NCERT Class 11 Part 1 Chapter 15: Life on Earth YouTube Lecture Handouts

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Watch Video Lecture on YouTube: NCERT Class 11 Part 1 Geography Chapter 15: Life on Earth

NCERT Class 11 Part 1 Geography Chapter 15: Life on Earth

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Biosphere

  • Lithosphere

  • Atmosphere

  • Hydrosphere

  • Affected by atmospheric elements like temperature, rain, sunlight and moisture

Environment and Ecosystem

  • Environment – biotic and abiotic

  • Diversity brings in balance

  • Ecological systems – interaction of group of elements with abiotic factors within particular habitat result in energy flow and material cycling

  • Ecology made from oikos meaning “house” and logy “means “study of” – Ernst Haeckal used term oekologie in 1869 – scientific study of interaction between life form and physical features

  • Habitat – totality of physical and chemical factors that constitute the environment

  • Ecological Adaptation – plants and animals get adapted through evolution

Types of Ecosystem

  • Ecosystem can be terrestrial and aquatic

  • Biome – plant and animal community covering large area and boundaries are set by climate – assemblage of plants and animals interacting in specific conditions

  • Examples – forest, grassland, desert and tundra

  • Aquatic – marine (ocean, coastal and coral reef) and freshwater (lakes, ponds, stream and bog)

Structure and Function of Ecosystem

  • Abiotic – temperature, train, humidity

  • Biotic – flora and fauna

  • Primary consumer, secondary consumer and decomposer

  • Food chain – detritus and grazing

  • Flow of energy

  • Food web

Types of Biomes

  • Forest – tropical (equatorial-acidic and poor in nutrient and deciduous-rich in nutrient), temperate and boreal

  • Desert – hot dry, semiarid, coastal and cold

  • Aquatic – freshwater and marine

  • Grassland – tropical savanna (warm hot climate – thin humus) and temperate steppe (hot summer and cold winter – rich in bases)

  • Altitudinal – slope is major factor, temperature and precipitation vary

Biogeochemical Cycles

  • Sun as main source of energy, life starts with photosynthesis

  • Living organisms exist in various associations

  • Balance is maintained by cyclic passage of plant and animal tissues

  • Cyclic movement of chemical substance of biosphere between organism and environment

  • Cycle can be gaseous and sedimentary

  • Water cycle – hydrological cycle – precipitation, evaporation and condensation takes place

Carbon Cycle

Image of a Carbon Cycle

Image of a Carbon Cycle

Image of a Carbon Cycle

  • Biosphere has half million carbon compounds

  • Start with photosynthesis; glucose many be converted sucrose, starch and cellulose

  • CO2 released by leaves

  • Oxygen Cycle

  • Oxygen generation – plants and sunlight

  • Oxygen consumption – respiration, decomposition, rusting and combustion

Nitrogen Cycle

Image of a Nitrogen Cycle

Image of a Nitrogen Cycle

Image of a Nitrogen Cycle

  • 79% of gases with amino acid, nucleic acid, protein, vitamin, pigments

  • 90% of fixed nitrogen is biological. Nitrogen can only be used when fixed.

  • Can also be fixed by lightning and radiation; green plants can assimilate it

  • Dead plants excrete nitrogenous waste which is converted to nitrites and finally nitrates

  • From nitrate to free nitrogen is denitrification

  • Other Cycles are potassium, calcium, Sulphur and phosphorus – from mineral salts dissolved, weathering, sedimentation and death of organisms

Ecological Balance

  • State of dynamic equilibrium within community of organisms in a habitat

  • Gradual changes occur by natural succession

  • Competition and cooperation coexists

  • Balance attained by species dependent on food and sustenance

  • Clearing of forest brings changes; change is due to competition and called as succession

  • Ecological balance can be disturbed by new species, natural hazard and human interference – this can lead to calamities like landslides, disease and floods

  • Knowledge and understanding of factors provides a base for protection and conservation of ecosystem

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