Biology

EcoRI was the first restriction endonuclease to be discovered and isolated. It is widely used in molecular biology for cutting DNA at specific recognition sites.
Step 2: Conclusion.
EcoRI was the first isolated restriction endonuclease.
Final Answer:

- Ex situ conservation (Option 1): Ex situ conservation involves the conservation of species outside their natural habitats, such as in zoos, botanical gardens, and seed banks.
- In situ conservation (Option 2): In situ conservation is the conservation of species in their natural habitats. Wildlife safari parks are a good example of in situ conservation, where animals are conserved within their natural ecosystems, with controlled interventions to protect and maintain biodiversity.
- Biodiversity hot spots (Option 3): Biodiversity hot spots are areas that are rich in biodiversity but are under threat from human activity. While safari parks may sometimes be located in biodiversity hotspots, the term "hotspots" refers to specific areas rather than a form of conservation.
- Sacred grooves (Option 4): Sacred grooves refer to areas that are preserved due to religious or cultural beliefs, which is different from the formal process of wildlife conservation.
Step 2: Conclusion.
Wildlife safari parks are examples of in situ conservation, as they help conserve species in their natural environment. Final Answer:

The geological periods are arranged in the following chronological order, from the latest to the oldest:
- Tertiary (C) is the latest period among the options listed.
- Jurassic (D) follows the Tertiary, and it is after the Triassic.
- Triassic (A) comes after the Jurassic.
- Carboniferous (B) is the oldest period among the choices.
\boxed{\text{Correct Order: (D), (B), (C), (A)}}

Sewage treatment involves multiple steps to break down organic waste and produce several by-products. The sequence in which the products are formed is as follows:
Step 1: Primary treatment (D) - Primary sludge.
In the first step of sewage treatment, solid particles like dirt, grit, and large debris are removed from sewage. This process results in the formation of primary sludge, which is solid waste that can be further treated.
Step 2: Secondary treatment (C) - Flocs.
In the second step, aeration and biological treatment of the remaining sewage occur. Microorganisms consume organic waste, forming flocs (clumps of bacteria and other microorganisms). These flocs help in the further breakdown of organic material in the water.
Step 3: Further treatment (B) - Activated sludge.
The flocs are then treated to form activated sludge, which contains a high concentration of bacteria that break down the organic matter in the sewage. Activated sludge is typically removed and further processed or disposed of.
Step 4: Final product (A) - Biogas.
During the treatment process, especially in anaerobic conditions, biogas is produced. This gas, primarily methane, can be used as a renewable energy source.
Step 2: Conclusion.
The correct sequence of sewage treatment products formed is: (C) Flocs → (D) Primary sludge → (B) Activated sludge → (A) Biogas.
Final Answer:

Step 1: Identify the role of Lippe's Loop, LNG-20, and Implants.
- Lippe's Loop: It is a form of intrauterine device used for contraception.
- LNG-20: It is also an intrauterine device that releases hormones.
- Implants: These are subcutaneous devices and not intrauterine devices.
Step 2: Identify the devices that are not part of IUDs.
- Saheli: This is a contraceptive pill, not an intrauterine device.
Conclusion:
Thus, the correct answer is (4) (C), (B) and (D) only.
Final Answer:

Step 1: Understanding PCR.
Polymerase Chain Reaction (PCR) is a molecular biology technique used to amplify a specific segment of DNA. It consists of a series of temperature-dependent steps.
Step 2: Key steps in PCR.
- Extension (A): During this step, the DNA polymerase synthesizes a new DNA strand complementary to the template strand. This occurs at an optimal temperature for the polymerase enzyme to function.
- Annealing (B): In this step, the primers (short DNA sequences) bind (anneal) to their complementary sequences on the single-stranded DNA template. This step occurs at a lower temperature.
- Propagation (C): This term generally refers to the replication process, but in PCR, it can refer to the amplification of the DNA segment in the presence of polymerase during the extension step.
- Denaturation (D): The DNA template is heated to a high temperature to break the hydrogen bonds between the complementary DNA strands, making them single-stranded.
Step 3: Conclusion.
All four steps (Extension, Annealing, Propagation, and Denaturation) are integral parts of the PCR process.
Final Answer:

In most ecosystems, the biomass pyramid is upright, with producers at the bottom and higher trophic levels on top. However, in some aquatic ecosystems like those with phytoplankton and zooplankton, the pyramid of biomass may be inverted, where the biomass of zooplankton (higher trophic level) is greater than that of phytoplankton (lower trophic level).
Step 2: Conclusion.
This scenario represents an inverted pyramid of biomass.
Final Answer:

Enzyme-linked immunosorbent assay (ELISA) is a laboratory technique used to detect and quantify substances such as peptides, proteins, antibodies, and hormones. The principle behind ELISA is the antigen-antibody interaction.
Step 1: Analyzing the options.
- Antigen - antibody interaction (Option 1): This is correct. ELISA is based on the specific binding of an antigen to its corresponding antibody. The antigen is typically attached to a surface, and the antibody is detected using an enzyme-linked secondary antibody.
- PCR (Option 2): PCR (Polymerase Chain Reaction) is a method for amplifying DNA, not related to ELISA.
- Radioactive molecule (Option 3): ELISA typically uses enzymes for detection, not radioactive molecules.
- Amount of DNA (Option 4): ELISA does not directly measure the amount of DNA, but rather the interaction between antigen and antibody.
Step 2: Conclusion.
ELISA is based on the principle of antigen-antibody interaction.
Final Answer:

Photosynthetically active radiation (PAR) refers to the portion of solar radiation that plants use for photosynthesis. It primarily consists of light in the visible spectrum (400–700 nm).
Step 1: Analyzing the options.
- 100% (Option 1): This is incorrect. Not all solar radiation is used in photosynthesis; only a small fraction is active for photosynthesis.
- Less than 50% (Option 2): This is also incorrect. The actual percentage is much smaller than 50%.
- 1-5% (Option 3): This is closer to the actual range but slightly lower than the true percentage.
- 2-10% (Option 4): This is the correct range. Around 2-10% of the incident solar radiation is converted into PAR, which plants use for photosynthesis.
Step 2: Conclusion.
The correct percentage of solar radiation that is photosynthetically active is 2-10%.
Final Answer:

Humification is the process by which organic matter, such as dead plant material, is decomposed by microorganisms in the soil to form humus. Humus is a dark, nutrient-rich substance that improves soil fertility, water retention, and structure.
Step 1: Analyzing the options.
- Soil erosion (Option 1): Soil erosion is the removal of soil by wind, water, or other agents, which is the opposite of humification.
- Soil conservation (Option 2): Soil conservation involves practices to prevent soil degradation, but humification specifically refers to the process of forming humus, not directly related to conservation.
- Accumulation of humus (Option 3): This is correct. Humification directly leads to the accumulation of humus in the soil, which is essential for soil health.
- Accumulation of salts (Option 4): Accumulation of salts is not related to humification; it can occur in saline soils but is not a product of humification.
Step 2: Conclusion.
Humification leads to the accumulation of humus in the soil, which improves its fertility.
Final Answer:

- Clostridium butylicum: Produces butyric acid.
- Aspergillus niger: Produces citric acid.
- Acetobacter aceti: Produces acetic acid.
- Lactobacillus: Produces lactic acid.
Thus, the correct match is:
(A) - (I), (B) - (II), (C) - (III), (D) - (IV).
Final Answer: