Biology 15

Question 1

Which plant tissue contains dead cells

Answer 1

Xylem tissues

Question 2

1. Meristematic Tissue:

Answer 2

• Found in growing regions of the plant such as root and stem tips.
• Composed of actively dividing cells.
• Responsible for plant growth and development.
• Can differentiate into various specialized cell types.

Question 3

Cambium Tissue:

Answer 3

• Found in the vascular tissue (between xylem and phloem) of stems and roots.
• Composed of meristematic cells.
• Responsible for secondary growth (increase in girth) in dicotyledonous plants.
• Divides to produce secondary xylem (wood) towards the inside and secondary phloem towards the outside.

Question 4

Mesophyll Tissue:

Answer 4

• Found in the interior of leaves.
• Composed of parenchyma cells.
• Responsible for photosynthesis, gas exchange, and storage.
• Contains chloroplasts in palisade mesophyll cells, which are involved in photosynthesis.

Question 5

Mesophyll Tissue:

Answer 5

Mesophyll Tissue:
• Found in the interior of leaves.
• Composed of parenchyma cells.
• Responsible for photosynthesis, gas exchange, and storage.
• Contains chloroplasts in palisade mesophyll cells, which are involved in photosynthesis.

Question 6

Mesophyll Tissue:

Answer 6

Mesophyll Tissue:
• Found in the interior of leaves.
• Composed of parenchyma cells.
• Responsible for photosynthesis, gas exchange, and storage.
• Contains chloroplasts in palisade mesophyll cells, which are involved in photosynthesis.

Question 7

Palisade Tissue:

Answer 7

• A type of mesophyll tissue found in the upper layer of leaves.
• Composed of elongated parenchyma cells arranged parallel to the leaf surface.
• Contains numerous chloroplasts for photosynthesis.
• Maximizes light absorption and facilitates photosynthesis.

Question 8

The external ear of mammals consists of three main parts:

Answer 8

Pinna (auricle): This is the visible part of the ear that protrudes from the side of the head. It helps collect sound waves and funnel them into the ear canal.
External auditory canal (ear canal): This is a tube-like structure that leads from the pinna to the eardrum (tympanic membrane). It helps transmit sound waves from the pinna to the middle ear.
Tympanic membrane (eardrum): This is a thin membrane that separates the external ear from the middle ear. It vibrates in response to sound waves and transmits these vibrations to the middle ear ossicles, initiating the process of hearing.

Question 9

The inner ear of mammals consists of several structures that play crucial roles in hearing and balance:

Answer 9

The inner ear of mammals consists of several structures that play crucial roles in hearing and balance:

1.	Cochlea: This spiral-shaped, fluid-filled structure is responsible for hearing. It contains specialized sensory cells called hair cells that convert sound vibrations into electrical signals, which are then transmitted to the brain via the auditory nerve.
2.	Vestibular system: This system consists of the vestibule and semicircular canals, which are responsible for balance and spatial orientation. The vestibule contains sensory structures called otolith organs, which detect linear acceleration and head position. The semicircular canals detect rotational movement of the head.
3.	Auditory nerve: Also known as the vestibulocochlear nerve, it carries electrical signals from the cochlea to the brainstem, where they are processed and interpreted as sound.

These structures work together to enable mammals to detect and interpret sound waves, maintain balance, and orient themselves in space.

Question 10

The auditory meatus, also known as the ear canal or external acoustic meatus, is a tube-like structure in the outer ear that leads from the auricle (pinna) to the eardrum (tympanic membrane). It serves several important functions:

Answer 10

1. Sound Transmission: The auditory meatus helps transmit sound waves collected by the pinna to the tympanic membrane, initiating the process of hearing.
   
   2. Protection: The ear canal is lined with specialized glands that produce cerumen (earwax), which helps lubricate the skin and trap foreign particles, dust, and insects, preventing them from reaching the eardrum.
   3. Amplification: The shape and length of the auditory meatus contribute to the amplification and resonance of certain frequencies of sound waves, improving hearing sensitivity.
   4. Thermoregulation: The ear canal helps regulate the temperature of the tympanic membrane and middle ear by dissipating excess heat.

Question 11

Structure of seed

Answer 11

Let’s break down each component:

1.	Coleorhiza: The coleorhiza is a protective sheath covering the radicle (embryonic root) of a germinating seed. It helps in the penetration of the soil during germination.
2.	Coleoptile: The coleoptile is a protective sheath covering the emerging shoot (plumule) of a germinating seed. It helps in the upward growth of the shoot through the soil.
3.	Large Endosperm: Endosperm is a tissue found in the seeds of flowering plants. It serves as a food reserve for the developing embryo. In some seeds, such as those of monocotyledonous plants, the endosperm remains large even after germination to provide nutrients to the growing seedling.
4.	Remains of Style: The style is a part of the female reproductive organ (pistil) of a flower. After fertilization, it may persist in the mature seed as a remnant.
5.	Scutellum: The scutellum is a specialized structure found in the seeds of grasses (Poaceae family). It is a modified cotyledon (seed leaf) that absorbs nutrients from the endosperm and transfers them to the developing embryo during germination.

Question 12

Seed

Answer 12

Seed:

•	A seed is the mature, fertilized ovule of a flowering plant.
•	It contains the embryo of a new plant, along with stored food reserves and a protective seed coat.
•	Seeds are produced by the ovary of the flower after fertilization.
•	The primary function of a seed is to germinate and grow into a new plant.

Question 13

Fruit

Answer 13

Fruit:

•	A fruit is the mature ovary of a flowering plant, often containing seeds.
•	It develops from the fertilized ovary after pollination and fertilization.
•	Fruits protect and help disperse seeds, often by enticing animals to eat them and then deposit the seeds elsewhere through feces.
•	Fruits come in various forms, including fleshy fruits like apples and berries, and dry fruits like nuts and grains.
•	While some fruits are consumed by animals and humans, their primary function in plants is reproductive, aiding in the dispersal and protection of seeds.

Question 14

Sure, here are the key points about strip cropping:

Answer 14

1. Soil erosion control: Strip cropping helps to reduce soil erosion by slowing down water runoff and trapping sediment, thereby protecting the soil from being washed away.
   
   2. Water conservation: The alternating strips of vegetation help to retain moisture in the soil, reducing water runoff and increasing water infiltration, which improves water conservation.
   3. Crop diversity: Strip cropping allows for the cultivation of different types of crops or vegetation in alternating strips, which can enhance biodiversity and provide habitat for beneficial insects and wildlife.
   4. Soil fertility: By reducing erosion and improving water retention, strip cropping can help to maintain soil fertility and productivity over time.
   5. Sloping land management: Strip cropping is particularly effective on sloping land where erosion is a concern, as it helps to stabilize the soil and prevent downhill movement of soil and sediment.
   6. Sustainable agriculture: Strip cropping is a form of conservation agriculture that promotes sustainable farming practices by minimizing soil erosion, conserving water, and promoting biodiversity.

Question 15

here are the key points about contour ridging:

Answer 15

1. Erosion control: Contour ridging is an agricultural practice used to control soil erosion on sloping land. By creating ridges along the contour lines of the land, water runoff is slowed down, reducing soil erosion caused by rainfall.
   
   2. Water conservation: The ridges created by contour ridging help to capture and retain rainwater, allowing it to infiltrate into the soil rather than running off the surface. This helps to improve water retention and soil moisture levels, especially in areas with limited rainfall.
   3. Soil fertility: Contour ridging can help to improve soil fertility by reducing erosion and retaining nutrients in the soil. By preventing soil loss, nutrients essential for plant growth are preserved, leading to healthier and more productive crops.
   4. Increased crop yields: By controlling erosion, conserving water, and improving soil fertility, contour ridging can lead to increased crop yields, particularly on sloping land where erosion is a significant concern.
   5. Sustainable land management: Contour ridging is a form of conservation agriculture that promotes sustainable land management practices. It helps to protect the soil, conserve water, and maintain soil fertility, supporting long-term agricultural productivity while minimizing environmental degradation.
   6. Adaptation to climate change: Contour ridging can also help farmers adapt to the impacts of climate change by reducing the risk of soil erosion and improving water management in areas prone to extreme weather events such as heavy rainfall and drought.

