Biology MCQs with answers Page - 1

• Primary phloem is part of the primary vascular system in plants and develops from the provascular tissue (also called procambium).
• Provascular tissue (Procambium) is a type of primary meristem that gives rise to primary xylem and primary phloem.
• Lateral meristem (e.g., vascular cambium) is responsible for secondary growth, not primary phloem formation.
• Protoderm gives rise to the epidermis, not vascular tissues.
• Extrastelar cambium is not directly involved in primary phloem development.

• Anopheles mosquitoes are primarily known for transmitting malaria (caused by Plasmodium parasites).
• However, they are also vectors of Filariasis, which is caused by Wuchereria bancrofti and Brugia malayi (parasitic worms).
• Dengue fever and Yellow fever are transmitted by Aedes mosquitoes.
• Encephalitis can be transmitted by Culex mosquitoes, such as in the case of Japanese Encephalitis.

• Halophytes are plants that can grow in saline (salty) water or soil, such as mangroves (Rhizophora, Avicennia).
• Hydrophytes grow in freshwater or aquatic environments (e.g., Lotus, Hydrilla).
• Mesophytes grow in moderate water conditions (e.g., Mango, Rose).
• Thallophytes are simple, non-vascular plants like algae, fungi, and lichens.

Pyorrhoea is a severe gum disease (periodontitis) that causes inflammation, bleeding, pus formation, and loosening of teeth.

It is caused by bacterial infection due to poor oral hygiene and can lead to tooth loss if untreated.

Prevention: Regular brushing, flossing, and dental check-ups.

The placenta is a temporary organ that develops during pregnancy.

It is formed by the interaction between the foetal chorionic tissue and the maternal uterine tissue.

The placenta functions as an interface for nutrient exchange, gas exchange, and waste removal between the mother and the developing foetus.

It also produces hormones like hCG (human chorionic gonadotropin), progesterone, and estrogen to support pregnancy.

Cytokinins (Kinins) are plant hormones that induce cell division (cytokinesis) and promote shoot growth.

They also help in delay of leaf senescence (aging) and work in coordination with auxins to regulate plant growth.

Auxins promote cell elongation, gibberellins stimulate stem elongation and seed germination, while domins is not a recognized plant hormone.

Neurospora (a type of bread mold) is widely used as a model organism in genetic studies.

One key reason is that meiotic products (ascospores) are arranged linearly in ordered tetrads within the ascus, making it easy to study genetic recombination and chromosome mapping.

It also has a short life cycle (~10 days) and can be easily grown in the lab, but the ordered tetrads arrangement is the main reason for its use in genetics.
 

Phloem is a vascular tissue in plants responsible for transporting organic nutrients, primarily sugars (produced in photosynthesis), from the leaves to other parts of the plant.

It consists of sieve tubes, companion cells, phloem fibers, and phloem parenchyma.

This process of nutrient transport is known as translocation.

It is a crucial part of the vascular system in plants, alongside xylem (which transports water).

The nitrogen cycle is responsible for maintaining the N₂ content in the biosphere. It involves several processes:

1. Nitrogen Fixation – Conversion of atmospheric N₂ into ammonia (NH₃) by nitrogen-fixing bacteria (e.g., Rhizobium, Azotobacter).

2. Nitrification – Conversion of ammonia to nitrites (NO₂⁻) and then to nitrates (NO₃⁻) by nitrifying bacteria.

3. Assimilation – Plants absorb nitrates from the soil and use them to make proteins.

4. Ammonification – Decomposition of organic matter releases ammonia.

5. Denitrification – Conversion of nitrates back to nitrogen gas (N₂) by denitrifying bacteria (e.g., Pseudomonas), returning it to the atmosphere.

This cycle ensures that nitrogen levels remain balanced in the biosphere.