Natural Resources and their Conservation for Class 7

Natural Resources

a) Natural resources are valuable assets found in nature that are not created by humans.
b) They can be classified into two types: living natural resources, which include plants and animals, and non-living natural resources, such as air, water, soil, and minerals.

1. Living Natural Resources: Living natural resources are organisms that play an essential role in ecosystems. They encompass diverse plant and animal species that contribute to the overall balance and functioning of the environment.
2. Non-living Natural Resources: Non-living natural resources are derived from different components of the Earth.

c) The lithosphere, which refers to the solid part of the Earth's crust, provides various minerals and materials that are vital for human activities. The hydrosphere encompasses water bodies like seas, rivers, and lakes, which are essential sources of freshwater and support aquatic life. The atmosphere, consisting of the air surrounding the Earth, provides us with oxygen, nitrogen, and other gases necessary for life.

Renewable and Non-renewable Resources

Natural resources are further classified into two main categories based on their renewability:

Renewable Resources

a) Renewable resources are the ones that can be generated again or replaced after they are used up.
b) These resources are present in abundant quantities in nature and can be replenished.
c) Examples of renewable resources include oxygen, sunlight, wind, and air.
d) These resources are called "inexhaustible resources" because they are constantly available and won't run out.

Non-Renewable Resources

a) Non-renewable resources, on the other hand, are the ones that cannot be replaced within a reasonable period of time once they are used up.
b) Once these resources are depleted, they cannot be easily regenerated.
c) Examples of non-renewable resources include minerals and fossil fuels. It takes millions of years for the remains of dead organisms to transform into fossil fuels like coal, oil, and natural gas.
d) These resources are "exhaustible" because they will eventually deplete and run out, possibly within a few hundred years.

Difference between Renewable and Non-Renewable Resources

Understanding the difference between renewable and non-renewable resources is important because it helps us make sustainable choices. We need to be mindful of our use of non-renewable resources and find alternative solutions to reduce our dependence on them. By prioritising the conservation and responsible use of renewable resources, we can ensure their availability for future generations and help protect the environment.

Water - A Renewable Resource

Water is an essential resource that is vital for life on Earth. It covers approximately 71% of the Earth's surface. However, it's important to note that not all water is readily available for human consumption. Out of the total water on Earth, around 97% is found in the oceans and seas, and it is too salty to be directly consumed or used for most purposes. The remaining 3% is freshwater, which is found in the form of rivers, lakes, and underground sources.

I. States of Water

Water can exist in three states:

a) Solid State: Water exists in a solid state as ice in polar regions, snow-covered mountains, and glaciers. These frozen forms of water play a crucial role in maintaining the planet's climate and water cycle.

b) Liquid State: Most of the water on Earth exists in a liquid state. It can be found in rivers, lakes, and oceans. This is the form of water that is readily available for human use, such as for drinking, agriculture, and various industrial purposes.

c) Gaseous State: Water can also exist as water vapour, which is the gaseous state of water. Water vapour is present in the air and is invisible to the naked eye. It plays a vital role in the Earth's climate system, contributing to the formation of clouds, precipitation, and the overall water cycle.

II. Renewability of Water

a) Water is often considered a renewable resource because it goes through a natural cycle known as the water cycle or hydrological cycle. This cycle involves the continuous movement of water between the Earth's surface, the atmosphere, and back again.
b) Through processes such as evaporation, condensation, and precipitation, water is constantly replenished in different forms.
c) However, it is important to note that water resources can be impacted by human activities and natural factors. Overuse, pollution, climate change, and improper water management practices can put a strain on water sources and affect their availability and quality. It is crucial to use water responsibly, conserve it, and protect water sources to ensure a sustainable and reliable supply of freshwater for current and future generations.

III. Water Cycle

The water cycle is the continuous movement of water within the Earth and atmosphere. It involves various processes that work together to recycle and redistribute water. Different steps involved in the water cycle are:

a) Evaporation: The process of evaporation occurs when the heat from the sun causes water on the Earth's surface, such as rivers, lakes, and oceans, to turn into water vapour. This water vapour then rises into the air.

b) Transpiration: Transpiration is the process by which water evaporates from the surface of plants, particularly through tiny openings called stomata on leaves. Just like evaporation from water bodies, transpiration adds water vapour into the air.

c) Condensation: As the water vapour rises higher into the atmosphere, it encounters cooler temperatures. This causes the water vapour to condense, forming tiny water droplets. These droplets come together to create clouds.

d) Precipitation: When the clouds become saturated with water droplets, they release moisture in the form of precipitation. Precipitation can take different forms, including rain, snow, hail, or sleet, depending on the temperature and atmospheric conditions.

e) Collection of Water: The water that falls from the clouds as precipitation gathers on the Earth's surface. It collects in various places such as lakes, rivers, seas, and oceans, and can also seep into the ground to replenish underground water sources. This collected water will eventually evaporate again, restarting the water cycle.

