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2025 JAMB Biology Mock questions and answers
1. Response to gravity by plants is?
A. Phototropism
B. Geotropism
C. Chemotropism
D. Hydrotropism
- Correct Answer: B. Geotropism
- Explanation: Plants need to know which way is up and which way is down! Roots need to grow down into the soil for water and anchorage, while shoots need to grow up towards the sunlight. This directional growth in response to gravity is called Geotropism (sometimes called Gravitropism). “Geo” refers to the Earth or ground.
- Phototropism is response to light.
- Chemotropism is response to chemicals.
- Hydrotropism is response to water.
- Biology Topic: Plant Responses / Plant Hormones / Tropisms
2. An excretory product of plant used in the production of medicine for malaria treatment?
A. Tanin
B. Alkaloid
C. Gum
D. Mucilage
- Correct Answer: B. Alkaloid
- Explanation: Plants produce various chemical compounds, some of which are considered waste or “excretory” products, while others serve protective roles. Alkaloids are a large group of naturally occurring chemical compounds containing nitrogen. Many have potent pharmacological effects. A famous example is Quinine, an alkaloid extracted from the bark of the Cinchona tree, which was historically the primary treatment for malaria. Tannins, gums, and mucilages are other types of plant products, but alkaloids are the category containing quinine.
- Biology Topic: Plant Physiology / Plant Excretion / Secondary Metabolites / Economic Botany
3. The method of vegetative propagation in Cocoa and Kolanut is?
A. Grafting
B. Layering
C. Budding
D. Cutting
- Correct Answer: C. Budding
- Explanation: Vegetative propagation means creating new plants from parts of a parent plant (like stems, leaves, or buds), essentially cloning it. This ensures the new plant has the same desirable characteristics as the parent. For valuable crops like Cocoa and Kolanut, maintaining specific traits (like high yield or disease resistance) is crucial. Budding is a common and effective technique where a bud from the desired parent plant is inserted onto the stem (rootstock) of another plant. While other methods might be possible, budding is a widely practiced and commercially important method for these specific crops.
- Biology Topic: Plant Reproduction / Vegetative Propagation / Horticulture / Agriculture
4. The depletion of ozone layer causes?
A. Soil erosion
B. Skin cancer
C. Flooding
D. Earthquake
- Correct Answer: B. Skin cancer
- Explanation: The ozone layer is like Earth’s natural sunscreen, located high up in the atmosphere. It filters out most of the harmful ultraviolet (UV) radiation from the sun. When the ozone layer gets thinner (“depleted”), more UV radiation reaches the Earth’s surface. Overexposure to UV radiation can damage the DNA in our skin cells, significantly increasing the risk of developing skin cancer. The other options (soil erosion, flooding, earthquake) are serious environmental issues but are not directly caused by ozone layer depletion.
- Biology Topic: Ecology / Environmental Science / Human Impact on the Environment
5. The type of placentation that is common in succulent fruit is?
A. Parietal
B. Marginal
C. Axile
D. Free-central
- Correct Answer: C. Axile
- Explanation: Placentation refers to how the ovules (which become seeds) are attached inside the ovary (which becomes the fruit). In many common succulent fruits, like tomatoes or oranges, the ovary is divided into multiple chambers (locules). The ovules are attached to the central axis where the partitions (septa) meet. This arrangement is called Axile placentation. Think of slicing a tomato or orange horizontally – you’ll see the seeds attached towards the center in distinct sections.
- Parietal: Ovules attached to the inner wall of the ovary.
- Marginal: Ovules attached along one edge (like peas in a pod).
- Free-central: Ovules attached to a central column, but without partitions.
- Biology Topic: Plant Anatomy / Botany / Angiosperm Reproduction / Fruit Morphology
6. The shape of a normal Red blood cell is?
A. Biconcave
B. Sickle
C. Amoeboid
D. Convex
- Correct Answer: A. Biconcave
- Explanation: Normal red blood cells (RBCs or erythrocytes) have a unique shape: they are Biconcave discs. Imagine a donut, but instead of a hole, the center is thinner and indented on both sides. This shape is brilliant because it increases the surface area for oxygen exchange and allows the cell to be flexible, squeezing through tiny blood capillaries.
- Sickle shape is characteristic of sickle cell anemia, a genetic disorder.
- Amoeboid (irregular, changing shape) is typical of white blood cells.
- Convex means curving outwards.
