Ecology
Human Impact and Conservation
5th Year · 6th Year (Leaving Cert)
- ✓By the end of this lesson students will be able to define and classify different types of pollution and identify their sources.
- ✓By the end of this lesson students will be able to explain the process of eutrophication and its ecological consequences.
- ✓By the end of this lesson students will be able to describe the importance of biodiversity and distinguish between in situ and ex situ conservation strategies.
- ✓By the end of this lesson students will be able to discuss human activities that impact ecosystems and propose methods for sustainable management and conservation.
Key concepts
Pollution is any undesirable change in the physical, chemical, or biological characteristics of air, water, or land that can harm living organisms and ecosystems. Pollutants are substances or energy forms that cause pollution. Human activities are the primary source of most pollution.
Pollution can be categorised based on the medium affected or the nature of the pollutant: 1. Air Pollution: Release of harmful substances into the atmosphere (e.g., sulfur dioxide, nitrogen oxides from burning fossil fuels leading to acid rain; carbon dioxide and methane leading to the enhanced greenhouse effect). 2. Water Pollution: Contamination of water bodies (e.g., by sewage, industrial waste, agricultural run-off containing fertilisers and pesticides). 3. Land Pollution: Degradation of land due to waste disposal (e.g., landfills, toxic waste, plastic accumulation). 4. Noise Pollution: Excessive or unwanted sound that can disrupt human or animal life. 5. Thermal Pollution: Increase or decrease in ambient water temperature caused by human activity (e.g., discharge of heated water from power plants). 6. Visual Pollution: Unattractive or intrusive elements in the landscape (e.g., excessive advertising, litter).
Eutrophication is the enrichment of an aquatic ecosystem (e.g., lakes, rivers, estuaries) with chemical nutrients, typically compounds containing nitrogen and phosphorus. These nutrients often originate from agricultural run-off (fertilisers), untreated sewage, or industrial effluent. This enrichment leads to an excessive growth of plants and algae (known as an algal bloom), which then has a cascade of negative ecological effects.
Biodiversity, or biological diversity, refers to the variety of life on Earth at all its levels, from genes to ecosystems, and the ecological and evolutionary processes that sustain it. It encompasses genetic diversity (variety within a species), species diversity (variety of different species), and ecosystem diversity (variety of different habitats and ecological communities). Biodiversity is crucial for ecosystem stability, provides essential resources (food, medicine, clean water), and holds aesthetic and cultural value.
Conservation is the protection, preservation, management, or restoration of wildlife and natural resources such as forests, soil, and water. The primary goal of conservation is to maintain biodiversity and ensure the sustainable use of natural resources for present and future generations. It involves a range of strategies to mitigate human impact on the environment.
In situ conservation involves protecting species in their natural habitats. This is often considered the most effective method as it allows species to continue to evolve and adapt within their natural environment. Examples include the establishment of National Parks, Nature Reserves, Wildlife Sanctuaries, and the protection of specific habitats.
Ex situ conservation involves protecting species outside their natural habitats. This method is typically used for species that are critically endangered or when their natural habitat is severely threatened. Examples include zoos, botanical gardens, seed banks (for plant genetic material), gene banks (for animal genetic material), and captive breeding programmes.
Key facts to remember
- 1Pollution is any undesirable change in the environment caused by human activities.
- 2Eutrophication is the enrichment of water bodies with excess nutrients (N, P), leading to algal blooms and subsequent oxygen depletion.
- 3Biodiversity refers to the variety of life at genetic, species, and ecosystem levels, crucial for ecosystem stability.
- 4Conservation aims to protect and manage natural resources and biodiversity for sustainable use.
- 5In situ conservation protects species within their natural habitats (e.g., National Parks).
- 6Ex situ conservation protects species outside their natural habitats (e.g., zoos, seed banks).
- 7Sustainable development seeks to meet present needs without compromising the ability of future generations to meet their own needs.
- 8Common pollutants include sewage, industrial waste, agricultural run-off, and greenhouse gases from burning fossil fuels.
Worked examples
Example 1
Outline the sequence of events that leads to eutrophication in an aquatic ecosystem.
Answer
Eutrophication begins with the introduction of excess nutrients (nitrates, phosphates) into an aquatic ecosystem, often from agricultural run-off or sewage. This causes an 'algal bloom' on the water surface, blocking sunlight and killing submerged plants. When the algae and plants die, decomposers (aerobic bacteria) break them down, consuming large amounts of dissolved oxygen. This oxygen depletion (increased BOD) leads to the death of fish and other aquatic organisms, severely impacting the ecosystem.
Remember to link each step logically and explain the role of oxygen depletion.
Example 2
Distinguish between in situ and ex situ conservation, providing one specific example for each method.
Answer
In situ conservation refers to the protection of species within their natural habitats, allowing them to continue to evolve and interact with their environment. An example is the designation of National Parks, like Killarney National Park, to protect native flora and fauna. Ex situ conservation, on the other hand, involves protecting species outside their natural habitats, often when their survival in the wild is severely threatened. An example is the use of seed banks to store seeds of endangered plant species, preserving their genetic diversity for future reintroduction or research.
Ensure your examples are distinct and clearly illustrate the definition of each method.
Example 3
Describe how the burning of fossil fuels contributes to air pollution and explain one significant environmental consequence of this pollution.
Answer
The burning of fossil fuels (coal, oil, gas) releases pollutants such as sulfur dioxide (SO2) and nitrogen oxides (NOx) into the atmosphere. These gases react with atmospheric water to form sulfuric and nitric acids, which then fall as acid rain. A significant environmental consequence of acid rain is the acidification of lakes and rivers. This lowers the pH of the water, making it toxic to aquatic organisms, leading to the death of fish and other invertebrates, and disrupting entire aquatic ecosystems.
You could also explain the enhanced greenhouse effect as an alternative consequence, but choose one and explain it thoroughly.
Common mistakes
- ✗Confusing the cause (excess nutrients) with the symptom (algal bloom) and the ultimate consequence (oxygen depletion and death of aquatic life) in eutrophication.
- ✗Not providing specific examples when asked to illustrate different types of pollution or conservation methods.
- ✗Failing to explain the *mechanism* by which a pollutant causes harm (e.g., simply stating 'acid rain is bad' instead of explaining how it affects pH and organisms).
- ✗Overlooking the role of decomposers and their oxygen consumption in the process of eutrophication.
- ✗Using vague or non-biological terms instead of precise scientific terminology (e.g., 'bad stuff' instead of 'pollutants' or 'nutrients').
Exam tips
- ★Define all key terms accurately and concisely. Practice writing definitions for terms like 'pollution', 'eutrophication', 'biodiversity', 'in situ conservation', and 'ex situ conservation'.
- ★When describing processes like eutrophication, use a clear, logical, step-by-step approach, numbering your points for clarity.
- ★Support your answers with specific, relevant examples. For instance, when discussing pollution, name specific pollutants and their sources.
- ★Pay close attention to the command words in the question (e.g., 'describe', 'explain', 'distinguish', 'outline') to ensure you answer precisely what is asked.
- ★Practise drawing and labelling diagrams for processes like eutrophication, as visual aids can help reinforce your understanding and may be useful for recall, even if not explicitly asked for in every question.
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