Life Science(Biology)

Soil is the upper weathered layer of the earth's crust.The vertical section through the upper crust of the earth is called soil profile . Study of soils is called pedology and the process of soil formation is called pedogenesis .1 cm soil formation takes about 200-400 years.    The removal of the fertile top layer of the earth or any slight disturbance in its structure is called soil erosion.   .    Photograph: Landslides at Kailashahar to     Dharmanagar road , 23 rd June,2024   Types of soil erosion:-  It is of two types: (A) Normal or Geological erosion: It is a very slow process  due to normal physical and biological equilibrium without any interference of human beings . (B) Accelerated Erosion: It occurs rapidly due to physical and biological activities.Rainfall, landslide, earthquake,overgrazing and human activities are the main factors in such case. Agents of soil erosion:  Water and wind are the main two ag...

  Courtesy:PV education   The process through which heat is trapped near Earth's surface by greenhouse gases is called greenhouse effect . These gases are - carbon dioxide, methane, nitrogen oxides and CFCs.These gases allowed the sunlight to shine onto Earth's surface but trap 90% of  the heat that reflects back to the atmosphere. Thus , these gases act as insulating glass walls of a greenhouse and keep the climate favorable for living beings by about 33° C.       Climate Scientists now agree that increase of greenhouse gases are directly linked to the increase of global temperature and affecting global climate.This is called climate change.       Greenhouse gas emissions increased 70% between 1970-2004 due to anthropogenic activities. Burning of fossil fuels to run power plants, vehicles,etc is responsible for the 80% increase of carbon dioxide in this timespan. Cutting of trees has accelerated the addition of this gas a...

       India is situatedat the tri- junction of three realms: Afrotropical, Indo-Malayan and Paleo - Arctic realms which makes it rich in biological diversity.It represents 10 Biogeography zones, 26 Biogeography provinces with  ecosystems like forest, wetland, desert,  costal and marine. Though India shares 2.4% of world's land area, but represents 11% flora and 6.5% fauna of the world.Out of 17 megabiodiverse nations India ranks 9th in terms of richness of  higher plant species.      Approximately 65% of Indian  geographical area has been survayed and over 46,000 plant  species and 81,000 animal species has been recorded .To preserve this rich biodiversity it has been divided into10 biogeographic zones:  (1) Trans Himalayas with 3 provinces : (A) Ladakh Mountains (B) Tibetan Plateau  (C) Sikkim Himalayas  (2) The Himalayas with 4 provinces: (A) North West Himalayas  (B) West Himalayas (C) Cent...

      .        The indiscriminate extraction of water resources, above the rechargeable levels of the aquifers is known as over-exploitation of fresh water,   meaning that more is taken out of the ground than can be sustainably replenished. Water which falls in the form of precipitation moves down into soil through rocks and gets accumulated as ground water . The layer of rock through which it parcolates is known as aquifers -- permiable water bearing rock and/ or sediment .Ground water found in two layers of soil : zone of aeration and zone of saturation. In the former soil gaps are filled by both of air and water,whereas in latter case it is filled by water only.    The process of precipitation replenishing the ground water supply is called recharge .This ground water remains in a constant motion. About 5.97 quintillion gallon of ground water reside in the upper 2 km of earth's surface.   Ground water can be extr...

       A rain with pH of about 5.2 or below due to the presence of sulphur dioxide and nitrogen oxides as a result of combustion of fossil fuels.     The term acid rain  was coined by Scottish chemist Robert Angus ( father of acid rain) in 1852. His findings were published in : Air and rain: The beginnings of a Chemical Climatology ,  1872. According to EPA ( Environmental Protection Agency) sulphur dioxide and nitrogen oxides released from thermal power plants , vehicles and oil refineries, volcanic activities, forest fire and bacterial decomposition of the organic matters are the main cause of acid rain. In the above reactions formation of these acids  in the atmosphere are described. Acid rain contains sulfuric acids or nitric acid and these may in any form of precipitation or dust, gases, snow,fog ,hail,etc.So, it may be of wet deposition or dry deposition. Normal pH of rain or ordinary water is around 5.6 because of the prese...