Ecology

227 questions

All types227 Multiple choice105 True / False13 Numeric8 Matching59 Ordering42

Mangrove plants growing in estuarine swamps face low oxygen availability in waterlogged soils. Which of the following morphological adaptations enables these plants to obtain atmospheric air for root respiration?

Specialized breathing roots (pneumatophores) growing upward above the mud

Deeply penetrating taproots for reaching underground water reservoirs

Sunken stomata located exclusively on the upper leaf surfaces

Broad floating leaves with thick waxy cuticles on both sides

Show answer & explanation

Answer: Specialized breathing roots (pneumatophores) growing upward above the mud

Answer

Specialized breathing roots (pneumatophores) growing upward above the mud

Pneumatophores are specialized erect roots produced by mangrove plants (halophytes). Because the muddy soil in estuarine environments is waterlogged and severely depleted of dissolved oxygen, these roots grow upward against gravity into the air. Tiny pores called lenticels on their surfaces allow atmospheric oxygen to diffuse into the root tissues for respiration.

Step-by-Step Solution

Identify the environmental challenge in the stem

Estuarine swamps have waterlogged, anaerobic (oxygen-poor) mud.

Roots require oxygen for cellular respiration to generate energy for nutrient absorption.

Match the organism group and environmental challenge to its specific structural adaptation

Halophytes (mangroves) develop negative geotropic roots called pneumatophores equipped with lenticels.

Pneumatophores extend above the water level into the atmosphere to absorb oxygen directly.

Key Concept

Morphological Adaptations of Halophytes to Anaerobic Soils

Question 42Question →

In an undisturbed grassland ecosystem, free-living aerobic soil bacteria continuously fix atmospheric nitrogen gas into organic compounds without forming symbiotic associations with plant roots. Which of the following bacterial genera is responsible for this process?

Rhizobium

Azotobacter

Nitrosomonas

Pseudomonas

Show answer & explanation

Answer: Azotobacter

Answer

Azotobacter is the free-living aerobic bacterium responsible for nonsymbiotic nitrogen fixation.

Azotobacter is an aerobic, free-living soil bacterium that directly fixes atmospheric nitrogen into soil organic compounds without requiring host plant tissue or root nodule symbiosis.

Step-by-Step Solution

Identify the ecological process described in the stem

Nonsymbiotic (free-living) aerobic atmospheric nitrogen fixation.

The stem specifies that nitrogen fixation occurs in soil bacteria without forming symbiotic host-plant relationships.

Distinguish between the biological roles of the given bacteria in the nitrogen cycle

Azotobacter is a free-living aerobic fixer. Rhizobium is a symbiotic fixer. Nitrosomonas is a nitrifying bacterium. Pseudomonas is a denitrifying bacterium.

Matching each organism to its specific chemical pathway resolves the correct genus.

Key Concept

Biological Nitrogen Fixation and Bacterial Functional Roles

Question 43Question →

Match each soil microorganism involved in the nitrogen cycle with its specific biochemical transformation role.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Nitrosomonas matches conversion of ammonium ions to nitrites; Nitrobacter matches conversion of nitrites to nitrates; Pseudomonas matches conversion of nitrates to gaseous nitrogen gas; Azotobacter matches free-living nitrogen fixation.

Each microorganism carries out a specific metabolic step in the nitrogen cycle: Nitrosomonas converts ammonium to nitrites, Nitrobacter converts nitrites to nitrates, Pseudomonas performs denitrification returning nitrogen gas to the atmosphere, and Azotobacter carries out free-living nitrogen fixation.

Step-by-Step Solution

Identify nitrifying bacteria

Nitrosomonas oxidizes ammonium to nitrite, while Nitrobacter oxidizes nitrite to nitrate.

Nitrification occurs in two distinct aerobic enzymatic stages.

Identify denitrifying bacteria

Pseudomonas reduces soil nitrates to nitrogen gas (

N_2

Denitrification reduces available soil nitrogen under oxygen-depleted soil conditions.

Identify free-living nitrogen-fixing bacteria

Azotobacter fixes atmospheric

N_2

independently without forming root nodules.

Distinguishes nonsymbiotic nitrogen fixers from symbiotic species such as Rhizobium.

