferns, like bracken fern (*Pteridium aquilinum*), are poisonous to cattle and sheep if eaten in large quantities. This can lead to illness or death of livestock, causing economic loss for farmers.
Guided Practice (With Solutions)
Instructions: Let's work through these questions together as a class.
Question 1: A food processing factory in Tema that packages sliced mangoes for export discovers that 20% of its stored mangoes are developing a fuzzy, blackish growth and have to be thrown away. Identify the likely organism causing this problem and explain two specific ways this situation results in economic loss. Solution: Organism: The likely organism is *Rhizopus* (a type of mould). Economic Losses: Loss of Raw Materials: The factory loses the money it spent to buy the 20% of mangoes that are now spoiled. If they bought 1000 kg of mangoes, they are losing the value of 200 kg. Loss of Potential Revenue: The spoiled mangoes cannot be processed and sold. This means the factory loses the profit it would have made from exporting those mangoes. This also includes the cost of labour and energy already spent on those mangoes before they were discovered to be spoilt. Reputation Damage (Indirect Cost): If a spoiled batch accidentally gets shipped, it could damage the company's reputation, leading to loss of future contracts and customers.