Lesson Notes By Weeks and Term v5 - Grade 10
Biodiversity and classification of micro-organisms – Week 4 focus
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Biodiversity and classification of micro-organisms – Week 4 focus
Download the Lessonotes Mobile South Africa app for faster lesson access on Android and iPhone.
Subject: Life Sciences
Class: Grade 10
Term: 3rd Term
Week: 4
Theme: General lesson support
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Micro-organisms (or microbes) are a vast and diverse group of living things, most of which are too small to be seen with the naked eye. They include bacteria, archaea, fungi, protists, and viruses. Understanding their biodiversity and how we classify them is crucial for various reasons. In South Africa, this knowledge is especially important for addressing challenges related to public health (disease prevention), agriculture (crop production and protection), food security (microbial contributions to food production), and environmental sustainability (bioremediation).
2.1 What are Micro-organisms? Micro-organisms are living organisms so small that they are usually invisible to the naked eye. They are incredibly diverse and found everywhere – in the air, water, soil, and even inside our bodies. They play essential roles in ecosystems, from decomposing organic matter to producing oxygen. 2.2 Major Groups of Micro-organisms: Bacteria: These are single-celled prokaryotic organisms (lacking a membrane-bound nucleus). They have a cell wall, cytoplasm, ribosomes, and a circular chromosome of DNA. Bacteria reproduce asexually through binary fission. They are classified based on their shape (e.g., cocci - spherical, bacilli - rod-shaped, spirilla - spiral) and cell wall structure (Gram-positive or Gram-negative, determined by Gram staining).
Examples: Escherichia coli (in the gut), Mycobacterium tuberculosis (causes TB). Streptococcus pyogenes (causes strep throat).
Gram Staining: This is a differential staining technique used to classify bacteria. Gram-positive bacteria have a thick peptidoglycan layer in their cell wall, which retains the crystal violet stain, making them appear purple. Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane, which prevents them from retaining the crystal violet stain. They are counterstained with safranin, making them appear pink or red. This difference in cell wall structure is important because it affects the bacteria's susceptibility to antibiotics.
Archaea: Similar to bacteria, archaea are also single-celled prokaryotic organisms.
However, they are genetically distinct from bacteria and have unique cell wall composition (lacking peptidoglycan) and metabolic pathways. Many archaea are extremophiles, meaning they thrive in extreme environments like hot springs, salty lakes, and acidic conditions. They are important in nutrient cycling and some are involved in methane production.
Fungi: These are eukaryotic organisms (having a membrane-bound nucleus) that can be unicellular (e.g., yeasts) or multicellular (e.g., molds). Fungi have cell walls made of chitin. They are heterotrophic, meaning they obtain nutrients from organic matter. They reproduce sexually and asexually through spores.
Examples: Saccharomyces cerevisiae (yeast used in bread making and brewing), Penicillium (mold that produces penicillin). Many fungi are decomposers. In South Africa, fungi are cultivated and consumed, like mushrooms and Morchella species (morels).
Protists: This is a diverse group of eukaryotic organisms that are not fungi, animals, or plants. They are mostly unicellular and can be autotrophic (e.g., algae) or heterotrophic (e.g., protozoa). Protists reproduce sexually and asexually.
Examples: Amoeba, Paramecium, Plasmodium (causes malaria). Algae are vital producers of oxygen in aquatic ecosystems.
Viruses: These are non-cellular infectious agents consisting of a nucleic acid (DNA or RNA) enclosed in a protein coat (capsid). Viruses are obligate intracellular parasites, meaning they can only replicate inside a host cell. They are not considered living organisms because they lack cellular structure and cannot reproduce on their own.
Examples: HIV (causes AIDS), Influenza virus (causes flu), SARS-CoV-2 (causes COVID-19). Viruses inject their genetic material into a host cell, hijacking the cell's machinery to produce more virus particles. 2.3 Binomial Nomenclature: This is a two-name naming system used to classify living organisms, including micro-organisms. The first name is the genus (capitalized), and the second name is the species (lowercase). Both names are italicized or underlined. For example, Escherichia coli. This system ensures that scientists worldwide can communicate clearly about specific organisms without confusion caused by common names, which can vary from place to place. Why is it important? Imagine trying to discuss a particular strain of bacteria causing an outbreak in KwaZulu-Natal if everyone used different local names for it. Binomial nomenclature avoids this confusion. 2.4 Beneficial and Harmful Roles of Micro-organisms: Beneficial Roles: Decomposition: Bacteria and fungi break down dead organic matter, recycling nutrients back into the ecosystem. Think about compost heaps – microorganisms are key!
Food Production: Yeast is used to make bread, beer, and wine. Bacteria are used to make yogurt, cheese, and amahewu.
Nitrogen Fixation: Certain bacteria in the soil convert atmospheric nitrogen into ammonia, a form that plants can use.
Bioremediation: Micro-organisms can be used to clean up pollutants in the environment, such as oil spills. This is especially important in industrial areas of South Africa.
Medicine: Antibiotics (like penicillin) are produced by fungi.
Harmful Roles: Disease: Many bacteria, viruses, and fungi cause diseases in humans, animals, and plants.
Examples: TB (bacteria), HIV/AIDS (virus), fungal infections.