Biology MCQs with answers Page - 3

Explanation:

• Anthocyanins are water-soluble pigments responsible for red, blue, and purple colors in plants.
• They are found in the vacuoles of plant cells and belong to the flavonoid group.
• The color variation depends on the pH of the cell sap:
  • Acidic conditions → Red
  • Neutral conditions → Purple
  • Alkaline conditions → Blue

Other Pigments:

• Carotene → Orange color
• Chlorophyll → Green color
• Xanthophylls → Yellow color

Xerophytes are plants that are adapted to dry (arid) conditions where water is scarce.

They have special features to reduce water loss and store water, such as:

Thick cuticles to minimize evaporation.

Sunken stomata to reduce transpiration.

Fleshy stems or leaves for water storage (e.g., Cactus).

Other Options:

Mesophytes → Grow in moderate water conditions (e.g., Mango, Rose).

Lithophytes → Grow on rocks (e.g., Lichens, Orchids).

Hydrophytes → Grow in water (e.g., Lotus, Water Hyacinth).

Psammophytes are plants that grow in sandy soils or desert environments where water retention is low.

They have adaptations like deep roots, small leaves, and waxy coatings to survive in dry, shifting sands.

Examples: Beach grasses, sand dune plants (e.g., Spinifex, Marram grass).

Other Options:

Chasmophytes → Grow in rock crevices.

Oxylophytes → Grow in acidic soils.

Lithophytes → Grow on rocks (like mosses, lichens, and orchids).

Ramapithecus → An early primate ancestor of humans that lived around 14 million years ago. Fossils suggest it might be an early link in human evolution.

Cro-Magnon Man → Lived around 40,000 years ago and is considered an early form of modern Homo sapiens with advanced tools, art, and culture.

Thus, both are considered ancestors of modern humans.

In a normal adult human male, the haemoglobin level typically ranges between 13.8 to 17.2 grams per 100 milliliters (g/dL) of blood.

• 10 g/dL → Considered low (may indicate anemia).
• 14 g/dL → Normal average for males.
• 18 g/dL → Upper limit of normal but can be found in certain conditions (e.g., high altitudes).
• 24 g/dL → Extremely high and not normal in humans.

Thus, 14 g/100 mL is the most appropriate answer.

Monotremes are a unique group of mammals that lay eggs instead of giving birth to live young.

They are the only egg-laying mammals and include species like the platypus and echidna.

They also produce milk, but they do not have nipples; instead, milk is secreted through specialized skin glands.

Thus, the defining characteristic of monotremes is that they lay eggs.

• Homologous structures are those that have a common evolutionary origin but may serve different functions.
• The poison glands of snakes evolved from salivary glands in vertebrates.
• In snakes, these glands have been modified to produce venom, which is delivered through specialized fangs.
• In other vertebrates, salivary glands primarily help in digestion and lubrication of food.

Thus, the poison glands of snakes are homologous to the salivary glands of vertebrates.

In plants, vascular bundles are the arrangements of xylem and phloem tissues that transport water, nutrients, and food throughout the plant. The arrangement of these vascular bundles can vary depending on the type of plant and the organ (stem, root, leaf, etc.).

In the case of radical vascular bundles, which are commonly found in roots, the xylem and phloem are positioned in such a way that they occur on different radii. This means that:

• The xylem is typically positioned towards the center of the vascular bundle (closer to the core of the root).
• The phloem is located on the outer side of the xylem, usually towards the periphery or outer part of the root.

This type of arrangement is characteristic of the root because the root structure is designed to absorb water and nutrients from the soil and transport them upward. The arrangement of the vascular bundles in the root helps in the efficient movement of these substances.

Here’s a breakdown of the other options:

(A) Xylem is surrounded by phloem: This is not true for radical vascular bundles, as it suggests a different type of vascular bundle arrangement found in some stems or leaves, but not typically in roots.

(B) Phloem is surrounded by xylem: This arrangement is often seen in collateral vascular bundles found in some stems, where the phloem is positioned outside the xylem.

(C) Xylem and phloem occur on the same radius: This arrangement is typical in conjoint vascular bundles (like in the stems of dicots), where the xylem and phloem are on the same radius but typically alternate. This is not the case in radical vascular bundles.

Thus, the correct answer is (D), where xylem and phloem are on separate radii, a common characteristic in the root vascular bundles.