 Dear students, in this module, we shall discuss the principles of conformity and regulation. These are two categories of animal responses to changes in their external environment. The conformer animals are those which are unable to maintain homeostasis for an environmental variable. These animals conform to that external variable, i.e. they compromise that the outside environment is like this, so we will run our body according to this. The degrees to which the conformers conform depend on their level of survival. The conditions to which the conformers are allowed to survive depend on the tolerance level of body tissues to that variable. We shall take a few examples of conformers. The conformers or conformation depend on the changing environmental variable. For example, if an animal conforms to water and salt levels that is called osmoconformer. The animal which conforms to the level of oxygen is called oxyconformer and the animal that conforms to temperature change is called thermoconformer. We shall take the example of osmoconformer first. The osmoconformers do not actively adjust their internal osmotic state. In these animals, their body tissues are kept isotonic to the external environment. They show increase in body fluid salinity in hypotonic solutions and decrease in body fluid salinity in hypotonic solutions. Oxyconformers consume oxygen when there is more level of oxygen in the air. They, if the oxygen availability is, there is no oxygen availability, they cannot regulate their body conditions to the lower level of oxygen. Similarly, the thermoconformers conform to the temperature of the environment. As the environment warms or cools, the animal's body also warms or cools. The outside temperature will work, the animal's temperature will also work, and if the outside temperature increases, the animal will get heated up. In contrast to conformers, the regulators use internal control mechanisms to regulate their internal conditions. In spite of fluctuations in the external environmental variables, so these animals maintain homeostasis. The regulators are also of various types depending on the environmental variable. They can be thermoregulators if they are regulating their body temperature. They can be oxyconformers and they can be osmoregulators, thermoregulators and oxyregulators. The osmoregulators maintain their body fluid concentration that differs from that of the environment. They can maintain the concentration of body ions and body fluids in hypotonic or hypotonic environments. If the environment is hypotonic, they will maintain the salt concentration in their body. If the environment is hypotonic, they will regulate the salt concentration in the body and will not give salinity to the tissue fluids. The osmoregulators adopt the strategy to regulate the amount of water in their tissues. They discharge excess water in hypotonic environments and they conserve water in hypotonic environments. In hypotonic environments, where the salt concentration is higher, they maintain the water concentration in their body fluids and otherwise water has a tendency to move from its lower concentration to its higher concentration to its lower concentration that is from the body to the outside environment. This is the conservation of their osmoregulatory strategy. The oxyregulators maintain their oxygen consumption at study level. If the oxygen level is more or less in the environment, then a regulator will use a required amount. If the oxygen level is less in the environment, then the animal keeps the utility of its oxygen consumption. However, if the level of oxygen is more or less in the environment, then the animal's systems are not able to complete the requirement, so as a result, the animal tries to be oxy-conformer. It maintains its systems at a low oxygen level until and unless it dies. Thermoregulators regulate the temperature of their body. If the temperature is low in the environment, then the temperature of the body remains at a higher level. If the temperature of the body is too high, then the temperature of the body can be cooled down. This is homeostasis. These types of animals are called homeotherms, that is, temperature-maintaining animals. Dear students, animals cannot be conformers or regulators for all the variables. An animal is conformer for one variable and may be a regulator for that variable. And if an animal is a regulator for some particular variable, he may be conformer for other variables. For example, fishes are thermoconformers and do not regulate the temperature, but are as thermoregulators and maintain the concentration of water and salts in the body.