What happens when we visit a place with extreme cold conditions? The chilly weather gives us goosebumps and we start shivering as soon as the cold wind hits us. Have you ever thought, what could be the reason behind this? How is it happening? This is actually the response of our body to the changes in temperature of our environment and this response varies from one organism to another.
In fact, not just temperature, but drastic changes in any abiotic factor of our environment induces a response which helps us to cope with the change. Have you ever wondered why we get so bothered by these changes?
This is because the living body exhibits maximum efficiency at an optimum level of internal temperature, pH and osmotic balance and strives to keep it constant. This phenomenon is known as homeostasis and drastic changes in our external environment disturbs the homeostasis of our internal environment.
You must be wondering, but I can go sit under the AC if it's too hot outside, that is not a big deal! But have you wondered how other plants and animals would cope with such extreme changes? While some organisms regulate their internal environment to keep it constant irrespective of the external changes, other conform to the environmental changes to survive. Let us go ahead and get a better understanding of this.
Regulators are organisms that use energy to maintain the internal environment at a steady-state regardless of the external environment.
The two most affected internal factors that require regulation are – Temperature and Osmolarity. The regulation of temperature is called thermoregulation and that of osmolarity is called osmoregulation.
An organism’s ability to maintain body temperature within a narrow range is called thermoregulation. It is also called heat regulation and is the maintenance of an optimum temperature range by an organism. Normal human body temperature is 370C.
In summer or desert environments where temperatures are higher than 370C, our body temperature also rises. This is sensed by our nervous system (hypothalamus), and it signals following changes:
And thus normal body temperature is maintained irrespective of the condition outside.
In contrast, in a cold environment where the temperatures are below 370C, our body temperature drops. This is sensed by our nervous system (hypothalamus), and it signals following changes:
And thus, normal body temperature is maintained irrespective of the condition outside.
Thermoregulators includes endotherms like birds and mammals. Endotherms are animals that use metabolism to generate heat and maintain their body temperature. It also includes a few lower vertebrates like tuna, some mackerels, great white shark and invertebrates which includes mostly winged insects. Plants cannot thermoregulate.
It is important to note that not all regulators are capable of regulating both temperature and osmolarity. For example, fishes cannot regulate their temperature, but they can very well maintain their osmolarity.
Active regulation of body fluid osmolarity is called osmoregulation. Mechanism of osmoregulation is different for freshwater fishes and marine fines as they live in different habitats.
In freshwater fishes, the body fluids are hypertonic compared to the surrounding water. This is because the gills of these fishes actively absorb ions from the surrounding water for bodily functions. As a result, water enters the body of the fish by endosmosis through gills and skin.
To get rid of excess incoming water, the fish excretes dilute urine.
In marine fishes, the body fluids are hypotonic compared to the surrounding sea or ocean water which leads to exosmosis of water from the fishes’ body into the surrounding. To prevent excess loss of water the marine fishes drink seawater. The salts ingested along with water are actively pumped out through gills. To balance the excess loss of water and surplus salts, the marine fishes excrete concentrated urine.
Most bony fishes are osmoregulators, but other marine organisms like crabs and molluscs come under osmoconformers (maintain their internal salinity similar to their ambient conditions). There are 99% of animals and nearly all plants which cannot maintain a constant internal environment like regulators. Examples - amphibians, reptiles, fishes, insects, etc. Such animals are called conformers and their internal environment is highly influenced by external factors. They do not use energy from metabolism to maintain their internal environment at a steady state.
Carefully observe this graph. You can clearly note that the regulator (human) can maintain a constant temperature even with rising temperature of its environment but the fish’s body temperature rises with rise in environmental temperature. Fishes cannot thermoregulate. The temperature of the external environment decides the body temperature of fish. So fish is a conformer.
Maintaining a constant internal environment requires a lot of energy input, which is not feasible. Therefore, most animals and plants do not regulate their internal environment and conform to the changes in the external environment.
This specifically holds true for smaller organisms such as the hummingbird. As heat loss or gain is a function of surface area of the body, small organisms like the hummingbird with a small volume but large surface area, tend to lose body heat rapidly under cold conditions.
In the graph you can observe that hummingbirds have the highest area to volume ratio followed by shrew and elephant. This means that the hummingbird must generate more energy compared to the others to keep its body temperature constant.
