Lesson Notes By Weeks and Term v5 - Grade 7

Lesson Video

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Performance objectives

• Define key terms like biotic, abiotic, habitat, and ecosystem.
• Identify different factors within a South African ecosystem.
• Explain how these factors interact and influence survival.
• Describe the difference between a population, community, and ecosystem.
• Analyze the impact of environmental changes on living organisms.

Lesson summary

This week, we delve deeper into understanding how living things, both plants and animals, interact with their surroundings. This is crucial because these interactions determine the health and stability of our ecosystems, which directly impact our lives here in South Africa. Our well-being, from the food we eat to the air we breathe, is dependent on healthy ecosystems. Understanding these relationships allows us to make informed decisions about how we manage and protect our natural resources, like our water, land, and biodiversity – all essential for a sustainable future for South Africa.

Lesson notes

2.1 Basic Terminology: Biotic Factors: These are the living components of an ecosystem. This includes all plants, animals, fungi, bacteria, and other microorganisms. Examples in a South African savanna ecosystem include acacia trees, zebras, lions, and dung beetles.

Abiotic Factors: These are the non-living components of an ecosystem. They include things like sunlight, temperature, water, soil, air, and minerals. Examples in a South African river ecosystem include the amount of sunlight reaching the riverbed, the water temperature, the pH of the water, the oxygen levels, and the type of rocks found in the river.

Habitat: This is the natural home or environment of an organism. It provides the organism with the resources it needs to survive, such as food, water, shelter, and space. The habitat of a dassie is often rocky outcrops or mountainous regions, providing shelter from predators and harsh weather.

Population: This is a group of individuals of the same species living in a particular area and interacting with each other. A population of springbok in the Karoo region of South Africa is an example. It's important that they are the same species.

Community: This is a group of different populations of organisms living and interacting with each other in a particular area. For instance, a community in a KwaZulu-Natal coastal forest might include populations of monkeys, birds, insects, trees, and shrubs.

Ecosystem: This is a community of living organisms (biotic factors) interacting with each other and with their non-living environment (abiotic factors). An ecosystem is a functional unit. Examples of South African ecosystems include the Fynbos biome, the Kruger National Park, and a small pond in a garden. The ecosystem is self-contained and interacting. 2.2 Interactions between Biotic and Abiotic Factors: Biotic and abiotic factors are interconnected and influence each other in various ways: Sunlight and Plants: Plants require sunlight for photosynthesis, the process by which they convert sunlight into energy. The availability of sunlight directly affects the distribution and abundance of plants in an ecosystem. For example, plants in the understory of a forest need to adapt to lower light levels.

Water and Animals: Animals need water for survival. The availability of water affects their distribution and behavior. During droughts, animals may migrate to areas with water sources, leading to increased competition for resources.

Temperature and Distribution: Temperature affects the metabolic rates of organisms. Extreme temperatures can limit the distribution of certain species. For example, the Knysna Loerie thrives in the warm, humid forests of the Southern Cape but cannot survive in the arid regions of the Northern Cape.

Soil and Plant Growth: The type of soil influences the types of plants that can grow in an area. Sandy soils drain quickly and may not retain enough water for some plants, while clay soils retain water but may be poorly aerated.

Predator-Prey Relationships: The population size of a predator is influenced by the availability of prey, and vice versa. A decline in the prey population can lead to a decline in the predator population. An example is the relationship between lions and wildebeest in the Kruger National Park.

Decomposers and Nutrient Cycling: Decomposers, such as bacteria and fungi, break down dead organic matter, releasing nutrients back into the soil. These nutrients are then used by plants for growth. This recycling of nutrients is essential for maintaining the health of the ecosystem. 2.3 Example Ecosystem: A South African Garden Let's consider a typical garden in South Africa: Biotic Factors: Plants (flowers, vegetables, herbs), insects (bees, butterflies, aphids), earthworms, birds, fungi, and bacteria.

Abiotic Factors: Sunlight, temperature, water (from rain or irrigation), soil, air, and the nutrients in the soil. The plants rely on sunlight and water to grow. Bees pollinate the flowers, which allows them to produce seeds. Earthworms aerate the soil, improving drainage and nutrient availability. Birds may eat insects, helping to control their populations. Fungi and bacteria decompose dead plant matter, returning nutrients to the soil. If the garden experiences a drought (a change in an abiotic factor), the plants may wilt and die, which would then affect the animals that depend on those plants for food or shelter. 2.4 Example Ecosystem: A Wetland (e.g., iSimangaliso Wetland Park) The iSimangaliso Wetland Park is a UNESCO World Heritage Site in KwaZulu-Natal, South Africa. It is a diverse ecosystem comprised of lakes, beaches, coral reefs, swamps, and grasslands.

Biotic Factors: Reeds, water lilies, crocodiles, hippos, various fish species, numerous bird species (including flamingos and pelicans), insects, mangroves, and bacteria.

Abiotic Factors: Water (freshwater and saltwater), temperature, sunlight, soil composition (sand, mud), salinity levels, and tidal patterns.