Responses to Abiotic Factors: Suspension, Migration, Practice problems and FAQs

Where do you stay? How is the climate of your hometown? You must be quite comfortable and used to such a climate right? Now imagine having to travel to a place which has a dramatically different climate compared to that of your hometown. You will have to carry the clothes accordingly, isn’t it?. You will prefer a sweater if it's a cold place and a cotton dress if it's hot.

Why do you think we do this? This is because we are well adapted to the climate of our habitats but changes in the external environment forces us to adopt measures that will help in adapting to such changes.

Have you visited any bird sanctuary? Are you aware that birds from colder countries fly down to the warmer places south of their habitat to avoid extreme cold weather? You will be amazed to know that this is one of the ways of responding to changes in the environment.

In fact, a seed remaining dormant before germinating is also one such mechanism. Seems interesting right? Let us dig deeper into these aspects.

Responses to abiotic factors

According to the changes in the environmental conditions, organisms respond in different ways to the changes in order to survive and maintain their reproductive fitness (ability to reproduce and give birth to healthy and fertile offspring). They can either regulate their internal environment to be constant, conform to the external changes, suspend their metabolic activities until the adverse changes in the environment are over or migrate to a place with a favourable environment.

Here we are going to discuss suspension and migration which occur when the unfavourable conditions are localised or short lived.

Suspension

Organisms avoid the stress by escaping in time through different methods such as hibernation, aestivation, diapause and dormancy.

Hibernation

Period of inactivity and reduced metabolism to pass harsh winters is commonly known as hibernation or winter sleep. In this state of minimal activity, metabolic rate decreases, heart rate slows down, rate of breathing slows down and body temperature also goes down. Examples of animals that hibernate are bears, ground squirrels, bats etc.

These animals wake up when the temperatures rise in the beginning of spring.

Aestivation

Periods of inactivity and reduced metabolism to pass dry summers are commonly known as aestivation or summer sleep.

Examples are - A thick dried mucus layer seals the opening, allowing the snail to survive till rainfall.

Frogs appear right after the first rainfall.

Diapause

Freshwater zooplankton enter a state of suspended development, known as diapause, under unfavourable conditions. Zooplanktons include small invertebrates, their larvae, protozoans etc. These zooplankton can enter diapause at any stage of development. Development is resumed when favourable conditions return.

Dormancy

Bacteria, fungi and lower plants can survive harsh environmental conditions by producing various kinds of thick-walled spores. These kinds of spores can survive from months to years and germinate to release the organisms, upon availability of a suitable environment. These spores are dormant stages in which the metabolic activities are suspended as long as the adverse conditions prevail.

In higher plants, dormancy is observed in buds and seeds. During certain unfavourable conditions, the metabolic activity of the bud or the embryo within the seed becomes very low. This state is called seed dormancy. Dormancy is maintained until an adequate amount of moisture, warmth and light is available.

Migration

Some organisms travel to far off places temporarily from stressful conditions to a more suitable condition for a brief period and return when the stressful period is over. Birds, in particular, migrate from north to south during winters to escape the snow and return at the end of winter.

Every winter migratory birds from cold northern regions like Siberia, China, Mangolia etc., come to Keoladeo National Park, Bharatpur in Rajasthan.

Practice Problems

Q1. An inactive phase that some organisms undergo during the winter to escape from the harsh conditions. Which of the following terms best suits this description?

a. Acclimatisation
b. Hibernation
c. Aestivation
d. Adaptation

Solution: Hibernation is a period of long physical inactivity and reduced metabolic activity that some animals undergo during the winter months. This helps them to evade the harsh cold climate and remain comfortable in their burrows or caves.

Hence the correct option is b.

Q2. Assertion : Many zooplankton species in lakes and ponds enter the state of diapause.

Reason : Diapause is a state of suspended development, in response to unfavourable conditions.

a. Both assertion and reason are true. The reason is the correct explanation for the assertion.
b. Both assertion and reason are true. The reason is not the correct explanation of the assertion
c. Assertion is true and the reason is false
d. Both assertion and reason are false

Solution: Diapause is a common mode of evading unfavourable conditions seen in zooplankton. It helps them to enter into a state of suspended development till the unfavourable conditions pass.

Hence the correct option is a.

Q3. Ritu wished to visit the Keoladeo National Park located in Bharatpur, Rajasthan during her summer vacation. Her father suggested to her that they will take up the trip in the winter season. What is the possible reason to plan a trip in winter ?

a. The birds in the park aestivate during the winter season
b. The birds in the park will hibernate during the summer
c. Many birds from colder countries like Siberia will migrate to the park during the winter
d. The overall cost of the trip will be much less if they plan a trip in winter

Solution: Winters in countries such as Siberia can be very harsh for the survival of several birds, e.g., Siberian Crane. Thus, they prefer migrating away to warmer habitats such as the one provided by the Keoladeo National Park. The winter in this National Park is mild and it is favourable for the birds.

Hence the correct option is c.

Q4. If the unfavourable conditions in the environment are localised or short-lived, which of the following responses is/are more likely to occur in organisms?

I. Hibernation
II. Diapause
III. Migration

a. I, II and III
b. Only I and III
c. Only III
d.Only II and III

Solution: Hibernation is a state of prolonged inactivity by sleeping during the winters. Aestivation is a period of suspended activity during the summer months. Diapause is a state of suspended development with reduced metabolic activity, in response to unfavourable conditions.

Hence the correct option is a.

FAQs

Question 1. How do bacteria respond to unfavourable conditions?
Answer: Bacterial cells develop thick walled spores around themselves and enter into a state of dormancy to evade unfavourable conditions. These spores germinate to release the bacterial cells, when the favourable conditions return.

Question 2. Which is the longest-distance migration of any bird?
Answer: The Arctic tern has the longest-distance migration of any bird. It flies for approximately 30,000 kilometres from the Arctic region to the Antarctic region .

Question 3. Do reptiles aestivate?
Answer: many reptiles such as crocodiles aestivate and enter into a state of prolonged sleep with reduced metabolic activity to evade the high temperatures in the summer. This is required as reptiles are cold-blooded and cannot maintain a constant body temperature.

Question 4. What is seed dormancy?
Answer: Seed dormancy is a condition in which the metabolic activities of an embryo is very low and its growth and development remains completely suspended.

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