Biology Quiz - 2, General Knowledge - SSC CHSL MCQ

O₂ released during photosynthesis originates from water.

The process of photosynthesis involves several key components:

• Water is split into oxygen and hydrogen. This occurs in the light-dependent reactions.
• The oxygen produced is released as a by-product into the atmosphere.
• Carbon dioxide (CO₂) is also essential, but it does not directly produce oxygen.
• Plants use sunlight to convert water and CO₂ into glucose, which is a form of sugar.

In summary, the oxygen that we breathe comes from the splitting of water molecules during the photosynthesis process.

The placenta is a vital structure that develops during pregnancy. It is formed through the following processes:

• It arises from the union of both foetal and uterine tissues.
• It serves as a crucial interface between the mother and the developing foetus.
• It facilitates the transfer of nutrients, gases, and waste products.

Understanding the formation of the placenta is essential for comprehending how it supports foetal development throughout pregnancy.

The hormone that promotes cell division in plants is known as:

• Auxins: These hormones play a role in various plant growth processes.
• Gibberellins: They are involved in seed germination and stem elongation.
• Kinins: Also referred to as cytokinins, they specifically stimulate cell division.
• Domins: This term is less commonly used and does not refer to a major plant hormone.

The correct answer is kinins, which are essential for encouraging cell division and overall growth in plants.

Neurospora is a valuable organism for genetic studies due to several key factors:

• Short life cycle: Neurospora completes its life cycle in just 10 days, allowing rapid experimentation.
• Meiotic analysis: The products of a single meiosis can be easily studied, providing clear insights into genetic processes.
• Ordered tetrads: Meiotic products are arranged in a linear fashion, forming ordered tetrads, which simplifies genetic analysis.
• Diploid fungus: Neurospora is a diploid organism, making it suitable for studying dominant and recessive traits.

Phloem is a vital tissue found in plants.

• It is responsible for the transport of nutrients, such as glucose, throughout the plant.
• Phloem consists of several cell types, including sieve elements and companion cells.
• These cells work together to facilitate the movement of organic compounds from the leaves to other parts of the plant.
• Phloem is essential for growth and development, enabling plants to thrive.

In summary, phloem plays a crucial role in a plant's ability to distribute nutrients effectively.

N₂ content in the biosphere is maintained through a natural process known as the nitrogen cycle. This cycle ensures a balance of nitrogen by:

• N₂ fixation: Certain bacteria convert atmospheric nitrogen into forms that plants can use.
• Decomposition: When organisms die, bacteria break down their bodies, returning nitrogen to the soil.
• Nitrification: Soil bacteria convert ammonia into nitrates, which are accessible to plants.
• Denitrification: Some bacteria convert nitrates back into nitrogen gas, releasing it into the atmosphere.

This cycle is crucial because:

• It ensures that plants receive the nitrogen they need for growth.
• It prevents excess nitrogen from accumulating in the environment.
• It supports the overall health of ecosystems.

Thus, the nitrogen cycle plays a fundamental role in keeping N₂ levels stable in the biosphere.

In cell membranes, the composition of proteins, lipids, and carbohydrates varies significantly.

• Lipids are the most abundant component, forming a bilayer that acts as a barrier to protect the cell.
• Carbohydrates are present in smaller amounts and play a crucial role in cell recognition and communication.
• Proteins are also essential, providing structural support and facilitating various functions within the membrane.

In summary:

• The majority of the cell membrane's structure consists of lipids.
• Carbohydrates are found in minimal quantities compared to lipids and proteins.
• Thus, the statement regarding carbohydrates being the least abundant is accurate.

A potato is a modified form of a stem.

• Potatoes are classified as tubers, which are thickened parts of a stem.
• They store nutrients and energy for the plant.
• As the plant grows, these tubers develop underground.
• The potato plant produces stems that grow above ground, while the tubers form below.
• This adaptation allows the plant to survive in various conditions.

In summary, potatoes are an essential part of the plant's structure and play a vital role in its survival.

Taxonomic categories are hierarchical classifications used in biology to organise living organisms. Each category represents a level of organisation, with some being more inclusive than others. The hierarchy progresses from broader to more specific categories. The main levels are:

• Domain
• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species
• Subspecies

Among these categories, Class is one of the higher levels, encompassing multiple orders. In contrast, Genus and Subspecies are more specific and represent smaller groupings within the hierarchy. Therefore, Class is the most inclusive among the options provided.

Prothrombin is a crucial protein in the body that plays a key role in the clotting of blood. It is produced by the liver and is essential for the coagulation process, which helps prevent excessive bleeding when injuries occur.