Overall, contour ridging is an effective soil conservation technique that helps to protect agricultural land, improve water management, and enhance crop productivity, especially on sloping terrain.

Question 16

Crop rotation

Answer 16

Certainly, here are the key points about crop rotation:

1.	Soil fertility: Crop rotation is a farming practice that involves planting different crops in the same area in sequential seasons or years. It helps to improve soil fertility by balancing nutrient uptake and replenishing soil nutrients. Different crops have different nutrient requirements, so rotating crops helps prevent depletion of specific nutrients from the soil.
2.	Pest and disease management: Crop rotation helps to reduce the buildup of pests and diseases in the soil. By changing the types of crops grown in a field, pests and diseases specific to one crop are less likely to become established and spread. This reduces the need for chemical pesticides and promotes natural pest control.
3.	Weed control: Crop rotation can also help control weeds by disrupting their life cycles and reducing weed pressure. Some crops, such as legumes, have allelopathic properties that suppress weed growth. Rotating crops with different growth habits and planting densities can further help to suppress weed growth and promote weed management.
4.	Sustainable agriculture: Crop rotation is a key component of sustainable agriculture. It helps to maintain soil health and productivity over time, reduces reliance on synthetic fertilizers and pesticides, and promotes biodiversity. Sustainable farming practices like crop rotation contribute to long-term environmental and economic sustainability.
5.	Improved crop yields: Crop rotation can lead to improved crop yields by optimizing soil fertility, reducing pest and disease pressure, and controlling weeds. By rotating crops with different nutrient requirements and growth habits, farmers can achieve more balanced and resilient cropping systems.
6.	Diversification: Crop rotation encourages diversification of agricultural systems by introducing a variety of crops into the rotation cycle. This diversification can provide multiple benefits, including risk mitigation against crop failures, increased resilience to environmental stresses, and expanded market opportunities for farmers.

Overall, crop rotation is a valuable farming practice that contributes to soil health, pest and disease management, weed control, sustainability, and improved crop yields.

Question 17

Bush fallow system

Answer 17

The bush fallow system, also known as shifting cultivation or slash-and-burn agriculture, is a traditional farming method practiced in tropical regions. Here are the key points about the bush fallow system:

1.	Land preparation: In the bush fallow system, farmers clear a patch of land by cutting down trees and vegetation. The vegetation is then left to dry and is eventually burned, creating a layer of ash that enriches the soil with nutrients.
2.	Crop cultivation: After burning, crops are planted in the cleared land. These crops are typically grown for a few seasons until soil fertility declines or weed pressure increases.
3.	Fallow period: Once the soil becomes less productive or weeds become problematic, the land is left fallow and allowed to regenerate naturally. During the fallow period, the land is left uncultivated, and natural vegetation is allowed to regrow.
4.	Rotation: After a period of fallow, the cycle begins again, and the farmer clears a new patch of land for cultivation. This rotation of land use helps to prevent soil degradation, maintain soil fertility, and control pests and diseases.
5.	Sustainability: The bush fallow system is sustainable when practiced with long fallow periods and small-scale farming. It allows the land to recover and regenerate between cropping cycles, minimizing soil erosion and nutrient depletion.
6.	Environmental impact: While the bush fallow system can be sustainable when practiced responsibly, improper land management and short fallow periods can lead to soil degradation, deforestation, loss of biodiversity, and greenhouse gas emissions from burning vegetation.
7.	Traditional knowledge: The bush fallow system is often based on indigenous knowledge and traditional farming practices that have been passed down through generations. It reflects the intimate relationship between farmers and their environment, as well as their understanding of local ecological processes.

Overall, the bush fallow system is a traditional farming method that has been practiced for centuries in tropical regions. When managed properly, it can be a sustainable way of farming that supports local livelihoods and preserves natural ecosystems. However, it requires careful land management and attention to environmental impacts to ensure long-term sustainability.

Question 18

Pyramid of numbers

Answer 18

The pyramid of numbers is a graphical representation of the number of organisms at each trophic level in an ecosystem. It typically takes the shape of a pyramid, with the primary producers forming the base and successively higher trophic levels stacked on top.

Key points about the pyramid of numbers:

1.	Trophic levels: The pyramid of numbers illustrates the hierarchical structure of energy flow in an ecosystem, with organisms grouped into different trophic levels based on their position in the food chain. At the base of the pyramid are the primary producers, such as plants, which convert solar energy into organic matter through photosynthesis. Above them are the primary consumers (herbivores), followed by secondary consumers (carnivores or omnivores), and so on.
2.	Number of organisms: The width of each tier in the pyramid represents the number of organisms at that trophic level. Typically, there are more individuals at lower trophic levels than at higher ones, leading to a pyramid-shaped structure.
3.	Energy transfer: The pyramid of numbers illustrates the principle of energy transfer and biomass accumulation in an ecosystem. As energy is transferred from one trophic level to the next, there is a decrease in the amount of available energy and biomass. This is because energy is lost as heat and through metabolic processes, resulting in fewer organisms at higher trophic levels.
4.	Exceptions: While the pyramid of numbers generally follows a pyramid-shaped pattern, there can be exceptions depending on the ecosystem and the specific interactions between organisms. In some cases, the pyramid may be inverted, with fewer individuals of primary producers supporting a larger number of consumers.

Overall, the pyramid of numbers provides valuable insights into the structure and dynamics of ecosystems, highlighting the interdependence of organisms and the flow of energy through food webs. It serves as a useful tool for ecologists to study and understand the complexity of natural systems.

Question 19

Key points about inhalation and exhalation in humans, considering the role of muscles and the diaphragm:

Answer 19

1. Inhalation (Inspiration):
   • During inhalation, the diaphragm contracts and flattens, increasing the volume of the thoracic cavity.
   • The external intercostal muscles between the ribs also contract, lifting and expanding the ribcage.
   • These muscle contractions expand the chest cavity, lowering the pressure inside the lungs.
   • As a result, air flows into the lungs from the atmosphere, following the pressure gradient from high to low pressure.
   
   2. Exhalation (Expiration):
      • During normal expiration, the diaphragm relaxes and returns to its dome-shaped position.
      • The external intercostal muscles relax, allowing the ribcage to lower and decrease in size.
      • In addition, the internal intercostal muscles may contract slightly to assist in lowering the ribcage further.
      • These muscle relaxations reduce the volume of the thoracic cavity, increasing the pressure inside the lungs.
      • Air is then expelled from the lungs passively, flowing out of the lungs and into the atmosphere due to the pressure gradient.
   3. Role of the diaphragm:
      • The diaphragm is the primary muscle involved in respiration and plays a crucial role in the expansion and contraction of the thoracic cavity.
      • Contraction of the diaphragm increases the volume of the thoracic cavity during inhalation, while relaxation of the diaphragm decreases the volume during exhalation.
   4. Role of intercostal muscles:
      • The external intercostal muscles assist in expanding the ribcage during inhalation by lifting the ribs upwards and outwards.
      • The internal intercostal muscles may assist in forced expiration by depressing the ribs, further reducing the volume of the thoracic cavity.
   5. Coordination of muscle actions:
      • The actions of the diaphragm and intercostal muscles are coordinated by the respiratory center in the brainstem, which regulates breathing rhythm and depth.
      • Nerve impulses from the respiratory center stimulate the contraction and relaxation of these muscles, ensuring smooth and efficient inhalation and exhalation.

Overall, inhalation and exhalation in humans involve the coordinated actions of the diaphragm and intercostal muscles, which work together to facilitate the exchange of air between the lungs and the atmosphere.

Question 20

Hypogeal germination:

Answer 20

• In hypogeal germination, the cotyledons remain below the soil surface.
• The embryo emerges from the seed, and the epicotyl (embryonic shoot) grows upward, pushing through the soil.
• The cotyledons remain within the seed coat and do not emerge above the soil surface.
• Examples of plants that exhibit hypogeal germination include beans, peas, and peanuts.