The water cycle is a continuous and natural process that helps distribute water across the Earth, ensuring the availability of freshwater for various living organisms and maintaining the overall balance of ecosystems. Understanding the water cycle is important as it highlights the interconnectedness of water resources and the need for responsible water management to sustain this vital resource.

IV. Sources of Water

Water, the essential resource for life, is derived from various sources that contribute to its availability.

1. Rainwater

a) Rainwater is one of the most significant sources of freshwater. It is formed when water vapour in the atmosphere condenses into droplets and falls to the Earth's surface as precipitation.
b) This collected rainwater contributes to surface water and replenishes groundwater reservoirs.

2. Groundwater

a) Groundwater is the water found beneath the surface of the Earth, below the water table of a particular area. The water table is the boundary between the uppermost layer of soil and the subsurface area where the spaces between sediments and cracks in rock become saturated with groundwater.
b) Groundwater is stored in underground layers of rock, sediment, or soil known as aquifers. These aquifers act as natural storage areas for groundwater. They are made up of permeable materials that allow water to flow through, such as porous rocks or gravel. Aquifers can vary in size and permeability.
c) Infiltration is the process by which water seeps into the ground and reaches the aquifers. It occurs when precipitation, such as rain or snow, soaks into the soil and percolates downward. Infiltration helps replenish groundwater by adding water to the underground reservoirs.
d) Groundwater is an essential resource as it serves as a source of fresh water for various purposes. It is used for drinking water supplies, irrigation in agriculture, and industrial processes.

3. Surface Water

a) Surface water includes various bodies of water, such as rivers, streams, creeks, and wetlands.
b) It is formed by the accumulation of precipitation, runoff from rainfall, and the melting of snow and ice.
c) Surface water is a vital source for agriculture, industry, and domestic use.

V. Depletion of Water Table

a) The water table of a specific area begins to decline when the amount of water being extracted exceeds the rate at which it is replenished.
b) Factors contributing to the depletion of the water table are:

1. Increasing population: As the population grows, the demand for water increases. More people require water for drinking, sanitation, and other daily needs. This higher demand puts pressure on water resources and can lead to over-extraction, depleting the water table.

2. Increase in agriculture and industrialisation: Agriculture and industries often require significant amounts of water. As agricultural practices expand and industries grow, more water is needed for irrigation, livestock, manufacturing processes, and cooling systems. If water usage is not managed sustainably, it can lead to the overuse of groundwater and the lowering of the water table.

3. Deforestation: Trees play a vital role in maintaining the water cycle and regulating groundwater levels. Deforestation, or the clearing of forests, reduces the number of trees that help absorb and retain water in the soil. Without the natural regulation provided by trees, more water runs off the surface and does not replenish the groundwater, resulting in a decline in the water table.

4. Low rainfall: Rainfall is a significant source of water that replenishes the water table. In regions with low or irregular rainfall, less water enters the ground to replenish the groundwater. This can contribute to a decrease in the water table level over time.

VI. Water Conservation

Water conservation is important to ensure the sustainable use of this valuable resource. Some methods and practices that can help conserve water are:

a) Avoid Wastage: Being mindful of water usage and avoiding unnecessary wastage is crucial. Simple actions like turning off taps when not in use and fixing leaks promptly can significantly reduce water waste.

b) Rainwater Harvesting: Encouraging rainwater harvesting is an effective way to conserve water. It involves collecting rainwater from rooftops or other surfaces and storing it for future use. This harvested rainwater can be used for various purposes like watering plants, cleaning, or even as a source of drinking water.

c) Efficient Irrigation Methods: Using efficient irrigation methods can greatly reduce water consumption in agriculture and landscaping. Drip irrigation, for example, delivers water directly to the plant roots using narrow pipes or tubes and ensures there is no wastage of water.

d) Proper Treatment of Wastewater: Avoiding water pollution is essential for the conservation of water bodies. Treating sewage and industrial wastewater before disposal helps reduce the contamination of water sources.