Here are some important points about prothrombin:

• Prothrombin is classified as a clotting factor, specifically factor II in the coagulation cascade.
• It is converted into thrombin in the presence of calcium ions and tissue factor, initiating the clotting process.
• Thrombin then acts on fibrinogen to form fibrin, which is the mesh that stabilises the blood clot.
• A deficiency in prothrombin can lead to a bleeding disorder, while its excess may increase the risk of thrombosis.

Overall, prothrombin is vital for maintaining haemostasis, the process that prevents and stops bleeding, thus ensuring the proper functioning of the circulatory system.

Myopia is a common vision condition where distant objects appear blurry, while close objects can be seen clearly. This condition primarily affects the eyes and is often caused by the shape of the eyeball or the curvature of the cornea.

• Causes: Myopia can develop due to genetic factors or prolonged close-up activities, such as reading or using screens.
• Symptoms: Individuals may experience difficulty seeing far away, such as road signs or presentations.
• Treatment: Common methods include corrective glasses, contact lenses, or refractive surgery.
• Prevention: Regular eye examinations and taking breaks during close-up tasks can help manage myopia progression.

Xerophytes are plants that have adapted to survive in dry conditions. They possess several unique features that enable them to thrive in environments where water is scarce. Here are some key characteristics:

• Water Storage: Xerophytes often store water in their stems or leaves, allowing them to use it during prolonged dry periods.
• Reduced Leaf Surface Area: Many xerophytes have small or no leaves to minimise water loss through transpiration.
• Thick, Waxy Coating: A thick cuticle covers their surfaces, reducing evaporation and protecting against harsh sunlight.
• Deep Roots: Their root systems are typically extensive and deep, enabling them to access water from deeper soil layers.

Examples of xerophytes include cacti and succulents, which showcase these adaptations effectively. These plants play a vital role in their ecosystems and offer insights into survival strategies in arid environments.

Plants growing on sand are called psammophytes. Here's why:

- Psammophytes: These are plants specially adapted to thrive in sandy soils. They have developed mechanisms to cope with water scarcity, shifting substrates, and nutrient-poor conditions.

- Other Options:
- Chasmophytes: Plants growing in rock crevices.
- Oxylophytes: Plants growing in acidic soils.
- Lithophytes: Plants growing on rocks.

Psammophytes have adaptations like deep root systems to access water and stabilize themselves in loose, sandy environments.

Excess sunlight exposure can cause our skin to darken.

This darkening occurs due to the production of a pigment called melanin. Here’s how it works:

• Melanin is responsible for the colour of our skin, hair, and eyes.
• When UV rays from sunlight strike the skin, they stimulate the production of melanin.
• This increased melanin helps protect the skin from further damage by absorbing harmful UV radiation.
• The more melanin produced, the darker the skin appears.

In summary, melanin acts as a natural defence mechanism against the harmful effects of the sun.

Ramapithecus and Cro-Magnon man are known to be important figures in human evolution.

They are considered:

• Part of the lineage leading to modern humans.
• Significant in understanding the development of early human traits.
• Distinct from other primates, highlighting the evolutionary path of humans.

These two species provide valuable insights into:

• The transition from early hominids to anatomically modern humans.
• The social and cultural advancements during the prehistoric era.

In summary, both Ramapithecus and Cro-Magnon man represent crucial steps in the evolutionary journey towards what we define as modern humanity.

The normal level of haemoglobin in adult males is an important indicator of health. Typically, this level is measured in grams of haemoglobin per 100 grams of blood.

• The average concentration is around 14 grams of haemoglobin per 100 grams of blood.
• Normal variations can occur, but levels generally fall within the range of 13.5 to 17.5 grams.
• Haemoglobin is essential for transporting oxygen throughout the body.
• Low haemoglobin levels may indicate conditions such as anaemia, while high levels could result from dehydration or other factors.

Maintaining proper haemoglobin levels is crucial for overall health, as it plays a vital role in the body's oxygenation and energy production.

Plants wilt due to excess transpiration.

Transpiration is the process where plants lose water through small openings in their leaves called stomata. When plants lose more water than they can absorb from the soil, they begin to wilt. Here are some key points to understand this process:

• Water Loss: Plants constantly lose water to the atmosphere.
• Absorption: Roots take up water from the soil, which is essential for photosynthesis.
• Balance: A healthy balance between transpiration and absorption is crucial for plant health.
• Environmental Factors: High temperatures and low humidity can increase transpiration rates, leading to wilting.