Question 21

Epigeal germination:

Answer 21

2. • In epigeal germination, the cotyledons emerge above the soil surface.
   • The embryo emerges from the seed, and both the epicotyl and hypocotyl (embryonic stem) grow upward.
   • The cotyledons are lifted above the soil surface as the epicotyl elongates.
   • Examples of plants that exhibit epigeal germination include sunflowers, tomatoes, and cucumbers.

Question 22

Epicotyl elongation:

Answer 22

• The epicotyl is the portion of the embryo above the point of attachment of the cotyledons.
• During germination, the epicotyl elongates and gives rise to the shoot system of the plant, including the stem, leaves, and eventually flowers.
• In epigeal germination, the epicotyl elongates to lift the cotyledons and first true leaves above the soil surface, allowing them to receive light for photosynthesis.

Question 23

Hypocotyl elongation:

Answer 23

• The hypocotyl is the portion of the embryo below the point of attachment of the cotyledons.
• During germination, the hypocotyl elongates and helps push the seedling upward through the soil.
• The hypocotyl also connects the root system of the seedling to the shoot system.
• In both hypogeal and epigeal germination, the hypocotyl plays a critical role in seedling emergence and early growth.

Question 24

Cryptogamy

Answer 24

:
• Cryptogamy refers to the reproductive process in plants that do not produce flowers or seeds, such as ferns, mosses, and algae.
• Cryptogamous plants reproduce by spores rather than seeds.
• This term is not relevant to the process of seed germination, so it is incorrect in this context.

Question 25

Mesogamy:

Answer 25

In mesogamy pollen tube enters the ovule through integument, whereas in porogamy pollen tube enters the ovule through micropyle.

Question 26

Perigamy:

Answer 26

• Perigamy refers to a type of fertilization in which the male and female gametes meet outside of the reproductive structures.
• It typically occurs in aquatic organisms where the sperm and eggs are released into the surrounding water.
• While perigamy involves fertilization, it does not relate to the process of seed germination.
• Therefore, it is incorrect in the context of seed germination.

Question 27

Endogamy:

Answer 27

•
• In biology, endogamy can also refer to the breeding of closely related individuals within a population.

Question 28

hypocotyl that elongates fast

Answer 28

B.

Explanation:
In epigeal germination, the hypocotyl elongates rapidly to push the seedling upward through the soil. This upward growth helps lift the cotyledons and first true leaves above the soil surface, allowing them to receive light for photosynthesis. Therefore, option B, “hypocotyl that elongates fast,” is the correct choice.

Question 29

here are the key differences between a dicot leaf and a monocot leaf:

Answer 29

1. Vein arrangement:
   • Dicot leaves typically have a branching network of veins, known as reticulate venation, where veins form a network pattern throughout the leaf.
   • Monocot leaves usually have parallel venation, where the veins run parallel to each other from the base to the tip of the leaf.
   
   2. Leaf shape:
      • Dicot leaves often have a broad, flattened shape with a distinct petiole (leaf stalk) and a blade (lamina) that is usually broader than it is long.
      • Monocot leaves can vary in shape but are generally long and narrow with parallel venation. They may lack a distinct petiole and have a sheath-like base surrounding the stem.
   3. Leaf margin:
      • Dicot leaves typically have a serrated (toothed) or lobed margin, with irregularities along the edge of the leaf.
      • Monocot leaves usually have a smooth, entire margin, lacking serrations or lobes.
   4. Leaf arrangement:
      • Dicot leaves often have an alternate or opposite arrangement on the stem, where one leaf arises from each node along the stem.
      • Monocot leaves usually have a basal rosette or alternate arrangement, where leaves are arranged in a spiral fashion around the stem or clustered at the base of the plant.
   5. Stomata distribution:
      • Dicot leaves typically have stomata (pores for gas exchange) distributed on both the upper and lower surfaces of the leaf.
      • Monocot leaves usually have stomata primarily located on the lower surface of the leaf, although some species may have stomata on both surfaces.

Question 30

In a dicot leaf, guard cells differ from other epidermal cells because:

Answer 30

contain chloroplasts.

Guard cells are specialized epidermal cells found in plant leaves that regulate the opening and closing of stomata. They contain chloroplasts, which enable them to photosynthesize and produce energy, unlike most other epidermal cells.

Question 31

Medullary rays

Answer 31

Medullary rays, also known as ray cells or wood rays, are structures found in the vascular cambium of woody plants, particularly in the stems and roots. They are composed of elongated cells that radiate outwards from the center of the stem or root. Medullary rays serve several functions, including:Transport: They facilitate lateral transport of water, nutrients, and other substances across the stem or root.Storage: Medullary rays store starch, oils, and other reserve materials.Support: They provide structural support to the stem or root, helping to maintain its integrity.Healing: Injured or damaged tissues can be regenerated through the activity of medullary rays.Medullary rays play a vital role in the growth and development of woody plants and contribute to their overall structure and function.

Question 32

Nastic movement

Answer 32

Nastic movements are non-directional responses to stimuli, typically environmental cues such as light, temperature, or touch, that cause reversible changes in plant movements. Unlike tropic movements, which are directional responses toward or away from a stimulus, nastic movements occur irrespective of the direction of the stimulus.

Nastic movements are often rapid and reversible and can involve various plant parts such as leaves, flowers, or stems. Examples of nastic movements include the closing of leaves in response to touch (thigmonasty), the opening and closing of flowers in response to temperature changes (thermonasty), and the folding of leaves in response to changes in light intensity (nyctinasty or photonasty).

These movements are typically controlled by changes in turgor pressure within specialized cells or tissues, leading to changes in shape or orientation of plant organs. Nastic movements allow plants to adapt quickly to changing environmental conditions and can aid in optimizing conditions for growth, reproduction, or protection from stressors.

Question 33

Labelled diagram of onion bud

Answer 33

Question 34

Groundnut ain’t really a nut

Answer 34

Correct, despite its name, a groundnut is not actually a nut in the botanical sense. Groundnut, also known as peanut, belongs to the legume family, Fabaceae. Botanically, it is classified as an arachis hypogaea, and it is not a true nut. Instead, it is a legume that grows underground, produced by a flowering plant. Groundnuts develop underground from the flower’s ovary after pollination. So, while it may be referred to as a “nut” in its common name, it is not a botanical nut.

Question 35

The main difference between a multiple fruit and an aggregate fruit lies in their development and structure:

Answer 35

1. Multiple Fruit:
   • A multiple fruit develops from the ovaries of multiple flowers that are closely packed together in an inflorescence.
   • During development, these individual ovaries fuse together to form a single, larger fruit.
   • Each segment of the multiple fruit originates from a separate flower, and they may or may not be distinguishable in the mature fruit.
   • Examples of multiple fruits include pineapple and fig.
   
   2. Aggregate Fruit:
      • An aggregate fruit develops from the ovaries of multiple separate flowers that are borne on a single receptacle.
      • Each individual ovary develops into a small, separate fruitlet, and they remain attached to a common receptacle.
      • In the mature aggregate fruit, each fruitlet is distinct and visible, often arranged around a central core or receptacle.
      • Examples of aggregate fruits include strawberry and raspberry.

Question 36

Various plant diseases

Answer 36

1. Rinderpest: A viral disease that affects cattle and other cloven-hoofed animals. It was declared eradicated in 2011, making it one of the only two infectious diseases to be eradicated, the other being smallpox.
   
   2. Maize rust: A fungal disease that affects maize (corn) plants, causing yellow-orange pustules on leaves, reducing photosynthetic capacity, and impacting crop yield.
   3. Newcastle disease: A highly contagious viral disease affecting birds, especially domestic poultry. It can cause respiratory, nervous, and digestive symptoms and often results in high mortality rates in infected flocks.
   4. Swine fever: This could refer to African Swine Fever, a highly contagious viral disease affecting domestic and wild pigs. It causes high fever, hemorrhages, and death in affected animals. It poses a significant threat to the swine industry globally.
   5. Cassava mosaic disease: A viral disease affecting cassava plants, an important staple food crop in many regions. It causes characteristic yellowing and distortion of leaves, stunting of plant growth, and reduced yield, posing a significant threat to food security in affected areas.