- Biology Topic: Animal Physiology / Circulatory System / Blood Components / Cell Biology
7. Decolorization of leaves is used for which test?
A. Protein test
B. Fat test
C. Vitamin C test
D. Starch test
- Correct Answer: D. Starch test
- Explanation: When testing a leaf for the presence of starch (which indicates photosynthesis has occurred), we typically use iodine solution. Iodine turns blue-black or purple in the presence of starch. However, the green chlorophyll pigment in the leaf can mask this color change. Therefore, a crucial step in the experiment is to first remove the chlorophyll. This is usually done by boiling the leaf in ethanol (alcohol), which dissolves the chlorophyll and decolorizes the leaf, making the results of the iodine test clearly visible.
- Biology Topic: Plant Physiology / Photosynthesis / Biological Molecules / Experimental Biology
8. The fin beside the gills in a fish is called?
A. Dorsal fin
B. Pectoral fin
C. Anal fin
D. Caudal fin
- Correct Answer: B. Pectoral fin
- Explanation: Fish have several types of fins used for movement, steering, and stability. The fins located on each side of the fish, typically just behind the gill covers, are the Pectoral fins. Think of them as being roughly in the position of arms or forelimbs on other vertebrates.
- Dorsal fin is on the back.
- Anal fin is on the underside, behind the anus.
- Caudal fin is the tail fin.
- Biology Topic: Animal Anatomy / Zoology / Ichthyology (Study of Fish)
9. Which is an advantage of monocropping?
A. Increased soil fertility
B. Simplicity in farming operations
C. Pest resistance
D. Diversity in produce
- Correct Answer: B. Simplicity in farming operations
- Explanation: Monocropping means growing large fields of a single crop species year after year. While it has significant disadvantages (like depleting specific soil nutrients and making crops vulnerable to pests), its main advantage is simplicity in farming operations. Planting, managing (fertilizing, pest control), and harvesting are much easier and more efficient, especially with mechanization (using large machines), when dealing with just one type of crop over a large area.
- Biology Topic: Agriculture / Ecology / Agronomy
10. Sudan savannah can be located in which states? (Assuming context is Nigeria based on state names)
A. Lagos and Ogun
B. Borno and Yobe
C. Delta and Edo
D. Bayelsa and Rivers
- Correct Answer: B. Borno and Yobe
- Explanation: Biomes are large ecological areas defined by their climate and dominant vegetation. The Sudan savannah is a tropical grassland biome with scattered trees, found across a belt in Africa south of the drier Sahel and north of the wetter Guinea savannah/forest region. In Nigeria, this biome stretches across the northern parts of the country. Borno and Yobe are states located firmly within this northern, Sudan savannah ecological zone.
- Lagos/Ogun are in the Southwest (Coastal/Forest/Derived Savanna).
- Delta/Edo/Bayelsa/Rivers are in the South-South/Niger Delta region (Swamp Forest/Rainforest).
- Biology Topic: Ecology / Biomes / Biogeography / Environmental Science
11. What type of vegetation is Kolanut?
- A. Forest
- B. Grassland
- C. Desert
- D. Montane
Topic: Plant Ecology / Biomes
Correct Answer: A. Forest
Explanation:
Kolanut trees (Cola acuminata and Cola nitida) are native to Africa and thrive in warm, humid environments with plenty of rainfall and shade. These conditions are characteristic of tropical rainforests. Grasslands are too open and often drier, deserts are far too dry, and montane (mountain) regions usually have different temperature and vegetation patterns. So, kolanut is a forest vegetation type.
12. Which of these has one body opening?
- A. Hydra
- B. Amoeba
- C. Euglena
- D. Paramecium
Topic: Animal Diversity / Invertebrate Zoology / Basic Physiology
Correct Answer: A. Hydra
Explanation:
Think of Hydra (a tiny freshwater relative of jellyfish and corals) as a simple sac. It has one opening that serves as both a mouth (to take in food) and an anus (to expel waste). This is called a “blind sac” or incomplete digestive system. Amoeba, Euglena, and Paramecium are single-celled organisms (protists). While they take in food and expel waste, they do so through processes like phagocytosis/exocytosis or specialized pores (like the cytoproct in Paramecium), not a single, distinct mouth/anus opening like Hydra.
13. The study of natural community is?
- A. Ecology
- B. Synecology
- C. Autecology
- D. Gynecology
Topic: Ecology (Branches of Ecology)
Correct Answer: B. Synecology
Explanation:
- Ecology is the broad study of interactions between organisms and their environment.
- Synecology specifically focuses on the study of groups of organisms, i.e., communities (populations of different species interacting in an area).