When the rate of transpiration exceeds the rate of water absorption, the plant cannot maintain its structure, resulting in wilting. Therefore, managing water levels is vital for maintaining plant vitality.

Poison glands in snakes share a developmental origin with the salivary glands found in vertebrates. This similarity is due to their common evolutionary background.

Key points to consider:

• Homologous structures are those that arise from a common ancestor, reflecting evolutionary relationships.
• Both poison glands and salivary glands are involved in the secretion of fluids, although their functions differ significantly.
• While poison glands are primarily used for defence and prey immobilisation, salivary glands aid in digestion by breaking down food.
• The presence of similar tissue types and developmental processes supports the idea of their homologous nature.

Understanding these similarities helps clarify the evolutionary connections among different species.

With the help of examples, explain the various types of vascular bundles.

In angiosperms the vascular bundles are mainly of three types (i) radial (ii) conjoint (iii) concentric.

(i) Radial : Presence of radial vascular bundles is the characteristic feature of roots. Those vascular bundles in which xylem and phloem are present on different radii are known as radial vascular bundles. In between xylem and phloem bundles parenchymatous cells are present.

(ii) Conjoint : In these vascular bundles xylem and phloem are present on the same radii. Conjoint vascular bundles may be collateral (phloem is present only outer to xylem) or bicollateral (phloem is present on both sides of xylem). If cambium is present between xylem and phloem then the vascular bundle is known as open, otherwise it is called closed.

(iii) Concentric : Those vascular bundles in which one type of vascular tissue is surrounded by another type are known as concentric vascular bundles. These bundles may be amphivasal or leptocentric(phloem is completely surrounded by xylem) or amphicribal or hardocentric (xylem is completely surrounded by phloem). Amphivasal bundles are found in Dracaena and Yucca. Amphicribal bundles are found in stamens of many dicots etc.

Radical vascular bundles are those in which xylem and phloem occur on the different radii.

Plants bend towards light due to a process called phototropism. This phenomenon occurs when plants detect light direction and adjust their growth accordingly. Here are some key points to understand phototropism:

• Phototropism is the growth response of a plant towards light.
auxin, which redistributes to the shaded side of the plant.
• This uneven distribution of auxin causes cells on the shaded side to elongate more than those on the light-exposed side.
• The result is a curvature that directs the plant towards the light source, maximising photosynthesis.

Phototropism is crucial for plants as it ensures they receive adequate light, which is essential for their growth and survival.

Monotremes are distinctive among mammals due to their unique reproductive traits. They exhibit the following characteristics:

• They possess hair.
• They lay eggs instead of giving birth to live young.
• They secrete milk, but unlike most mammals, they do not have teats; instead, the milk is released through openings in the skin.
• Monotremes are the only group of mammals that lay eggs, making them quite rare and special.

These features highlight the diversity of mammalian reproduction and underscore the evolutionary significance of monotremes.

Plants have unique characteristics that differentiate them from animals. One of the key components found in plants is cellulose, which is not present in animals. This structural carbohydrate plays a vital role in the formation of plant cell walls.

• Cellulose provides strength and rigidity to plant cells, helping them maintain shape.
• It contributes to the overall structure of plants, allowing them to grow tall and withstand environmental pressures.
• In contrast, animals lack cellulose, as their cells are supported by different structures.
• Instead of cellulose, animals utilise proteins and fats for various functions, including energy storage and structural support.

In summary, cellulose is a distinctive feature of plants that supports their structure, whereas animals do not possess this carbohydrate.

Osmosis is the movement of water through a semi-permeable membrane from a region of higher concentration to a region of lower concentration. The following points clarify the concept:

• The term "higher concentration" refers to a solution with more solute particles.
• The term "lower concentration" indicates a solution with fewer solute particles.
• A semi-permeable membrane allows certain molecules, like water, to pass through while blocking others.
• This process is essential for maintaining the balance of fluids in biological systems.

It is important to note that:

• For osmosis to occur, there must be a difference in concentration.
• The membrane must be selectively permeable to facilitate this movement.

In summary, osmosis is a vital biological process that helps regulate fluid balance across cell membranes.

Ptyalin is an important enzyme that plays a key role in the digestion of carbohydrates. It is produced in the salivary glands and is essential for breaking down starches into simpler sugars during the initial phase of digestion.

• Location of Production: Ptyalin is produced in the salivary glands.
• Function: It helps to convert starches into sugars, making them easier to digest.
• Activation: Ptyalin becomes active in the mouth when food is mixed with saliva.
• Importance: This enzyme is crucial for efficient digestion and nutrient absorption.