Desert ecosystem – structure and function MCQs With Answer

Introduction: The desert ecosystem – structure and function MCQs With Answer is a focused study resource for B. Pharm students exploring desert ecology, adaptations, and pharmacognosy links. This topic covers abiotic factors, trophic structure, nutrient cycling, water relations, CAM photosynthesis, soil microbiota, and medicinal desert plants relevant to drug discovery. Understanding energy flow, ecosystem services, and human impacts like desertification helps pharmacy students appreciate bioactive compound sources and conservation. These MCQs emphasize practical concepts such as sampling methods, productivity, and biochemical adaptations that influence plant metabolite production. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the primary abiotic factor defining most desert ecosystems?

• High soil fertility
• Low and unpredictable precipitation
• High species diversity
• Frequent flooding

Correct Answer: Low and unpredictable precipitation

Q2. Which photosynthetic pathway is most commonly associated with water-use efficiency in many desert succulents?

• C3 pathway
• C4 pathway
• CAM (Crassulacean Acid Metabolism)
• Photorespiration

Correct Answer: CAM (Crassulacean Acid Metabolism)

Q3. Which plant adaptation reduces water loss by having thickened, fleshy stems for water storage?

• Deciduous leaves
• Succulence
• Hydrophily
• Epiphytism

Correct Answer: Succulence

Q4. In desert food webs, which trophic level typically has the lowest biomass but high turnover rate?

• Primary producers
• Primary consumers (herbivores)
• Decomposers
• Apex predators

Correct Answer: Primary consumers (herbivores)

Q5. Which soil property in deserts often limits plant growth by reducing water availability?

• High organic matter
• High clay content with good water retention
• Coarse texture with low water-holding capacity
• Neutral pH

Correct Answer: Coarse texture with low water-holding capacity

Q6. Which desert microbial group is key for nitrogen fixation in arid soils?

• Denitrifying archaea
• Free-living cyanobacteria and rhizobia
• Fungal decomposers
• Halophilic viruses

Correct Answer: Free-living cyanobacteria and rhizobia

Q7. Which physiological mechanism helps desert plants maintain cell turgor under drought?

• Reducing osmolyte synthesis
• Active osmotic adjustment via solute accumulation
• Increasing stomatal opening
• Elevating transpiration rates

Correct Answer: Active osmotic adjustment via solute accumulation

Q8. CAM plants open their stomata at night primarily to:

• Increase daytime CO2 uptake
• Avoid nighttime herbivores
• Minimize water loss while fixing CO2 as malate
• Enhance photorespiration

Correct Answer: Minimize water loss while fixing CO2 as malate

Q9. Which secondary metabolite class frequently produced by desert plants has significant pharmacological uses such as laxative effects?

• Anthraquinones
• Polysaccharides
• Chlorophylls
• Silicones

Correct Answer: Anthraquinones

Q10. Which desert plant genus is well-known for mucilaginous gel used in pharmaceuticals and skin products?

• Opuntia
• Aloe
• Prosopis
• Larrea

Correct Answer: Aloe

Q11. Desert biocrusts composed of cyanobacteria, lichens, and mosses primarily contribute to:

• Increasing erosion rates
• Nitrogen fixation and soil stabilization
• Reducing soil organic matter
• Promoting soil salinization

Correct Answer: Nitrogen fixation and soil stabilization

Q12. Which process describes the conversion of organic nitrogen to inorganic forms usable by plants in desert soils?

• Photosynthesis
• Nitrification and mineralization
• Denitrification only
• Volatilization of nitrate

Correct Answer: Nitrification and mineralization

Q13. Xerophytic leaves often have which anatomical feature to reduce transpiration?

• Large, thin lamina
• Thick cuticle and sunken stomata
• Numerous hydathodes
• Highly lobed margins

Correct Answer: Thick cuticle and sunken stomata

Q14. Desertification primarily refers to:

• Conversion of deserts to wetlands
• Land degradation in arid and semi-arid areas from climatic variations and human activities
• Natural expansion of plant communities
• Increase in soil moisture

Correct Answer: Land degradation in arid and semi-arid areas from climatic variations and human activities

Q15. Which index derived from satellite data is commonly used to estimate vegetation greenness in deserts?

• Soil Moisture Index (SMI)
• Normalized Difference Vegetation Index (NDVI)
• Albedo Ratio Index
• Evapotranspiration Quotient

Correct Answer: Normalized Difference Vegetation Index (NDVI)

Q16. In desert ecosystems, primary productivity is often limited by:

• Excess nitrogen
• Light deficiency
• Water availability and nutrient limitation
• High humidity levels

Correct Answer: Water availability and nutrient limitation

Q17. Which sampling method is most appropriate for estimating plant cover across a desert-vegetation gradient?

