Tiêu đề Chapter 13 Our Environment.pdf ✅

SCIENCE (Biology) Chapter 13: Our Environment
(1) 13 OUR ENVIRONMENT •They can be broken down into non- poisonous substances by the action of microorganisms. •They change their form and structure over time and become harmless. •They do not pollute the environment. •Examples: Spoilt food, vegetable peels, paper, leather etc. BIODEGRADABLE WASTES •They cannot be broken down into harmless substances by any biological processes. •They remain unchanged over a long period of time. •They continue to pollute the environment. •Examples: Glass bottles, metal cans, polythene bags, synthetic fibres etc. NON-BIODEGRADABLE WASTES Our Environment Everything that surrounds us is environment. It includes both living (biotic) and non-living (abiotic) components. Interaction between these biotic and abiotic components form an ecosystem. In an ecosystem living components depend on each other for their food which give rise to food chains and food webs in nature. Human activities lead to environmental problems such as depletion of ozone layer and production of huge amount of garbage. Biodegradable and Non-Biodegradable Wastes Ecosystem An ecosystem is a self-contained area composed of different kinds of organisms which interact with each other as well as with the physical conditions such as sunlight, air, water, soil and climatic factors prevailing in the area. Types of Ecosystem
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(3) 13 OUR ENVIRONMENT Components of an Ecosystem An ecosystem consists of two main components: biotic components and abiotic components. Biotic Components The biotic components are the living components of an ecosystem. They constitute the food- obtaining steps or trophic levels of the ecosystem. Trophic level I (Green plants/Autotrophs) • They produce food through the process of photosynthesis. • These include trees, bushes and grasses. Trophic level II (Herbivores/ Primary consumers) • They directly eat plants or their products such as leaves, grains, etc. for food or suck plant sap from their leaves or stems. • These include animals such as deer, rabbits, rats, pigeons, parrots, grasshoppers, bees etc. Trophic level III (Carnivores/ Secondary consumers) • They capture their prey and eat it. • These include tigers, wolves, snakes, lizards, certain birds etc. Trophic level IV (Large carnivores/ Tertiary consumers) • They capture smaller carnivores and eat them. • These include peacock, eagle etc. Parasites • They live inside or on the body surface of another organism, called the host, and obtain their food or nourishment from the host. • Worms which live in the guts of animals and fleas which live on the skin of animals such as dogs are examples of parasites. Decomposers/ Microconsumers/ Detritivores • They breakdown the complex organic compounds present in these dead organisms into simpler substances. • These include certain bacteria and fungi, vultures, kites, crows, some insects etc. Abiotic Components The abiotic components are the non-living components of an ecosystem. Sunlight • The energy obtained from sunlight is essential for the production of food by photosynthesis. Air • Oxygen from the air is essential to animals for respiration. • Carbon dioxide is useful to plants for photosynthesis. Water • Water is the chief constituent of protoplasm in cells. • It is required for various biochemical reactions which occur in organisms. Temperature • Temperature affects the distribution of living organisms in the environment. • It affects the enzymatic activities in organisms. Soil • Soil provides the substratum for the growth of plants. • It contains water and mineral nutrients such as sodium and potassium required by plants. Food Chain