Key Concept

Bacterial Roles in the Nitrogen Cycle

Question 44Question →

Match each pollutant or human activity listed on the left with its primary environmental effect on the right.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Sulfur dioxide matches with the formation of acid rain; crude oil spill matches with the smothering of marine life and coastal organisms; chlorofluorocarbons match with the depletion of the stratospheric ozone layer; agricultural fertilizer runoff matches with eutrophication of aquatic bodies.

Sulfur dioxide (

SO_2

) forms acid rain when dissolved in cloud droplets. Crude oil forms a insoluble floating film that smothers aquatic life and coastal birds. Chlorofluorocarbons (CFCs) degrade ozone molecules in the stratosphere. Fertilizer runoff enriches water with nitrates and phosphates, prompting rapid algal growth (eutrophication).

Step-by-Step Solution

Identify the atmospheric reaction of sulfur dioxide (

SO_2

Sulfur dioxide combines with water vapor to form acid rain.

Industrial gaseous emissions of

SO_2

are the primary cause of acid precipitation.

Analyze the physical impact of crude oil on aquatic ecosystems.

Oil forms a thick surface layer blocking light and oxygen, smothering organisms.

Crude oil is less dense than water and insoluble, creating a persistent surface barrier.

Recall the chemical action of chlorofluorocarbons in the upper atmosphere.

CFCs decompose under UV light to produce chlorine atoms that destroy ozone.

CFCs are unreactive in the troposphere but break down ozone in the stratosphere.

Determine the ecological outcome of nutrient-rich runoff entering water bodies.

Excess nutrients trigger excessive algal blooms leading to eutrophication.

Nitrates and phosphates act as limiting nutrients in aquatic systems.

Key Concept

Pollutant Types, Causes, and Primary Ecological Effects

Question 45Question →

Marine teleost fishes maintain osmotic balance in hypertonic seawater by drinking large amounts of water and actively excreting sodium and chloride ions across specialized cells in their gills.

True

False

Show answer & explanation

Answer: True

Answer

The statement is TRUE. Marine teleost fishes inhabit a hypertonic environment, causing continuous osmotic loss of water. To adapt, they drink seawater to replenish water and actively transport excess monovalent ions out of body fluids using specialized chloride cells in the gill epithelia.

The statement accurately captures the dual physiological and behavioral adaptations of marine teleost fishes. Living in a hypertonic environment, they face constant osmotic water loss. They compensate by drinking seawater and using specialized chloride cells in their gills to actively excrete excess monovalent salts.

Step-by-Step Solution

Analyze the osmotic relationship between marine teleost body fluids and seawater.

Marine teleost body fluids are hypoosmotic (lower salt concentration,

\approx 300\text{ mOsm/L}

) relative to hypertonic seawater (

\approx 1000\text{ mOsm/L}

This concentration difference creates a strong osmotic gradient causing passive water loss and passive salt gain across respiratory surfaces.

Evaluate the behavioral adaptation to passive water loss.

The fish drinks large volumes of seawater to absorb water through the intestinal tract.

Drinking seawater compensates for continuous fluid loss to the environment.

Evaluate the physiological mechanism for eliminating absorbed salt load.

Specialized chloride cells (ionocytes) in the gill epithelia actively pump excess sodium (

\text{Na}^+

) and chloride (

\text{Cl}^-

) ions out into the surrounding sea against their concentration gradients.

Active excretion via gills prevents toxic salt accumulation while preserving internal fluid balance.

Key Concept

Hypoosmotic regulation and active ion excretion in marine teleost fishes

Question 46Question →

Desert succulents and submerged aquatic plants experience vastly different environmental pressures regarding water availability and gaseous exchange. Which of the following processes represents a physiological adaptation in desert succulents that minimizes transpirational water loss during carbon fixation?

Fixing carbon dioxide at night into malic acid via Crassulacean Acid Metabolism so stomata remain closed during the day

Absorbing atmospheric water vapor through non-vascular rhizoid structures instead of internal vascular root tissues

Translocating manufactured organic solutes upward through xylem vessels to leaf tissues during peak sunlight hours

Releasing oxygen gas as a byproduct during dark reaction pathways to maintain internal turgor pressure

Show answer & explanation

Answer: Fixing carbon dioxide at night into malic acid via Crassulacean Acid Metabolism so stomata remain closed during the day

Answer

Fixing carbon dioxide at night into malic acid via Crassulacean Acid Metabolism so stomata remain closed during the day

Fixing carbon dioxide at night into malic acid via Crassulacean Acid Metabolism allows desert succulents to open stomata during cooler night hours, significantly reducing transpirational water loss compared to daytime stomatal opening.