These are just a few examples of water conservation practices. Conserving water not only helps to sustain our current needs but also preserves water resources for future generations. By adopting water-saving habits and promoting responsible water management, we can contribute to a more sustainable and water-secure future.

Wastewater

Wastewater refers to all liquid water that comes from various sources such as households, hospitals, industries, and agricultural fields. It is the water that has been used and becomes contaminated, making it unsuitable for further use.

a) Composition: Wastewater from households contains a mixture of used water, urine, faeces, detergents, food particles, and traces of oil. Additionally, rainwater that enters drains contributes sediment, pebbles, leaves, and other plant materials to the wastewater. The collective term for wastewater flowing through drainage pipes is sewage.

b) Contaminants: Wastewater contains dissolved and suspended impurities known as contaminants. These contaminants can include chemicals, pathogens, organic matter, nutrients, and other pollutants that can be harmful to the environment and human health.

c) Treatment: Wastewater undergoes treatment processes to remove or reduce contaminants before being discharged back into the environment or reused. Treatment methods may involve physical, biological, and chemical processes to remove solids, bacteria, viruses, and other pollutants.

d) Environmental Impact: If untreated or improperly treated, wastewater can have detrimental effects on water bodies, ecosystems, and human health. Contaminants from wastewater can pollute rivers, lakes, and oceans, harming aquatic life and affecting the overall ecosystem balance.

e) Reuse Opportunities: Treated wastewater can be reused for various purposes such as irrigation, industrial processes, and even replenishing groundwater reserves. Reusing wastewater can reduce pressure on freshwater resources and promote sustainable water management.

I. Composition of Sewage

a) Sewage, which is the wastewater flowing through drainage pipes, contains various types of impurities and substances.
b) Sewage can contain inorganic impurities such as nitrates, phosphates, and metals. These substances can come from sources like fertilisers, detergents, and industrial discharges.
c) Organic impurities in sewage include human excreta, urine, food waste, fruits and vegetable residues, and even pesticides. These organic materials contribute to the organic load of sewage and can serve as a source of nutrients for bacteria and other organisms.
d) Sewage often contains bacteria, viruses, and other microbes that can cause waterborne diseases. These pathogens can be present in human waste and can contaminate water sources if the sewage is not properly treated or disposed of.
e) Sewage can also carry construction-related waste, such as cement, paints, and chemicals. These substances may enter the sewage system as a result of construction activities or improper disposal practices.

II. Wastewater Management

Wastewater undergoes a series of physical, chemical, and biological processes to treat and remove impurities before it can be safely released back into the environment. Here is an overview of the typical wastewater treatment process:

Screening

a) The wastewater is initially passed through screens or grids to remove larger objects like plastic bags, cans, and sticks. This helps prevent clogging and damage to subsequent treatment processes.
b) The wastewater then goes through a grit and sand removal tank to separate smaller particles like sand and gravel.

Primary Treatment

a) After screening, the wastewater enters large tanks where solid waste settles at the bottom through a process called sedimentation.
b) Mechanical equipment like scrapers removes this settled solid waste, known as sludge.
c) Floatable materials, called scum, are skimmed off the surface. The remaining wastewater, known as clarified water, continues to the next stage.

Secondary Treatment

a) The clarified water undergoes secondary treatment, which involves transferring it to an aeration tank. Here, air is pumped into the water to promote the growth of aerobic bacteria.
b) These bacteria break down organic contaminants that may have escaped the primary treatment process. The bacteria and other solids, known as activated sludge, settle at the bottom of the tank.

Final Treatment Stage

a) The activated sludge is then passed through a sand drying machine where the sludge is dried, and water is filtered out.
b) The filtered water is then treated with chemicals, such as chlorine, to disinfect it and remove any remaining pathogens. This treated water can be safely discharged into rivers or oceans.
c) The dried sludge, which has been separated from the water, can be reused as a fertiliser.

Wastewater treatment processes aim to remove or reduce contaminants, solids, and pathogens from the wastewater, making it safe for the environment and minimising the potential for waterborne diseases. Effective wastewater management is essential to protect water resources and maintain the health of ecosystems.

