Biology (Part-III) (UPSC)

Total Questions: 50

21. Among living organisms, which one of the following is the most responsible factor for bringing about the origin of a new species? [2002]

Correct Answer: (b) Mutation
Solution:

Mutation is the most responsible factor for origin of new species.
A mutation is a change that occurs in our DNA sequence, either due to mistakes when the DNA is copied or as the result of environmental factors such as UV light and cigarette smoke.
• Isolation : Refers to the separation of populations, which prevents gene flow between them. This is a crucial factor in the formation of new species (speciation) as it allows the separated populations to evolve independently. Isolation can be geographic or reproductive.
• Natural selection : The process where individuals with advantageous traits are more likely to survive and reproduce, passing those traits to their offspring. It leads to populations adapting to their environment.
• Sexual reproduction : The process of producing new organisms by the fusion of male and female gametes, which increases genetic diversity within a population through recombination.

22. Ticks and mites are actually [2002]

Correct Answer: (a) Arachnids
Solution:

Ticks and mites are categorized under order Arachnids of phylum Arthopoda of animal kingdom.
• Arachnids include a diverse group of invertebrates: spiders, scorpions, ticks, mites, etc. There are over 100,000 species of arachnids.
• The name Arachnida derives from the Greek arachnē, which means spider. The vast majority of arachnids are spiders.
• Most arachnids are carnivorous, typically preying on insects, and terrestrial, living on land. They lack both wings and antennae.
• Their mouthparts often have narrow openings, which restricts them to eating liquefied prey.
• They help in keeping insect populations under control.

23. With reference to the blood in a normal person, which one of the following statements is correct? [2002]

Correct Answer: (d) The blood has more platelets than WBC.
Solution:Blood has more platelets than corpuscles. A microlitre of blood contains 5,000-10,000 of White blood cells (WBC) and 150,000-500,000 platelets.
WBC – White blood cells are also called leukocytes or leucocytes. They are cells of the immune system, which is mainly responsible for:
• Protecting and fighting against invading pathogens
• Stimulates the production of the progesterone hormone
• Play a vital role in the human reproductive system by producing a network of blood vessels within the ovary
On an average, the total count of white blood cells in every microliter of blood ranges between 4 and 11 thousands and a healthy person will produce around 80 to 100 billions of white blood cells every day. The lifespan of white blood cells ranges between 13 and 20 days.
White blood cells are nucleated blood cells which are white in color, hence they are called white blood cells. These blood cells are characterized into granulocytes and agranulocytes

24. Octopus is : [2003]

Correct Answer: (d) a mollusc
Solution:Octopus is an animal of class-Cephalopoda and phylum Mollusca. The shell is absent. It is found at bottom of the sea. It kills its prey with poisonous saliva. It can change its colour.
An octopus is a soft-bodied sea creature with a bulbous head and eight arms, hence it is named as the octopus. The name octopus was originally derived from a Greek word meaning number eight. These sea or marine creatures lack skeletal system and are grouped into Kingdom: Animalia, Phylum: Mollusca, Class: Cephalopoda and Genus: Octopus. According to the World Animal Foundation, there are around 289 to 300 species of octopus.
Octopuses are carnivores, which feed on other creatures available in their area including clams, shellfish, shrimp, lobsters, fish, sharks, and even birds. These sea creatures are found in all oceans and usually live on the ocean floor, within shells, crevices, and reefs. Let’s look into several amazing octopus facts.

25. Consider the following conditions of a sick human body : [2003]

1. Swollen lymph nodes

2. Sweating at night

3. Loss of memory

4. Loss of weight

Which of these are symptoms of AIDS?

Correct Answer: (d) 1, 2, 3 and 4
Solution:

Some people infected by HIV get a flu-like illness within 2 to 4 weeks after the virus enters the body. This stage may last a few days to several weeks. Some people have no symptoms during this stage.
Possible symptoms include:
• Fever.
• Headache.
• Muscle aches and joint pain.
• Rash.
• Sore throat and painful mouth sores.
• Swollen lymph glands, also called nodes, mainly on the neck.
• Diarrhea.
• Weight loss.
• Cough.
• Night sweats.
These symptoms can be so mild that you might not notice them. However, the amount of virus in your bloodstream, called viral load, is high at this time. As a result, the infection spreads to others more easily during primary infection than during the next stage.

