In India's Western Ghats, the introduction of invasive species like Lantana camara has led to reduced native plant diversity and altered nutrient cycling. This phenomenon best demonstrates which ecological principle?
AResource partitioning among competing species
BCompetitive exclusion and niche displacement of native species
CFacilitation model of ecological succession
DMutualistic relationships in plant-herbivore interactions
Correct Answer:
B. Competitive exclusion and niche displacement of native species
EXPLANATION
Lantana camara outcompetes native vegetation through superior resource acquisition and allelopathy, leading to competitive exclusion. This reduces niche availability for native species, fundamentally altering community structure and ecosystem functions like nutrient cycling.
Which of the following statements about energy flow in an aquatic ecosystem is correct?
AApproximately 90% of energy is transferred from one trophic level to the next
BPrimary consumers always have greater biomass than secondary consumers
COnly about 10% of energy is available for the next trophic level due to metabolic losses
DDecomposers occupy the highest trophic level and receive maximum energy
Correct Answer:
C. Only about 10% of energy is available for the next trophic level due to metabolic losses
EXPLANATION
The 10% energy transfer rule states that only ~10% of energy is passed to the next trophic level; the remaining 90% is lost through respiration, heat, and excretion. This is fundamental to understanding ecosystem energy dynamics.
A population of deer in a forest reserve shows an increase from 500 to 2000 individuals over 5 years despite constant food availability. Which of the following best explains this population growth pattern?
AExponential growth due to low initial population density and absence of limiting factors
BLogistic growth as the carrying capacity has been reached
DZero population growth due to density-dependent regulation
Correct Answer:
A. Exponential growth due to low initial population density and absence of limiting factors
EXPLANATION
With abundant resources and low initial population density, the deer population exhibits exponential growth (J-shaped curve). The carrying capacity has not yet been reached as numbers are still increasing rapidly without stabilization.
In the context of India's monsoon-dependent ecosystems, which adaptive strategy is most evident in deciduous forest species?
AIncreased leaf surface area for water absorption
BLeaf fall during dry season to conserve water
CDeep root systems throughout the year
DReduced photosynthetic capacity
Correct Answer:
B. Leaf fall during dry season to conserve water
EXPLANATION
Deciduous trees in Indian dry and moist deciduous forests shed leaves during the dry season (March-May) as an adaptation to seasonal water scarcity, reducing transpirational water loss while maintaining survival.
Which succession model proposes that early colonizing species modify the environment to facilitate or inhibit later species establishment?
ATolerance model
BFacilitation model
CInhibition model
DStochastic model
Correct Answer:
B. Facilitation model
EXPLANATION
The facilitation model (Connell & Slatyer) proposes that pioneer species modify environmental conditions to make them more suitable for subsequent species, gradually changing the ecosystem toward climax community.
The concept of ecosystem services refers to the benefits humans obtain from ecosystems. Which of the following is classified as a REGULATING service?
AFood and water provision
BClimate regulation and pollination
CCultural and recreational values
DNutrient cycling regulation
Correct Answer:
B. Climate regulation and pollination
EXPLANATION
Regulating services include processes like climate regulation, pollination, disease control, and water purification that maintain ecosystem functions benefiting humans, distinct from provisioning, cultural, or supporting services.
Which of the following ecological concepts explains why small isolated populations are more vulnerable to extinction?
AMetapopulation dynamics
BGenetic drift and inbreeding depression
CIntermediate disturbance hypothesis
DNiche partitioning
Correct Answer:
B. Genetic drift and inbreeding depression
EXPLANATION
Small, isolated populations experience increased genetic drift, loss of genetic diversity, and inbreeding depression, reducing fitness and adaptive capacity, making them highly vulnerable to extinction from random events.
Which of the following would represent a density-independent limiting factor in an ecosystem?
AIntraspecific competition for resources
BTerritorial behavior
CSevere drought or natural disaster
DDisease prevalence increasing with population density
Correct Answer:
C. Severe drought or natural disaster
EXPLANATION
Density-independent factors (like weather, drought, floods) affect populations regardless of their density, whereas disease and competition are density-dependent as their impact increases with higher population density.
Which of the following is NOT a characteristic of r-selected species?
ASmall body size
BHigh reproductive rate
CLong parental care period
DEarly sexual maturity
Correct Answer:
C. Long parental care period
EXPLANATION
r-selected species (like insects and small rodents) typically produce many offspring with minimal parental investment and care. K-selected species (like elephants and humans) show extended parental care.
