Read the passage carefully. Attempt the questions.
An overwhelming majority (99 per cent) of animals and nearly all plants cannot maintain a constant internal environment. Their body temperature changes with the ambient temperature. In aquatic animals, the osmotic concentration of the body fluids change with that of the ambient water osmotic concentration. These animals and plants are simply conformers. Considering the benefits of a constant internal environment to the organism, we must ask why these conformers had not evolved to become regulators. Recall the human analogy we used above; much as they like, how many people can really afford an air conditioner? Many simply 'sweat it out' and resign themselves to suboptimal performance in hot summer months. Very small animals are rarely found in polar regions. During the course of evolution, the costs and benefits of maintaining a constant internal environment are taken into consideration. Some species have evolved the ability to regulate, but only over a limited range of environmental conditions, beyond which they simply conform.
If the stressful external conditions are localised or remain only for a short duration, the organism has two other alternatives for survival.
Identify the animal which is NOT a conformer.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Polar Bear
Note 1: The given answer is as per the official NTA Answer Key. However, the question can have more than one correct answer, i.e. Option (1), Option (2) and Option (3), as explained below.
Birds and mammals are regulators: they keep a constant body temperature. Lizards are reptiles whose body temperature changes with the surroundings, so they are conformers.
Option (1) Humming bird — Not a conformer (also correct). Hummingbirds are birds and keep a constant body temperature. NCERT names humming birds among the small animals for which this thermoregulation is energetically expensive, so they are regulators.
Option (2) Shrew — Not a conformer (also correct). Shrews are mammals and keep a constant body temperature. NCERT names shrews with humming birds as small animals that spend much energy on thermoregulation, so they are regulators.
Option (3) Polar Bear — Not a conformer. This is the answer given by NTA. The polar bear is a mammal that keeps its body temperature constant even in the Arctic.
Option (4) Lizard — A conformer. The lizard’s body temperature changes with the surroundings.
Note 2: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
Note 3: This question is from the topic “Responses to Abiotic Factors” in Chapter 13, Organisms and Populations, of the pre-rationalised NCERT book. This portion is not in the present NCERT book, where the chapter is now Chapter 11, Organisms and Populations. The extract below is from the pre-rationalised edition.
NCERT Extract (Pre-rationalised edition, Chapter 13, Organisms and Populations):
Responses to Abiotic Factors – “… An overwhelming majority (99 per cent) of animals and nearly all plants cannot maintain a constant internal environment. Their body temperature changes with the ambient temperature. In aquatic animals, the osmotic concentration of the body fluids change with that of the ambient air, water osmotic concentration. These animals and plants are simply conformers.”
Responses to Abiotic Factors – “… Thermoregulation is energetically expensive for many organisms. This is particularly true for small animals like shrews and humming birds.”