ORGANISM AND POPULATION BY-SHIVAM SHARMA
Annual variations in the intensity and duration of temperature and precipitation are responsible for the formation of major biomes. . The major biomes are: 1. Arctic & alpine tundra 2. Coniferous forest 3. Temperate forest 4. Grasslands 5. Tropical Forest 6. Desert.
Abiotic factors :The most important abiotic factors of the environment are temperature, water, light and soil. Biotic factors: Biotic factors are pathogens, parasites, predators, competitors etc. .Temperature: The physiological functions and geographical distribution of organisms is governed by temperature. Temperature affects the kinetics of enzymes, BMR (Basic Metabolic Rate) and other physiological actions in organisms. Eurythermal: A few organisms which can tolerate wide range of temperatures are called eurythermal organisms. .Stenothermal: Many organisms which can tolerate narrow range of temperatures are called stenothermal organisms. Water: Important factor influence the life of organisms. The productivity and distribution depends on water. For aquatic organisms, chemical composition, pH, salinity and temperature of water are important. Euryhaline: The organisms which can tolerate wide range of salinity are called euryhaline organisms. Stenohaline: The organisms which can tolerate narrow range of salinity stenohaline organisms.
Light: light is important abiotic factor bcoz the autotrophs prepares its food by photosynthesis. sciophytes : Small herbaceous plants and some shrubs live under the canopy forest trees are adapted to photosynthesis under very low light intensities. These are called sciophytes Animal use the seasonal variations in the light intensity and photoperiod as cues for timing of forage, reproduction and migration . The distribution of red, green and brown algae at difference depths of water depends on the light, red algae can live in very deep water. Soil: Nature and properties of soil depends on climate, weathering process. . The physical and chemical properties of soil determine the type of plants that can grow in a particular habitat. The characteristics of the bottom sediments of aquatic environment determine type of benthic animals that can live there.
Organisms responses to environment: . Regulation: Organisms maintain homeostasis in constant body temperature and osmotic concentration Conformation: Majority (99%) of animals and plants cannot maintain a constant internal environment. Such animals and plants are simply called as conformers . Their body temperature varies according to ambient temperature . In aquatic animals the osmotic concentration of bodv fluid varies with ambient water osmotic concentration Thermoregulation is energy-expensive process. Heat loss or gain is a function of surface area. therefore small animals are not found in polar region
Migration: Organisms can move away temporarily from stressful conditions to another habitat is called migration Suspension: Organisms that cannot migrate, suspend their metabolic functions during stressful period. It is called suspensio . E.g. Hibernation, aestivation, Diapuse. . Hibernation: Hibernation is a process by which the animals avoid the stress and become inactive during winter. Ex: Polar bear, Frogs, Lizards Aestivation: Aestivation is a process by which the animals avoid the stress and summer related problems and become inactive during summer. Ex: snails and fishes Diapause: It is a stage of suspended development seen in many zooplanktons to avoid unfavorable conditions.
e Adaptation: Adaptation is any changes of the organism (morphological, physiological, and behavioral) that enables to survive and reproduce in its habitat. Adaptations have evolved over a long period of time and are genetically controlled Examples: .Desert Plants: have thick cuticle on leaf surface. Sunken stomata. leaves modified into spines. .Due to CAM pathway photosynthesis the stomata remain closed during the day. : Ex : Opuntia, cactus etc.
Aquatic Plants: Have evolved aerenchyma for buoyancy and floating. leaves have waxy covering. . Desert animal: Kangaroo rat living in the desert of North America never drink water. The water requirement is by internal fat oxidation (in which water is the by product). It is also able to concentrate its urine so that the minimal volume of water is lost during excretion