General Science

Step 1: Understanding foliar buds.
Foliar buds are adventitious buds that develop on leaves and help in vegetative propagation.
Step 2: Evaluating the options.
(A) Begonia: Correct. Begonia produces foliar buds on the leaf surface.
(B) Bryophyllum: Incorrect. Buds arise from leaf margins, not the surface.
(C) Kalanchoe: Incorrect. Similar to Bryophyllum, buds form on margins.
(D) Bignonia: Incorrect. It does not show foliar bud propagation.
Step 3: Conclusion.
The correct answer is (A) Begonia.

Step 1: Understanding plant protection methods.
Plants can be protected from pathogens using chemical, biological, physical, or genetic approaches.
Step 2: Evaluating effectiveness and cost.
Producing resistant varieties provides long-term protection without recurring costs or environmental damage.
Step 3: Conclusion.
Hence, developing resistant plant varieties is the most effective and economical method.

Step 1: Understanding fossils.
Fossils are the preserved remains, imprints, or traces of organisms from the past. Fossils help in understanding the habit, environment, and behaviors of extinct animals.
Step 2: Analyzing the options.
(A) Fossils of primitive forms of organisms occupy upper layers of the earth during fossilization: Incorrect — Fossils are generally found at various levels depending on the age of the organism.
(B) Fossils help in understanding the habit of extinct animals: Correct — Fossils allow scientists to study the behavior and living conditions of extinct species.
(C) Actual remains of fossils are generally formed on land: Incorrect — Fossils can form both on land and in aquatic environments.
(D) Moulds are the most common type of fossils: Incorrect — While moulds are common, the most common type of fossils are impressions, not just moulds.
Step 3: Conclusion.
The correct answer is (B).

Step 1: Understanding nuclear size.
The size of the nucleus is primarily influenced by factors like the amount of DNA and the volume of the cell, as these factors are related to the nuclear material and the space required to house it.
Step 2: Analyzing the options.
(A) volume of the cell: Correct — The volume of the cell can affect the size of the nucleus, as larger cells require larger nuclei to house the DNA.
(B) shape of the cell: Incorrect — The shape of the cell does not directly affect the size of the nucleus.
(C) amount of proteins: The amount of proteins can affect the function of the nucleus, but it does not directly influence its size.
(D) amount of DNA: Correct — The amount of DNA is directly proportional to the size of the nucleus.
Step 3: Conclusion.
The correct answer is (B) shape of the cell, as the shape of the cell does not directly determine the size of the nucleus.

Step 1: Understanding the role of DNA ligase.
DNA ligase is an enzyme used in genetic engineering to join DNA fragments together. Specifically, it is used to insert the desired gene into a vector, forming recombinant DNA.
Step 2: Analyzing the options.
(A) polymerase chain reaction: Incorrect — DNA ligase is not used in the polymerase chain reaction (PCR); instead, DNA polymerase is used in PCR.
(B) fragmentation of DNA: Incorrect — DNA ligase does not fragment DNA; it helps to join DNA fragments.
(C) joining the desired gene into vector: Correct — DNA ligase is used to ligate (join) the desired gene into a vector.
(D) reverse transcription: Incorrect — Reverse transcription is performed by the enzyme reverse transcriptase, not DNA ligase.
Step 3: Conclusion.
The correct answer is (C) joining the desired gene into vector, as DNA ligase is used for this purpose in genetic engineering.

Step 1: Understanding the path of urine transport.
Urine is formed in the kidneys and passes through a series of structures to be excreted. The correct order of transport is from the collecting duct, through the minor and major calyces, and finally into the renal pelvis before being transported to the bladder.
Step 2: Analyzing the options.
(A) major calyx minor calyx collecting duct renal pelvis: This is incorrect as the transport begins in the collecting duct, not the calyces.
(B) renal pelvis minor calyx major calyx collecting duct: Incorrect — The collecting duct is where urine is initially formed.
(C) collecting duct major calyx minor calyx renal pelvis: Incorrect order of calyces.
(D) collecting duct minor calyx major calyx renal pelvis: Correct — This is the correct order of transport for urine.
Step 3: Conclusion.
The correct answer is (D) collecting duct minor calyx major calyx renal pelvis.

