Our Environment Notes - Ecosystem, Food Chain, Ozone Depletion and Waste Management

• The biotic and abiotic factors which surround any living organism are called its environment.

ECOSYSTEM – WHAT ARE ITS COMPONENTS?

• Organisms and physical surroundings interact with each other and maintain a balance in nature.
• All the interacting organisms in an area together with the non-living constituents form an ecosystem.
• Biotic components: Include all living organisms.
• Abiotic components: Include physical factors like temperature, rainfall, wind, soil, and minerals.
• Natural ecosystems: Forests, ponds, lakes, etc.
• Human-made (artificial) ecosystems: Gardens, crop fields, aquariums, etc.
• An aquarium is a self-sustaining system because it includes biotic factors (fishes, aquatic plants, animals, etc.) and abiotic factors (free space, water, oxygen, and food).
• Organisms can be grouped as producers, consumers, and decomposers.

Producers:

• They make food from inorganic compounds, e.g., green plants and some bacteria.
• Green plants make organic compounds (sugar and starch) from inorganic substances using solar radiant energy in the presence of chlorophyll. This is called photosynthesis.

Consumers:

• Organisms that directly or indirectly depend on producers for food. They consume food from producers or by feeding on other consumers.
  • Herbivores: E.g., grasshopper, rabbits, deer, etc.
  • Carnivores: E.g., frog, tiger, lion, etc.
  • Omnivores: E.g., humans, bears, birds, dogs, etc.
  • Parasites: E.g., roundworms, tapeworms, leech, etc.

Decomposers:

• They break down dead remains and waste products of organisms (complex organic substances) into simple inorganic substances. Inorganic substances go into the soil and are used by plants.
• If an aquarium is not cleaned, fishes and plants will die. Microorganisms (bacteria and fungi) break down the dead remains and waste products of organisms.
• If decomposers are absent, garbage, dead animals, and plants will not decompose, leading to accumulation of organic materials and causing pollution.

Food Chains and Webs

• A food chain is the series of organisms feeding on one another or organisms taking part at various biotic levels.
• Each step or level of the food chain forms a trophic level.
• Autotrophs (producers): First trophic level.
• Herbivores (primary consumers): 2^nd trophic level.
• Small carnivores (secondary consumers): Third trophic level.
• Larger carnivores (tertiary consumers): Fourth trophic level.

• Food is a fuel to provide energy. Thus, the interactions among various components involve the flow of energy.
• Autotrophs capture solar energy and convert it into chemical energy.
• From autotrophs, energy goes to heterotrophs and decomposers.
• The study of the flow of energy reveals that:
  • Green plants in a terrestrial ecosystem capture about 1% of the solar energy that falls on their leaves and convert it into food energy.
  • When primary consumers eat green plants, a lot of energy is lost as heat, some is used for metabolism, growth, and reproduction. About 10% of the food is turned into body. This is the average amount of organic matter present at each step and reaches the next level of consumers.
  • Food chains generally consist of only 3 or 4 steps since so little energy is available for the next trophic level.
  • There are generally many individuals at the lower trophic levels. Producers are in the greatest number.
  • Each organism is generally eaten by two or more kinds of organisms, which in turn are eaten by several other organisms. This series of branching relationships of food chains is called a food web.

• Energy flow diagram shows the following features:
  • Energy flow is unidirectional. It does not revert back from autotrophs to the Sun or from consumers to autotrophs.
  • Energy available at each trophic level gets diminished progressively due to loss of energy at each level.
• Some harmful chemicals may enter bodies through the food chain, e.g., pesticides and other chemicals are washed into the soil or water. From the soil, plants absorb them. From water bodies, aquatic plants and animals take them up, thus entering the food chain.
• Non-degradable chemicals get accumulated at each trophic level. This is called biological magnification. Thus, cereals, vegetables, fruits, and meat contain pesticide residues. Their concentration is maximum in the human body because humans occupy the top level in any food chain.
• Methods to reduce intake of pesticides:
  • Minimize the use of chemical pesticides.
  • Wash fruits and vegetables thoroughly before use.
  • Use organic fruits and vegetables.

HOW DOES OUR ACTIVITY AFFECT THE ENVIRONMENT?

Ozone Layer and Its Depletion

• Ozone (O₃) is a deadly poison. However, at higher levels of the atmosphere, ozone shields the Earth's surface from dangerous ultraviolet (UV) radiation from the Sun. UV radiation causes harmful effects such as skin cancer.
• At higher levels of the atmosphere, higher-energy UV radiation splits some O₂ into free oxygen (O) atoms, which combine with O₂ to form ozone (O₃).

• In the 1980s, the amount of ozone began to drop sharply due to chemicals like chlorofluorocarbons (CFCs), which are used as refrigerants and in fire extinguishers.
• In 1987, the United Nations Environment Programme (UNEP) made an agreement to freeze CFC production at 1986 levels. It is now mandatory to make CFC-free refrigerators.
• Other ozone-depleting substances: Hydrofluorocarbons (HFCs), halons, etc.
• The size of the ozone hole has increased in recent years.

Managing the Garbage We Produce

• Garbage is unwanted material that people have thrown away.
• In organisms, specific nutrients are needed to break down a particular substance. Similarly, bacteria or other saprophytes have no enzymes to break down artificial materials like plastics.
• Substances that are broken down by biological processes are called biodegradable, e.g., fruits, vegetables, leaves, meat, paper, rubber, etc.
• Substances that are not broken down by biological processes are called non-biodegradable. They are inert, and persist for a long time, or may harm the ecosystem, e.g., plastics, glass, nylon, etc.

• There are biodegradable plastics such as Polylactic acid, Polyhydroxyalkanoates, Polybutylene succinate, etc.
• At home and in the classroom, various biodegradable and non-biodegradable wastes are produced. They have to be collected separately and treated properly.
• The local body (panchayat, municipal corporation, resident welfare association) has mechanisms to treat biodegradable and non-biodegradable wastes separately.
• Improvements in lifestyle and changes in attitude have generated a large amount of waste material.
• Changes in packaging have resulted in much of our waste becoming non-biodegradable.

Electronic & electrical wastes (e-wastes):

• Include mobile phones, computers, televisions, etc.
• They contain dangerous chemicals such as mercury, lead, cadmium, polybrominated flame retardants, barium, and lithium. They cause damage to the brain, heart, liver, kidney, and skeletal system.