To keep up with this energy demand, the hummingbirds must eat throughout the day consuming food weighing half their body weight! Do you think that is convenient? Definitely not! No wonder small creatures are hardly found in the Polar regions.
Some species of animals have evolved to regulate their internal environment within a limited range of environmental conditions, beyond which they conform to the changes in their environment.
Example: Ground squirrels – below a set point their body temperature varies with atmosphere, but above the point it becomes stable irrespective of external condition.
Question 1. Study the following graph and identify the correct option.
a. i) - can maintain homeostasis ii) - can not maintain homeostasis iii) - can maintain homeostasis after a certain level
b. i) - can not maintain homeostasis ii) - can maintain homeostasis iii) - can maintain homeostasis after a certain level
c. i) - can maintain homeostasis after a certain level ii) - can’t maintain homeostasis iii) - can maintain homeostasis
d. i) - can not maintain homeostasis ii) - can maintain homeostasis after a certain level iii) - can maintain homeostasis
Solution: Curve (i) represents conformers who cannot maintain homeostasis and hence external and internal factors keep varying with time.
Curve (ii) represents regulators that can maintain homeostasis and hence the internal environment remains constant even when the external environment changes. Curve (iii) reresents partial regulators that conform till a certain level and maintain homeostasis after that.
Hence the correct option is b.
Question 2. Consider the following statements.
Assertion: Animals like shrews and hummingbirds are conformers.
Reason: These animals have large volume compared to their surface area which leads to rapid heat loss from the body.
a. Both assertion and reason are true and the reason is the correct explanation for the assertion.
b. Both assertion and reason are true but the reason is not the correct explanation for the assertion
c. Assertion is true but the reason is false
d. Both assertion and reason are false
Solution: Small animals like shrews and hummingbirds are conformers and are not able to maintain a constant internal environment. This is because these animals have a large surface area compared to their volume. Loss or gain of heat is a function of the surface area of an organism and hence these organisms lose body heat rapidly during cold conditions. Generating this huge amount of heat by metabolism is not feasible for these organisms and hence they conform.
Hence the correct option is c.
Question 3. Which of the following statements is incorrect ?
a. All homeotherms are regulators
b. Fishes are strict osmoregulators
c. Thick cuticle in plants help in water conservation
d. Spore formation in bacteria is a mechanism to evade unfavourable conditions
Solution: Fishes are aquatic organisms and maintaining a proper osmotic balance of the body is extremely important for their survival. Fishes can be both osmoregulators or osmoconformers.
Some fishes (freshwater fish) are capable of maintaining a constant osmotic concentration and are called osmoregulators, whereas some fishes (rays) change their osmotic concentration to suit their environment and are called osmoconformers.
Hence the correct option is b.
Question 4. Heat loss or gain is a function of ___i___ and heat generation in the body is a function of ___ii____.
a. i - volume, ii - surface area
b. i - surface area, ii - volume
c. i - surface area, ii - circumference
d. i - volume, ii - circumference
Solution: Small animals like hummingbirds have a large surface area compared to their volume. Larger surface area indicates that more area of the organism's body is exposed to the surroundings for heat exchange. Heat production on the other hand is the function of volume, i.e, more the volume of an organism, more is the heat generated. Due to their small size, the volume of hummingbirds is less compared to their surface area.
Hence the correct option is b.
Question 1. What do you mean by homeostasis?
Solution: Homeostasis refers to the capacity of the body to maintain the stability of internal variables, such as temperature, acidity and water level against constant environmental disturbance.
Question 2. How does the human body regulate its body temperature during summer?
Solution: In summer when temperatures are higher than 370C, our body temperature also rises. This is sensed by our nervous system (hypothalamus), and it signals changes like dilation of capillaries near skin to lose body heat and sweating to cool the body. And thus normal body temperature is maintained irrespective of the condition outside.
Question 3. What is the major difference between regulators and conformers?
Solution: Regulators are organisms that use energy to maintain the internal environment at a steady state regardless of the external environment. Conformers are organisms whose internal environment changes with changes in external envionment.
Question 4. What happens to the ecosystem when there is a change in the abiotic factor?
Solution: Abiotic factors can affect an organism’s ability to survive and reproduce. So abiotic factors can restrict the growth of populations. As a result it will affect the numbers of organisms that are able to exist in the environment.