Step 1: Understanding pollination.
Pollination is the process of transferring pollen from the male to the female reproductive organs of a plant. In Salvia and Cestrum, insects are the primary agents of pollination.
Step 2: Analyzing the options.
(A) insects: Correct — Both Salvia and Cestrum rely on insects, especially bees, for pollination.
(B) wind: Wind-pollinated plants have different characteristics, and Salvia and Cestrum are not wind-pollinated.
(C) bats: While bats pollinate certain plants, they are not the primary pollinators for Salvia and Cestrum.
(D) birds: Birds may be involved in some pollination, but not for Salvia and Cestrum.
Step 3: Conclusion.
The correct answer is (A) insects, as they are the primary pollinators for both Salvia and Cestrum.

Step 1: Understanding haemophilia.
Haemophilia is a genetic disorder caused by a deficiency of clotting factors VIII or IX, located on the X chromosome. It is unrelated to the shape of red blood cells. Sickle cell anemia is a different disorder that affects the shape of RBCs.
Step 2: Analyzing the options.
(A) Haemophilia is caused due to deficiency of VIII and IX clotting factor: Correct — Haemophilia is caused by a deficiency in clotting factors VIII or IX.
(B) Gene for normal clotting is present on non-homologous region of X chromosome: Correct — The genes for clotting factors VIII and IX are located on the X chromosome.
(C) In haemophilia, RBCs are sickle shaped: Incorrect — This statement is false. Sickle-shaped RBCs are characteristic of sickle cell anemia, not haemophilia.
(D) Carrier female for haemophilia has one recessive gene on X chromosome: Correct — Carrier females have one normal and one mutated gene for haemophilia on their X chromosomes.
Step 3: Conclusion.
The correct answer is (C) In haemophilia, RBCs are sickle shaped., as it is an incorrect statement.

Step 1: Understanding the types of lichen.
Lichens are symbiotic organisms that consist of a fungus and a photosynthetic partner. The types of lichens differ in their growth forms, such as crustose (crust-like), foliose (leaf-like), and fruticose (bushy). Rhizines are structures used by foliose lichens for attachment.
Step 2: Analyzing the options.
(A) Crustose: Incorrect — Crustose lichens are flat and adhere tightly to the surface, without rhizines for attachment.
(B) Foliose: Correct — Foliose lichens have leaf-like structures with rhizines that help them attach to the substrate.
(C) Shruby: Incorrect — Shruby lichens are not a recognized form, and rhizines are not a characteristic feature.
(D) Fruticose: Incorrect — Fruticose lichens are bushy and do not typically use rhizines for attachment.
Step 3: Conclusion.
The correct answer is (B) Foliose, as they use rhizines for attachment to substrates.

Step 1: Understanding dwarfism.
Dwarfism in humans can result from a variety of endocrine disorders. Frohlich and Lorain dwarfs have a deficiency in somatotropin (growth hormone), leading to stunted growth. This condition results from hyposecretion of somatotropin.
Step 2: Analyzing the options.
(A) hyposecretion of somatotropin: Correct — A deficiency of somatotropin causes growth retardation, resulting in dwarfism.
(B) hyposecretion of thyrotropin: Incorrect — Thyrotropin regulates thyroid function but does not directly cause dwarfism.
(C) hypersecretion of thymosin: Incorrect — Thymosin is related to immune function, not growth, and its hypersecretion does not cause dwarfism.
(D) hypersecretion of secretin: Incorrect — Secretin is involved in digestive processes, not growth, and its overproduction is not linked to dwarfism.
Step 3: Conclusion.
The correct answer is (A) hyposecretion of somatotropin, as it directly causes dwarfism in these conditions.