Question 37

Banana, plantain, and pineapple can indeed be grouped together in terms of their reproduction through suckers or offsets:

Answer 37

Banana, plantain, and pineapple can indeed be grouped together in terms of their reproduction through suckers or offsets:

1.	Banana and Plantain: Both banana and plantain plants reproduce asexually through suckers, which are shoots that emerge from the base of the plant or its rhizome. These suckers grow into new plants, genetically identical to the parent plant.
2.	Pineapple: Pineapple plants also reproduce through suckers, which are known as “slips.” These are shoots that develop from the base of the plant and can be replanted to grow into new pineapple plants.

So, while these plants may differ in their botanical classification and fruit type, they share the characteristic of reproducing through suckers or offsets.

Question 38

Rabbit

Answer 38

1. Rabbit:
   • Incisors: 2/1
   • Canines: 0/0
   • Premolars: 3/2
   • Molars: 3/3
   So, the dental formula for a rabbit is: 2/1 0/0 3/2 3/3

Question 39

Young Child (Deciduous Teeth):

Answer 39

2. Young Child (Deciduous Teeth):
   • Incisors: 2/2
   • Canines: 1/1
   • Premolars: 2/2
   • Molars: 3/3

Question 40

Sheep

Answer 40

3. Sheep:
   • Incisors: 0/3
   • Canines: 0/0
   • Premolars: 3/3
   • Molars: 3/3
   So, the dental formula for a sheep is: 0/3 0/0 3/3 3/3

Question 41

Dog

Answer 41

4. Dog:
   • Incisors: 3/3
   • Canines: 1/1
   • Premolars: 4/4
   • Molars: 2/3
   So, the dental formula for a dog is: 3/3 1/1 4/4 2/3

Question 42

Parchment paper

Answer 42

parchment paper is the only one that will not allow osmosis. Parchment paper is made from cellulose, which is a type of plant-based fiber. It is not permeable to water or other substances, so it does not allow osmosis to occur.

Question 43

Osmosis

Answer 43

pig bladder, cow’s bladder, cellophane, and transparent polythene are all materials that can allow osmosis to some extent. Bladders are biological membranes that are permeable to water and certain solutes. Cellophane and transparent polythene are synthetic materials that are semi-permeable, allowing certain molecules to pass through, including water.

Question 44

Auxins and region of curvature

Answer 44

The region of curvature in the growth of plants refers to the area where a plant organ, such as a stem or root, bends or curves in response to an external stimulus, such as light or gravity. This bending response is known as tropism.

Auxins, a class of plant hormones, play a significant role in regulating tropic responses and the region of curvature. In response to an external stimulus, auxins are redistributed within the plant, causing differential growth rates on opposite sides of the organ. This differential growth results in bending towards or away from the stimulus.

For example:

•	In phototropism, where plants bend towards a light source, auxins accumulate on the shaded side of the stem, promoting elongation and bending towards the light.
•	In gravitropism, where plants bend in response to gravity, auxins accumulate on the lower side of the stem or root in horizontal orientation, promoting elongation and bending downwards (roots) or upwards (stems).

The region of curvature is where these differential growth rates occur, leading to the observable bending or curving of the plant organ. Auxins play a central role in mediating this response by regulating cell elongation and growth in the tissues of the plant organ.

Question 45

Root tuber

Answer 45

Root Tubers:
• Root tubers are enlarged, fleshy structures that develop from the roots of the plant.
• They are formed by the thickening of storage roots, which are specialized for nutrient storage.
• Root tubers typically grow underground and serve as a food reserve for the plant during periods of dormancy or drought.
• Examples of plants that produce root tubers include:
• Sweet potato (Ipomoea batatas)
• Taro (Colocasia esculenta)
• Yam (Dioscorea species)

Question 46

Stem tuber

Answer 46

Stem Tubers:
• Stem tubers are swollen, underground stems that store nutrients and energy for the plant.
• They are formed from the thickening of the stem tissue, usually at or near the soil surface.
• Stem tubers often have buds or “eyes” from which new shoots can emerge, allowing the plant to propagate vegetatively.
• Examples of plants that produce stem tubers include:
• Potato (Solanum tuberosum)
• Jerusalem artichoke (Helianthus tuberosus)
• Tapioca (Manihot esculenta)

Question 47

Here’s why cassava is not a stem tuber:

Answer 47

1. Origin: The storage roots of cassava develop from the primary root system, not from the stem. Stem tubers, on the other hand, are swollen, underground stems that store nutrients and energy. They originate from the stem tissue of the plant.
   
   2. Structure: The storage roots of cassava have a different anatomical structure compared to stem tubers. Cassava roots are typically tapered and elongated, with a fibrous outer layer and starchy inner tissue. Stem tubers, such as potatoes, have a more rounded shape and are composed of swollen stem tissue.
   3. Function: Cassava roots serve as the primary storage organ for the plant, containing starch and other nutrients that the plant can utilize during periods of drought or dormancy. Stem tubers also store nutrients, but they often have buds or “eyes” that can sprout new shoots, allowing the plant to propagate vegetatively

Question 48

Diastema

Answer 48

Diastema refers to a gap or space between two teeth, typically found in the dental arches of mammals. These gaps can occur between any two adjacent teeth but are most commonly observed between the incisors and the molars.

In many herbivorous mammals, such as rodents, rabbits, and ungulates, diastemas are common and serve various functions. They can provide space for the tongue to manipulate food, aid in chewing and grinding of tough plant material, and prevent the teeth from wearing down unevenly. In some cases, diastemas may also accommodate the enlargement of certain teeth, such as the canines or tusks, in species where these teeth are present.

In humans, diastemas are less common but can occur naturally or result from various factors such as genetics, tooth size discrepancies, habits like thumb-sucking, or periodontal disease. Some individuals may have diastemas between their front teeth, commonly referred to as “midline diastema,” which can be treated through orthodontic procedures if desired.

Question 49

Prothallus

Answer 49

The prothallus of a fern, also known as a gametophyte, is a small, heart-shaped structure that represents the haploid stage in the fern life cycle. Here are key points about the prothallus:

1.	Haploid Stage: The prothallus is haploid, meaning it contains a single set of chromosomes. It is produced by the spores released from the sporangia on the underside of fern fronds.
2.	Sexual Reproduction: The prothallus is the stage in the fern life cycle where sexual reproduction occurs. It produces both male and female reproductive structures called gametangia.
3.	Archegonia: The female gametangia, called archegonia, produce egg cells (haploid) that are fertilized by sperm cells.
4.	Antheridia: The male gametangia, called antheridia, produce sperm cells (haploid) that swim to the archegonia for fertilization.
5.	Fertilization: After fertilization, a diploid zygote is formed, which develops into a new sporophyte (the familiar fern plant with fronds).
6.	Rhizoids: Prothalli have rhizoids, which are thread-like structures that anchor the prothallus to the soil and absorb water and nutrients.
7.	Transient Stage: Prothalli are small and short-lived structures. They are typically found on the forest floor, often in moist, shaded areas.
8.	Morphology: The prothallus is typically heart-shaped and green, containing chlorophyll for photosynthesis. It lacks vascular tissue found in the sporophyte stage.

Understanding the prothallus and its role in the fern life cycle is crucial for studying fern reproduction and evolution.

Question 50

Male and female toads

Answer 50

In many species of toads, including common species like the American toad (Anaxyrus americanus), the primary differences between males and females are related to their reproductive anatomy and behavior. Here are some general differences:

1.	Size: In some toad species, females tend to be larger than males, although this is not always the case.
2.	Reproductive Anatomy:
•	Male toads typically have paired testes for producing sperm, while females have ovaries for producing eggs.
•	Males may have specialized structures such as vocal sacs or nuptial pads on their forelimbs, which they use during mating calls and amplexus (mating behavior), respectively.
•	Females may have a slightly broader body shape, particularly during the breeding season when they are carrying eggs.
3.	Vocalization: Male toads often produce mating calls or advertisement calls to attract females during the breeding season. These calls are usually absent or much less frequent in females.
4.	Behavior:
•	During the breeding season, male toads are typically more actively engaged in seeking out potential mates and competing with other males for access to females.
•	Female toads may be more selective in choosing a mate and may exhibit behaviors related to oviposition (egg-laying) and guarding their eggs after mating.
5.	Egg-laying: Female toads are responsible for laying eggs, usually in water or moist environments, where the eggs are fertilized externally by the male’s sperm.

