Biology Matters GCE O Level Textbook - Organisms and Their Environment PDF

## Chapter 13 Organisms and Their Environment ### What you will learn - How does energy flow through an ecosystem? - What are ecological pyramids? - How are nutrients recycled through an ecosystem? - What are carbon sinks? - How do we affect the ecosystem? - Why is there a need for conservation?...

## Chapter 13 Organisms and Their Environment ### What you will learn - How does energy flow through an ecosystem? - What are ecological pyramids? - How are nutrients recycled through an ecosystem? - What are carbon sinks? - How do we affect the ecosystem? - Why is there a need for conservation? Ants are such a common sight that they may seem almost insignificant. Is this really true? Imagine a world without ants. There would be no ant infestations in our houses and the amount of insecticides used would also be reduced. Let us assume that for a brief moment that we manage to wipe out all the ants on the Earth. What role do ants play in the environment? How would their absence affect other organisms? How would our lives change in a world without ants? If someone told you that we would be at risk of dying of hunger if ants did not exist, would you believe him or her? Why? ### 13.1 How does energy flow through an ecosystem? - Describe the non-cyclical nature of energy flow. - Describe the roles of producers, consumers and decomposers in food chains and food webs. - Explain how energy losses occur along food chains, and discuss the efficiency of energy transfer between trophic levels. #### Nutrient and Energy Flow The living organisms in any ecosystem can be categorized as producers, consumers or decomposers, based on their mode of nutrition. Energy and nutrients are transferred from producers to consumers to decomposers through feeding.  #### Word Alert **Ecosystem:** A community of organisms interacting with one another and with its non-living environment. #### Disciplinary Idea **Systems:** All living organisms are part of a complex network of interactions called the web of life. The interrelationships between living things and the environment include two major processes, the cycling of nutrients and flow of energy. #### What are Producers? A producer is an organism that makes its own food. It contains chlorophyll that absorbs light to convert carbon dioxide and water into glucose, through a process known as photosynthesis. Glucose is a chemical store of energy. Oxygen is also released in the process. Examples of producers are plants and algae. #### What are Consumers? Consumers are organisms that are not able to make their own food. They obtain energy and nutrients by feeding on other organisms. Consumers may be classified as primary, secondary and tertiary according to their position in a food chain. | Consumer Type | Description | | ----------- | ----------- | | Primary Consumers | These are organisms that feed on plants only. | | Secondary Consumers | These are organisms that feed on primary consumers. | | Tertiary Consumers | These are organisms that feed on secondary consumers. | #### What are Decomposers? Decomposers are organisms that get their energy by breaking down dead organisms, faeces and excretory products. Their activities return nutrients like mineral salts to the environment. Examples of decomposers are bacteria and fungi.  #### Helpful Note The image below shows how organisms interact with one another and their environment at various levels of organisation. * **Population:** A group of organisms of the same species that live together in a habitat. * **Community:** A community is made up of all the populations of different species living and interacting with one another in a habitat. * **Ecosystem:** An ecosystem is a community of organisms interacting with one another and with its non-living environment. **Food Chains** A food chain is a series of organisms, beginning with the producer, through which energy and nutrients are transferred. We can represent the feeding relationships between organisms in an ecosystem using food chains. Each organism in a food chain feeds on the organism before it and provides food for the organism after it. A food chain always begins with a producer.  #### Food Webs A food web consists of a network of interconnected food chains.  #### Non-cyclic Energy Flow in an Ecosystem In an ecosystem, energy does not flow in a cycle. The energy flow is non-cyclical (linear). Living organisms cannot use heat to do work. They can only use light and chemical energy. Energy in the form of light has to be constantly supplied to the ecosystem. Hence, the Sun is the principal source of energy input to biological systems. The Sun provides energy in the form of light.  #### Short Food Chains Are More Efficient in Energy Transfer A large amount of energy does not get passed from one trophic level to the next, as it is lost to the environment as heat, or transferred to uneaten body parts, faeces and excretory products. There will be less and less energy available for the organisms at the next trophic level as we move along the food chain. Hence, food chains are generally short. The shorter the food chain, the greater the amount of energy available to the final consumer, because less energy is transferred to the environment. We say that short food chains are more energy-efficient than long food chains. For example, more energy will be available to a man if he feeds directly on the crop plants grown on a given area, rather than eating rabbits that feed on the crop plants grown on the same given area. #### Why Do Food Chains Usually Have Fewer Than Five Trophic Levels? Energy transfer along the food chain is inefficient. About 90% of the energy is lost as it is passed from one trophic level to the next. - The energy is transferred to the environment as heat during respiration. - The energy is also transferred to uneaten body parts, faeces and excretory products. Hence, there is insufficient energy to support a long food chain. #### Predator-prey Relationship An animal that feeds on another animal is called a predator. An animal that is eaten by another animal is called the prey. For example, ospreys (also called sea hawks) eat fish, so ospreys are the predators of fish. Fish are the prey of ospreys.  #### Word Alert **Fluctuation:** Irregular rise and fall in number or amount. The fluctuation in the populations of predators and prey can be illustrated by the graph below.  An increase in the population size of the prey means that more food is available for the predators. This leads to an increase in the number of the predators, causing a decrease in the population of the prey. This in turn results in an inevitable decrease in the population of the predators as less food is available. The decrease in the number of the predators leads to an increase in the number of the prey. This cycle of predator-prey relationship repeats over time. The increase and decrease in the population of the predators follow the corresponding increase and decrease in the population of the prey. The average size of the population of the prey is larger than that of the predator. Although there are other factors involved, predation plays an important role in regulating natural populations. ### 13.2 What are ecological pyramids? - Describe and interpret pyramids of numbers and biomass. Food and energy relationships can be shown using horizontal bar diagrams. The producers are placed at the bottom, the primary and secondary consumers in the middle, and the tertiary consumers at the top. Such diagrams form ecological pyramids. We can compare the trophic levels in food chains using ecological pyramids.  #### Pyramids of Numbers A pyramid of numbers allows us to compare the number of organisms present in each trophic level at a particular time. **How is a Pyramid of Numbers Constructed?** Consider the food chain: grass → rabbit → snake → eagle. - There are ten eagles in a given area, and each eagle needs to feed on one snake every day. In a month, the ten eagles will need 300 snakes to keep them alive. - If each snake eats two rabbits every day, 300 snakes will need 18 000 rabbits in a month. - If each rabbit eats about 15 grass plants every day, 18 000 rabbits will need about 8 100 000 grass plants in a month. The number of organisms in each trophic level can be used to construct a pyramid of numbers. The length of the bar in the pyramid represents the number of organisms present at that time For this food chain, the pyramid will be broad at the base and narrow towards the top.  #### Word Alert **Juvenile:** A young organism #### What are some limitations of using a pyramid of numbers to represent a food chain? - It does not consider the size and mass organism. - It does not consider whether the organism is an adult or a juvenile. #### Pyramid of Biomass A pyramid of biomass allows us to compare the mass of organisms present in each trophic level at a particular time. **How Is a Pyramid of Biomass Constructed?** The pyramid of biomass is constructed based on the standing mass - the dry mass of organisms in each trophic level at any one time. The dry mass of an organism is the mass of the organism when all its water has been removed. Consider the food chain: grass → rabbit → snake → eagle. The biomass of the lower trophic level is larger than the biomass of the next trophic level.  #### What are some reasons for and limitations of using a pyramid of biomass to represent a food chain? | Reasons | Limitations | | ----------- | ----------- | | It considers the size and mass of organisms. Hence, it is a more accurate representation of energy flow through a food chain than a pyramid of numbers. | Organisms have to be killed to obtain biomass. | | | It has to be constructed at a particular point in time. | #### Variations in Ecological Pyramids Most ecological pyramids are pyramid-shaped, but there are exceptions. A pyramid of numbers may be upside down or inverted if: - Organisms of one trophic level are parasitic on organisms of another trophic level. - Many small organisms of one trophic level feed on a large organism of another trophic level. Consider the following food chain: tree → bird → flea In this case, the pyramid of numbers is inverted.  However, the pyramid of biomass is not inverted. This is because one tree has a comparatively large biomass to support the other populations  More examples of variations in ecological pyramids are shown below: | Food Chain | Pyramid of Numbers | Pyramid of Biomass | | ----------- | ----------- | ----------- | | grass → rabbit → snake → eagle | | | | tree → aphid → ladybird → small bird | | | | grass → zebra → tsetse fly | | | **Let's Practise 13.2** 1. Why is the pyramid of biomass a better representation of the energy flow through a food chain than a pyramid of numbers? ### 13.3 How are nutrients recycled through an ecosystem? - Describe how carbon is cycled within an ecosystem. #### Nutrient Cycling In an Ecosystem Carbon, oxygen, nitrogen and water are essential substances in nutrients needed for life. In natural ecosystems, these substances are released back into the soil when organisms die. Decomposers, such as fungi and bacteria, break down dead organisms. In this way, materials locked up in the dead organisms can be returned to the physical environment, to be used again by green plants. Hence, in a balanced ecosystem, nutrients are never lost but are continuously recycled. The cycling of these nutrients is brought about by physical, chemical and biological processes. #### The Carbon Cycle Carbon is constantly being removed from and released into the environment, in the form of carbon dioxide. Hence, the concentration of carbon dioxide in the environment remains relatively constant. The various processes by which carbon, in the form of carbon dioxide, is removed from and released into the environment make up the carbon cycle.  #### What is the importance of the carbon cycle? - Ensures that there is a continuous supply of carbon dioxide for plants to carry out photosynthesis.* - Enables energy to flow through the ecosystem. Carbon compounds carry the stored energy from organism to organism in the food chains of an ecosystem. - Regulates the amount of carbon dioxide in the atmosphere. #### Let's Practise 13.3 1. Figure 13.17 shows the flow of carbon compounds in the carbon cycle. The letters A, B, C and D represent carbon compounds in plants, animals, decomposers and the atmosphere. Assume that B represents plants, answer the following questions.  a. State what each letter, A, C and D, represents. b. Name the processes represented by the numbers 1, 2, 3 and 4. c. Which processes, 1, 2, 3 or 4, do not return carbon dioxide to the atmosphere? d. Which process, 1, 2, 3 or 4, converts carbon from a simple form into another, more complex form? ### 13.4 What are carbon sinks? - Outline the role of forests and oceans as carbon sinks. A carbon sink is an area that stores carbon from the atmosphere for a long period of time. It stores more carbon than it releases. In other words, a carbon sink is a carbon reservoir. The two main natural carbon sinks are forests and oceans. Carbon sinks remove carbon dioxide from the atmosphere. **Oceans as carbon sinks**. Oceans are the largest carbon sinks on Earth. About one-third of the carbon dioxide released by human activities is absorbed by oceans. The role of oceans as carbon sinks is driven by two processes, namely solubility and photosynthesis. The carbon dioxide that dissolves in the ocean's water is absorbed and used by aquatic plants in photosynthesis. A portion of the carbon compounds found in oceans is buried in the seabed and is in the form of fossil fuels such as natural gas and oil.  **Forests as carbon sinks** Forests are also important carbon sinks. Atmospheric carbon dioxide is absorbed by the plants and used in photosynthesis. In forests, a large amount of carbon compounds is stored in trees. When trees die, their remains may be buried deep in the ground. After millions of years, these remains form coal, a type of fossil fuel. Studies of the Asian, African and South American tropical forests show that forests absorb about 20% of all the carbon dioxide released by the burning of fossil fuels.  