26. With reference to the work of human kidney, consider the following statements : [2003]

1. After the waste is removed in the kidney, the clean blood is sent back through renal artery.

2. From Bowman's capsule, the filtered liquid passes through tiny tubes where much of the glucose is reabsorbed and sent back to the blood in the renal vein.

Which of these statements is/are correct?

Correct Answer: (b) Only 2
Solution:A nephron consists of a network of tiny blood vessels, the glomerulus surrounded by Bowman's capsule. Pressure forces much of the blood plasma through the glomerulus and inte Bowman's capsule. The resulting tubular fluid, which contains water and dissolved chemicals then passes into convoluted tubule and loop of Henle. This capillary network provides a mean for pick up and delivery of materials that are reabsorbed and secreted by the kidney.

27. Which one of the following statements is not correct? [2003]

Correct Answer: (a) Milk contains none of the B-vitamins.
Solution:Milk contains vitamin B1 (Thiamin) and vitamin B2 (riboflavin). So, statement (a) is not correct.

Milk contains various fat soluble vitamins like vitamin A, D, E, K, along with water soluble vitamins like vitamin C and B complex vitamins and provitamins. However, concentration of some of these vitamins is very less.

28. With reference to normal human beings, consider the following statements: [2003]

1. In response to the presence of HCI, secretin is produced from the duodenum.

2. Enterogastrone is produced in the small intestine in response to the presence of fatty acids.

Which of these statements is/are correct?

Correct Answer: (c) Both 1 and 2
Solution:Both the statement is correct. HCI is secreted, providing an acid medium for pepsin action and kill most bacteria and helps in digestion of food. When the food enters in duodenum (small intestine), secretin is produced by intestine that stimulates pancreas for pancreatic juice secretion. Enterogastrone is produced in small intestine.

29. Consider the following statements: [2004]

1. Non-functioning of lachrymal gland is an important symptom of deficiency of Vitamin A.

2. Deficiency of Vitamin B, can lead to indigestion and heart enlargement.

3. Vitamin C deficiency can lead to pain in the muscles.

4. Deficiency of Vitamin D causes increased loss of Ca in urine.

Which of the statements given above are correct?

Correct Answer: (d) 1, 2, 3 and 4
Solution:Lachrymal is a tear produced gland which does not function due to deficiency of vitamin -A. Deficiency of vitamin B, causes loss of appetite, heart disorders, muscular weakness etc.
• Lack of Vitamin C causes muscle pain (myalgia), swollen/bleeding gums, and general weakness.
• Vitamin D Deficiency: This impairs calcium absorption, causing increased calcium excretion (loss in urine) and affecting bone mineralization, which results in muscle weakness and bone pain.

30. The hormone insulin is a : [2004]

Correct Answer: (c) peptide
Solution:

Insulin is a peptide hormone composed of 51 amino acids. Insulin secrets from pancreas (Islets of Langerhans).
• Insulin is a peptide hormone produced by beta cells of the pancreatic islets; it is considered to be the main anabolic hormone of the body.
• It regulates the metabolism of carbohydrates, fats and protein by promoting the absorption of glucose from the blood into liver, fat and skeletal muscle cells.
• In these tissues the absorbed glucose is converted into either glycogen via glycogenesis or fats (triglycerides) via lipogenesis, or, in the case of the liver, into both.
• Glucose production and secretion by the liver is strongly inhibited by high concentrations of insulin in the blood.
• Circulating insulin also affects the synthesis of proteins in a wide variety of tissues.
• It is therefore an anabolic hormone, promoting the conversion of small molecules in the blood into large molecules inside the cells.
• Low insulin levels in the blood have the opposite effect by promoting widespread catabolism, especially of reserve body fat.