It’s important to note that these differences can vary depending on the species of toad and may not apply universally to all species. Additionally, there may be subtle differences in coloration or patterning between males and females in some species, but these can be challenging to discern without close examination.

Question 51

Diagram of feather

Answer 51

Question 52

Factors that affect dnzymes

Answer 52

Several factors can affect the activity of enzymes besides pH, including:

1.	Temperature: Enzymes have an optimal temperature at which they function most efficiently. High temperatures can denature enzymes, disrupting their three-dimensional structure and decreasing activity, while low temperatures can slow down enzymatic reactions.
2.	Substrate Concentration: Increasing substrate concentration typically increases the rate of enzymatic reactions, up to a certain point. Beyond this point, enzyme active sites become saturated, and further increases in substrate concentration do not increase the rate of reaction.
3.	Enzyme Concentration: Increasing the concentration of enzymes can increase the rate of reaction, as there are more enzyme molecules available to catalyze the conversion of substrate to product.
4.	Presence of Cofactors and Coenzymes: Many enzymes require cofactors (inorganic ions) or coenzymes (organic molecules) to function properly. These molecules may bind to the enzyme and assist in catalysis.
5.	Inhibitors: Inhibitors can bind to enzymes and reduce their activity. Competitive inhibitors compete with the substrate for binding to the enzyme’s active site, while non-competitive inhibitors bind to another site on the enzyme and alter its shape, inhibiting substrate binding.
6.	Activators: Activators can enhance the activity of enzymes. Allosteric activators bind to regulatory sites on enzymes, causing a conformational change that increases the enzyme’s catalytic activity.
7.	pH Stability: Enzymes vary in their tolerance to changes in pH. Some enzymes are stable over a wide range of pH values, while others are more sensitive and have a narrow pH optimum.

Understanding these factors is crucial for optimizing enzymatic reactions in various applications, including industrial processes, medical diagnostics, and biochemical research.

Question 53

The Biuret test is a biochemical assay used to detect the presence of proteins or peptides in a solution. Here are the key points about the Biuret test:

Answer 53

1. Principle: The Biuret test relies on the reaction between copper ions (Cu²⁺) in a basic solution and peptide bonds (-CONH-) in proteins or peptides. The copper ions form a violet-colored complex with the peptide bonds.
   
   2. Reagents: The reagent used in the Biuret test is typically a solution of copper sulfate (CuSO₄) mixed with sodium hydroxide (NaOH). This reagent is commonly known as Biuret reagent.
   3. Procedure: To perform the Biuret test, the sample solution containing proteins or peptides is mixed with Biuret reagent. The appearance of a violet or purple color indicates a positive result, indicating the presence of proteins or peptides.
   4. Sensitivity: The Biuret test is sensitive to the presence of peptide bonds, which are characteristic of proteins and peptides. It is less sensitive to free amino acids or other nitrogen-containing compounds.
   5. Limitations: The Biuret test is a qualitative assay and does not provide quantitative information about the concentration of proteins or peptides in the sample. It is also less specific than other protein assays and may give false positive results with certain substances that contain nitrogen.

Overall, the Biuret test is a simple and widely used method for detecting the presence of proteins or peptides in biological samples, making it a valuable tool in biochemical analysis and research.

Question 54

runners/stolons

Answer 54

Runners: Runners, also known as stolons, are horizontal stems that grow above the ground and spread out along the soil surface. They produce new shoots and roots at nodes along their length, allowing the plant to propagate vegetatively and spread across the ground. Examples of plants that produce runners include strawberry plants (Fragaria spp.) and certain species of grasses.

Question 55

Corms

Answer 55

Corms: Corms are modified underground stems that serve as storage organs for nutrients. Unlike bulbs, which have layers of modified leaves, corms have a solid, swollen stem base surrounded by dry, protective scales. Corms are typically found in plants such as crocuses, gladioli, and taro.

Question 56

Scolex

Answer 56

Tapeworms have specialized structures called scolex, which are used to attach themselves to the intestinal wall of their host. The scolex is equipped with hooks, suckers, or both, depending on the species of tapeworm. These structures help the tapeworm anchor itself firmly to the intestinal lining, allowing it to absorb nutrients from the host’s digestive tract.
Rostellum is part of scolex

Question 57

Rostellum

Answer 57

Yes, the rostellum is indeed a part of the tapeworm’s scolex. The rostellum is a specialized structure located at the anterior end of the scolex. It is often armed with hooks or spines, which the tapeworm uses to firmly attach itself to the intestinal wall of its host. The rostellum plays a crucial role in the tapeworm’s ability to anchor itself securely in the host’s intestine, allowing it to survive and absorb nutrients.

Question 58

Diagram of egg

Answer 58

Question 59

Egg of chicken

Answer 59

The egg of a chicken is a complex structure with several distinct parts, each serving specific functions. Here are the main parts of a chicken egg and their functions:

1.	Shell: The outermost layer of the egg is the shell, composed primarily of calcium carbonate. The shell provides protection to the developing embryo and helps prevent microbial contamination.
2.	Shell Membranes: Beneath the shell are two membranes, the inner and outer shell membranes. These membranes help maintain the structural integrity of the egg and act as barriers against bacterial invasion.
3.	Air Cell: Located at the blunt end of the egg, the air cell forms as the egg cools after laying. It provides a pocket of air for the developing chick to breathe as it matures.
4.	Albumen (Egg White): The albumen is the clear, viscous fluid that surrounds the developing embryo. It consists mainly of water and protein and serves to cushion and protect the embryo, as well as providing a source of hydration and nutrients.
5.	Chalaza: The chalaza is a pair of spiral-shaped structures made of protein fibers that anchor the yolk in the center of the egg. They help keep the yolk suspended and centered within the egg, reducing the risk of damage to the embryo during movement.
6.	Yolk: The yolk is the yellow, spherical structure at the center of the egg. It contains the embryo’s food supply, consisting of proteins, fats, vitamins, and minerals necessary for growth and development.
7.	Germinal Disc: Also known as the blastoderm, the germinal disc is a small, circular area on the surface of the yolk where fertilization occurs. It contains the genetic material (DNA) of the developing chick.

Together, these parts of the chicken egg provide an optimal environment for the development of the embryo, supplying essential nutrients, protection, and support until hatching occurs.

Question 60

Cervical vertebrate

Answer 60

Among the regions of the vertebral column – cervical, thoracic, lumbar, sacral, and caudal – the cervical region is the one that occurs in equal numbers in rabbits, rats, and humans.

Cervical vertebrae are located in the neck region and are characterized by having a small body, a large vertebral foramen, and transverse foramina. In rabbits, rats, and humans, the cervical region typically consists of seven vertebrae.

While the other regions of the vertebral column (thoracic, lumbar, sacral, and caudal) may vary in number and structure between these species, the cervical region remains consistent, with seven vertebrae in each. Therefore, the cervical region occurs in equal numbers in rabbits, rats, and humans.

Question 61

in older roots, the piliferous layer is typically replaced by cork cells

Answer 61

Yes, in older roots, the piliferous layer is typically replaced by cork cells as part of the process of secondary growth and development.

As a root matures and ages, it undergoes secondary growth, which involves the formation of secondary tissues such as cork and secondary vascular tissues (secondary xylem and secondary phloem). Cork cells are produced by the cork cambium (also known as the phellogen), a lateral meristem that forms within the cortex of the root.

The cork cells form a protective outer layer called the cork or bark, which replaces the piliferous layer and provides additional protection to the root against mechanical damage, desiccation, and pathogens. The cork layer is impermeable to water and gases, helping to prevent water loss and protect the inner tissues of the root.

As a result of this process, the root loses its ability to produce root hairs and absorb water and nutrients from the soil through the piliferous layer. Instead, the primary function of the mature root becomes structural support and anchorage, while the absorption of water and nutrients is primarily carried out by the younger, more actively growing parts of the root system.