Step-by-Step Solution

Identify the primary physiological challenge faced by desert succulents

Desert succulents must fix carbon dioxide for photosynthesis while limiting water loss through transpiration in high daytime temperatures.

Stomatal opening during the day causes severe water loss due to high transpiration rates.

Evaluate the metabolic mechanism of Crassulacean Acid Metabolism (CAM)

CAM plants open stomata at night when temperatures are lower, taking up

CO_2

and storing it as malic acid in vacuole storage, then closing stomata during the day.

This temporal separation of initial carbon fixation and the Calvin cycle conserves significant amounts of water.

Distinguish between physiological adaptations and morphological or non-applicable plant features

CAM is a biochemical/physiological process, distinguishing it from structural features or incorrect tissue mechanisms described in other options.

Rhizoids are non-vascular structures in bryophytes, xylem conducts water (not sugars), and photolysis generates

O_2

in light reactions.

Key Concept

Crassulacean Acid Metabolism (CAM) as a physiological adaptation to arid environments

Estimated Time:1m 30s

Question 47Question →

Which of the following environmental management practices directly aids in conserving forest resources while preserving biodiversity?

Selective logging accompanied by re-afforestation

Uncontrolled bush burning to rapidly release bound nutrients into the soil

Complete land clearing of mature trees to initiate primary succession artificially

Replacing natural forest ecosystems with monoculture crop plantations to optimize trophic energy

Show answer & explanation

Answer: Selective logging accompanied by re-afforestation

Answer

Selective logging accompanied by re-afforestation effectively conserves forest resources by harvesting mature timber sustainably while replanting trees to preserve habitat continuity and biodiversity.

Selective logging coupled with re-afforestation ensures that timber is harvested sustainably without destroying the entire forest canopy. Replanting ensures continuous forest renewal and protects wildlife habitats and soil integrity.

Step-by-Step Solution

Identify the primary goals of forest resource conservation.

Forest conservation aims to maintain ecological balance, protect biodiversity, and ensure sustainable timber yields without destroying wildlife habitats.

Natural resource management balances resource utilization with environmental protection.

Evaluate the effectiveness of selective logging and re-afforestation.

Selective logging harvests only specific mature trees rather than clear-cutting, and re-afforestation replaces harvested trees to maintain forest cover.

This practice minimizes habitat destruction and prevents soil degradation while renewing forest cover.

Key Concept

Forest Conservation and Sustainable Management Practices

Question 48Question →

In ecological studies of environmental degradation, chemical pollutants disrupt ecosystem stability through distinct biochemical, aquatic, and atmospheric mechanisms. Match each environmental pollutant listed on the left with its corresponding primary ecological impact on the right.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Agricultural runoff matches eutrophication and high BOD; Persistent organochlorines (DDT) match trophic biomagnification; Industrial sulphur dioxide and nitrogen oxides match acid rain precipitation and soil nutrient leaching; Stratospheric CFCs match catalytic ozone depletion and increased surface UV-B exposure.

Each pollutant matches its precise ecological degradation mechanism: agricultural nutrient runoff drives aquatic eutrophication and elevated BOD; organochlorine pesticides like DDT undergo trophic biomagnification; industrial sulphur and nitrogen oxides form acid precipitation; and stratospheric CFCs catalyze the breakdown of the ozone layer.

Step-by-Step Solution

Analyze the biochemical impact of inorganic agricultural fertilizer runoff in aquatic environments.

Excess nitrates and phosphates cause eutrophication, leading to algal bloom, high microbial oxygen consumption during decay, and elevated biochemical oxygen demand (BOD).

Identify the primary mechanism of water pollution caused by nutrient enrichment.

Examine the bioaccumulative trajectory of lipophilic pesticides like DDT through food chains.

Because DDT is persistent and non-biodegradable, its concentration amplifies at higher trophic levels (biomagnification).

Trace the movement of non-metabolized organochlorine toxic compounds across trophic layers.

Evaluate the atmospheric interactions of gaseous sulphur dioxide (

\text{SO}_2

) and nitrogen oxides (

\text{NO}_x

These gases form weak acids in rainwater, yielding acid rain which acidifies aquatic systems and leaches soil cations (

\text{Ca}^{2+}

\text{Mg}^{2+}

Relate atmospheric gaseous effluents to precipitation acidity and soil chemistry alterations.

