Samacheer Class 6 Science - Our Environment

The Pacific Ocean is indeed an example of an aquatic ecosystem where living organisms interact with their physical environment. Bacteria and fungi are correctly called decomposers because they break down dead organic matter and return nutrients to the soil and water. However, human and animal wastes are examples of biodegradable waste, not non-biodegradable waste, because they can be decomposed by microorganisms and natural processes. Excessive use of pesticides leads to land pollution and water pollution, not just air pollution, as pesticides seep into soil and water bodies. Additionally, in schools, waste management rules require us to separate waste into three categories: wet waste (biodegradable), dry waste (recyclable), and hazardous waste, not just two categories. This three-category system helps ensure proper disposal and recycling of different types of waste.

Biodegradable waste refers to materials that can be easily broken down and decomposed by natural agents and microorganisms. These natural agents include water, oxygen, ultraviolet rays from the sun, and decomposing microorganisms such as bacteria and fungi. Common examples of biodegradable waste include vegetable and fruit peels, leftover food, grass clippings, leaves, twigs, paper, cardboard, and animal manure. When biodegradable waste is disposed of properly, it decomposes naturally and returns to the soil as nutrients, enriching it and making it fertile for growing plants. This type of waste is environmentally friendly because it does not persist in the environment and does not cause long-term pollution like non-biodegradable materials do.

Water pollution can be significantly reduced by adopting responsible practices in our daily lives. We should never pour leftover cooking oil, old medicines, or other chemical waste down the drain or into the toilet, as these substances contaminate water bodies and harm aquatic life. We must reduce the use of chemical pesticides and fertilizers in agriculture because these chemicals seep into groundwater and pollute rivers and lakes. Similarly, reducing the use of detergents and bleach when washing clothes helps prevent these harmful chemicals from entering water systems. We should also avoid littering and always dispose of waste properly in designated waste bins instead of dumping it in water bodies or on land. Additionally, we can conserve water by fixing leaks, using water efficiently, and supporting industries that treat their wastewater before releasing it into the environment. These collective efforts help protect our water resources and maintain healthy aquatic ecosystems.

The food chain is important for understanding the structure and functioning of ecosystems in several ways. Learning about food chains helps us understand the feeding relationships and interactions between different organisms in any ecosystem, showing how energy and nutrients move from one organism to another. It enables us to appreciate the energy flow through different trophic levels, from producers to primary, secondary, and tertiary consumers, and understand how energy is transferred and lost at each level. Food chains also help us understand nutrient circulation in ecosystems, showing how essential elements like carbon, nitrogen, and phosphorus cycle through living and non-living components. Additionally, studying food chains allows us to understand the movement of toxic substances through the ecosystem, a process called bioaccumulation, where harmful chemicals accumulate in organisms at higher trophic levels and cause serious health impacts. This knowledge is crucial for environmental conservation and helps us make informed decisions about protecting ecosystems and reducing pollution.

We can avoid waste by making conscious choices in our daily lives. One important way to avoid waste is to avoid buying packaged foods, as packaging materials contribute significantly to the waste problem. Another way is to refuse to buy 'use-and-throw' plastic products such as plastic bags, cups, and cutlery, which are used for only a short time but persist in the environment for many years. To reduce waste that we have already generated, we can write on both sides of paper instead of using a fresh sheet for every note, which cuts paper consumption in half. We can also share newspapers and magazines with others in our family, school, or community rather than each person buying their own copy. These practices help minimize the amount of waste entering landfills and reduce the demand for new raw materials and packaging.

Noise pollution affects the environment. We all like a quiet and peaceful place since unpleasant or loud sounds disturb us.
Loud music, the sounds of motor vehicles, fireworks and machines cause noise pollution. Continuous noise disturbs our sleep and does not let us study.
Noise pollution has been directly linked to stress and health impacts such as high blood pressure and hearing loss.
Loud noise or even loud music can damage our ears. Noise pollution also disturbs animals.
Birds have to communicate (talk) louder so that, they can hear each other in noisy areas.
Even underwater noise pollution from ships can make whales lose their way as they use sounds to navigate.
Reduce noise pollution :
Turn off your electronics when you do not use them.
Avoid fireworks.
Speak, do not shout.
Remind drivers not to use the horn too much.
Lower the volume when you watch TV (or) listen to music.

