Lesson Notes By Weeks and Term v5 - Grade 8

Lesson Video

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Performance objectives

• Define an ecosystem and its components (biotic & abiotic).
• Describe interactions like predation, competition, and symbiosis.
• Explain energy flow using food chains and food webs.
• Understand human impact on ecosystems.

Lesson summary

This week, we delve into the fascinating world of ecosystems and how different organisms interact within them. Understanding ecosystems is crucial because South Africa is blessed with incredible biodiversity, from the fynbos biome to the Kruger National Park. Understanding how these ecosystems function is vital for their conservation and for ensuring that we, as South Africans, can continue to benefit from the resources they provide. We will explore the intricate relationships between living organisms and their environment, and how these interactions shape the health and stability of ecosystems.

Lesson notes

What is an Ecosystem? An ecosystem is a community of living organisms (biotic factors) interacting with each other and with their non-living environment (abiotic factors). It's a dynamic system where energy flows and nutrients cycle.

Biotic Factors: These are the living components of an ecosystem. Examples include plants, animals, fungi, and bacteria. They interact with each other in various ways, such as through feeding relationships (food chains and food webs).

Abiotic Factors: These are the non-living components of an ecosystem. Examples include sunlight, temperature, water, soil, air, and minerals. These factors influence the distribution and abundance of organisms within the ecosystem.

Examples of Ecosystems in South Africa: Fynbos: This unique ecosystem in the Western Cape is characterized by its shrubland vegetation. Abiotic factors include a Mediterranean climate with hot, dry summers and mild, wet winters. Biotic factors include proteas, ericas, and various bird and insect species.

Savanna: Found in areas like the Kruger National Park, the savanna is characterized by grasslands with scattered trees. Abiotic factors include high temperatures and seasonal rainfall. Biotic factors include lions, elephants, zebras, and various grass species.

Marine Ecosystems: Our coastlines boast diverse marine ecosystems, including kelp forests and coral reefs. Abiotic factors include salinity, water temperature, and wave action. Biotic factors include fish, seaweed, and marine mammals.

Interactions Between Organisms: Organisms in an ecosystem interact in various ways, including: Predation: One organism (the predator) kills and eats another organism (the prey).

Example: A lion hunting a zebra in the savanna.

Competition: Organisms compete for the same limited resources, such as food, water, or space.

Example: Zebras and wildebeest competing for grazing land. This can be intraspecific (within the same species, like two male impala fighting for a mate) or interspecific (between different species, like the zebras and wildebeest).

Symbiosis: A close and long-term interaction between two different species.

There are three main types: Mutualism: Both species benefit from the interaction.

Example: Bees pollinating flowers. The bee gets nectar, and the flower gets pollinated.

Commensalism: One species benefits, and the other is neither harmed nor helped.

Example: Birds nesting in a tree. The bird gets shelter, and the tree is unaffected.

Parasitism: One species (the parasite) benefits at the expense of the other species (the host).

Example: Ticks feeding on a dog.

Food Chains and Food Webs: Food Chain: A linear sequence showing the transfer of energy from one organism to another when one organism eats another.

Example: Grass → Zebra → Lion.

Producers: Organisms that make their own food through photosynthesis (e.g., grass).

Consumers: Organisms that eat other organisms.

Primary Consumers: Herbivores that eat producers (e.g., zebra).

Secondary Consumers: Carnivores that eat primary consumers (e.g., lion).

Tertiary Consumers: Carnivores that eat secondary consumers.

Decomposers: Organisms that break down dead organisms and waste products, returning nutrients to the soil (e.g., bacteria and fungi).

Food Web: A complex network of interconnected food chains in an ecosystem. It shows the more realistic and varied feeding relationships in an ecosystem.