Question 62

The piliferous layer, also known as the root hair zone or piliferous region,

Answer 62

The piliferous layer, also known as the root hair zone or piliferous region, is a specialized region of plant roots where root hairs develop. Here are the key points about the piliferous layer of a root:

1.	Location: The piliferous layer is located just behind the root cap and extends a short distance along the root. It is found in the zone of maturation, which is the region where cells differentiate and mature.
2.	Root Hairs: Root hairs are slender, elongated extensions of epidermal cells that protrude into the soil. They greatly increase the surface area of the root for absorption of water and minerals.
3.	Function: The primary function of the piliferous layer is to increase the absorptive surface area of the root, facilitating the uptake of water and nutrients from the soil. The root hairs in this region play a crucial role in absorbing water and dissolved minerals through osmosis and active transport.
4.	Adaptations: The piliferous layer is well adapted for efficient water and nutrient absorption. The root hairs are thin-walled, which allows for rapid water uptake, and they have a large surface area-to-volume ratio, maximizing contact with soil particles containing nutrients.
5.	Development: Root hairs are produced by the differentiation of epidermal cells in the piliferous layer. As new cells are produced in the root meristem, they undergo elongation and maturation, eventually developing into root hairs.
6.	Sensitivity: The piliferous layer is sensitive to environmental factors such as soil moisture, nutrient availability, and pH levels. Changes in these factors can influence the development and growth of root hairs, affecting the overall efficiency of nutrient uptake by the plant.

Overall, the piliferous layer of the root is a critical adaptation that enables plants to efficiently absorb water and nutrients from the soil, contributing to their growth and development.

Question 63

Yes, the piliferous layer, or root hair zone, gradually breaks down and is replaced by cork cells

Answer 63

Yes, the piliferous layer, or root hair zone, gradually breaks down and is replaced by cork cells as the root ages and undergoes secondary growth. This process is part of the natural maturation and development of the root.

As the root grows older, the production of new root hairs in the piliferous layer decreases, and the existing root hairs eventually senesce and are shed. At the same time, the cork cambium, a lateral meristem, becomes active and begins producing cork cells toward the outer layers of the root.

The cork cells form a protective layer of cork tissue, which gradually replaces the piliferous layer and extends outward, providing additional protection to the root as it matures. The cork layer serves to protect the inner tissues of the root against mechanical damage, pathogens, and desiccation.

As a result of this process, the piliferous layer ultimately breaks down and is replaced by cork cells, leading to changes in the structure and function of the root over time. While the root loses its ability to produce root hairs and absorb water and nutrients through the piliferous layer, it gains enhanced protection and structural support from the cork layer as it ages.

Question 64

Monoecious plants

Answer 64

Monoecious flowering plants are plants that have both male and female reproductive structures (staminate and pistillate flowers) on the same individual plant. In other words, a single monoecious plant can produce both male and female flowers, though they may not be located on the same flower.

Here are some key points about monoecious flowering plants:

1.	Reproductive Structures: Monoecious plants have separate male and female flowers. The male flowers typically contain stamens with pollen-producing anthers, while the female flowers contain pistils with ovules.
2.	Examples: Many common plant species are monoecious, including corn (maize), squash, cucumber, and most varieties of oak trees. These plants have both male and female flowers on the same plant, allowing for self-pollination or cross-pollination by wind or insects.
3.	Advantages: Being monoecious can be advantageous for plant reproduction, as it ensures that pollen from one flower can reach the stigma of another flower on the same plant, facilitating fertilization and seed production.
4.	Variation: While monoecy is common in certain plant families, such as the Cucurbitaceae (gourd family), some species within these families may exhibit dioecy (separate male and female plants) or other reproductive strategies.
5.	Pollination: In monoecious plants, pollination can occur through various mechanisms, including self-pollination, where pollen is transferred from the staminate flowers to the pistillate flowers of the same plant, or cross-pollination, where pollen is transferred between different plants of the same species.

Overall, monoecious flowering plants play an essential role in ecosystems and agriculture, providing a range of benefits through their reproductive strategies and contributing to genetic diversity within plant populations.

Question 65

Fertilization and pollen tube

Answer 65

During fertilization in flowering plants, the pollen tube grows from the pollen grain to transport the male gametes (sperm cells) to the ovule for fertilization. Inside the pollen tube, there are typically two nuclei: one generative nucleus and one tube nucleus.

1.	Generative Nucleus: The generative nucleus divides mitotically to produce two sperm cells. These sperm cells are eventually released from the pollen tube and involved in fertilization.
2.	Tube Nucleus: The tube nucleus plays a role in guiding the growth of the pollen tube through the style of the flower toward the ovule.

So, during fertilization, a pollen tube typically contains two nuclei: one generative nucleus, which gives rise to two sperm cells, and one tube nucleus, which guides the growth of the pollen tube.

Question 66

Transect method

Answer 66

The transect method is a commonly used technique in ecology to study the distribution and abundance of organisms across a particular habitat or ecosystem. It involves systematically sampling a linear or strip-like area, called a transect, to gather data on the presence and characteristics of organisms and their environment. Here’s how the transect method works:

1.	Selection of Transect: Researchers select a linear path or line transect that traverses the habitat of interest. Transects can be established along gradients of environmental factors, such as elevation, soil type, or vegetation structure, to capture variation in ecological communities.
2.	Sampling along the Transect: Along the transect line, researchers sample the organisms and environmental variables at regular intervals or predetermined points. This can involve various sampling techniques, such as quadrats, point sampling, or line-intercept sampling, depending on the study objectives and the characteristics of the habitat.
3.	Data Collection: At each sampling point, researchers record relevant data, such as the species present, abundance, density, biomass, and environmental conditions (e.g., temperature, humidity, soil moisture). This data can be collected using direct observation, specimen collection, measurements, or other field techniques.
4.	Analysis: Once data collection is complete, researchers analyze the data to assess patterns of distribution and abundance of organisms along the transect. Statistical analyses may be used to quantify relationships between organisms and environmental variables, identify patterns or gradients, and infer ecological processes.
5.	Interpretation and Conclusion: The results obtained from the transect sampling are interpreted in the context of the ecological questions or hypotheses under investigation. Researchers draw conclusions about the composition, structure, and dynamics of ecological communities, as well as their responses to environmental gradients or disturbances.

The transect method allows ecologists to systematically study ecological patterns and processes across spatial scales, providing valuable insights into the distribution, abundance, and interactions of organisms within their habitats. It is widely used in various ecological studies, including biodiversity assessments, community ecology, and habitat monitoring.

Question 67

Penicillium

Answer 67

: Penicillium reproduces both sexually and asexually. Asexual reproduction occurs through the formation of conidia, which are specialized spores produced on the tips of specialized hyphae called conidiophores. Sexual reproduction involves the fusion of compatible mating strains to form sexual structures called ascocarps, which produce sexual spores called ascospores.

Question 68

Paramecium

Answer 68

: Paramecium reproduces primarily through asexual binary fission, where the cell divides into two daughter cells. Additionally, they may undergo a form of sexual reproduction called conjugation, where genetic material is exchanged between two mating cells.

Question 69

Amoeba

Answer 69

: Amoeba reproduces primarily through asexual reproduction by binary fission, where the parent cell divides into two daughter cells. However, they may also undergo sexual reproduction in certain conditions, such as the formation of resistant cysts or the fusion of gametes.

Question 70

Mucor and Rhizopus:

Answer 70

Mucor and Rhizopus are common examples of fungi that reproduce asexually through the formation of sporangia. Sporangia contain spores called sporangiospores, which are released into the environment and can germinate to form new individuals. They also reproduce sexually through the formation of specialized structures called zygospores, which result from the fusion of gametangia.

Question 71

Ascaris:

Answer 71

Ascaris reproduces sexually, with male and female individuals producing eggs and sperm, respectively. Fertilization occurs internally within the female reproductive tract, leading to the formation of fertilized eggs. These eggs are then passed out of the host’s body through feces.

Question 72

Spirogyra

Answer 72

: Spirogyra reproduces asexually through fragmentation, where a filament breaks into fragments, each of which can grow into a new filament. Additionally, they reproduce sexually through a process called conjugation, where genetic material is exchanged between two adjacent filaments to form zygospores.