Indiscriminate deforestation has damaging effects. Hence, efficient forest management is important. Canada has about 10% of the world's forests. It claims that less than 0.5% of its forests are harvested in any given year. These harvested areas are allowed to regenerate into forests again. The goal of the Paris Agreement is to keep the rise in global average temperature to below 2 °C. It aims to limit the temperature increase to 1.5 °C. This is expected to substantially reduce the effects of climate change. Carbon emissions should be reduced as soon as possible and reach net-zero by middle of the 21st century. The Paris Agreement is an international treaty on climate change, which covers climate change mitigation, adaptation and finance. The Agreement was negotiated by 196 parties at the 2015 United Nations Climate Change Conference in France. Singapore signed the Paris Agreement on 22 April 2016. By November 2021, 193 members of the United Nations Framework Convention on Climate Change (UNFCCC) are parties to the Agreement. Singapore launched a Climate Action Plan in July 2016. The Plan provides details of the strategies for adapting to the impact of climate change, such as implementing coastal and infrastructure protection measures. It also mentions ways to reduce carbon emissions up to 2030, such as improving energy efficiency, reducing carbon emissions from power generation and developing cutting-edge low-carbon technologies. These are the steps that have been drawn up in Singapore's climate pledge under the UNFCCC.  **Let's Practise 13.4** 1. What is a carbon sink? 2. Why carbon sinks are important? Suggest how the number of carbon sinks on Earth can be increased? ### 13.5 How do we affect the ecosystem? - Describe how human activities, such as deforestation and use of fossil fuels, cause an increase in atmospheric carbon dioxide concentration, leading to global warming. - Discuss how human actions can reduce the effects of global warming. - Describe the effects of pollution caused by: sewage in water; plastic wastes in the marine environment; insecticides and their biomagnification up food chains, impacting top carnivores. You probably have a rubbish bin in your kitchen. Where does all the waste go, and what would happen if it were not removed? Would your kitchen and home end up buried under a mountain of rubbish, and be unfit for living? Earth is a limited resource and has limited space. It is also our home, and if we do not maintain it, we will ruin it. #### Disciplinary Idea **Systems:** Human activities can have positive and negative impact on the local and global environment, which are natural-occurring systems #### Word Alert **Depleting:** Reducing in number or quantity Natural resources are resources supplied by nature. Air, water, soil, forests and wildlife are renewable natural resources. They can be replaced in the ecosystem by natural cycles as long as humans do not overuse them. On the other hand, natural resources such as fossil fuels take millions of years to form naturally. Since their formation takes millions of years, they cannot be replaced quickly enough. They are called non-renewable natural resources. Human beings are continually using and depleting the Earth's natural resources. This upsets the balance of nature and causes lasting damage to the environment. The environmental damage caused is largely irreversible. Thus, human activities must be carefully planned and monitored to preserve and conserve the environment for the future. In this section, you will learn about the effects some human activities have on the ecosystem. The extraction of natural resources may lead to habitat destruction, through deforestation and pollution.   These effects interrupt the food chains and food webs in the ecosystem. Through altering food chains and food webs, humans can have a negative impact on habitats. An example that has a great effect on the habitat is deforestation. ### Deforestation Before 1819, Singapore's population numbered about 150 villagers. There were very few houses and most of Singapore's land area was covered by swampy jungle and forests. As of 2021, the population is about 5.9 million people! Tall buildings have sprung up almost everywhere and roads cover Singapore's land area. Singapore is referred to as a 'concrete jungle. #### Word Alert **Natural heritage:** All components of biodiversity, including flora and fauna, ecosystems and geological structures that have some special value for future generations Although land is still being cleared in Singapore, there are areas of green spaces that are marked for conservation. These areas have large extent of greenery and natural heritage that should be conserved. #### Why are forests cleared? The clearing of forests is known as deforestation. Forests are cleared to meet the increasing demands for land and materials such as wood. With modern technology, forests are cleared at a much faster rate than they can be replaced.  #### What are the undesirable effects of deforestation? Clearing forests for land and materials can have devastating effects on the local wildlife and environment, such as extinction and reduction in biodiversity. Deforestation can also have more far-reaching consequences. It can lead to an increase of carbon dioxide in the atmosphere, which contributes greatly to global warming. * **Extinction and reduction in biodiversity** Clearing forests leads to habitat destruction for many species of animals. The remaining amount of forested land may not be big enough to support a breeding population of these animals. The animals may become endangered or extinct. This may result in a loss of biodiversity. * **Global warming** When trees in the forests are growing, photosynthesis occurs at a higher rate than respiration. The excess carbon is stored in tree trunks, roots and in the soil. When trees in the forests are cut down, they release into the atmosphere all the carbon dioxide they have been storing. Further emissions of carbon dioxide are created when the trees are left to rot on the forest floor or when they are burnt. Carbon dioxide is the most commonly produced greenhouse gas. Deforestation will result in the decrease in the number of trees which function to remove carbon dioxide from the atmosphere through the process of photosynthesis. Hence, the concentration of carbon dioxide in the atmosphere will increase, leading to global warming. **Helpful Note** - Deforestation causes soil erosion. The leafy canopy of the trees in forests protects the soil from the impact of the falling rain. When trees are removed, the soil is directly exposed to the force of the rain. There are also no roots to bind the soil. The topsoil, the most fertile layer, is eroded (gets washed away) during heavy rains, especially if the rain falls on steep slopes. - Soil erosion due to deforestation can lead to floods. The eroded soil may be deposited in rivers and streams, blocking the flow of water. The water levels in rivers rise rapidly, causing floods. - When forests are cleared, the leafy canopy of trees no longer exists. Sunlight falls directly onto the soil. Water evaporates rapidly from the soil, causing it to harden. The land becomes barren, and plants cannot grow in the soil. This is known as desertification. The survival of organisms that depend directly or indirectly on plants for food are also threatened. #### Effect of human activities on global warming Human activities that cause an increase in carbon dioxide concentration in the atmosphere, leading to global warming include: - Deforestation: Without the trees to absorb atmospheric carbon dioxide for photosynthesis, the concentration of carbon dioxide in the atmosphere will increase. Annual rainfall in the area will decrease. - Combustion of fossil fuels like coal and gas - Combustion of plastic waste - Emission from motor vehicles #### Effects of carbon dioxide pollution - **Greenhouse effect** Carbon dioxide is a greenhouse gas. It forms a layer over Earth's surface. Heat is trapped within this layer around Earth. This is the greenhouse effect that causes global warming. An enhanced greenhouse effect may result in climate change. Ice sheets in Greenland and Antarctica may melt. Sea levels may rise, causing flooding in some countries. - **Loss of biodiversity** The rise in seawater temperature may result in a loss of biodiversity. For example, it causes coral bleaching and death of corals in coral reefs. Coral reefs provide a habitat for a large variety of marine organisms. Corals rely on colourful algae which live in their tissue and produce food for the corals. When corals are stressed by changes in light, water or temperature, they expel the algae that live in them and turn white. This process is known as coral bleaching. Corals that have been bleached lose their ability to support as many species, leading to a loss in biodiversity. #### Rising atmospheric temperatures and extreme weather such as floods Rising atmospheric temperatures and extreme weather such as floods could mean more breeding grounds for mosquitoes. More outbreaks of mosquito-borne diseases such as dengue could occur. **Helpful Note:** Singapore uses Wolbachia-Aedes suppression technology to control the spread of dengue, a mosquito-borne disease. The Wolbachia bacteria is found naturally in some mosquito species. The National Environment Agency of Singapore (NEA) breeds a large number of male Aedes mosquitoes that carry the Wolbachia bacteria, and regularly releases them into the environment. When these mosquitoes mate with the urban female Aedes mosquitoes that spread dengue, the eggs produced do not hatch. Hence, no offspring are produced. This leads to a decline in the population of Aedes mosquitoes and a decline in dengue cases. - **Effect on aquatic ecosystems** High atmospheric carbon dioxide concentrations affects the aquatic ecosystems. More atmospheric carbon dioxide dissolves in the sea water which becomes more acidic. The acid dissolves calcium compounds in the shells of shellfish. This weakens their shells, making them more vulnerable to predators.  #### Difference between Global Warming and Climate Change Global warming is the rise in global temperature. This process is accelerated by human activities that cause increasing concentrations of greenhouse gases, such as carbon dioxide, in the atmosphere. Climate change refers to the changes in temperature and weather patterns over a long period of time. The effects of climate change include rising sea levels, melting of ice sheets in Greenland and Antarctica, shifts in flowering or plant blooming times and unpredictable weather changes. In some countries, there may be more frequent and intense hurricanes and winter storms.  **Tech Connect:** Climate change is a real problem that is affecting many parts of the world today. In recent years, scientists and engineers have focused on slowing down climate change. This has led to the discovery of a type of technology called Green Technology. In 2017, the United Nations Environment Programme identified eight main areas where scientists and engineers could develop green technologies. Here are five of those areas: - Designing lighting equipment that consumes less energy. - Designing buildings that do not demand large amounts of energy to maintain. - Managing the use of energy, especially in a building. - Developing energy-efficient devices in information and communications technology. - Moving towards electric passenger transportation vehicles such as cars and trains. **How Human Actions Can Reduce the Effects of Enhanced Global Warming** - Reduce the use of fossil fuel. Use renewable sources of energy like solar energy and wind. - Reduce our consumption of energy. We can save electricity by using more efficient devices, e.g. use LED light bulbs. - Replace petrol-powered vehicles with hybrid or electric vehicles. - Reduce daily consumption of electricity, water, paper and plastic. - **Forest management:** - Conservation of forest: Disruption of natural cycles such as the carbon cycle can be prevented, and this helps to prevent global warming. Indiscriminate felling of trees should be prevented. - Reforestation: New seedlings can be planted to replace trees that have been removed or destroyed. - Control of forest fires: Some forest fires are man-made. People set fires to clear forests to provide land for agriculture. This must be prevented. Education programmes should be conducted to make people aware of the importance of forests to our lives and the methods by which forests can be conserved. The Singapore Green Plan 2030 is a nationwide movement to advance Singapore's national agenda on sustainable development. It aims to ensure that Singapore will remain a green and liveable home for current and future generations. Some of the key initiatives include: - to reduce carbon emissions, keep our environment clean - to save resources and energy - to use cleaner energy and lower our carbon footprint **Let's Practise 13.5** 1. How does discharge of raw sewage into nearby rivers cause eutrophication? ### `13.6 Why is there a need for conservation?` - Discuss how the conservation of species and sustainable use of natural resources contribute to the maintenance of biodiversity and a balanced ecosystem (e.g. coral reef, tropical rainforest, mangrove). We know that if we do not spend our allowance carefully, we will not have enough to last through till the next time we receive some. Wisdom tells us that it is good to spend less than what we receive or earn. This ensures that we are not short of money for emergencies. Conservation is similar making sure we do not overuse and managing the natural resources, so that we do not cause lasting damage. #### The Need For Conservation No one knows for sure what the total number of species on Earth is. There may be 10 million or 100 million species! However, out of this vast number of species, barely two million have been identified and studied by scientists. Many organisms in aquatic habitats have not been discovered or intensively studied due to human and technological limitations. Tropical rainforests have the most diverse ecosystem in the world. #### Cool Career **Nature conservation officer** Do you have a keen interest in protecting the environment? Do you enjoy working outdoors? The main responsibilities of a nature conservation officer involve planning and implementing schemes aimed at preserving and protecting areas of natural beauty, and promoting biodiversity. These officers also increase the awareness of