- Autecology focuses on the study of a single species and its relationship with the environment.
- Gynecology is a branch of medicine dealing with the female reproductive system (completely unrelated!).
Since the question asks about the study of a natural community (multiple species interacting), Synecology is the most precise answer.
14. The ability to taste PTC is an example of which variation?
- A. Quantitative
- B. Qualitative
- C. Discontinuous
- D. Continuous
Topic: Genetics / Human Genetics / Variation
Correct Answer: C. Discontinuous (Often linked with B. Qualitative)
Explanation:
The ability to taste Phenylthiocarbamide (PTC) is a classic example of a trait where individuals fall into distinct categories: you either can taste it (taster) or you cannot (non-taster). There isn’t really an “in-between” spectrum of tasting ability controlled by this specific gene.
- Discontinuous (or Qualitative) variation involves traits that fall into clear-cut categories (e.g., blood groups A, B, AB, O; tasting PTC).
- Continuous (or Quantitative) variation involves traits that show a range or spectrum of phenotypes (e.g., height, weight, skin color) often influenced by multiple genes and the environment.
While “Qualitative” describes the nature of the trait (a quality you have or don’t), “Discontinuous” describes the pattern of variation (distinct groups). In many contexts, they are used interchangeably for such traits. Discontinuous is often preferred when contrasting with continuous variation.
15. An example of sex-linked trait is?
- A. Skin color
- B. Colour blindness
- C. Height
- D. Body shape
Topic: Genetics / Human Genetics / Sex-Linked Inheritance
Correct Answer: B. Colour blindness
Explanation:
Sex-linked traits are traits whose genes are located on the sex chromosomes (X or Y). Red-green colour blindness is a classic example of an X-linked recessive trait. This means the gene responsible is on the X chromosome. Because males have only one X chromosome (XY), they are more likely to express recessive X-linked traits than females (XX). Skin color, height, and body shape are complex traits influenced by many genes (polygenic) located on autosomes (non-sex chromosomes) and environmental factors.
16. Secondary thickening occurs in?
- A. Monocot stem
- B. Dicot root
- C. Monocot root
- D. Dicot stem
Topic: Plant Anatomy / Plant Growth
Correct Answer: D. Dicot stem (and B. Dicot root)
Explanation:
Secondary thickening (or secondary growth) is the process that increases the girth or diameter of stems and roots, primarily through the activity of the vascular cambium (producing secondary xylem and phloem) and cork cambium (producing bark). This process is characteristic of dicots (like trees and shrubs) and gymnosperms. Monocots (like grasses, corn, palms) generally lack the vascular cambium needed for significant secondary thickening in their stems and roots. Both dicot stems and dicot roots typically undergo secondary growth. Given the options, Dicot stem is a primary site. (Note: Dicot roots also undergo secondary thickening, so option B is also technically correct, but secondary thickening is often more pronounced and commonly discussed in dicot stems). If only one answer is allowed, Dicot stem is a very strong candidate.
17. Protein is synthesized in?
- A. Cytoplasm
- B. Ribosome
- C. Mitochondrion
- D. Nucleus
Topic: Cell Biology / Molecular Biology
Correct Answer: B. Ribosome
Explanation:
Ribosomes are the molecular machines within the cell responsible for protein synthesis (also called translation). They read the instructions carried by messenger RNA (mRNA) from the nucleus and assemble amino acids into protein chains. While ribosomes are found in the cytoplasm (and on the rough endoplasmic reticulum, which is also in the cytoplasm), the ribosome itself is the specific site of synthesis. Mitochondria are for energy production (ATP synthesis), and the Nucleus contains the DNA and is where transcription (making mRNA) occurs, but not protein synthesis itself.
18. The community that persists for a long time is?
- A. Climax community
- B. Pioneer community
- C. Temporary community
- D. Neutral community
Topic: Ecology / Ecological Succession
Correct Answer: A. Climax community
Explanation:
Ecological succession is the process of change in the species structure of an ecological community over time.
- Pioneer communities are the first species to colonize a barren area (like lichens on bare rock). They are usually simple and don’t last long.
- Temporary communities are stages along the way.
- A Climax community is the final, relatively stable stage of succession for a particular environment. It’s mature, self-sustaining, and resists change, persisting for a long time unless disturbed.
- “Neutral community” isn’t a standard term in this context.