Question 73

Blood clotting

Answer 73

When a blood vessel is injured, the process of blood clotting, also known as coagulation, is initiated to prevent excessive bleeding. Here’s a short summary of the blood clotting process when a vessel is cut and exposed to air:

1.	Vasoconstriction: Initially, the injured blood vessel constricts (vasoconstriction) to reduce blood flow to the site of injury, helping to limit blood loss.
2.	Platelet Adhesion: Platelets, tiny cell fragments circulating in the blood, adhere to the exposed collagen fibers at the site of injury, forming a temporary plug to seal the wound.
3.	Platelet Activation: Once adhered, platelets become activated and release signaling molecules called cytokines and chemicals like thromboxane A2, which attract more platelets to the injury site and stimulate further activation.
4.	Formation of Platelet Plug: Activated platelets change shape and release substances that help them stick together, forming a platelet plug or platelet aggregation at the site of injury.
5.	Activation of Coagulation Cascade: In response to tissue injury and exposure to air, a complex series of biochemical reactions known as the coagulation cascade is initiated. This cascade involves the sequential activation of clotting factors, leading to the conversion of inactive proenzymes into active enzymes, ultimately resulting in the formation of fibrin, a protein that stabilizes the platelet plug.
6.	Fibrin Mesh Formation: Fibrin strands form a meshwork around the platelet plug, trapping red blood cells and reinforcing the clot. This fibrin mesh, along with the platelet plug, forms the solid clot that seals the wound and prevents further blood loss.
7.	Clot Retraction and Repair: Over time, the clot retracts as the wound begins to heal. Meanwhile, other repair processes, such as tissue regeneration and remodeling, take place to restore the injured blood vessel and surrounding tissue.
8.	Clot Dissolution: Once the injury is healed, the clot is gradually dissolved by specialized enzymes called fibrinolytic enzymes, such as plasmin, allowing normal blood flow to resume.

Overall, the blood clotting process is a complex and tightly regulated series of events that ensures rapid and effective hemostasis in response to vascular injury, preventing excessive bleeding while promoting tissue repair and healing.

Question 74

Ridging Down the Slope (Contour Ridging):

Answer 74

Ridging down the slope involves constructing ridges perpendicular to the slope contour lines. This technique helps to slow down the flow of water running down the slope, allowing it to infiltrate into the soil and reducing the velocity of surface runoff. Contour ridges act as barriers that intercept and detain runoff, allowing sediment to settle out and reducing erosion. This method is particularly effective on slopes with gentle gradients and can help to retain soil moisture and nutrients.

Question 75

Ridging Across the Slope (Cross-Contour Ridging):

Answer 75

Ridging across the slope involves constructing ridges parallel to the slope contour lines. This technique helps to break the flow of water and reduce the speed of surface runoff, thereby minimizing erosion. Cross-contour ridging can help to trap sediment and slow down the movement of water across the slope, reducing the risk of soil erosion. However, the effectiveness of this method may vary depending on the slope gradient and the spacing and design of the ridges.

Question 76

In an angiosperm leaf, the xylem is typically located

Answer 76

above the phloem.

In the leaf of an angiosperm (flowering plant), vascular tissues responsible for transporting water and nutrients are organized into vascular bundles. These bundles consist of xylem, which transports water and minerals from the roots to the leaves, and phloem, which transports sugars and other organic nutrients produced in the leaves to other parts of the plant.

In most angiosperm leaves, the arrangement of vascular bundles follows a characteristic pattern called the “vascular bundle arrangement” or “vascular bundle system.” In this system, the xylem is typically located above the phloem within the vascular bundle. This arrangement allows for efficient transport of water and nutrients throughout the leaf.

The position of the xylem above the phloem is advantageous for several reasons:

1.	Water Transport: Placing the xylem above the phloem allows water absorbed by the roots to be transported upward to the leaf more efficiently. Water moves upward through the xylem due to transpiration (water loss from the leaf surface) and cohesion-adhesion properties of water molecules.
2.	Nutrient Transport: By positioning the xylem above the phloem, the leaf can efficiently transport nutrients synthesized in the leaf (e.g., sugars) downward to other parts of the plant via the phloem.
3.	Structural Support: The arrangement of vascular bundles with xylem above phloem provides structural support to the leaf, helping it withstand mechanical stress and maintain its shape.

Overall, the organization of vascular bundles with xylem above phloem in angiosperm leaves reflects the plant’s adaptation to efficiently transport water, nutrients, and sugars, contributing to the plant’s growth, development, and overall function.

Question 77

Monocotyledonous Plants (Monocots):

Answer 77

1. Central Pith: Monocot stems typically lack a distinct central pith. Instead, the vascular bundles are scattered throughout the ground tissue, which may appear homogeneous when viewed in cross-section.
   
   2. Wide Cortex: Monocot stems often have a wide cortex surrounding the vascular bundles. This cortex may contain parenchyma cells and may serve functions such as storage and support.
   3. Narrow Cortex: Some monocot species may have a narrow cortex, especially in grasses and other herbaceous monocots. However, the width of the cortex can vary depending on the species.
   4. Pericyclic Fibers: Monocots generally lack pericyclic fibers, as these fibers are more commonly associated with dicotyledonous plants. Pericyclic fibers are part of the pericycle, a layer of cells located just inside the endodermis in dicot stems.

Question 78

Dicotyledonous Plants (Dicots):

Answer 78

1. Central Pith: Dicot stems often have a distinct central pith composed of parenchyma cells. The pith may store nutrients and provide support to the stem.
   
   2. Wide Cortex: Dicot stems may have a wide cortex surrounding the central pith and vascular bundles. This cortex can contain various types of cells, including parenchyma, collenchyma, and sclerenchyma, and may serve functions such as storage, support, and protection.
   3. Narrow Cortex: Some dicot species may have a narrow cortex, particularly in woody dicots. The width of the cortex can vary depending on factors such as species and growth habit.
   4. Pericyclic Fibers: Pericyclic fibers are commonly found in dicot stems, especially in woody species. These fibers are located in the pericycle and provide mechanical support to the vascular bundles, aiding in the strength and rigidity of the stem.

Question 79

Medullary rays

Answer 79

Yes, medullary rays are found in both monocotyledonous (monocot) and dicotyledonous (dicot) plants. They are radial structures that extend from the pith to the secondary phloem in the stems of both types of plants.

In monocots, medullary rays are typically uniseriate (composed of a single layer of cells) and are often made up of parenchyma cells. They function in the storage and lateral movement of nutrients within the stem.

In dicots, medullary rays can be uniseriate or multiseriate (composed of multiple layers of cells) and may contain various cell types, including parenchyma, sclerenchyma, and vascular elements. They serve similar functions as in monocots, aiding in the radial transport of water, nutrients, and sugars, as well as providing mechanical support and facilitating storage within the stem.

Overall, while there may be differences in the structure and composition of medullary rays between monocots and dicots, they are present in both types of plants and play important roles in their growth and function.

Question 80

Medullary rays

Answer 80

Medullary rays, also known as wood rays or simply rays, are radial structures found in the secondary xylem (wood) of both gymnosperms and angiosperms. Therefore, medullary rays are common in both types of plants.

In gymnosperms, such as conifers, medullary rays are typically uniseriate (composed of a single layer of cells) and often consist of parenchyma cells. In angiosperms (flowering plants), medullary rays can be either uniseriate or multiseriate (composed of multiple layers of cells), and they may contain various cell types, including parenchyma, sclerenchyma, and even vascular elements.

Medullary rays serve several important functions in woody plants, including the radial transport of water, nutrients, and sugars, as well as providing mechanical support and facilitating storage and lateral movement of materials within the stem. Additionally, medullary rays play a role in the radial growth of the stem during secondary growth, contributing to the overall structure and function of the plant.

Question 81

Common Features:
Monocot and dicot

Answer 81

1. Primary Tissues: Both monocot and dicot roots consist of primary tissues, including the epidermis, cortex, endodermis, pericycle, vascular tissues (xylem and phloem), and a central pith in some cases.
   
