General Knowledge Notes For All Competitive Exams - Biology-Part -02

Earth is the only planet to support life. Earth provides soil, water and air to support it. Environment is defined as the physical, chemical and biotic conditions that surround and influence on living organisms.
Abiotic components: Abiotic components of environment are temperature, light, humidity, precipitation, wind minerals and the composition of air.The three physical components of earth are atmosphere, lithosphere and hydrosphere.

Biotic components: It  include plants, animals and microorganisms.

Ecology: Ecology is defined as the study of relationship between organisms and their environment. Ecology deals with various form of interaction between the organisms and their environment.

Genes:The levels of organisation in the living system starting from genes to community.

Ecosystem: It is defined as functionally independent unit of nature where living organisms interact among themselves as well as with their physical environment.Terrestrial and aquatic ecosystems are the two categories of natural ecosystems. Croplands and aquarium are the examples of artificial ecosystem.These biotic components of ecosystem interact with each other to give a physical character. These represent structural features of an ecosystem to an ecosystem.The important structural features of an ecosystem may be represented by its species composition, stratification, food relationship (trophic level food chain and food web).The structural components interact in a unit and produce certain functional aspects of an ecosystem such as productivity, energy flow and nutrient cycle etc. Humans occupy both primary and secondary levels of consumers.
Food Chain: Transfer of food from the plants (producers) through a series of organisms with repeated eating and being eaten is called food chain.

Food Web: A network of a connected food chains interrelated form a food web.

Flow of Energy: The process of transfer of energy through various trophic levels of the food chain is known as flow of energy.The quantity of energy flowing through the successive trophic level decreases. This is because a part of the energy is lost as heat and a part of energy used by the organism for its metabolism. Only 10% of the energy that enters the trophic level is transferred to the next trophic level. This is known 10% law. The flow of energy in an ecosystem is always linear. The number of trophic level in a food chain is limited in number (4 or 5).

Ecological Pyramid:The graphical representation of standing crop expressed as number biomass or energy is called pyramid of number. Pyramid of biomass and pyramid of energy respectively. These are collectively known as ecological pyramid.

Biome: A biome is a large ecosystem which is embracing the large landscape. Each biome is characterised by a specific flora and fauna.

Nutrient Cycle: The cycling of the nutrients in the biosphere is called biogeochemical or nutrient cycle. Carbon cycle and water cycle are two such example. Photosynthesis, respiration, decomposition and combustion are the important processes in carbon cycle. Evaporation, condensation and precipitation are the important processes in water cycle.

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