Step 1: Understanding t-RNA.
Transfer RNA (tRNA) is a small RNA molecule that helps decode messenger RNA (mRNA) into proteins. It has a specific 3D structure, folded on itself to form a "cloverleaf" shape, which is crucial for its function.
Step 2: Analyzing the options.
(A) Folded on itself: Correct — tRNA is folded into a three-dimensional structure, which is essential for its function in protein synthesis.
(B) Self replicating: Incorrect — tRNA is not self-replicating; replication is a property of DNA.
(C) Largest molecule: Incorrect — tRNA is a small molecule compared to other forms of RNA like mRNA.
(D) Has two strands: Incorrect — tRNA is a single-stranded RNA molecule, not double-stranded.
Step 3: Conclusion.
The correct answer is (A) Folded on itself, as tRNA has a folded structure essential for its function.

Step 1: Understanding the question.
The question asks about the cell responsible for secreting the outer chitinous layer of a sponge’s gemmule.
Step 2: Analyzing the options.
(A) choanocytes: Choanocytes are the collar cells of sponges that are involved in feeding and water flow but do not secrete the chitinous layer of the gemmule.
(B) interstitial cells: These are cells found between other cells in sponges and do not play a role in secreting the chitinous layer of gemmules.
(C) amoebocytes: Correct — Amoebocytes are the cells that secrete the chitinous outer layer of the gemmule in sponges.
(D) archaeocytes: Archaeocytes are involved in many functions within sponges, such as reproduction and digestion, but are not responsible for secreting the chitinous layer of the gemmule.
Step 3: Conclusion.
The correct answer is (C) amoebocytes, as these cells are responsible for secreting the chitinous layer of the sponge's gemmule.

Step 1: Understanding the question.
The question asks about the best method to eliminate harmful recessive genes in animal breeding.
Step 2: Analyzing the options.
(A) inter-specific hybridization: This refers to the breeding of animals from different species and is not the best method to eliminate recessive genes.
(B) outcrossing: Outcrossing is the process of breeding animals from different families within the same species. While it can introduce genetic diversity, it does not specifically target harmful recessive genes.
(C) in-breeding: Correct — Inbreeding involves breeding closely related animals to concentrate desirable traits, but also helps eliminate harmful recessive genes when done carefully.
(D) cross-breeding: Cross-breeding refers to the mating of animals from different species or breeds and is not the most efficient method for eliminating harmful recessive genes.
Step 3: Conclusion.
The correct answer is (C) in-breeding, as it is the technique most effective in eliminating harmful recessive genes.

Step 1: Understanding the question.
The question asks for the name of the disease affecting rice plants that causes them to grow tall, thin, and pale. This is a typical description of Bakane disease.
Step 2: Analyzing the options.
(A) Rust disease: Rust disease affects the leaves of plants, causing spots and not typically leading to the described symptoms.
(B) Hill bunt disease: This disease affects the grain of rice, causing grain abnormalities, not the described symptoms.
(C) Bakane disease: Correct — This disease is characterized by rice plants growing tall, thin, and pale due to a hormonal imbalance caused by the infection.
(D) Black-rot disease: This disease typically affects vegetables like cabbage, not rice, and does not match the described symptoms.
Step 3: Conclusion.
The correct answer is (C) Bakane disease, which causes rice plants to grow tall, thin, and pale.

Step 1: Understanding colour vision.
Cone cells in the retina are responsible for colour vision.
Step 2: Cause of colour blindness.
Non-functional or defective cone cells result in colour blindness.
Step 3: Eliminating incorrect statements.
Y-linked inheritance is not criss-cross, X-linked disorders are more common in males, and carrier females are not colour blind.

Step 1: Understanding chromosome number variations.
A diploid organism normally has two copies of each chromosome (2n).
Step 2: Extra chromosome condition.
When one extra chromosome is added to the diploid set, the condition becomes (2n + 1).
Step 3: Terminology.
This condition is known as trisomy. A common example is Down syndrome (Trisomy 21).

Step 1: Photoexcitation of chlorophyll.
When chlorophyll-a absorbs light energy, its electrons get excited to a higher energy level.
Step 2: Return to ground state.
If the excited electron does not participate in photochemical reactions, it quickly returns to the ground state.
Step 3: Time duration.
The excited electron returns to the ground state within seconds}, releasing excess energy as heat or fluorescence.