Our Environment Class 10 Notes Science Chapter 15

What are Our Environment ?

  • Environment is everything that is around us which includes both biotic and abiotic components.
  • Abiotic components are the non-living components i.e., the physical factors like temperature, light, wind, water, humidity, soil, minerals, etc.
  • The biotic components are the living organisms like plants, animals, human beings etc. Both biotic and abiotic components interact with each other to form the environment as a whole.
  • An ecosystem includes all living organisms along with the abiotic components which interact with each other to maintain a balance in the nature.
  • The term ecosystem was introduced by Tansley in 1935.
  • Producers are mainly autotrophs.
  • Consumers cannot prepare their own food. They depend on autotrophs directly or indirectly for food. They are primary consumers [which eat plants or plants products], secondary consumers. [Feed upon primary consumers], tertiary consumers [feed upon secondary consumers], quaternary consumers [feed upon tertiary consumers and are at the top most level of food chain].
  • Decomposers like bacteria, fungi etc., feed upon the decay of dead producers and consumers.
  • The transfer of food energy from plant sources through a series of organisms in an ecosystem is known as food chain.
  • The interlinking sequence starting from an autotroph to herbivores, carnivores and top most level consumers is called a food chain.
  • A food chain shows one path how energy in form of food flows from producers to consumers.
  • A food web shows many paths i.e., it is a network of food chains where an organism eats several types of organisms or eaten by many different organisms.
  • The distinct sequential steps in the food chain where transfer of energy occurs are referred to as different trophic level, which is represented as under.
  • Energy flow in an ecosystem is unidirectional i.e., it flows from autotrophs to herbivores to secondary consumers, tertiary consumers in one direction.
  • At each trophic level some amount of energy is lost. Lindeman suggested a Ten percent rule which states that the rate of transfer of energy from one trophic level to the next trophic level is of the order of 10%.
  • For example if energy produced by a green plant is 100 calories only 10 calories is available to herbivores then 1 calorie to secondary consumers and very less energy i.e., 0.1 calorie to tertiary consumers. So at each trophic level the energy goes on decreasing hence a food chain or food web consists of 3-4 levels or maximum 5.
  • Biomagnification is the process which involves the progressive increase in the concentration of toxic or harmful substances at different trophic levels. So the organisms that are at the top of food chain have accumulated a maximum concentration of harmful chemicals in their body. Example : Accumulation of pesticides like DDT.
  • Ozone layer prevents the harmful UV rays of sun from entering to the earthโ€™s surface.
  • CFCs which is the main cause of depletion of ozone layer and is found mainly in aerosol sprayers, refrigerators, air-conditioners etc.
  • The depleting ozone layer has many harmful consequences like it causes cancer, causes genetic variations due to mutation, damages our eyes, decline of photosynthesis rate in plants.
  • The first ozone hole was discovered over Antarctica.
1. Ecosystem: It is the structural and functional unit of biosphere which comprises of both biotic and abiotic components that interact with each other to form a stable and self-supporting system. 6. Food chain: The sequential interlinking of organisms involving transfer of food energy starting with a producer through a series of organisms
2. Natural ecosystem: The ecosystems which operate themselves in nature without any interference of human beings are called natural ecosystems. 7. Trophic levels: The distinct sequential steps in the food chain where transfer of energy occurs are referred to as trophic levels.
3. Artificial ecosystem: The ecosystem which is maintained by human beings like croplands, aquarium etc. is called artificial ecosystem. 8. Food web: A network of food chains which are interconnected at various trophic levels to form a number of feeding connections among different organisms is called a food web.
4. Abiotic components: The non-living physio-chemical factors like soil, humidity, sunlight, rainfall, temperature etc. are the abiotic components. 9. Biodegradable wastes: The wastes which get degraded in a natural process by the action of microbes into simpler forms are called biodegradable wastes. Example, food waste, human waste, paper waste, manure, sewage etc.
5. Biotic components: The living organisms like autotrophs, heterotrophs form the biotic components. 10. Non-biodegradable wastes: The wastes which cannot be degraded by the action of microbes in a natural way and they persist in environment for a longer period of time are called non-biodegradable wastes. Examples, Glass, metal, batteries, plastic bottles, tetra packs.