• Mark-recapture of animals
• Point transect or line intercept transect
• Electrophoresis
• Light trapping

Correct Answer: Point transect or line intercept transect

Q18. Halophytes are plants adapted to which specific desert-related stress?

• Extreme cold
• High salinity in soil or water
• Low irradiance
• High nutrient availability

Correct Answer: High salinity in soil or water

Q19. Which desert animal adaptation helps reduce water loss by concentrating urine?

• Low renal concentrating ability
• Highly efficient kidneys with long loops of Henle
• High sweat gland density
• Thin skin permeable to water

Correct Answer: Highly efficient kidneys with long loops of Henle

Q20. Which ecological term describes the capacity of a desert ecosystem to return to its original state after disturbance?

• Resistance
• Resilience
• Productivity
• Carrying capacity

Correct Answer: Resilience

Q21. Larrea tridentata (creosote bush) is significant in desert pharmacology for producing which bioactive compound?

• Nordihydroguaiaretic acid (NDGA)
• Digitoxin
• Penicillin
• Ephedrine

Correct Answer: Nordihydroguaiaretic acid (NDGA)

Q22. Which factor most directly affects evaporation rates from soil in deserts?

• Soil color only
• Air temperature, wind speed, and vapor pressure deficit
• Presence of large mammals
• Subsurface bedrock type only

Correct Answer: Air temperature, wind speed, and vapor pressure deficit

Q23. Which statement best describes desert food webs compared to mesic ecosystems?

• They have higher primary productivity per unit area
• They are simpler with fewer trophic links and greater reliance on episodic productivity
• They contain more aquatic food chains
• They have no decomposer activity

Correct Answer: They are simpler with fewer trophic links and greater reliance on episodic productivity

Q24. Reproductive strategies of many desert plants that synchronize germination with rare rainfall events are called:

• Perennial vegetative propagation
• Seed dormancy and rapid opportunistic germination
• Clonal fragmentation
• Viviparity

Correct Answer: Seed dormancy and rapid opportunistic germination

Q25. Which process in deserts is often slower than in wetter ecosystems due to low moisture and temperature extremes?

• Photosynthetic CO2 uptake
• Decomposition and organic matter breakdown
• Soil mineral weathering
• Solar radiation absorption

Correct Answer: Decomposition and organic matter breakdown

Q26. Which plant anatomical change reduces leaf surface area to minimize transpiration in deserts?

• Development of large broad leaves
• Leaf reduction to spines or scales
• Increased chloroplast number per cell
• Formation of aerial roots

Correct Answer: Leaf reduction to spines or scales

Q27. Which measurement would best estimate net primary productivity (NPP) in a desert shrubland study?

• Annual litterfall and biomass increment measurements
• Count of animal species present
• Soil pH measurement only
• Number of rainy days per year

Correct Answer: Annual litterfall and biomass increment measurements

Q28. Ephedra species, found in some desert regions, are pharmacologically important because they contain:

• Alkaloids such as ephedrine
• High concentrations of vitamin C only
• Sterile lipids with no activity
• Only polysaccharides

Correct Answer: Alkaloids such as ephedrine

Q29. Mycorrhizal associations in desert plants primarily enhance which function?

• Seed dispersal
• Water and nutrient uptake from poor soils
• Photosynthetic pigment synthesis
• Leaf abscission

Correct Answer: Water and nutrient uptake from poor soils

Q30. Which factor often leads to increased soil salinity in desert agricultural lands?

• Excessive freshwater flushing
• Irrigation without adequate drainage and high evaporation
• Planting only halophytes
• High annual rainfall

Correct Answer: Irrigation without adequate drainage and high evaporation

Q31. Which ecological service provided by desert ecosystems is directly relevant to pharmaceutical bioprospecting?

• Provision of abundant freshwater
• Source of unique secondary metabolites from endemic plants
• High timber production
• Low potential for novel compounds

Correct Answer: Source of unique secondary metabolites from endemic plants

Q32. Which behavioral adaptation reduces thermal stress in desert animals?

• Diurnal activity at noon
• Nocturnality or crepuscular activity patterns
• Continuous basking in sun
• Breeding during hottest months

Correct Answer: Nocturnality or crepuscular activity patterns

Q33. In arid soils, which component is often low and limits microbial activity and nutrient cycling?

• Soil texture
• Available moisture and organic carbon
• Mineral diversity
• Total nitrogen content above normal levels

Correct Answer: Available moisture and organic carbon

Q34. Which term refers to organisms that obtain energy from chemoautotrophy and can be important in extreme desert niches?

