Lesson Notes By Weeks and Term v5 - Grade 9

Lesson Video

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Performance objectives

• Define the biosphere and biodiversity.
• Describe the three levels of biodiversity with South African examples.
• Identify major threats to biodiversity in South Africa.
• Explain the importance of biodiversity for ecosystem services.
• Evaluate the role of conservation efforts.

Lesson summary

The biosphere encompasses all living organisms on Earth and their interactions with the non-living environment (atmosphere, lithosphere, and hydrosphere). Biodiversity, short for biological diversity, refers to the variety of life at all levels, from genes to ecosystems, and includes the ecological and evolutionary processes that maintain it. This week, we will delve deeper into the biosphere and biodiversity, focusing on their interconnectedness, importance, and threats, particularly within the South African context.

Lesson notes

2.1 The Biosphere The biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere (earth), hydrosphere (water), and atmosphere (air). Think of it as the "zone of life" on Earth. It's not a separate layer, but rather a collection of interconnected ecosystems. 2.2 Biodiversity Biodiversity is the variety of life at all levels. It can be broken down into three main categories: Genetic Diversity: The variation in genes within a species. This is crucial for a species' ability to adapt to changing environments.

Example: The different coat colors and disease resistance found within a population of African Wild Dogs. A wider range of genes makes the population more resilient to disease outbreaks or climate change.

Species Diversity: The variety of different species in a given area or ecosystem. South Africa is incredibly rich in species diversity, hosting a large number of plant, animal, and insect species.

Example: The Kruger National Park is home to a vast array of animal species, including the Big Five (lion, leopard, elephant, rhino, and buffalo) and countless other mammals, birds, reptiles, amphibians, and insects.

Ecosystem Diversity: The variety of different ecosystems in a region or on Earth. Ecosystems include forests, grasslands, wetlands, deserts, and marine environments. Each ecosystem provides different habitats and supports different communities of organisms.

Example: South Africa boasts a wide range of ecosystems, from the fynbos biome of the Western Cape (known for its unique plant species) to the succulent Karoo in the Northern Cape and the subtropical forests of KwaZulu-Natal. 2.3 Interconnectedness of the Biosphere and Biodiversity Biodiversity is the content of the biosphere. A healthy biosphere requires high biodiversity. Different species play different roles in ecosystems. Some are producers (plants), some are consumers (animals), and some are decomposers (fungi and bacteria). These roles are interconnected through food webs and nutrient cycles. Loss of biodiversity weakens the biosphere, making ecosystems less resilient and less able to provide essential services.

Example: Consider a South African grassland ecosystem. Grasses are the primary producers, feeding herbivores like zebras and wildebeest. These herbivores are then preyed upon by carnivores like lions and hyenas. Decomposers break down dead organisms, returning nutrients to the soil, which are then used by the grasses. If the population of zebras declines due to poaching, the lions may struggle to find food, affecting their population. If the grasses are overgrazed due to overpopulation of cattle (driven by human activity), the soil can erode, leading to desertification and loss of habitat for many species. This illustrates how the loss of a single species or habitat can have cascading effects throughout the ecosystem. 2.4 Threats to Biodiversity in South Africa Habitat Loss: The destruction or degradation of natural habitats due to agriculture, urbanization, mining, and deforestation.

Example: The expansion of sugarcane plantations in KwaZulu-Natal has led to the loss of natural grasslands and forests, impacting species like the Oribi antelope and various bird species.

Poaching: The illegal hunting or killing of animals, often for their meat, hides, or other body parts.

Example: The poaching of rhinos for their horns is a major threat to their survival in South Africa. Rhino horn is sold on the black market for use in traditional medicine.

Pollution: The contamination of air, water, and soil with harmful substances.

Example: Industrial pollution from factories and mines can contaminate rivers and streams, harming aquatic life. Agricultural runoff containing fertilizers and pesticides can also pollute waterways.

Invasive Species: The introduction of non-native species that can outcompete native species for resources and disrupt ecosystems.

Example: The Australian wattle tree is an invasive species that has spread throughout South Africa, displacing native vegetation and altering soil conditions.

Climate Change: Changes in global weather patterns that can alter habitats, disrupt ecosystems, and lead to species extinctions.

Example: Rising temperatures and changes in rainfall patterns are affecting the fynbos biome, increasing the risk of wildfires and impacting the distribution of plant and animal species. 2.5 Ecosystem Services and Economic Value Ecosystem services are the benefits that humans receive from ecosystems.

These include: Pollination: Insects and other animals pollinate crops, ensuring food production.

Water Purification: Wetlands and forests filter water, providing clean drinking water.

Climate Regulation: Forests absorb carbon dioxide, helping to regulate the climate.

Soil Formation and Fertility: Healthy ecosystems maintain soil fertility, supporting agriculture. Biodiversity also has economic value.