 III. Alternative Wastewater Management Practices

1. Better Housekeeping Practices

To ensure responsible wastewater management and prevent the introduction of harmful substances into the sewage system, it is important to follow certain housekeeping practices.

a) Avoid draining cooking oils and fats down the kitchen sink. These substances can solidify and cause blockages in the pipes, leading to plumbing issues.
b) Refrain from disposing of chemicals like paints, insecticides, and medicines in the sink or toilet. Properly dispose of them according to local guidelines or take them to designated collection centres for safe disposal.
c) Avoid draining tea leaves, vegetable and animal food waste, and eggshells down the sink or toilet. These materials can contribute to clogs and interfere with the wastewater treatment process. Dispose of food waste in compost bins or designated organic waste collection systems.

  2. Vermicomposting Toilet

a) Vermicomposting toilets provide an alternative approach to waste management that involves the use of earthworms to decompose organic waste.
b) In a vermicomposting toilet system, the waste sewage slurry is treated by introducing specific types of earthworms like wigglers and tiger worms. These worms consume and break down the organic waste materials present in the slurry.
c) Vermicomposting toilets offer a simple and hygienic method of waste treatment. They require low water consumption and have no odour problems when properly maintained.
d) The worms in the vermicomposting toilet system digest the organic waste, converting it into nutrient-rich vermicompost. This compost can be used as a valuable fertiliser for gardens and plants.
e) Vermicomposting toilets reduce the reliance on traditional sewage systems and minimise the release of untreated waste into water bodies.

Implementing better housekeeping practices and exploring alternative waste management systems like vermicomposting toilets can contribute to reducing water pollution, conserving water resources, and promoting sustainable living.

Forest - A Natural Resource

Forests are vast areas of land densely covered with trees, bushes, and other vegetation. They are considered renewable resources because they can be replenished over time through natural processes. Forests provide numerous benefits and play a vital role in maintaining the health of our planet.

I. Importance of Forests

a) Vegetation Layers: Forests consist of different layers of vegetation. Trees form the uppermost layer, followed by shrubs, and then the herbaceous layer of smaller plants. This diverse vegetation provides habitat, food, and shelter for a wide range of birds, insects, and animals.

b) Soil Erosion Prevention: Forests help prevent soil erosion by holding the soil in place with the intricate root systems of trees. Their dense vegetation and leaf litter also act as a natural protective cover, reducing the impact of raindrops on the soil surface.

c) Oxygen Production and Carbon Dioxide Absorption: Trees in forests are essential for oxygen production through the process of photosynthesis. They absorb carbon dioxide, a greenhouse gas, helping to mitigate climate change and maintain the balance of gases in the atmosphere.

d) Wildlife Habitat: Forests provide critical habitats for a diverse array of wildlife. They offer shelter, nesting sites, and sources of food, supporting a wide range of animal species, including mammals, birds, reptiles, and insects.

e) Flood Prevention and Water Table Regulation: Forests play a crucial role in preventing floods by intercepting rainfall and slowing down the flow of water. They also contribute to maintaining the water table by absorbing and retaining water, releasing it gradually into rivers and groundwater.

f) Rainfall Enhancement: Forests can influence local weather patterns and enhance rainfall through a process called transpiration. Trees release water vapour into the atmosphere through their leaves, contributing to cloud formation and increased precipitation.

g) Resource Extraction: Forests provide us with a variety of valuable products. Timber is used for construction and furniture, while wood pulp is used in the production of paper. Forests also yield essential oils, spices, and medicinal plants, which are utilised for various purposes.

Understanding the importance of forests as natural resources helps us appreciate their ecological, economic, and social value. Sustainable forest management and conservation are crucial to protect these valuable ecosystems and ensure their benefits for future generations.

II. Deforestation

Deforestation refers to the large-scale cutting down of trees. It has significant effects on the environment and ecosystems. Some key effects of deforestation are:

a) Air Pollution: Deforestation contributes to increased air pollution as trees play a vital role in absorbing carbon dioxide and releasing oxygen. The removal of trees reduces the Earth's capacity to regulate greenhouse gases, leading to higher levels of carbon dioxide in the atmosphere.

b) Global Warming: Trees act as carbon sinks, storing carbon dioxide and reducing its concentration in the atmosphere. Deforestation disrupts this process, resulting in increased greenhouse gas emissions, which contribute to global warming and climate change.

c) Floods: Forests help regulate water flow by absorbing rainfall and releasing it gradually into rivers and groundwater. Deforestation disrupts this natural water regulation system, leading to increased surface runoff, soil erosion, and a higher risk of flooding.

d) Loss of Habitat and Biodiversity: Deforestation destroys the habitat of countless plant and animal species. Many species depend on forests for food, shelter, and reproduction. The loss of forests leads to a decline in biodiversity and can even lead to the extinction of certain species.

