Lesson Notes By Weeks and Term v5 - Grade 9

Lesson Video

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Performance objectives

• Define biosphere and biodiversity.
• Describe the different levels of biodiversity.
• Identify major threats to biodiversity.
• Explain the importance of biodiversity for ecosystem services.
• Suggest actions to conserve biodiversity.

Lesson summary

This week, we delve into the biosphere and biodiversity. The biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere, hydrosphere, and atmosphere. Biodiversity, or biological diversity, refers to the variety of life on Earth at all its levels, from genes to ecosystems, and can encompass the evolutionary, ecological, and cultural processes that sustain life. Understanding these concepts is critically important, especially in South Africa, a country renowned for its exceptional biodiversity and a vital part of the global biosphere.

Lesson notes

The Biosphere: The biosphere is the sum of all ecosystems. It encompasses all life on Earth and its interactions with the atmosphere, hydrosphere (water), and lithosphere (land). It is the zone where life exists. Key processes within the biosphere include: Energy Flow: Primarily from the sun, converted to chemical energy by producers (plants), and transferred through food chains and food webs.

Nutrient Cycling: The movement and reuse of essential elements (carbon, nitrogen, phosphorus, etc.) through the biosphere. These cycles are crucial for sustaining life. For example, the carbon cycle involves plants absorbing carbon dioxide during photosynthesis, which is then passed through food chains. When organisms die, decomposers break down their remains, releasing carbon back into the atmosphere or soil. Human activities like burning fossil fuels disrupt this cycle.

Water Cycle: The continuous circulation of water between the oceans, atmosphere, and land. This cycle is vital for all living organisms. Deforestation can disrupt the water cycle, leading to droughts and floods.

Biodiversity: The variety of life on Earth at all its levels, from genes to ecosystems.

It has three main components: Genetic Diversity: The variation in genes within a species. This is essential for adaptation and survival in changing environments. A population with high genetic diversity is more likely to withstand disease or environmental stress. For instance, in maize, different varieties have different genes that provide resistance to various pests and diseases. If all maize varieties were genetically identical, a single disease could wipe out the entire crop.

Species Diversity: The number and abundance of different species in a particular area. This is what most people think of when they hear the term biodiversity. South Africa is a megadiverse country, meaning it has a high number of species found nowhere else (endemic species). The fynbos biome in the Western Cape is an example of a biodiversity hotspot, with a high concentration of unique plant species.

Ecosystem Diversity: The variety of habitats, ecological communities, and ecological processes in a given region. Examples include forests, grasslands, wetlands, and marine ecosystems. Each ecosystem provides unique services, such as water purification, climate regulation, and habitat for different species. The Drakensberg mountain range, for example, represents high ecosystem diversity, with various habitats ranging from grasslands to forests, supporting a rich array of flora and fauna.

Threats to Biodiversity: Habitat Loss: The destruction or degradation of natural habitats due to deforestation, urbanization, agriculture, and mining. This is the leading cause of biodiversity loss. For example, the expansion of sugarcane farming in KwaZulu-Natal has led to the loss of natural grasslands and forests, impacting biodiversity.

Pollution: The contamination of air, water, and soil by harmful substances. This can have devastating effects on ecosystems and human health. Examples include industrial pollution in rivers and plastic pollution in the oceans.

Invasive Species: Non-native species that outcompete native species for resources and disrupt ecosystems. Invasive plants, such as the Australian wattles in the fynbos biome, can consume large quantities of water and increase the risk of wildfires.

Climate Change: Changes in global weather patterns due to increased greenhouse gas emissions. This can lead to changes in temperature, rainfall, and sea levels, impacting ecosystems and species distributions. For example, rising temperatures are affecting the distribution of many plant and animal species in South Africa. The Cape Floral Kingdom is particularly vulnerable to climate change.

Overexploitation: Unsustainable harvesting of natural resources, such as overfishing and poaching. This can lead to the depletion of populations and even extinction. Rhino poaching is a severe problem in South Africa, threatening the survival of these iconic animals.

Importance of Biodiversity: Ecosystem Services: Biodiversity provides essential ecosystem services that support human well-being, including pollination, water purification, climate regulation, soil fertility, and pest control.

Economic Benefits: Biodiversity provides resources for food, medicine, and tourism. Ecotourism is a significant source of revenue for many communities in South Africa.

Cultural Value: Biodiversity is an integral part of many cultures and traditions. Many indigenous communities have deep connections to the land and its resources.

Ethical Considerations: Many people believe that we have a moral responsibility to protect biodiversity for future generations. Guided Practice (With Solutions)

Question 1: Define biosphere and biodiversity. Explain how they are related.