Chapter 29, Problem 20A

Summary Introduction

Introduction:

Birds are important parts of food chains as predators of small mammals, arthropods and other invertebrates. They have features that make them well- adapted for flying. They have light weight bones, excellent vision, feathers and wings for flight and can generate their own body heat. Birds have well developed digestive system, circulatory system, brain and excretory system. Many birds are threatened with extinction as their habitat are destroyed and degraded by overuse of pesticides and pollutants. Illegal bird trade is also increasing.

Correct answer :

The correct answer is option D. amniotic egg, cloaca, kidney, amnion

Explanation/justification for the correct answer:

Option D. amniotic egg, cloaca, kidney, amnion − Birds have kidneys as organs of excretion. Kidneys filter wastes from the blood and convert it to uric acid. Birds have cloaca where water is reabsorbed from uric acid. Amnion is not a part of excretory system. It is a part of an egg. Therefore, amnion does not belong to this group. Hence this is the correct option.

Explanation for incorrect answer:

Option A. ventricle, atrium, oxygenated blood, deoxygenated blood − All the words in this group belong to the circulatory system of birds. Birds have four chambered heart; two ventricles and two atria that keeps oxygenated and deoxygenated blood separated. Left atrium receives oxygenated blood from lungs which is then pumped to left ventricle and out to the body. deoxygenated blood from the rest of the body enters the right atrium, then moves to right ventricle and onto the lungs where it again becomes oxygenated. Hence this is not the correct option.

Option B. kidney, nitrogenous waste, uric acid, cloaca- All the words in this group belong to the excretory system of birds. Kidneys filter wastes from the blood and convert it to nitrogenous waste like uric acid. Birds have cloaca where water is reabsorbed from uric acid. Hence this is not the correct option.

Option C. cerebellum, cerebrum, optic lobes, medulla − All the words in this group are parts of brain of birds. The brains of birds are comparatively larger than their body size. The cerebellum helps to coordinate movements and balance during flight. The optic lobes coordinate visual input. The cerebrum is the integrating center of the brain. It controls eating, singing, flying and instinctive behavior. The medulla oblongata controls heartbeat and respiration. Hence this is not the correct option.

Answer to Problem 20A

Correct answer :

The correct answer is option D. amniotic egg, cloaca, kidney, amnion

Explanation of Solution

Explanation/justification for the correct answer:

Option D. amniotic egg, cloaca, kidney, amnion − Birds have kidneys as organs of excretion. Kidneys filter wastes from the blood and convert it to uric acid. Birds have cloaca where water is reabsorbed from uric acid. Amnion is not a part of excretory system. It is a part of an egg. Therefore, amnion does not belong to this group. Hence this is the correct option.

Explanation for incorrect answer:

Option A. ventricle, atrium, oxygenated blood, deoxygenated blood − All the words in this group belong to the circulatory system of birds. Birds have four chambered heart; two ventricles and two atria that keeps oxygenated and deoxygenated blood separated. Left atrium receives oxygenated blood from lungs which is then pumped to left ventricle and out to the body. deoxygenated blood from the rest of the body enters the right atrium, then moves to right ventricle and onto the lungs where it again becomes oxygenated. Hence this is not the correct option.

Option B. kidney, nitrogenous waste, uric acid, cloaca- All the words in this group belong to the excretory system of birds. Kidneys filter wastes from the blood and convert it to nitrogenous waste like uric acid. Birds have cloaca where water is reabsorbed from uric acid. Hence this is not the correct option.

Option C. cerebellum, cerebrum, optic lobes, medulla − All the words in this group are parts of brain of birds. The brains of birds are comparatively larger than their body size. The cerebellum helps to coordinate movements and balance during flight. The optic lobes coordinate visual input. The cerebrum is the integrating center of the brain. It controls eating, singing, flying and instinctive behavior. The medulla oblongata controls heartbeat and respiration. Hence this is not the correct option.