III. Conservation of Forests

To conserve forests and their valuable resources, va rious steps can be taken:

a) Prevention of Overgrazing: Controlling the grazing of animals in forest areas helps prevent damage to vegetation and allows forests to regenerate naturally.

b) Protection against Poaching and Hunting: Strict enforcement of laws and regulations to prevent illegal poaching and hunting helps protect wildlife populations and maintain the ecological balance of forests.

c) Forest Fire Control: Implementing measures to prevent and control forest fires is crucial. Proper fire management practices, including firebreaks, early detection systems, and community awareness, can help minimise the devastating impact of wildfires.

d) Afforestation: Promoting afforestation by planting more trees helps increase forest cover and restore degraded areas. Reforestation efforts can help in the conservation of biodiversity, soil stabilisation, and climate regulation.

By taking these conservation measures, we can protect and preserve our forests, ensuring their ecological, economic, and social benefits for present and future generations.

Food Chain

a) The food chain is a way of illustrating how living organisms in an ecosystem depend on each other for their food source. It shows the sequence of "who eats whom" in nature.
b) At the very beginning of the food chain, we have plants, which are known as producers. They produce their own food through a process called photosynthesis, using sunlight, water, and nutrients from the soil to create sugars.
c) Next, there are animals that consume plants. These animals are called primary consumers or herbivores. They are the first level of consumers, relying on plants as their source of energy. Examples of primary consumers include rabbits, cows, and deer.
d) Moving up the food chain, we encounter animals that feed on other animals. These creatures are known as secondary consumers or carnivores. Their energy comes from consuming the primary consumers or herbivores. For instance, a lion is a secondary consumer because it preys on herbivores like zebras.
e) In some cases, there are animals that eat the secondary consumers, and they are called tertiary consumers. Tertiary consumers are the top predators in the food chain. For example, a crocodile might be a tertiary consumer if it preys on lions, or a hawk might be one if it eats other birds.
f) In addition to the primary, secondary, and tertiary consumers, there's another group of organisms called decomposers. Decomposers, like bacteria and fungi, play a vital role in breaking down dead plants and animals into smaller pieces. They recycle the nutrients back into the soil, allowing plants to grow again and sustaining the food chain.

I. Flow of Energy Through Food Chain

a) It's important to understand that energy flows through the food chain. Plants obtain their energy from the sun, and then that energy transfers from the plants to the primary consumers (herbivores), and from there to the secondary consumers (carnivores).
b) This transfer of energy happens because each level of the food chain uses some of the energy for its own needs and activities.

Food Web

a) A food web is like a giant puzzle made up of interconnected food chains in an ecosystem. While a food chain shows a straightforward path of who eats whom, a food web reveals the intricate connections and dependencies among various organisms in a more complex way.
b) In any ecosystem, there is a wide variety of plants and animals, each playing a role in the web of life. Some animals have specific diets, while others are more versatile in what they eat. A food web helps us see how all these organisms are linked through their eating habits.

Example of a Food Web:

a) In the forest, there are trees, grass, rabbits, mice, owls, and snakes.
Trees are a source of food for rabbits and mice.
Rabbits and mice, in turn, become prey for owls and snakes.
Owls may also eat snakes if they come across them.
b) This is just the start of the food web, and there may be many more connections in the forest. For instance, owls might also eat insects, and snakes could eat frogs or other small creatures. These additional connections make the food web more intricate and closer to how things work in nature.

Soil

Soil is the layer of earth that covers the surface of the planet. It is made up of various materials, including disintegrated rock, organic matter, and inorganic substances. Soil is essential for the growth of plants, as it provides them with nutrients, water, and support for their roots.