   2. Root Cap: Both types of roots have a root cap at the apex (tip) of the root, which protects the delicate apical meristem as the root pushes through the soil during growth.
   3. Root Hairs: Both monocot and dicot roots may develop root hairs from the epidermal cells, which increase the surface area for absorption of water and nutrients from the soil.
   4. Primary Growth: Both types of roots exhibit primary growth, which involves the elongation of cells produced by the apical meristem at the root tip.

Question 82

Key Differences:
Monocot and dicot

Answer 82

1. Vascular Bundles Arrangement:
   • Monocot Roots: Monocot roots have a scattered arrangement of vascular bundles throughout the ground tissue (pith and cortex). These bundles are not arranged in a distinct pattern.
   • Dicot Roots: Dicot roots have a radial arrangement of vascular bundles, with xylem located towards the center and phloem positioned between the arms of the xylem in the form of a cross or star shape.
   
   2. Secondary Growth:
      • Monocot Roots: Monocot roots typically do not undergo significant secondary growth. They maintain a primary growth pattern throughout their lifespan.
      • Dicot Roots: Dicot roots may undergo secondary growth, resulting in the formation of secondary tissues such as secondary xylem (wood) and secondary phloem. This process increases the girth of the root over time.
   3. Periderm Formation:
      • Monocot Roots: Monocot roots do not usually develop a well-defined periderm (cork cambium and cork layer) during secondary growth.
      • Dicot Roots: Dicot roots may develop a periderm, which consists of cork cambium (phellogen) and cork cells (phellem), as part of secondary growth. The periderm provides protection to the root as it expands in diameter.
   4. Taproot vs. Fibrous Root System:
      • Monocot Roots: Monocot roots typically have a fibrous root system characterized by numerous thin roots of similar diameter originating from the base of the stem.
      • Dicot Roots: Dicot roots typically have a taproot system with a main primary root (taproot) that grows vertically downward and gives rise to lateral roots (secondary roots).

Question 83

Sudan 3

Answer 83

A substance that produces a red coloration with Sudan 3 is a lipid or a substance containing lipids. Sudan 3 is a lipophilic dye, meaning it has an affinity for lipids and will bind to them, causing them to appear red-orange in color.

Examples of substances that may produce a red coloration with Sudan 3 include:

1.	Lipid droplets in cells, such as those found in adipose tissue (fat cells).
2.	Triglycerides and fatty acids in biological samples.
3.	Lipoproteins, which are complexes of lipids and proteins found in blood plasma.
4.	Lipid-rich structures in tissues, such as myelin sheaths in nerve cells.

When applied to a sample containing lipids, Sudan 3 will selectively bind to the lipids, causing them to stain red-orange. This staining can be useful in various laboratory applications, including histology, cytology, and lipid analysis.

Question 84

Chyme

Answer 84

Chyme is the semi-fluid mass of partially digested food and gastric juices that is formed in the stomach during digestion. After food is swallowed, it enters the stomach where it is mixed with gastric secretions, such as hydrochloric acid and digestive enzymes. This mixture forms chyme, which is then gradually released into the small intestine for further digestion and absorption of nutrients. Chyme typically has a thick, soupy consistency and plays a crucial role in the digestive process.

Question 85

Germinating seeds produce alcohol:

Answer 85

Some plant tissues, such as germinating seeds, can undergo alcoholic fermentation in the absence of oxygen, leading to the production of alcohol.

Question 86

Sebaceous glands

Answer 86

Sebaceous glands in mammals are responsible for producing sebum, which is an oily, waxy substance. The main functions of sebaceous glands include:

1.	Moisturizing the Skin: Sebum helps to keep the skin moisturized by forming a protective barrier on its surface. This barrier helps to prevent excessive loss of moisture from the skin, keeping it hydrated.
2.	Lubricating Hair and Skin: Sebum coats the hair shafts and skin, providing lubrication and preventing them from becoming dry and brittle. This lubrication helps to keep the hair flexible and prevents it from breaking easily.
3.	Protecting Against Infections: Sebum has antimicrobial properties, which help to protect the skin against bacterial and fungal infections. The fatty acids present in sebum create an acidic environment on the skin’s surface, making it inhospitable for the growth of certain microorganisms.
4.	Regulating Body Temperature: Sebum can also help to regulate body temperature by forming a thin layer on the skin’s surface, which can reduce heat loss from the body.

Overall, the function of sebaceous glands is essential for maintaining the health and integrity of the skin and hair in mammals.

Question 87

Protandrous flower

Answer 87

A protandrous flower is a type of flower in which the male reproductive organs (stamens) mature and release pollen before the female reproductive organs (pistils) become receptive to pollen. In other words, the flower starts as functionally male and then transitions to functionally female. This sequential maturation pattern helps to reduce the likelihood of self-pollination within the same flower, promoting cross-pollination and genetic diversity. Many plant species exhibit protandry as a reproductive strategy to enhance pollination success.

Question 88

Crotolaria

Answer 88

In Crotalaria flowers, pollen release typically requires a specific action by pollinators, such as insects. The pollinator must depress or exert pressure on a specialized structure within the flower called the keel. The keel is a part of the flower’s structure that contains the reproductive organs, including the stamens (male reproductive organs) and pistil (female reproductive organ).

When the pollinator lands on the flower and applies pressure to the keel, it triggers the release of pollen from the stamens. This mechanism ensures that pollen is effectively transferred to the pollinator, facilitating pollination. In some species of Crotalaria, the keel may be structured in a way that requires specific pollinator behaviors, such as a certain amount of force or pressure, to release the pollen. This ensures that only certain types of pollinators, typically those capable of exerting the required pressure, are effective in pollinating the flower.

Question 89

Irish potato is a ____ tuber

Answer 89

Stem.

Question 90

Young plants showing yellow leaves

Answer 90

A young plant showing yellow leaves may be deficient in several nutrients, but one common cause of yellowing leaves in plants is a deficiency in nitrogen. Nitrogen is an essential nutrient for plant growth and is a component of chlorophyll, the pigment responsible for the green color of leaves. When a plant lacks sufficient nitrogen, chlorophyll production decreases, leading to yellowing of the leaves.

However, yellowing leaves can also indicate deficiencies in other nutrients such as iron, magnesium, potassium, or sulfur, or it may be caused by environmental factors such as water stress, poor drainage, or soil pH imbalance. To accurately determine the cause of yellowing leaves and address the deficiency, it is essential to examine the plant’s overall health, soil conditions, and nutrient levels.

Question 91

An old man is likely to be long-sighted because of changes

Answer 91

in the eye associated with aging. As people age, the lens of the eye becomes less flexible, making it harder to focus on nearby objects. This condition, known as presbyopia, is a type of long-sightedness where close-up vision becomes blurred while distance vision remains relatively unaffected. Presbyopia typically becomes noticeable around middle age and progressively worsens with age.

Question 92

Mineral particles in the soil originate from

Answer 92

Mineral particles in the soil originate from various geological processes that break down rocks and minerals over time. Some of the primary sources of mineral particles in soil include:

1.	Weathering of Rocks: Physical and chemical weathering processes break down rocks into smaller particles over time. Physical weathering includes processes such as freeze-thaw cycles, abrasion by wind or water, and plant root action. Chemical weathering involves reactions that alter the mineral composition of rocks, such as hydration, hydrolysis, oxidation, and dissolution.
2.	Erosion and Transportation: Once rocks are weathered, the resulting mineral particles can be transported by water, wind, ice, or gravity. These processes can move mineral particles over long distances, depositing them in new locations and contributing to the formation of soil.
3.	Volcanic Activity: Volcanic eruptions can release large quantities of volcanic ash and lava, which eventually weather and break down to form mineral-rich soils.
4.	Deposition of Sediments: Sedimentary rocks, such as sandstone and shale, are formed from the deposition and consolidation of sediment particles. Over time, these rocks can weather and contribute mineral particles to the soil.
5.	Organic Matter Decomposition: Organic matter in the soil, such as dead plant and animal remains, also contributes to the formation of mineral particles as it decomposes. This process releases nutrients and minerals stored within organic matter, enriching the soil with essential elements for plant growth.

Overall, the origin of mineral particles in soil is a complex interplay of geological, physical, chemical, and biological processes that occur over long periods of time.