conservation in the community by educating the public. Sadly, many species, are becoming extinct even before they can be discovered or studied. As you have learnt, human activities can upset the balance of nature, often with disastrous results. We have depleted many of our precious natural resources, such as forests and fish. Pollution caused by our activities also harms many organisms and destroys habitats. As a result, the rich biodiversity on Earth is being threatened. Conservation is necessary to maintain Earth's biodiversity. #### Biodiversity Biodiversity refers to the range of species that are present in a particular ecosystem. **Conservation** is the protection and preservation of natural resources in the environment.  #### Maintaining biodiversity by preventing the extinction of species Maintenance of a large gene pool is important as many wild plants and animals possess favorable genes. By cross-breeding the different varieties of wild plants and animals, we can improve agricultural produce. For example, plants with better resistance to diseases and drought can be produced by crossing domestic species with wild species. Many tropical plants are of great importance as they are sources of medicinal drugs. Examples include quinine, an anti-malarial drug from the bark of Cinchona, and vinblastine, a drug used to treat leukemia (a type of cancer) derived from the Madagascar rosy periwinkle. Many more medicinal drugs in plant species remain to be discovered. To prevent extinction of a species, genetic diversity must be maintained. Any change in environmental conditions is less likely to wipe out the whole species. #### Reasons for Conservation - For scientific research The study of wildlife provides useful information to humans. For example, we learn about evolution from studying wildlife. - **For economic purposes** Marine life needs to be conserved as they are a major source of human food. Tropical rainforests also provide food. Rice, pineapple and banana are some examples of food plants that were developed from rainforest plants. Tropical plants provide raw materials for industries. For example, rattan is used to make furniture, rubber from the latex of rubber trees is used to make tyres, and fibres from cotton plants are used to make cloth. - **To maintain a stable and balanced ecosystem** This prevents disruption of natural cycles such as the carbon cycle, and prevents global warming. - **To preserve natural scenery and wildlife for people to appreciate** Natural resources enable outdoor recreational activities such as fishing, hiking and skiing.  #### How Can Resources Be Conserved and Managed Sustainably? The forest, mangrove swamp and coral reefs are balanced ecosystems. They are carbon sinks and rich in biodiversity. Conservation measures and lifestyle changes are needed to maintain such a rich diversity of life. #### Conservation of Forests Forest conservation has already been discussed. #### Conservation of Mangrove Swamps Some countries have a Mangrove Restoration Project. Volunteers plant mangrove seedlings over a portion of the mangrove swamp. The trees that develop will protect low-lying areas against strong wind, waves and tides.  **Adopt a Mangrove Programme** is a campaign initiated at Pulau Ubin to raise awareness about conservation and restoration of degraded areas to reduce the impact of global warming and climate change. #### Conservation of Coral Reefs Beautiful corals can be found in places such as the Great Barrier Reef in Australia. People visiting coral reefs should practise safe and responsible diving. Divers should not touch the reefs as they may damage the coral animals. Divers should not anchor their boats on the reef as they may kill the corals. Some guidelines for visitors to the reefs should be followed: - Avoid using sunscreen as some ingredients in sunscreen can be harmful to corals. - Avoid purchasing living corals as this will encourage people to extract live corals for sale. - Avoid polluting the coastline with trash, especially non-biodegradable plastic. Such marine debris may be blown or washed away into the ocean. They can be harmful to coral reefs.  #### Let's Practise 13.6 1. Why is it important to maintain biodiversity? 2. How will controlling the human population size help in conservation? ### Let's Map It  #### Our Impact on the Ecosystem  **Let's Reflect:** What can you do to help conserve natural resources and protect the environment? You can make a difference by reducing your use of fossil fuels, by promoting environmental awareness and by supporting organizations that are working to conserve and protect our natural resources. You can also make small changes in your daily life, such as recycling, reducing your use of plastic, and choosing sustainable food sources. Every little bit helps!