I. Layers of Soil

Soil is composed of different layers known as horizons, and each layer has its own unique characteristics.

a) Horizon O - Humus: This layer is dark and thin, and it's very fertile. It's mainly made up of decomposed matter like dead plants and animals. The humus layer is a nutrient-rich food source for plants, helping them grow strong and healthy.

b) Horizon A - Topsoil: The topsoil is where plants grow their roots. It's soft and porous, allowing air and water to pass through easily. Topsoil is full of organic material, including the humus layer, which nourishes plants and provides essential nutrients for their growth.

c) Horizon B - Subsoil: Below the topsoil, we have the subsoil. It contains larger particles like gravel, rocks, and stones. Subsoil allows water to pass through it and move deeper into the ground, helping to supply water to plants' roots.

d) Horizon C - Regolith:

The regolith layer consists of small pieces of rocks. However, it doesn't allow water to pass through it easily. Instead, it slows down water movement, helping to prevent erosion.

e) Horizon D - Bedrock:

The bedrock is the hard layer of solid rock lying beneath all the other soil layers. It serves as the foundation of the soil. Plant roots cannot penetrate the bedrock, but it provide stability to the soil above.

II. Types of Soil

Soil can be classified into four main types based on its texture:

a) Sandy Soil:

1. Sandy soil is made up of tiny particles of weathered rocks like granite and quartz. 
2. It feels gritty and is not very good for growing plants because it lacks nutrients and cannot hold much water. However, it's excellent for drainage, which means water can flow through it easily.

b) Silt Soil:

1. Silt soil has even smaller particles than sand, and it feels smooth like powder. It holds water better than sandy soil and is found near rivers and lakes. 
2. Silt soil is more fertile and suitable for growing plants, which is why it's used in agriculture to improve soil fertility.

c) Clay Soil:

1. Clay soil has the tiniest particles among the three types.
2. It feels sticky when wet and can be hard for plants to grow in because it doesn't allow much air and water to pass through. But it's great at holding water, making it good for certain crops like wheat.

d) Loamy Soil:

1. Loamy soil is a mix of sand, silt, and clay, combining the best qualities of each. 
2. Loamy soil retains moisture and nutrients, making it perfect for most plants to grow strong and healthy. That's why it's also known as agricultural soil and is commonly used for farming.

III. Uses of Different Types of Soil

IV. Soil Erosion

1. Soil erosion is a natural process in which the top layer of fertile soil is carried away by forces like wind and water.
2. It can also happen due to human activities like farming or construction. When soil erosion occurs, it can be harmful because the fertile soil needed for growing plants gets washed or blown away. This makes the land less suitable for agriculture and can disrupt the balance of ecosystems.

V. Soil Conservation

Soil conservation is important because healthy soil is crucial for agriculture, supporting wildlife, and maintaining a balanced environment. Some important ways to conserve soil are:

Plant Trees: Trees have strong roots that hold the soil together. By planting and preserving trees, we can prevent soil from eroding and keep it in place.

Avoid Overgrazing: When too many animals graze in one area, they eat all the grass, leaving the soil exposed and vulnerable. Proper management of grazing can help protect the soil.

Use Cover Crops: Farmers can plant special crops called cover crops when their main crops are not growing. These cover crops cover the soil and protect it from erosion caused by wind and rain.

Build Embankments: Along rivers, building embankments can control the flow of water, preventing floods and soil erosion along riverbanks.

Reduce Construction Impact: During construction, measures can be taken to prevent soil erosion, like using erosion control blankets or sediment barriers.

Frequently Asked Questions

1.Why is it important to conserve non-renewable resources?

It is important to conserve non-renewable resources because once they are depleted, they cannot be replenished. Using them excessively leads to resource shortages, environmental damage, and increased pollution, impacting future generations.

2. Even though water is renewable, why is it important to use it wisely?

It is important to use water wisely because while water is renewable, fresh, clean water is limited. Pollution, overuse, and climate change can reduce the availability of fresh water for drinking, agriculture, and industry.

3. What is wastewater, and why does it need to be treated?

Wastewater is water that has been used in households, industries, or agriculture and is no longer clean. It needs to be treated to remove harmful substances like chemicals, waste, and bacteria before being released back into the environment to prevent pollution and protect public health.

4. Why are forests considered an important natural resource?

Forests are important natural resources because they provide timber, fuel, and food, help regulate the climate by absorbing carbon dioxide, maintain the water cycle, prevent soil erosion, and provide habitats for a wide variety of plants and animals.

5. Why are food webs more realistic representations of ecosystems than food chains?

Food webs are more realistic because most organisms eat more than one type of food and are eaten by multiple predators. Food webs show the complex interactions and dependencies in an ecosystem, rather than the simple, straight-line flow of energy shown in food chains.