19. The ability of an organism to survive in an environment is?
- A. Adaptation
- B. Competition
- C. Colonization
- D. Speciation
Topic: Ecology / Evolution
Correct Answer: A. Adaptation
Explanation:
Adaptation refers to the traits (structural, physiological, or behavioral) that increase an organism’s ability to survive and reproduce in its specific environment. Competition is the struggle between organisms for limited resources. Colonization is the process of establishing in a new area. Speciation is the evolutionary process by which new species arise. The core ability to survive relies on having the right adaptations.
20. Net result of natality and mortality gives?
- A. Emigration
- B. Population density
- C. Immigration
- D. Growth rate
Topic: Population Ecology / Population Dynamics
Correct Answer: D. Growth rate (specifically, the natural rate of increase)
Explanation:
- Natality is the birth rate (number of new individuals produced).
- Mortality is the death rate (number of individuals dying).
The difference between natality and mortality (Natality – Mortality) gives the natural rate of population increase or decrease. This is a key component of the overall population growth rate. - Emigration (moving out) and Immigration (moving in) also affect population size, but the question specifically asks about the net result of births and deaths.
- Population density is the number of individuals per unit area.
21. A short, sharp and curved beak is an adaptation for?
- A. Sucking nectar
- B. Tearing flesh
- C. Crushing seeds
- D. Pecking wood
Topic: Animal Adaptations / Ornithology (Study of Birds)
Correct Answer: B. Tearing flesh
Explanation:
Think of birds of prey like eagles, hawks, or owls. They have strong, short, sharp, hooked (curved) beaks. This shape is perfectly adapted for tearing flesh from their prey.
- Nectar feeders (like hummingbirds) usually have long, thin beaks.
- Seed crushers (like finches or grosbeaks) often have short, thick, conical beaks.
- Woodpeckers have strong, chisel-like beaks for pecking wood.
22. The filtrated blood leaving the kidney by the renal vein is?
- A. Oxygenated
- B. Deoxygenated
- C. Filtered and waste-free
- D. Contaminated
Topic: Human Physiology / Excretory System / Circulatory System
Correct Answer: B. Deoxygenated (and C. Filtered and waste-free – relative term)
Explanation:
This question has potentially two correct aspects, but let’s break it down:
- Oxygenation: Blood enters the kidney via the renal artery (oxygenated) to be filtered. The kidney cells use up oxygen for their metabolic processes. Therefore, the blood leaving the kidney via the renal vein is deoxygenated.
- Filtration: The primary job of the kidney is to filter waste products (like urea) from the blood. So, the blood leaving the renal vein has been filtered and should have significantly less waste than the blood that entered – making it relatively “waste-free” compared to the arterial blood.
However, standard circulatory knowledge emphasizes that veins carry deoxygenated blood back towards the heart (except pulmonary veins). The filtration aspect describes the kidney’s function. In many test contexts focusing on circulation, Deoxygenated (B) is the expected answer regarding blood state in a systemic vein. Option C describes the result of kidney function on blood composition (cleanliness), not its gas content.
Self-correction: While C is true regarding waste, B is fundamentally true about the oxygen state of blood in any systemic vein after passing through an organ.
(Question 23 is missing)
24. The sense organ for balancing is?
- A. Eyes
- B. Ear
- C. Nose
- D. Tongue
Topic: Human Physiology / Sensory Organs / Nervous System
Correct Answer: B. Ear
Explanation:
While eyes provide visual cues that help with balance, the primary sense organ dedicated to detecting motion, orientation, and balance (equilibrium) is located in the inner ear. Structures like the semicircular canals (detecting rotational movement) and the otolith organs (utricle and saccule, detecting linear acceleration and gravity) are crucial for our sense of balance. The nose is for smell, and the tongue is for taste.
25. Lamarck’s theory is a theory of?
- A. Survival of the fittest
- B. Use and disuse
- C. Mutation
- D. Natural selection
Topic: Evolution / History of Evolutionary Thought
Correct Answer: B. Use and disuse
Explanation:
Jean-Baptiste Lamarck proposed one of the early theories of evolution. Its main ideas were:
- The Principle of Use and Disuse: Body parts used frequently become stronger and larger, while unused parts deteriorate. (e.g., a giraffe stretching its neck makes it longer).
- The Inheritance of Acquired Characteristics: Traits acquired during an organism’s lifetime could be passed on to its offspring. (e.g., the giraffe passes its longer neck to its babies).
While influential, Lamarck’s theory (especially the inheritance of acquired traits) has been largely superseded by Darwin’s theory. “Survival of the fittest” and “Natural selection” are key concepts in Darwin’s theory. “Mutation” is the source of new genetic variation, understood much later.
