Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

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Performance objectives

• Define biodiversity and taxonomy.
• Describe the hierarchical classification system.
• Discuss the five kingdoms of life.
• Explain and use the binomial nomenclature system.
• Explain why viruses are not classified in the five kingdoms.

Lesson summary

This week, we embark on an exciting journey into the incredible diversity of life on Earth, specifically focusing on plants and animals. Understanding this diversity is crucial, not just for academic reasons, but also because it directly impacts our lives in South Africa. From the food we eat (think of the variety of maize, fruits, and vegetables cultivated here) to the animals that form part of our rich cultural heritage (like the Big Five in our national parks or the endemic bird species), biodiversity is all around us.

Lesson notes

2.1 Biodiversity and Taxonomy Biodiversity: This refers to the variety of life on Earth at all its levels, from genes to ecosystems, and includes the ecological and evolutionary processes that sustain it. South Africa is a biodiversity hotspot, meaning we have a high concentration of endemic species (species found nowhere else in the world).

Taxonomy: This is the science of naming, describing, and classifying organisms. Think of it as the organized system that helps us make sense of the vast array of living things. Why Classify? Without classification, studying the millions of different organisms would be an impossible task.

Classification: Provides a universal system for communication: A scientific name means the same thing to a scientist in South Africa and a scientist in Brazil. Helps us understand evolutionary relationships: Organisms that are classified together are likely to be more closely related than those that are placed in different groups.

Aids in identifying organisms: Using a classification key, we can identify an unknown organism by comparing its characteristics to known species.

Supports conservation efforts: By understanding which species are most threatened, we can better target our conservation efforts. 2.2 The Hierarchical Classification System The hierarchical classification system is a nested system, meaning that each level is contained within the level above it. The levels, from broadest to most specific, are: Kingdom: The broadest category.

Phylum (Animals)/Division (Plants): Groups organisms with similar body plans (animals) or fundamental structural features (plants).

Class: Groups organisms within a phylum/division that share more specific characteristics.

Order: Groups organisms within a class that are even more closely related.

Family: A group of closely related genera.

Genus: A group of closely related species.

Species: A group of organisms that can interbreed and produce fertile offspring. This is the most specific level.

Mnemonic: To remember the order, use: "King Phillip Came Over For Good Soup."

Example: Let's classify the African Lion ( Panthera leo ): Kingdom: Animalia (Animals)

Phylum: Chordata (Animals with a backbone)

Class: Mammalia (Mammals – have hair and mammary glands)

Order: Carnivora (Meat eaters)

Family: Felidae (Cats)

Genus: Panthera (Big cats)

Species: leo (Lion) 2.3 The Five Kingdoms Scientists currently recognize five kingdoms of living organisms: Monera (Bacteria): These are prokaryotic organisms (cells lacking a nucleus). They are unicellular and can be either autotrophic (make their own food) or heterotrophic (obtain food from other organisms). Examples include Escherichia coli (E. coli) and Streptococcus (responsible for strep throat). They play a crucial role in nutrient cycling.

Protista: These are eukaryotic organisms (cells with a nucleus) that are mostly unicellular but can also be multicellular. Some are autotrophic (like algae), and others are heterotrophic (like amoebas). They are diverse and include algae, protozoa, and slime molds. Plasmodium, the parasite causing malaria, is a protist.

Fungi: These are eukaryotic, mostly multicellular, heterotrophic organisms that obtain their food by absorption. They have cell walls made of chitin. Examples include mushrooms, molds, and yeasts. They are important decomposers and also have uses in food production (like bread making) and medicine (like penicillin).

Plantae (Plants): These are eukaryotic, multicellular, autotrophic organisms that make their own food through photosynthesis. They have cell walls made of cellulose. Plants provide food and oxygen for other organisms and are essential for maintaining ecosystems. Examples include mosses, ferns, conifers, and flowering plants. In South Africa, plants like the Fynbos are ecologically very important.

Animalia (Animals): These are eukaryotic, multicellular, heterotrophic organisms that obtain their food by ingestion. They lack cell walls. Animals are incredibly diverse and play various roles in ecosystems, from predators to pollinators. Examples include insects, fish, amphibians, reptiles, birds, and mammals. 2.4 Binomial Nomenclature Binomial nomenclature is the system of giving each organism a two-part scientific name. This system was developed by Carolus Linnaeus.

The two parts are: Genus: The first part of the name and is always capitalized.

Species: The second part of the name and is always written in lowercase. The entire scientific name is always written in italics or underlined if handwritten. Why Use Scientific Names? Common names can be confusing because the same organism may have different common names in different regions. Scientific names provide a universal and unambiguous way to refer to an organism.

Examples: Human: Homo sapiens Maize: Zea mays Marula Tree: Sclerocarya birrea 2.5 Why Viruses Are Not Classified into Kingdoms Viruses are not considered living organisms and are therefore not classified into any of the five kingdoms.