If an organism is removed from the food chain, the entire food chain will be disrupted and the ecosystem will become imbalanced. The removal of even a single organism can have cascading effects throughout the entire system. Consider a food chain: Plants → grasshoppers → frogs → snakes → hawks. If frogs were to die off in this chain due to disease or pollutants, the population of grasshoppers, which are the food source for frogs, will increase dramatically because there are fewer predators to eat them. This increase in grasshoppers will cause a major problem because they will consume more plants, leading to overgrazing and depletion of vegetation. At the same time, the predators of frogs, such as snakes and hawks, will face a shortage of food and their populations will decline. This demonstrates how the removal of a single organism creates an imbalance in the ecosystem, affecting multiple species and disrupting the flow of energy and nutrients through the food chain.

Waste, particularly non-biodegradable waste, creates conditions that are ideal for the breeding of disease-carrying mosquitoes. Non-biodegradable substances such as plastic materials, metal scraps, aluminium cans, and bottles cannot be broken down or decomposed into the soil by natural agents and accumulate in open dumps and landfills. When it rains, water collects in the plastic garbage and other waste materials at dump sites, creating small pools and stagnant water bodies. These pools of water provide perfect breeding grounds for mosquitoes, particularly the Aedes aegypti mosquito, which is the primary vector responsible for dengue transmission. The Aedes aegypti mosquito breeds in solid waste, mud pots, and other junk materials found in and around waste dumps. Similarly, other mosquito species breed in dirty, stagnant water environments created by accumulated waste. Once mosquitoes breed in these contaminated areas, they can spread dangerous diseases like dengue and malaria to nearby human populations. This demonstrates the critical link between improper waste management, unsanitary conditions, and the transmission of vector-borne diseases in communities.

We can reduce noise pollution through several practical measures in our daily lives. We should turn off our electronics and appliances when we are not using them, as they contribute to unnecessary noise. We can lower the volume when we watch television or listen to music, both for our own benefit and to avoid disturbing others. We should remind drivers not to use vehicle horns excessively, as honking is a major source of noise pollution in urban areas. We should avoid using fireworks and firecrackers, which produce loud, sudden noises that startle people and animals. Finally, we should speak in normal tones rather than shouting, as this helps maintain a quieter environment in our homes, schools, and communities.

Natural ecosystems and artificial ecosystems differ in their origin and how they are maintained. A natural ecosystem is an ecosystem that originated without human intervention and exists independently in nature. Examples of natural ecosystems include seas, rivers, lakes, and forests, where living organisms interact with each other and their physical environment in a self-sustaining manner. An artificial ecosystem is an ecosystem that has been created and is maintained by humans for specific purposes. Examples of artificial ecosystems include paddy fields used for growing rice, gardens where plants are cultivated, and aquariums where aquatic organisms are kept in controlled conditions. While natural ecosystems have evolved over long periods and maintain their own balance through complex interactions, artificial ecosystems require human management and intervention to function properly.

Animal bones are biodegradable, but they decompose at a much slower rate compared to other types of organic material and tissue. In suitable aerated peaty soil with adequate moisture, microorganisms such as bacteria and fungi will eventually break down the bones. In warm, damp environments, bacteria and fungi attack the proteins in the skeleton, causing the bones to decompose over a period of several decades. However, the rate of decomposition depends heavily on environmental conditions. In dry climates with low moisture and limited microbial activity, bones can take thousands of years to fully decompose. This is why bones are sometimes found intact in archaeological sites and fossil records. Despite their slow decomposition rate, bones are still classified as biodegradable because they will eventually be broken down by natural biological processes, unlike non-biodegradable materials such as plastics and metals.

Not all types of clothes are biodegradable. Biodegradability depends on the type of fibres and materials used to make the fabric. Natural fibres such as cotton, silk, and hemp are biodegradable because they come from plants and can be broken down by microorganisms in the environment. However, synthetic fibres like polyester are not biodegradable. Polyester is a polymer, which is a long chain of repeating molecular units, essentially making it a form of plastic. Synthetic fabrics are made from artificial and chemical components that resist natural decomposition. Additionally, the more chemicals used in processing and treating the fabric, the longer it takes to biodegrade. Therefore, clothes made from natural fibres will decompose relatively quickly in the environment, while those made from synthetic materials like polyester will persist for many years, contributing to environmental pollution. Understanding the biodegradability of different fabrics helps us make environmentally conscious choices about the clothes we wear and dispose of.