Lesson Notes By Weeks and Term v5 - Grade 7

Lesson Video

This page supports the lesson note with a companion video and a short classroom-ready summary.

For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.

Performance objectives

• Define levels of ecological organization.
• Explain biotic and abiotic factors.
• Describe interactions between organisms.
• Understand food chains and food webs.
• Identify producers, consumers, and decomposers.

Lesson summary

Our planet teems with life! From the smallest bacteria to the largest elephants, all living things are interconnected and depend on their environment for survival. This week, we delve deeper into understanding these relationships and how living organisms interact with each other and their surroundings. This is particularly important in South Africa, a country with incredible biodiversity facing unique environmental challenges. Understanding these relationships is crucial for making informed decisions about conservation, resource management, and ensuring a sustainable future for all.

Lesson notes

Let's start by defining some key terms: Ecology: The study of how organisms interact with each other and their environment.

Levels of Ecological Organization: Ecologists study life at different levels, from the individual organism to the entire planet. Think of it as zooming out to see the bigger picture.

Individual: A single organism (e.g., one zebra, one baobab tree, one dung beetle).

Population: A group of the same species living in the same area (e.g., a herd of zebras grazing on the savanna, a group of baobab trees in Limpopo). In South Africa, a population of African Penguins on Robben Island is a good example.

Community: All the different populations living together in an area (e.g., zebras, lions, giraffes, grasses, and trees in a savanna ecosystem).

Ecosystem: The community of living organisms interacting with the non-living (abiotic) environment (e.g., the savanna, including the soil, rainfall, sunlight, and temperature). Consider a dam ecosystem; it includes the fish, plants, algae, insects, and the water itself, along with the minerals in the water and the sunlight reaching it.

Biome: A large geographic area characterized by specific climate conditions, animal populations, and plant communities. Examples in South Africa include the Fynbos (known for its unique shrub vegetation), the Savanna (grasslands with scattered trees), the Nama Karoo (arid shrubland), and the Succulent Karoo (also arid, but with more succulent plants).

Biosphere: All the ecosystems on Earth, encompassing all life and its environment.

Biotic and Abiotic Factors: Ecosystems are shaped by two main types of factors: Biotic Factors: Living components of an ecosystem, such as plants, animals, fungi, and bacteria.

Examples: Plants providing food and shelter, predators hunting prey, decomposers breaking down dead organisms.

Abiotic Factors: Non-living components of an ecosystem, such as sunlight, water, temperature, soil, and air.

Examples: Sunlight for photosynthesis, rainfall for plant growth, temperature affecting animal distribution, soil providing nutrients for plants.

Example: In the Fynbos biome, biotic factors include the Protea plants, sunbirds, and Cape foxes. Abiotic factors include the low-nutrient soil, hot summers, and winter rainfall.

Interactions Between Organisms: Organisms interact in various ways, affecting each other's survival and reproduction: Competition: When two or more organisms require the same limited resource (e.g., food, water, space, sunlight).

Example: Lions and hyenas competing for the same prey (wildebeest) on the savanna.

Predation: When one organism (the predator) kills and eats another organism (the prey).

Example: A leopard hunting an impala.

Mutualism: A relationship where both organisms benefit.

Example: Bees pollinating flowers. The bee gets nectar for food, and the flower gets pollinated. Another local example is the relationship between oxpeckers and cattle/rhinos. The oxpeckers eat ticks and other parasites off the animals, benefiting both species.

Parasitism: A relationship where one organism (the parasite) benefits at the expense of the other organism (the host).

Example: Ticks feeding on the blood of a dog. The tick benefits, while the dog is harmed.

Commensalism: A relationship where one organism benefits, and the other is neither harmed nor helped.

Example: Birds nesting in trees. The bird benefits from the shelter, while the tree is neither helped nor harmed.

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

For example: Grass → Zebra → Lion. The arrow indicates the direction of energy flow (who eats whom).

Food Web: A network of interconnected food chains in an ecosystem. It shows the complex feeding relationships between different organisms. Food webs are more realistic than food chains because organisms often eat multiple things and are eaten by multiple predators. Producers, Consumers, and Decomposers: Producers: Organisms that make their own food through photosynthesis (using sunlight, water, and carbon dioxide). Plants are producers. They form the base of the food chain.

Consumers: Organisms that eat other organisms for energy.

There are different types of consumers: Herbivores: Eat only plants (e.g., zebra, giraffe).

Carnivores: Eat only animals (e.g., lion, leopard).

Omnivores: Eat both plants and animals (e.g., humans, baboons, warthogs).

Decomposers: Organisms that break down dead organisms and waste, returning nutrients to the soil. Bacteria and fungi are important decomposers. Without decomposers, nutrients would be locked up in dead material, and plants would not be able to grow. Example Food Web for a South African School Garden: Producers: Grass, vegetable plants (e.g., spinach, tomatoes)

Herbivores: Grasshoppers, snails, caterpillars Carnivores: Spiders, frogs, birds (that eat insects)

Omnivores: Chickens (if present), some bird species.

Decomposers: Bacteria and fungi in the soil.