Lesson Notes By Weeks and Term v5 - Grade 10

Lesson Video

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Performance objectives

• Define 'micro-organism' and list the major groups.
• Describe the basic characteristics of bacteria, fungi, protists, and viruses.
• Explain the principles of classification, like binomial nomenclature.
• Identify the beneficial and harmful roles of micro-organisms.
• Explain the importance of microbial biodiversity.

Lesson summary

Micro-organisms are all around us! They're in the air we breathe, the food we eat, and even inside our bodies. While some cause diseases, many are essential for life on Earth. They play vital roles in nutrient cycling, decomposition, and even the production of food and medicines. Understanding their diversity and how we classify them is crucial for fields like medicine, agriculture, and environmental science. In South Africa, understanding microbes is particularly important for managing food spoilage in rural communities, combatting diseases like tuberculosis, and utilizing micro-organisms in industries like brewing and winemaking.

Lesson notes

What are Micro-organisms? Micro-organisms, also known as microbes, are organisms that are too small to be seen with the naked eye. They are typically unicellular (single-celled), but some can be multicellular. They are incredibly diverse and found in virtually every environment on Earth, from the deepest ocean trenches to the highest mountain peaks.

Major Groups of Micro-organisms: Bacteria: These are prokaryotic cells, meaning they lack a true nucleus and other membrane-bound organelles. They have a simple cell structure with a cell wall, cytoplasm, ribosomes, and a single circular chromosome. They reproduce primarily through binary fission. Bacteria are extremely adaptable and can be found in various shapes, including spherical (cocci), rod-shaped (bacilli), and spiral (spirilla).

Examples: Escherichia coli (E. coli), Streptococcus pneumoniae. Many bacteria are beneficial, aiding in digestion and nutrient cycling, but some are pathogenic, causing diseases like pneumonia and food poisoning.

Fungi: Fungi are eukaryotic organisms, meaning their cells have a nucleus and other membrane-bound organelles. They can be unicellular (e.g., yeasts) or multicellular (e.g., molds and mushrooms). Fungi have cell walls made of chitin. They obtain nutrients by absorbing organic matter from their surroundings (saprophytes) or by parasitizing other organisms. They reproduce through spores.

Examples: Saccharomyces cerevisiae (yeast used in bread making), Penicillium (source of penicillin), Aspergillus (some species cause diseases, others are used in food production). In South Africa, some fungi are important decomposers in the Fynbos biome.

Protists: Protists are a diverse group of eukaryotic organisms that are not fungi, plants, or animals. They are mostly unicellular but some are multicellular. They can be autotrophic (making their own food through photosynthesis) or heterotrophic (obtaining food from other organisms). They reproduce both sexually and asexually.

Examples: Amoeba, Paramecium, Euglena, Plasmodium (causes malaria). Protists are crucial components of aquatic ecosystems.

Viruses: Viruses are not cells. They are acellular infectious agents consisting of genetic material (DNA or RNA) enclosed in a protein coat called a capsid. Viruses are obligate intracellular parasites, meaning they can only reproduce inside a host cell. They hijack the host cell's machinery to replicate their genetic material and produce more virus particles.

Examples: HIV (causes AIDS), influenza virus (causes flu), SARS-CoV-2 (causes COVID-19). Viruses are responsible for a wide range of diseases in humans, animals, and plants.

Classification of Micro-organisms: Classification is the process of grouping organisms based on their shared characteristics. This helps us to organize and understand the diversity of life. The classification of micro-organisms, like all living organisms, follows a hierarchical system developed by Carl Linnaeus. This system is based on the idea of grouping organisms based on their evolutionary relationships.

The main levels of classification are: Domain: The broadest level, encompassing Bacteria, Archaea, and Eukarya.

Kingdom: Within each domain, organisms are further classified into kingdoms (e.g., Bacteria Kingdom, Fungi Kingdom, Protist Kingdom).

Phylum (Division in Botany): Groups organisms with similar body plans or characteristics.

Class: Further subdivides phyla based on more specific traits.

Order: Groups families with related characteristics.

Family: Groups genera with common ancestry.

Genus: A group of closely related species.

Species: The most specific level, representing a group of organisms that can interbreed and produce fertile offspring (though this definition is less straightforward for micro-organisms that reproduce asexually).

Binomial Nomenclature: Scientists use a two-name naming system called binomial nomenclature to identify each species. This system consists of the genus name (capitalized) followed by the species name (lowercase). Both names are written in italics or underlined. For example, Homo sapiens is the scientific name for humans. This system ensures that each organism has a unique and universally recognized name.