How Nature Works in HarmonyClass 8 Science Notes

How Do We Experience and Interpret Our Surroundings?

A habitat is simply a place where an organism lives. This could be a large area like a forest, or a small area like the bark of a tree. In their habitats, plants and animals interact with each other and adapt to the conditions around them to survive.

Habitats contain different kinds of plants and animals. To understand a habitat, you need to identify both the living organisms and the non-living components within it.

Biotic and Abiotic Components

When you observe a habitat, you'll notice that it has both living and non-living things. Living things are called biotic components, while non-living things are called abiotic components.

• Biotic components: These include all the living organisms in a habitat, such as plants, animals, and microorganisms.
• Abiotic components: These include all the non-living things in a habitat, such as water, soil, air, sunlight, and temperature.

Different organisms live in different habitats because every organism needs specific conditions to survive. Some organisms live on land, while others live in water, because each habitat offers different living conditions.

How Organisms Survive in a Habitat

A habitat provides everything an organism needs to survive, including food, oxygen, shelter, and space to grow.

Different organisms in a habitat may use the resources in different ways, allowing them to coexist.

Who All Live Together in Nature?

In a habitat, you'll usually find many organisms of the same kind living together. A population is a group of organisms of the same type living in a habitat at a given time.

Communities

A community is made up of different populations sharing the same habitat. The biotic components of a habitat, such as plants, animals, and microorganisms, together form a community. These organisms interact and depend on one another for survival.

A habitat cannot usually have only one type of living organism. If all organisms are the same, they would have the same requirements for food, water, and space, leading to competition and possible scarcity of resources.

Pollination

Pollination is the process where pollen is carried from the stamens (male part) to the carpels (female part) of flowers, either on the same flower or different flowers. Wind, water, insects, bats, and birds help carry pollen. Pollination is essential for the formation of fruits and seeds.

Does Every Organism in a Community Matter?

Every organism in a community plays a role, and the presence or absence of one organism can affect the entire community.

Overfishing by humans can change this balance by reducing the fish population, which can have cascading effects on the living and non-living parts of the habitat.

What Are the Different Types of Interactions Among Organisms and their Surroundings?

Living organisms depend on non-living things for their survival. Plants and animals also depend on each other for nutrition, respiration, and reproduction. These are interactions among the biotic components. Both types of interactions – among biotic components, and between biotic and abiotic components – are important for survival in any habitat.

Interactions Between Biotic and Abiotic Components

These interactions influence life processes like nutrition, respiration, and reproduction in biotic components.

Interactions Between Two Abiotic Components

These interactions may influence the physical characteristics of a habitat.

Interactions Among the Biotic Components

These interactions may influence the availability of resources needed for life processes like nutrition, respiration, and reproduction.

Ecosystems

The biotic components (plants, animals, and microorganisms) and the abiotic components (air, water, soil, sunlight, and temperature) in a habitat interact with each other to form an ecosystem.

Organisms in an ecosystem interact with abiotic components for food, shelter, and protection. There are two main types of ecosystems:

• Aquatic ecosystems: These include ponds, rivers, and lakes.
• Terrestrial ecosystems: These include forests, farms, or even large trees.

Ecosystems can be large or small and can overlap. Farmland is a human-made ecosystem.

Dependence of Biotic and Abiotic Components

Living organisms depend on the non-living components of an ecosystem.

Abiotic components also depend on biotic components.

Who Eats Whom?

Producers, Consumers, and Heterotrophs

Plants make their own food by the process of photosynthesis, so they are called producers or autotrophs.

Organisms that cannot produce their own food and depend on other organisms for their food are called consumers or heterotrophs.

There are different types of heterotrophs:

• Herbivores: Organisms that eat only plants, such as deer and hare.
• Carnivores: Organisms that eat only animals, such as leopard.
• Omnivores: Organisms that eat both plants and animals, such as crows, foxes, and mice.

Food Chains

The interactions between biotic components based on feeding relationships can be represented in the form of a linear chain. A food chain is a simple sequence showing 'who eats whom' in an ecosystem.

Trophic Levels and Food Pyramids

Each organism in a food chain has a specific position, called a trophic level:

• Producers (like green plants) are at the first trophic level.
• Herbivores (like hares and deer) are at the second level.
• Small carnivores (like frogs) are at the third level.
• Large carnivores (like tigers or vultures) occupy the next level.

The number of organisms at each trophic level can be represented in the form of a pyramid, called a food pyramid.

Food Webs

In an ecosystem, food chains are interlinked with each other to form a network, called a food web. Each of the organisms may be eaten by two or more types of organisms.

What Happens to Waste in Nature?

During their life cycle, organisms produce a lot of waste, including dead matter and food waste.

Decomposers

Decomposers or saprotrophs are microorganisms like fungi and bacteria that break down complex substances in dead plants and animals into simpler ones. This process is called decomposition. Decomposition returns important nutrients to the soil.

Decomposers play an important role in recycling nutrients. In nature, nothing is wasted – everything is reused.

