Biology Chapter 1 (Part A)
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CHAPTER – 1
Homeostatis
Definition
Home means same and statis means state. So the regulatory mechanism which maintained the internal environment of a organism is called homeostatis.
Important Aspects of Homeostatis
There are three important aspects of homeostatis.
Osmoregulation
Thermoregulation
Excretion
Feed Back System
The check and balance system in a body is called feed back system. In a feed back system three organs are involved.
1. Receptor
The organ which receive any change in the internal environment of the body are called Receptor.
2. Effector
The central nervous system which send the message to a particular organ are called effector. Take part in particular action.
3. Central Nervous System
The receptor transfer message to a central nervous system such as brain.
Types of Feed Back System
There are two type of feed back system.
Positive Feed Back System
Negative Feed Back System
1. Positive Feed Back System
When there is a change in the internal environment and it is further increase by the process are called positive feed back system.
2. Negative Feed Back System
When there is a change in the internal environment and it is further decreased by the process called negative feed back system.
Osmoregulation
Definition
The regulatory mechanism which maintain the balance between water and solute context of a cell is called osmoregulation.
Osmoregulation in Plant
Due to the availability of water there are four groups of plant.
Hydrophyte
Halophyte
Xerophyte
Mesophyte
Hydrophyte
The group of plant which is grow in fresh water are called hydrophyte.
Characteristic of Hydrophyte
■The plant do not have layer of cuticle.
■The leave have stomata in the upper surface with take part in transpiration.
■The root are either absent or poorly developed.
Example
Hydrilla, Lotus, Lily plant
Halophytes
The group of plant which is grow in marshy soil or salty soil are called halophyte.
Characteristic of Halophyte
■These plant absorb water from such a soil, which is higher salt concentration and low water potential.
■Halophyte actively absorption salt into their roots.
■In the leaves of plants salt glands are present which helps in the removal of salt and water from the body.
■Some halophytes absorb humidity by leave.
Example
Glass wort, Cord grass
Mesophyte
The group of plant which is grow in well watered soil are called mesophyte.
Characteristics of Mesophyte
■Their roots are well developed.
■Their body is covered by a layer called cuticle.
■They contain stomata for evaporation of extra water.
■Some mesophyte excrete out water in the form of drop this process is called guttation.
Xerophyte
The group of plant which is grow in dry places such as desert are called Xerophyte.
Characteristic of Xerophyte
■Some plants do not face dry consition and produce seed are called ephemeral plant. During raining season seeds germinate.
■Their root are well develop which go deep into the soil to absorb water.
■Some plant have horizontal root on the surface to absorb rain water rapidly.
■Some plant leaves are modified into spine to prevent transpiration.
■Stem and leave covered by cuticle.
■Some plant store water in cell (succulent)
Example
Cacuts, Euphorbia.
Excretion
Definition
The removal of harmful substance produce in the metabolic process from the body is called Excretion.
Excretion in Plant
In plant rate of catabolic process is very slow and waste product are produce in less amount. They are used again in their anabolic process.
Waste Substance of Plant
The substance which are produce in excess amount are
■Water
■CO2 and O2
■Ions
Removal of Water
Extra water is removed from the body of plant by two methods.
Transpiration
The extra amount of water removed in the form of vapor through stomata is called transpiration.
Guttation
When water is removed from plant in the form of drop this process is called Guttation. Guttation occur special opening called hydathods. Guttation take place in those plant which grow in tropical rain forest.
Release of Oxygen and Carbondioxide
■In day time plant used CO2 for photosynthesis process and released O2.
■In night time plant released CO2 and inhale O2 gas.
Ions
Excess amount of ion are deposit into dead cell of plant body such as bark.
Thermoregulation
The maintained the temperature of the body with in a range is called thermoregulation.
Thermoregulation in Plant
The normal range of temperature in plant is 10oC to 35oC. The adaption of plant to low and high temperature are as follows.
Low Temperature
■At low temperature the nature of plasma membrane is changed and produce crystalline structure due to which transport of solute is slow.
■To control this condition plant cell produce unsaturated.
■At freezing point ice crystal are formed in the cell. But the plant of cold region change the composition of solute of cell so ice crystal are not formed in cytoplasm they form in cell wall. This condition is known as freezing tolerance.
High Temperature
■High temperature has more harmful than low temperature for plant.
■Due to high temperature all enzyme are denature and metabolic process stop. So plant increase rate of transpiration and cool the body.
■At above 40oC plant produce heat shock protein. They protect the enzyme from destroying.
■In some plant shiny cuticle is present which protest them from high temperature.
■In some plant leaves are reduce in size.
Osmoregulation In Animal
Osmoregulation in Terrestial Animal
In land animals excretion of water take place through body surface so they have develop number of strategies to maintain Osmoregulation.
Water Proof External Covering Epidemics present in reptile, mammal cuticle present in insect which prevent the water loss from their body.
Storage and Excretion of Solid Wastes
In birds, reptile and insect store nitrogenous waste uric acid. Uric acid insoluble in water and help to reabsorption of water in cloeca. Uric acid excreted the body in the form of paste and crystal.
Use of Metabolic Water
Some mammal fat is converted into simple compound and during this process water is produce which is reused in the body. Camel, Kangroo used metabolic water.
Storage of Harmful Waste
In mammal urea in kidney which is helps in reabsorption of water.
Osmoregulation in Aquatic Animal
Osmoregulation in fresh water animal is maintained by two methods.
1. By Contractile Vacuole
2. By producing dilute urine
1. By Contractile Vacuole
Fresh water unicellular organism have contractile vacuoles. Water with dissolved CO2 and uric acid is collected from the endoplasm into the contractile vacuole, which increase in size up to a maximum and burst released the extra substance in environment. In Amoeba and Paramicium the amount of water and other substance remain in balanced by contractile vacuole.
2. By Producing Dilute Urine
Fresh water fishes have hypertonic body fluid as compare to surrounding water. Fisher released extra amount of water in the form of dilute urine and absorb some essential ion from outside to maintain the salt and water content in the body.
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