Regulate, conform, migrate or suspend

What do you do on a hot day?

On a hot day you sweat. On a cold day you shiver. Your body stays at about 37 °C in both. A lizard on the same hot day does something else. Its body gets warmer as the air does.

Organisms meet hard conditions in four ways. NCERT names them: regulate, conform, migrate and suspend.

Regulate

Some organisms keep their internal environment steady, even when the surroundings change. This is homeostasis. Two kinds are common.

• Thermoregulation: keeping a constant body temperature.
• Osmoregulation: keeping a constant concentration of salts and water in the body fluids.

Birds and mammals are the best regulators. A few lower vertebrates and a few invertebrates also regulate. In humans the body temperature stays at about 37 °C. In summer we sweat, and the evaporation cools the body. In winter we shiver, and the muscles make heat.

Why do organisms spend so much energy on this? The enzymes of the body work best in a narrow range of temperature. A steady inside means that the body works well all through the year, in a hot place or a cold one.

Conform

Most animals and nearly all plants cannot keep a steady inside. Their body temperature changes with the temperature of the surroundings. A water animal may have body fluids that change their salt concentration with the water around it. Such organisms are called conformers.

Some species have evolved the power to regulate, but only over a limited range. Beyond the limits, they simply conform.

Regulation costs a lot of energy. Think of a very small animal such as a shrew or a hummingbird. It has a large surface for its small volume, so it loses heat fast in cold weather. It must make heat all the time to stay warm. This is why very small animals are rarely found in the polar regions. You will see the numbers in the next lesson.

Migrate

Some animals leave a place when it becomes hard to live in, and return when it is better. This is migration. Many birds migrate. The Siberian crane comes in winter to the Keoladeo National Park at Bharatpur, and goes back in spring.

Suspend

When an organism cannot move away, it can slow down and wait. This is a suspension of its activity. NCERT gives these examples.

• Hibernation: a winter sleep. Bears hibernate in winter.
• Aestivation: a summer sleep, to escape heat and drying. Some snails and some fish aestivate.
• Diapause: a stage of suspended development. Many zooplankton of lakes and ponds enter diapause under bad conditions.
• Spores: thick walled spores of bacteria, fungi and lower plants survive bad conditions. They germinate when the conditions are right.
• Seeds and some vegetative parts of higher plants do the same. They go into a state of dormancy with a very low metabolism, and they grow when moisture and temperature are right.

You should find that the conformer follows the surroundings at every point. The regulator stays at 37 °C inside its limits, and outside them it also follows the surroundings.

Try it in Python

The program takes the body temperatures that were measured at five air temperatures. It works out the slope of the best straight line. A slope near 0 is a regulator, and a slope near 1 is a conformer.

Practise with new numbers

Common mistakes

• Saying that a regulator never changes. It regulates over a range. Outside its limits it conforms.
• Saying that plants regulate their temperature like mammals. Plants have no such mechanism. Most plants are conformers.
• Mixing up hibernation and aestivation. Hibernation is in winter, and aestivation is in summer.
• Calling migration a suspension. In migration the animal moves away. In suspension it stays and slows down.

Remember these

• Four responses: regulate, conform, migrate, suspend.
• Regulate: homeostasis, as in birds and mammals. Conform: the inside follows the outside, as in most animals and plants.
• Migrate: Siberian crane at Bharatpur. Suspend: hibernation (bear), aestivation (snail, fish), diapause (zooplankton), spores, seeds.
• Small animals lose heat fast, so they are rare in polar regions.

Check yourself

Try each one on your own first. If you are stuck, open a hint. Then check with Show the answer.

1. Name the four responses of organisms to a hard environment.

2. What is homeostasis? Give two kinds.

3. Are most plants regulators or conformers? Say why.

4. A snail seals itself in its shell during a hot dry spell. What is this called?

5. Why are shrews not found in the polar regions?

References

• NCERT (2023). Biology, Textbook for Class XII, chapter 11, Organisms and Populations, section on responses to abiotic factors.
• Campbell Biology, 12th edition (2021), Pearson, chapter 40, Basic Principles of Animal Form and Function: regulators and conformers.
• OpenStax Biology 2e (2018), chapter 44, Ecology and the Biosphere.