How Does One Change Lead to Another?

One small change in an ecosystem can lead to many others.

The Impact of Human Intervention

Intervention in nature can have unintended consequences.

An ecosystem stays in balance when interactions among organisms and their environment keep populations and resources stable. This balance is dynamic, not fixed, and can be disrupted by natural or human-made changes.

How Do Interactions Maintain Balance in Ecosystems?

Besides feeding relationships, organisms also compete for common resources like food, water, physical space, or sunlight. This competition helps control population size and keeps the ecosystem balanced. Without it, one species could multiply too much, causing an imbalance in the ecosystem.

Other Types of Relationships

There are other types of relationships between organisms:

• Mutualism: Both organisms benefit. For example, honeybees and flowers.
• Commensalism: One organism benefits while the other is not affected. For example, orchids on trees.
• Parasitism: One organism benefits while the other is harmed. For example, ticks on the body of dogs.

What Are the Benefits of an Ecosystem?

Biotic components and abiotic components of an ecosystem depend on each other and support various life processes. Humans also benefit from ecosystems.

Ecosystems also offer aesthetic and recreational value. This benefits and supports our well-being and shows how closely nature and humans are connected. However, when we overuse or misuse natural resources, we disturb the balance in nature.

The Sundarbans: A Threatened Ecosystem

The Sundarbans have the largest mangrove forests in the world. Located where the Ganges and Brahmaputra Rivers meet between India and Bangladesh, the Sundarbans’ forests and rivers are home to various flora and fauna, many of which are endangered. The Sundarbans protect us by slowing down strong winds and waves during storms and floods. The trees also absorb carbon dioxide from the air and release oxygen. The United Nations Educational, Scientific and Cultural Organization (UNESCO) declared the Sundarbans a World Heritage Site in 1987.

The Sundarbans are under a serious threat. Mangrove trees are being cut for fuelwood and farming. Illegal hunting and overuse of forest resources are a threat to the wildlife living there. Pollution from industrial waste and untreated sewage in rivers is also damaging the water and habitat. These human activities disrupt the natural way ecosystems work.

Similarly, other ecosystems across India are also under threat. Problems like deforestation, overuse of natural resources, the spread of invasive species, unsustainable land use, and pollution are damaging forests, rivers, scrublands, wetlands, grasslands, and coastal areas.

Protected Areas

Protected areas are parts of land or water set aside to conserve wildlife and their habitats. India has many protected areas like national parks, wildlife sanctuaries, biosphere reserves, and community conserved areas. These places help protect entire habitats, including endangered animals, birds, and many rare plants.

Protected areas play a big role in saving nature for future generations.

Human-Made Ecosystems

Humans have created artificial ecosystems like fish ponds, farms, and parks to meet their needs. When well designed, these can help reduce pollution, support biodiversity, and provide recreational spaces for people. Unlike natural ecosystems, these need human care and management.

How Do Healthy Ecosystems Serve Our Farms?

Farming, a major livelihood in India, can become unsustainable if not managed well by applying environment-friendly farming practices.

Humans have been practicing farming for thousands of years to grow food. As the population grew, our dependence on agriculture increased. Between 1950 and 1965, India faced a food crisis due to low crop production. In the mid-20th century, the use of tractors, machines, synthetic fertilizers, and pesticides helped increase food production. This period is known as the Green Revolution.

However, these farming methods are now considered unsustainable because of the overuse of synthetic chemicals, excessive groundwater extraction, and growing only one type of crop for commercial gain. These practices harm both the environment and human health.

Many scientists believe that overusing pesticides and growing the same type of crop repeatedly on the same land leads to soil degradation. Understanding ecosystems can help us adopt better and more sustainable farming practices.

The Impact of Synthetic Fertilizers and Pesticides

Synthetic fertilizers and pesticides have played a vital role in improving crop production and helped countries like India become food secure. However, their long-term use can affect the environment and soil health.

Overuse of synthetic fertilizers may reduce soil fertility by decreasing friendly microorganisms in soil and lowering organic matter (humus), which helps bind soil particles. Without enough humus, soil becomes prone to erosion. Also, it reduces the population of natural predators, which ultimately increase the population of pests. Heavy irrigation and repeated plowing can also disturb soil organisms like earthworms and snails, which are important for maintaining ecological balance.

Some pests may develop resistance to pesticides, making them difficult to control. Growing the same crop repeatedly, known as monoculture, can reduce crop diversity and affect pollinators, which are crucial for food production.

To make farming more sustainable, some farmers are exploring organic and natural farming methods. These aim to reduce the use of synthetic fertilizers and support sustainable farming, with minimal interference in natural ecosystems.

Vrikshayurveda

The ancient text Vrikshayurveda emphasizes soil health and nourishment. The text strongly advocates for the continuous nourishment of the soil through organic manure like Kunapa Jala (a liquid fertilizer made from animal and plant waste by the process of fermentation that breaks complex substances into simpler ones) and other composted materials.