• Photoautotrophs
• Chemoautotrophs such as nitrifying bacteria
• Heterotrophic herbivores only
• Detritivorous mammals

Correct Answer: Chemoautotrophs such as nitrifying bacteria

Q35. Seed banks in desert soils are important because they:

• Promote continuous germination regardless of conditions
• Allow persistence through long dry periods until favorable conditions occur
• Reduce genetic diversity
• Increase soil salinity

Correct Answer: Allow persistence through long dry periods until favorable conditions occur

Q36. Which of the following is a common indicator species of desert disturbance and soil compaction?

• Abundant lichens
• Colonization by invasive annual grasses
• Increase in native perennial shrubs
• Proliferation of biocrusts

Correct Answer: Colonization by invasive annual grasses

Q37. Which mechanism allows some desert plants to reflect excess solar radiation and reduce leaf temperature?

• Dark green glossy leaves
• Light-colored pubescence or reflective hairs
• High stomatal density
• Thin transparent cuticle

Correct Answer: Light-colored pubescence or reflective hairs

Q38. Which desert process increases the spread of salts to the soil surface, worsening salinity?

• Capillary rise of saline groundwater and evaporation at surface
• Deep groundwater recharge by rain
• Frequent leaching by heavy rainfall
• Plant uptake of sodium ions

Correct Answer: Capillary rise of saline groundwater and evaporation at surface

Q39. Which desert-derived compound class is often investigated for anti-inflammatory and antioxidant properties?

• Inorganic salts only
• Polyphenols and flavonoids
• Sugars exclusively
• Simple hydrocarbons with no functional groups

Correct Answer: Polyphenols and flavonoids

Q40. In experimental design for desert ecology studies, replication and randomization are essential to:

• Increase sampling bias
• Control variability and allow statistical inference
• Ensure identical measurements each time
• Guarantee no environmental variation

Correct Answer: Control variability and allow statistical inference

Q41. Which term describes the stable zones of vegetation that persist in deserts despite climatic fluctuations?

• Transient communities
• Refugia
• Ephemeral patches
• Monocultures

Correct Answer: Refugia

Q42. Which physiological trait in desert seeds often ensures longevity until favorable germination conditions occur?

• Thin seed coat that lets water enter easily
• Hard seed coat and physiological dormancy mechanisms
• High microbial colonization
• Immediate germination upon dispersal

Correct Answer: Hard seed coat and physiological dormancy mechanisms

Q43. Which desert restoration practice can help reduce erosion and promote recovery of native vegetation?

• Removing all native shrubs
• Stabilizing soils with native plantings and reducing grazing pressure
• Continuous off-road vehicle use
• Excessive irrigation with saline water

Correct Answer: Stabilizing soils with native plantings and reducing grazing pressure

Q44. Which desert animal group often acts as important seed dispersers promoting plant recruitment?

• Large fish
• Rodents and ants
• Subterranean nematodes
• Marine birds

Correct Answer: Rodents and ants

Q45. Which xerophytic feature allows some desert plants to perform photosynthesis while minimizing water loss from leaves?

• Sunken stomata and CAM or C4 photosynthesis
• High stomatal conductance during midday
• Thin mesophyll and no chloroplasts
• Lack of cuticle

Correct Answer: Sunken stomata and CAM or C4 photosynthesis

Q46. Which human activity accelerates desertification by removing protective vegetation cover?

• Sustainable grazing
• Overgrazing and deforestation
• Controlled restoration planting
• Soil conservation techniques

Correct Answer: Overgrazing and deforestation

Q47. Which property of desert soils can limit pharmaceutical extraction of plant compounds because of strong adsorption?

• High organic carbon binding capacity and clay mineral content
• Absence of any minerals
• Excessive water content
• Neutral pH with no adsorption sites

Correct Answer: High organic carbon binding capacity and clay mineral content

Q48. Which characteristic of desert ecosystems contributes to high potential for novel drug leads?

• Low evolutionary pressure on metabolites
• Unique selection pressures leading to specialized secondary metabolites
• Identical chemistry to temperate plants
• Absence of chemical defenses in plants

Correct Answer: Unique selection pressures leading to specialized secondary metabolites

Q49. Which conservation approach is most effective for protecting medicinal plant diversity in deserts?

• Ex situ conservation only, without habitat protection
• Integrated in situ conservation, habitat protection, and sustainable harvesting
• Unlimited commercial harvesting
• Conversion of habitat to intensive agriculture

Correct Answer: Integrated in situ conservation, habitat protection, and sustainable harvesting

Q50. Which ecological metric would help compare species diversity across different desert sites?

• Simple count of total area only
• Species richness and diversity indices (e.g., Shannon index)
• Only maximum plant height
• Number of rocks per square meter

Correct Answer: Species richness and diversity indices (e.g., Shannon index)

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

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