ANIMALS AND THEIR ABIOTIC ENVIRONMENT
- Habitat: All living (biotic) and nonliving (abiotic) characteristics of the a ea in which an animal lives is called habitat. Abiotic characteristics are a ailability of oxygen and inorganic ions, light, temperature, and current or wind velocity.
- Tolerance range: Certain range. of values in which an animal live is c lied tolerance range for any environmental factor. Physiological ecologists are studying the tolerance range of different animals. One or more essential functions cease at either limit of the tolerance range.
- Range of optimum: A certain range of values within the tolerance range which defines the conditions under which an animal is most successful is ailed the range of optimum.
- Limiting factor: The factor which become out, of tolerance range of an animal is called limiting factor. Combinations of abiotic factors are necessary for survival and reproduction of an. animal. For example, a stream
in t may have the proper substrate for shelter. It has adequate current of
water. This current of water brings food and helps in dispersal of wastes. It ha proper ions for growth and development. But it has inadequate supplies of oxygen. It makes its life impossible. Thus oxygen is limiting factor for the ins -ct.
- Ta es: The orientation of an animal in response to an abiotic factor is called taxis. The orientation in response to light is called phototaxis There are two types of phototaxis:
- Positive phototaxis: The movement of animal towards light is called positive phototaxis. Well lighted environment favours some animals. Therefore, they move toward a light source.
- Negative phototaxis: The movement of animal away from the light source is calIed negative phototaxis. Some animals prefer low light intensities. Therefore, they move away from a light source.
Fig: (a) Tolerance range of animals (b) Energy btidget of animals
The ability to do work is called energy. Everything from foraging for food to moving molecules within cells is a work. The animals obtain energy by different methods.
(a)Heterotrophic: The animals which ingest other organisms are called
(b)Autotrophic: The organisms (e.g., plants) which carry out photosynthesis or other carbon fixing activities for obtaining energy are called autotrophic. Following terms are used for energy:
- Energy budget: The accounting of total energy of an animal and P description of how that energy is used and lost is called energy budget. Favorable energy budgets are sometimes difficult to attain. It is especially difficult to attain in temperate regions. Winter often reduces the food supplies in these regions.
- Energy intake: The total energy contained in the food of an animal that it eats is called gross energy intake. Some of this energy is lost in feces and through excretion (excretory energy). Some of this energy is required for minimal maintenance activities. These activities are pumping blood, exchanging gases, and supporting repair processes (existence energy).
- Productive energy: The energy left after existence and excretory functions is ailed productive energy. Productive energy is used for growth, mating, esting, and caring for young. Enough amount of productive energy is equired for the survival of an animal.TEMPERATUREAn animal spend part of its energy in regulating body temperature. Temperature influences the rates of chemical reactions in animal cells (metabolic rate). It also aft- ts overall activities of the animals. There is an inequality between heat loss and heat gain. Therefore, the body temperature of an animal does not remain constant.
Loss of heat:
Heat is lost from the body of an animal in following forms:
- Infrared and heat radiation.
- eat is lost to the air by convection and evaporative heat. Gal of heat: The animals gain heat in following forms:
- Solar radiation
- Infrared and heat radiation from the objects in the environment
- I efficient metabolic activities -generate heat as a byproduct of cellular f notions.
The maintenance of body temperature within the body is called thermoregulation. Thermoregulatory needs influence many habitat requirements. These requirements are availability of food, water, and shelter. Differ nt animals have different mechanism of thermoregulation: Sometime, there is shortage of food. Sometimes, animals are not feeding for other reasons. Then. ore, they are subject to starvation. Thus their metabolic activities are decreased. There are following methods of decreasing metabolic activities:
- Torpor: The daily time of- decreased ‘metabolism and lowered body temperature is called torpor. Torpor takes place in bats, hummingbirds, and other animals. They must feed almost constantly when they are active. Torpor allows these animals to survive periods when they do not feeding.
- Hibernation: Hibernation is a time Of decreased metabolism and lowered bo y temperature during winter. True hibernation occurs in small mammals like rodents, shrews, and bats. The set point of a thermoregulatory center of hibernator drops to 200 C. But thermoregulation is not suspended.
- Winter sleep: Winter sleep occurs in some larger animals. They have large energy reserves. The mammal uses this energy reserved during periods of win r inactivity. Body temperatures do not drop substantially. The sleeping ani als can wake and become active very quickly.
- Aestivation: The period of inactivity in some animals for withstanding dry period is called aestivation. The animal enters into a burrow during dry environment. It does not eat or drink. It again emerges after moisture 13 restored. Aestivation is common in many invertebrates, reptiI0, and amphibians.OTHER ABIOTIC FACTORSOther important abiotic factors for animals are moisture., light, geology, and soils.
- Water: All the processes of life occur in the watery environment of the cell. Water is lost–from the body. This lost water must be replaced.
- Light: The amount of light and the length of the light period changes in a 24- hour day. It shows seasonal change. Light set the timing for many activities of – the animals, These activities are reproduction and migration.
- Soil: Geology and soils often directly or indirectly affect organisms. The characteristics of soil are texture, amount of organic matter, fertility, and water-holding ability. These characteristics directly influence the number and kinds of animals. These characteristics also influence the plants. The animals feed on these plants.