26. The phenotypic ratio of F2 generation from a cross between TT RR and tt rr is?
- A. 9:6:3:1
- B. 9:3:1:3
- C. 9:3:3:1
- D. 9:1:3:3
Topic: Genetics / Mendelian Genetics / Dihybrid Cross
Correct Answer: C. 9:3:3:1
Explanation:
This describes a classic dihybrid cross involving two traits, assuming independent assortment and simple dominance (T = tall, t = short; R = round, r = wrinkled, for example).
- Parental (P): TT RR (Tall, Round) x tt rr (short, wrinkled)
- F1 Generation: All offspring are Tt Rr (Tall, Round – heterozygous for both traits).
- F2 Generation (crossing F1 x F1: Tt Rr x Tt Rr): When you work out the Punnett square for this cross, you get four possible phenotypes (observable traits) in the following ratio:
- 9/16 will show both dominant traits (Tall, Round – T_ R_)
- 3/16 will show the first dominant and second recessive (Tall, wrinkled – T_ rr)
- 3/16 will show the first recessive and second dominant (short, Round – tt R_)
- 1/16 will show both recessive traits (short, wrinkled – tt rr)
Thus, the standard phenotypic ratio for a dihybrid cross of this type is 9:3:3:1.
27. The incisors in rabbit are used for?
- A. Gnawing
- B. Chewing
- C. Breaking
- D. Tearing
Topic: Animal Anatomy / Mammalogy / Feeding Adaptations
Correct Answer: A. Gnawing
Explanation:
Rabbits, like rodents, have prominent incisor teeth at the front of their mouths that grow continuously. These teeth are adapted specifically for gnawing on vegetation – biting off pieces of plant material. Chewing (grinding) is done primarily by the molars and premolars further back in the mouth. Tearing is more associated with canines (which rabbits lack) or sharp beaks, and breaking might be done by molars or incisors depending on the food. For rabbits, the primary function of incisors is gnawing.
28. Pitcher plant is an example of?
- A. Carnivore
- B. Omnivore
- C. Herbivore
- D. Insectivorous
Topic: Plant Biology / Specialized Nutrition in Plants / Ecology
Correct Answer: D. Insectivorous (a type of Carnivore)
Explanation:
Pitcher plants are fascinating plants that typically grow in nutrient-poor soils (especially low in nitrogen). They have evolved modified leaves that form pitfall traps (pitchers) containing digestive fluids. Insects are attracted to the pitchers, fall in, drown, and are digested by the plant to obtain nutrients.
- Insectivorous means insect-eating.
- Carnivorous means meat-eating (in plants, this usually means trapping and digesting small animals, mostly insects).
While “Carnivore” (A) is technically correct as insects are animals, Insectivorous (D) is more specific and commonly used for plants like pitcher plants, Venus flytraps, and sundews. Given the options, Insectivorous is the best fit.
29. Animals obtain Carbon by?
- A. Absorbing carbon dioxide
- B. Releasing oxygen
- C. Atmosphere
- D. Eating plants
Topic: Ecology / Biogeochemical Cycles (Carbon Cycle) / Nutrition
Correct Answer: D. Eating plants (or other animals)
Explanation:
The carbon cycle describes how carbon moves through the environment.
- Plants are producers: They take carbon dioxide (CO2) from the atmosphere and use photosynthesis to convert it into organic carbon compounds (sugars, starches, cellulose, etc.).
- Animals are consumers: They cannot absorb CO2 directly from the atmosphere for nutrition. They obtain the carbon they need for their bodies by eating plants (herbivores) or by eating other animals that ate plants (carnivores/omnivores).
Releasing oxygen (B) is a byproduct of photosynthesis. Absorbing CO2 (A) is what plants do. While carbon exists in the atmosphere (C), animals don’t directly absorb it for building their bodies.
30. The joint that allows movement in all directions?
- A. Pivot joint
- B. Hinge joint
- C. Sliding joint
- D. Ball and socket joint
Topic: Human Anatomy / Skeletal System / Joints
Correct Answer: D. Ball and socket joint
Explanation:
Different types of synovial joints allow different ranges of motion:
- Hinge joint (like elbow, knee): Allows movement in one plane (flexion/extension).
- Pivot joint (like between the first two vertebrae in the neck): Allows rotation around an axis.
- Sliding (or Plane) joint (like between carpal bones in the wrist): Allows limited gliding movements.
- Ball and socket joint (like shoulder, hip): Features a rounded head (ball) fitting into a cup-like depression (socket). This structure allows the greatest range of motion, including movement in all directions (flexion, extension, abduction, adduction, rotation, circumduction).
