Lesson Notes By Weeks and Term v5 - Grade 10
Biodiversity and classification of micro-organisms – Week 3 focus
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Biodiversity and classification of micro-organisms – Week 3 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: 3
Theme: General lesson support
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Micro-organisms, despite being invisible to the naked eye, play a colossal role in our lives and the environment. They are essential for nutrient cycling, decomposition, and even the production of many foods and medicines we rely on. In South Africa, understanding micro-organisms is particularly important because of their role in agriculture, disease, and the production of traditional foods like amahewu and umqombothi. This week, we will focus on the diversity and classification of these tiny but mighty organisms.
What are Micro-organisms? Micro-organisms, also known as microbes, are living organisms that are generally too small to be seen with the naked eye. They include bacteria, archaea, protists, fungi, and viruses. (While viruses are not strictly considered living organisms because they require a host cell to replicate, they are often studied alongside micro-organisms.) The Five Kingdoms of Micro-organisms We will focus on five groups, though recognize this is a simplification: Bacteria, Archaea, Protista, Fungi and Viruses (though viruses aren't technically a kingdom).
Bacteria: These are prokaryotic organisms (meaning they lack a membrane-bound nucleus). They are single-celled and have a simple structure. Bacteria are found everywhere - in the soil, water, air, and even inside other organisms.
Examples: Escherichia coli (some strains are harmless and live in our gut, others can cause food poisoning), Streptococcus (causes strep throat).
Structure:* Bacteria have a cell wall, cell membrane, cytoplasm, ribosomes, and DNA (in a circular chromosome). Some bacteria also have flagella for movement and pili for attachment.
Reproduction:* Bacteria reproduce asexually through binary fission (splitting into two).
Importance: Bacteria play essential roles in nutrient cycling (e.g., nitrogen fixation by Rhizobium in plant roots), decomposition, and food production (e.g., yogurt production by Lactobacillus). Some are pathogenic.
South African Context:* Understanding nitrogen fixation is crucial for sustainable agriculture in South Africa, where many farmers face challenges related to soil fertility.
Archaea: Like bacteria, archaea are prokaryotic.
However, they are genetically and biochemically distinct from bacteria. Many archaea are extremophiles, meaning they can survive in extreme environments such as hot springs, salty lakes, and acidic environments.
Examples: Methanogens (produce methane gas), Halophiles (live in salty environments), Thermophiles (live in hot environments).
Structure:* Similar to bacteria, archaea have a cell wall, cell membrane, cytoplasm, ribosomes, and DNA (in a circular chromosome). Their cell walls and membranes often have unique compositions compared to bacteria, allowing them to survive in harsh environments.
Reproduction:* Archaea reproduce asexually through binary fission, budding, or fragmentation.
Importance:* Archaea are important in the global carbon cycle (methanogens), and some are used in industrial processes.
South African Context:* The study of archaea in extreme environments in South Africa could lead to the discovery of novel enzymes and biotechnological applications.
Protista: These are eukaryotic organisms (meaning their cells have a membrane-bound nucleus) that are not fungi, plants, or animals. Protists are a diverse group, including single-celled organisms like amoebas and paramecia, as well as multicellular algae.
Examples: Amoeba, Paramecium, Euglena, algae (e.g., seaweeds).
Structure:* Protists are eukaryotic, meaning they have a nucleus and other membrane-bound organelles. Their structure varies greatly depending on the type of protist.
Reproduction:* Protists can reproduce sexually or asexually.
Importance: Protists are important primary producers in aquatic ecosystems (algae), and some are responsible for diseases (e.g., malaria caused by Plasmodium).
South African Context:* Algae blooms can impact water quality in South African dams and rivers, affecting water supply and ecosystems. Understanding protists is thus important.
Fungi: Fungi are eukaryotic organisms that are heterotrophic, meaning they obtain nutrients from organic matter. Most fungi are multicellular, but some are unicellular (e.g., yeast).
Examples: Yeast (used in baking and brewing), Mushrooms, Molds (e.g., Penicillium).
Structure:* Fungi are eukaryotic and have cell walls made of chitin. Multicellular fungi consist of thread-like structures called hyphae.
Reproduction:* Fungi can reproduce sexually or asexually, often through spores.
Importance:* Fungi are important decomposers, breaking down dead organic matter. Some are used in food production (e.g., mushrooms, cheese), and some are used to produce medicines (e.g., penicillin). Others are pathogenic, causing diseases in plants and animals.
South African Context:* Fungal diseases can significantly impact South African agriculture, affecting crop yields. Understanding fungal biology is crucial for developing effective control measures.
Viruses: Viruses are not cells; they are infectious agents composed of genetic material (DNA or RNA) enclosed in a protein coat (capsid). Viruses can only replicate inside a host cell.
Examples:* HIV (causes AIDS), Influenza virus (causes flu), Coronavirus (causes COVID-19).
Structure:* Viruses are composed of genetic material (DNA or RNA) surrounded by a protein coat (capsid). Some viruses also have an outer envelope.
Reproduction:* Viruses cannot reproduce on their own.