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class 10th homeostasis chapter 11 | homeostasis in plants | guttation class 10 | osmotic adjustment in plants

 CHAPTER 11

                       HOMEOSTASIS


Most organisms are able to control their internal conditions (e.g. body temperature and water level). They use various methods to maintain their internal conditions.


Homeostasis and its Importance


The ability to maintain the internal environment constant is called homeostasis. For living organisms, it is not always easy to keep internal conditions constant when the outside environment keeps on changing. But it is important so that all cells can function properly. The following are the examples of major homeostatic functions in living organisms.


  • The amounts of water and salts in body fluids are kept constant. If the amount of water and salts is not normal, the body fluids become more concentrated or dilute. In such conditions, cells.cannot carry out metabolism. Excretion is the main process which helps in osmoregulation regulation of the amount of water and salts


  • The temperature of the environment keeps on changing. These changes also affect the internal temperatures of bodies. Living organisms control their internal body temperature. The mechanism, by which organisms keep their internal temperature constant, is called thermoregulation.


11.1-Homeostasis in Plants

homeostasis in plants

Like other organisms, plants also have the abilities of homeostasis. They respond to the changes occurring in the external environment and keep their internal conditions constant.



Mechanisms Adaptations in plants for Excretion


a- Excretion of extra Carbon dioxide and Oxygen


During the day, the carbon dioxide produced during cellular respiration is utilized in photosynthesis. So it is not a waste product during the day. At night, plants cannot utilize carbon dioxide, so it becomes a waste product. Plants remove this carbon dioxide through their general surfaces and stomata.


By During, the  day Oxygen produced by photosynthesis is used for Cellular  Respiration.The extra oxygen is released out through stomata.


b-Excretion of Extra Water


Plants store large amounts of water in their cells space.It results in turgor, which provides support to the soft parts of the bod amounts of water, they remove it in two ways. body If plants have extra amounts of water,they removed it in two eyes.


1:- Transpiration. During the day, plants remove their extra water by transpiration are three types of transpiration i.e. through stomata stomatal transpiration  cuticle cuticular transpiration  and through lenticels lenticular transpiration.


2. Guttation: Transpiration does not occur at night. So, many plants store extra water in their xylem and remove it during the day. Some plants such as grasses use a special method to drain excess water at night. They leaves have  small holes in the tips or edges.They drain excess water through these holes.This water comes out in the form of small drops. This process is called guttation.


c-Excretion of other Metabolic Wastes


Plants adopt different methods to deal with other metabolic wastes. Some plants store wastes in their bodies in the form of harmless crystals. Some plants keep their wastes in leaves. When their leaves fall, plant body also gets rid of wastes.


Some plants use force to dispose of their waste through special holes.For example, rubber plant excretes latexes, keekar tree (Acacia nilotica) excretes gums, coniferous trees excrete resins, and ladyfinger excretes mucilage.


Osmotic adjustments in Plants


On the basis of habitats, there are four types of plants.


Mesophytes (meso medium, phyte plant):


These are the terrestrial plants which live in lands where medium quantity of water is available They absorb water through roots. Most of their body surface is covered with waxy cuticle, which prevents water loss. They also control extra transpiration by closing their stomata. Examples of mesophytes are maize (corn), clover and rose etc.


2. Hydrophytes (hydro water, phyte plant) 


These plants live in freshwater ponds, and lakes etc.or in wet soil. Water is absorbed through the entire surface of the plant. They use different methods to remove extra water from their bodies. For example, many hydrophytes have broad leaves which float on the surface of water. These leaves have large number of stomata on their upper surfaces. Water moves out of their bodies through these stomata.Lily is the Greatest example of such a  plants.



3. Xerophytes (xero dry, phyte plant)

These plants live in dry environments (deserts) They have deep roots to absorb water from almost dry soil. Their body surface has very few stomata. It is also covered with thick waxy cuticle to reduce the loss of water. Some xerophytes e.g. Cacti singular: Cactus store water in their specialized stems or roots/Such stems or roots are soft and juicy and are called succulent organs.


4. Halophytes (halo salt, phyte plant): 


These plants live in habitats with salty waters e.g. sea or salty marshes Water tries to move out from their hypotonic bodies into the hypertonic environment. Such plants absorb salts from water and make their bodies hypertonic. thats  way the, water doesn't come out. Excess salt can be stored in cells or excreted  from the salt glands on the leaves. Sea grasses belongs to this Group.


11.2-Homeostasis in Humans


In humans and other higher animals, skin, fungs and kidneys are involved in homeostasis.


Role of Skin


Skin performs important role in the regulation of body temperature The thin layer of fat cells beneath epidermis does not allow heat to enter or leave the body. In cold conditions, muscles attached at the base of skin hairs contract. As a result, the skin hairs stand up and bumps (goose bumps) are formed on skin. They make the goosebumps and  the hair a blanket of warm air. It does not allow body's heat to go out.


In warm conditions, skin provides cooling effect when sweat is produced by sweat glands. This way the ,excess body heat escapes is released through the vapor. Sweating also helps the body get rid of some extra water, salts, and nitrogenous wastes.


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