31. Which of the following is used to lubricate joints?
- A. Synovial membrane
- B. Ligaments
- C. Synovial fluid
- D. Tendons
Topic: Human Anatomy / Skeletal System / Joints
Correct Answer: C. Synovial fluid
Explanation:
Within freely movable joints (synovial joints):
- The Synovial membrane (A) lines the joint capsule and produces the synovial fluid.
- Ligaments (B) are tough connective tissues that connect bone to bone, providing stability.
- Synovial fluid (C) is a viscous fluid that fills the joint cavity. Its main functions are to lubricate the joint (reducing friction between cartilages) and nourish the articular cartilage.
- Tendons (D) are tough connective tissues that connect muscle to bone.
Therefore, the substance that directly lubricates the joint is the synovial fluid.
32. Reduction of chromosome number to haploid in meiosis occurs in?
- A. Sex cells
- B. Somatic cells
- C. Zygote
- D. Genes
Topic: Cell Biology / Genetics / Cell Division (Meiosis)
Correct Answer: A. Sex cells (or germline cells that produce them)
Explanation:
Meiosis is a special type of cell division that reduces the chromosome number by half, creating four haploid cells (n) from one diploid cell (2n). This process occurs in the germline cells within the reproductive organs (testes and ovaries in animals) specifically to produce gametes (sex cells – sperm and eggs).
- Somatic cells (B) are regular body cells; they divide by mitosis, maintaining the diploid number.
- A Zygote (C) is the diploid cell formed by the fusion of two haploid gametes (fertilization); it divides by mitosis to grow.
- Genes (D) are segments of DNA, not cells where division occurs.
The reduction to haploid happens during the formation of sex cells through meiosis.
33. Which of the following increases competition?
- A. Emigration
- B. Intense predators
- C. Immigration
- D. Mortality
Topic: Population Ecology / Community Ecology
Correct Answer: C. Immigration
Explanation:
Competition occurs when organisms require the same limited resources (food, water, space, mates). Factors affecting population size influence competition intensity:
- Emigration (A) is individuals leaving the population, which would decrease density and potentially competition.
- Intense predators (B) would reduce the prey population size, likely decreasing competition among the prey.
- Immigration (C) is individuals entering the population. This increases the population size and density, leading to more individuals needing the same resources, thus increasing competition.
- Mortality (D) is the death rate, which decreases population size and would likely decrease competition.
34. Nitrifying bacteria convert?
- A. Ammonium salts to nitrates
- B. Atmospheric nitrogen to nitrate
- C. Nitrogen to nitrite
- D. Nitrate to ammonia
Topic: Ecology / Biogeochemical Cycles (Nitrogen Cycle) / Microbiology
Correct Answer: A. Ammonium salts to nitrates (in a two-step process)
Explanation:
Nitrification is a crucial step in the nitrogen cycle where ammonia (NH3) or ammonium ions (NH4+, formed from ammonia in water/soil, often referred to as ammonium salts) are converted into nitrates (NO3-), which are the form of nitrogen most readily absorbed by plants. This is a two-step process carried out by different groups of nitrifying bacteria:
- Ammonia/Ammonium is oxidized to nitrite (NO2-) (e.g., by Nitrosomonas).
- Nitrite (NO2-) is oxidized to nitrate (NO3-) (e.g., by Nitrobacter).
So, the overall conversion is from ammonium/ammonia to nitrate.
- (B) Converting atmospheric nitrogen (N2) is Nitrogen Fixation.
- (C) Is only the first step of nitrification.
- (D) Converting nitrate back to ammonia or N2 is Denitrification or Ammonification.
35. The function of guard cells in plants is to?
- A. Absorb water
- B. Store food
- C. Regulate stomatal opening
- D. Protect leaf surfaces
Topic: Plant Physiology / Plant Anatomy
Correct Answer: C. Regulate stomatal opening
Explanation:
Stomata (singular: stoma) are tiny pores, usually on the underside of leaves, that allow for gas exchange (CO2 in, O2 out) and transpiration (water vapor release). Each stoma is flanked by two specialized cells called guard cells. These guard cells control the opening and closing of the stomatal pore by changing their shape (turgor pressure). When guard cells swell (become turgid), the pore opens; when they lose water and become flaccid, the pore closes. This regulates gas exchange and water loss. While epidermal cells protect the leaf surface (D), and roots absorb water (A), the specific job of guard cells is controlling the stomata.
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