Question Discussion & Solution

Shark, Barracuda and Whale are types of aquatic animals but Humming is a bird.

The correct answer is Copper.

Key Points

• Conductor of electricity
  • In physics and electrical engineering, a conductor is an object or type of material that allows the flow of charge in one or more directions.
  • Materials made of metal are common electrical conductors. 
  • Copper is considered to be a conductor because it conducts the electron current or flow of electrons fairly easily. Most metals are considered to be good conductors of electrical current. Copper is just one of the more popular materials that are used for conductors. Hence, Option 4 is correct.
  • If you have to define the meaning of electrical conductors in the simplest way, they are materials that allow electricity to flow through them easily.
  • If we compare two types of material and the first one allows better flow of electricity through it, then that material is said to be a good conductor of electricity.
  • An electrical conductor allows the electric charges to easily flow through them. The property of conductors to conduct electricity is called conductivity.
  • Such materials offer less opposition or resistance to the flow of charges.
  • Conducting materials allow easy charge transfer because of the free movement of electrons through them.

Additional Information

• • Some examples of conductors of electricity are
    • Copper
    • Aluminum
    • Silver
    • Gold
    • Graphite
    • Platinum
    • Water
    • People

The correct answer is Cell.

Key Points

• Cell:
  • A cell is the smallest unit capable of independent existence which can reproduce itself. Hence, Option 3 is correct.
  • All living organisms, except for viruses, are composed of one or more cells.
  • Single-cell organisms; such as, bacteria, protozoa, and other micro-organisms are termed unicellular, while plants and animals that contain many cells are termed multicellular.
  • Highly complex organisms; such as, human beings consist of billions of cells, all of which are adapted to carry out specific functions; for example, groups of these specialized cells are organized into tissue and bodily organs.
  • Although cells may differ widely in size, appearance, and function, their essential features are similar.

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Important Points

• Almost all cells perform biochemical processes, generate and process energy, and store genetic information to be passed down to future generations of cells.
• Advanced single-celled and multicelled organisms have nuclei that carry the DNA, primitive cells; such as, bacteria, have no nucleus and carry their DNA loosely in coils throughout the cells
• The number of cells in an organism varies; for example, bacteria are single-celled organisms; the average adult human body has about one hundred trillion cells.
• Cells are the structural unit of all organisms and come in a range of sizes and shapes.
• Animal cells contain only an outside cell membrane.
• In most fungi, bacteria, and plants; there is a rigid cell wall outside the membrane.
• Each cell is composed of a mass of jelly-like substance called the cytoplasm, surrounded by a membrane.

Additional Information

The correct answer is Potato.

Modifications of Root

1. For storage of food
   • Roots are modified in some plants for storing reserve food materials.
   • These modified roots usually are swollen and assume different forms such as spindle-shaped, e.g., radish; top-shaped, e.g., beet, turnip; cone-like, e.g., carrot; indefinite shape, e.g., sweet potatoes.
   • Dahlia, Asparagus, Portulaca are some other examples of plants with modified roots for food storage.
2. Nodulated roots
   • The roots of pea and other leguminous plants have numerous swollen nodules on fine branches of roots.
   • These nodules are formed due to the symbiotic association of Rhizobium (bacterium) that live inside the root cortical cells of the roots.
   • They fix nitrogen and an active nodule is pink in colour.
3. For mechanical support
   • Roots are modified to provide mechanical support as seen in a banyan tree which has roots growing vertically/obliquely downwards (prop roots); sugarcane/maize in which roots arise from the nodes in the cluster at the base of the stem (stilt roots) and betel/black pepper in which nodes and internodes bear roots which help in climbing.
4. For gaseous exchange
   • Pneumatophores or breathing roots are found in plants growing in mangroves or swamps with saline water for exchange of gases.
   • They are erect peg-like structures with numerous pores through which air circulates e.g., Rhizophora mangle.

• Modifications of Stem

1. For storage of food
   • Stems get modified into underground structures for storage of food as seen in potato (tuber), ginger (rhizome), garlic (bulb), yam (corm).
   • Presence of an eye (node) in potato, distinct nodes with internodes and scaly leaves in ginger/yam, a cluster of roots at the base of the reduced stem in garlic/ onion, all indicate that these underground plant parts are modified stem.
2. For vegetative propagation
   • Plants besides reproducing sexually also propagate through vegetative parts.
   • For this purpose, stems may be modified into a runner (Cyanodon dactylon, Oxalis). Runners are slender prostrate branches arising from axillary buds;
   • stolon (e.g., mint, strawberry) which is a slender lateral branch arising from the base of the stem grows upward and then down to develop new daughter plants;
   • offset having a single long horizontal internode growing up to some distance and producing a tuft of leaves above and a cluster of roots below at the apex (Eichornia, Pistia) and
   • sucker, which arises from the underground part of the stem, grow obliquely and gives rise to a new shoot. (Chrysanthemum, Banana, Pineapple).
3. For protection
   • Some modified stem provides protection as thorns which are hard, pointed structures each representing a branch that arises from the axil of a leaf.
   • Thorns are found in plants like Duranta, Pomegranate, Acacia, Ber, Prosopis, Bougainvillea, Citrus, etc.
4. For support
   • Tendrils are modifications of the stem to provide support to plants, e.g., Vitis, passionflower, Bignonia etc.
5. For photosynthesis
   • Stems are also modified into Phylloclade, to facilitate photosynthesis.
   • Phylloclades are flattened/cylindrical stem or branches of unlimited growth (Cactus).

The disease Kala-Azar is caused by the protozoan Leishmania donovani

Leishmania donovani: 

• It is a parasitic protozoan belonging to the class Mastigophora or flagellata.
• It is a human parasite that is dimorphic (i.e. shows two forms) & digenetic in nature
• It causes the disease Kala-azar or Dumdum fever by sand fly (phelobotomus)
• The disease is spread by the bite of infected sand-fly
• It can affect the Skin (Cutaneous Leishmaniasis), the mucous membrane of the mouth, throat, and nose (Mucocutaneous Leishmaniasis), Liver, lymph nodes, spleen, and bone marrow (Visceral Leishmaniasis)
• Symptoms include: Cutaneous Leishmaniasis - Skin ulcers
• Mucocutaneous Leishmaniasis - Ulcers in mouth, throat, and nose, Nosebleed, Difficulty in breathing.
• Visceral Leishmaniasis - Weakness, weight loss, loss of appetite, enlarged spleen, liver, lymph nodes, a decrease in the production of blood cells.

Diagram showing the two different forms of Leishmania donovani