Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

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Performance objectives

• Define population ecology and its key factors.
• Interpret exponential and logistic growth curves.
• Explain human impacts like pollution and deforestation.
• Discuss causes and consequences of pollution.
• Explain the importance of conservation in South Africa.

Lesson summary

This week, we delve into the fascinating world of population ecology and examine the profound impact humans have on our environment. Understanding population dynamics is crucial because it allows us to predict how populations of various species, including our own, will change over time. This knowledge is vital for effective resource management, conservation efforts, and addressing environmental challenges like pollution and habitat destruction. In South Africa, with our rich biodiversity and unique environmental pressures such as water scarcity and land degradation, these concepts are incredibly relevant to our everyday lives.

Lesson notes

2.1 Population Ecology: Population ecology is the study of populations in relation to their environment, including environmental influences on population density and distribution, age structure, and variations in population size. A population is a group of individuals of the same species living in the same area at the same time.

Key Factors Influencing Population Size: Birth Rate (Natality): The number of births in a population per unit time. A high birth rate increases population size.

Death Rate (Mortality): The number of deaths in a population per unit time. A high death rate decreases population size.

Immigration: The movement of individuals into a population from another area. Increases population size.

Emigration: The movement of individuals out of a population to another area. Decreases population size. Population Change = (Birth Rate + Immigration) - (Death Rate + Emigration) 2.2 Population Growth Curves: Exponential Growth: This occurs when a population has unlimited resources (food, space, etc.) and reproduces at its maximum rate. The population size increases rapidly, resulting in a J-shaped curve. This is unrealistic in the long term because resources are always limited.

Example: Imagine a small colony of bacteria placed in a petri dish with plenty of nutrients. Initially, the population grows exponentially as they reproduce rapidly.

Logistic Growth: This is a more realistic model of population growth. As a population grows, resources become limited, and the growth rate slows down. Eventually, the population reaches its carrying capacity (K), which is the maximum population size that the environment can sustain. The population growth curve is S-shaped.

Carrying Capacity (K): The maximum population size that a particular environment can support, given available resources such as food, water, shelter, and space. It is determined by limiting factors.

Limiting Factors: Environmental factors that restrict population growth. These can be density-dependent (e.g., competition, predation, disease) or density-independent (e.g., natural disasters, weather). 2.3 Human Impact on the Environment: Human activities have a significant and often negative impact on biodiversity and ecosystem stability.

Pollution: The contamination of the environment with harmful substances.

Water Pollution: Caused by sewage, industrial waste, agricultural runoff (fertilizers, pesticides), and oil spills. Consequences include the death of aquatic organisms, eutrophication (excessive nutrient enrichment leading to algal blooms and oxygen depletion), and human health problems. South African

Example:* Acid mine drainage from abandoned gold mines pollutes many rivers and streams, harming aquatic life and contaminating water sources.

Air Pollution: Caused by burning fossil fuels (coal, oil, gas), industrial emissions, and vehicle exhaust. Consequences include respiratory problems, acid rain, and climate change. South African

Example:* High levels of air pollution in industrial areas like Secunda and the Vaal Triangle contribute to respiratory illnesses and environmental damage.

Soil Pollution: Caused by pesticides, herbicides, industrial waste, and improper waste disposal. Consequences include reduced soil fertility, contamination of crops, and groundwater pollution. South African

Example:* Improper disposal of e-waste (electronic waste) contaminates soil with heavy metals in many areas.

Deforestation: The clearing of forests for agriculture, urbanization, and logging. Consequences include habitat loss, soil erosion, climate change, and reduced biodiversity. South African

Example:* Deforestation for agriculture and firewood collection in certain rural areas leads to soil erosion and loss of valuable habitats.

Alien Species (Invasive Species): Species introduced to an area outside their natural range. They can outcompete native species, disrupt ecosystems, and cause economic damage. South African

Example: The water hyacinth ( Eichhornia crassipes ) is an invasive aquatic plant that clogs waterways, blocks sunlight, and harms native aquatic life. Black wattle (Acacia mearnsii) is another example, taking over grassland biomes.

Overexploitation: Harvesting resources at a rate faster than they can be replenished. Consequences include depletion of fish stocks, extinction of species, and ecosystem collapse. South African

Example:* Overfishing of certain fish species along the coast has led to declining populations and disrupted marine ecosystems. Poaching of rhinos for their horns is a serious problem leading to possible extinction. 2.4 Conservation and Sustainable Resource Management: Conservation involves protecting and preserving natural resources and ecosystems. Sustainable resource management involves using resources in a way that meets the needs of the present without compromising the ability of future generations to meet their own needs.