Determine the photochemical reaction of chlorofluorocarbons (CFCs) in the upper atmosphere.

UV photolysis releases chlorine atoms that catalytically destroy ozone (

\text{O}_3

) molecules, depleting the stratospheric ozone layer.

Connect synthetic halogenated hydrocarbons to stratospheric ozone degradation.

Key Concept

Pollution Mechanisms and Ecological Degradation Pathways

Question 49Question →

Ecological succession involves a predictable series of community changes over time. Match each ecological succession stage in List I with its corresponding characteristic feature in List II. Which pairings correctly represent these succession stages and their features?

Click a left item, then click its matching right item

Show answer & explanation

Answer

Primary Succession Pioneer Stage matches with colonization of bare rock by lichens and mosses; Secondary Succession Pioneer Stage matches with rapid emergence of annual weeds on pre-existing soil; Seral Intermediate Stage matches with transitional communities of shrubs modifying soil organic content; and Climax Community Stage matches with stable, self-perpetuating ecosystem with maximum biomass.

The correct pairings accurately reflect ecological succession principles: primary pioneers colonize bare substrates lacking organic soil (lichens/mosses on bare rock), secondary pioneers capitalize on pre-existing soil after disturbance (annual weeds), seral stages represent intermediate transitional vegetation, and the climax community represents the mature, stable terminal state.

Step-by-Step Solution

Differentiate between primary and secondary succession starting substrates.

Primary succession begins on abiotic bare substrates (like lava or bare rock) with lichens, whereas secondary succession starts where soil already exists (like abandoned farmland) with weeds.

Presence or absence of soil determines pioneer species requirements.

Identify transitional versus final stable stages.

Seral stages are temporary intermediate communities modifying the environment, leading up to a mature climax community.

Community structure evolves dynamically until reaching equilibrium.

Key Concept

Distinction between pioneer, seral, and climax stages in primary vs. secondary ecological succession.

Estimated Time:1m 30s

Question 50Question →

Petroleum and natural gas are classified as renewable natural resources because they are naturally formed within the Earth's crust over geological time scales.

True

False

Show answer & explanation

Answer: False

Answer

The statement is false. Petroleum and natural gas are non-renewable resources because they take millions of years to form and exist in finite quantities.

Fossil fuels such as petroleum and natural gas require millions of years to form inside the Earth. Because they are being consumed at a rate drastically higher than their natural rate of formation, they exist in limited supplies and are classified strictly as non-renewable resources.

Step-by-Step Solution

Identify the natural resource types being referenced.

Petroleum and natural gas are fossil fuels formed from decomposed organic matter under high pressure and temperature over millions of years.

Categorizing resources requires understanding their origin and formation timeframe.

Distinguish between renewable and non-renewable natural resources.

Renewable resources (such as solar energy or wind) replenish naturally within a short human timeframe, while non-renewable resources (fossil fuels, minerals) take geological epochs to form and cannot be replenished once depleted.

Evaluating the statement requires applying the standard biological and environmental definitions of resource sustainability.

Key Concept

Distinguishing Renewable from Non-Renewable Natural Resources

Estimated Time:45s

Question 51Question →

After a severe bushfire destroys a tropical forest ecosystem, fast-growing herbaceous plants and grasses quickly colonize the area by utilizing ash nutrients and seeds preserved within the intact soil. Which of the following best explains why this ecological sequence is classified as secondary succession?

The process originates on a pre-existing soil substrate that already contains organic matter and dormant propagules.

The sequence begins on a bare, uncolonized rock surface devoid of organic matter and previous biological activity.

The pioneer colonizers consist of bryophytes that utilize true vascular tissues to rapidly absorb soil nutrients.

The community bypasses all intermediate seral stages to instantly form a stable climax forest.

Show answer & explanation

Answer: The process originates on a pre-existing soil substrate that already contains organic matter and dormant propagules.

Answer

Secondary succession is defined by ecological recolonization that takes place on pre-existing soil containing organic material and dormant seeds following a disturbance.

Secondary succession occurs when a disturbance disrupts an existing ecosystem without eliminating the soil. Because soil, nutrients, and dormant seeds (propagules) remain intact, recolonization proceeds rapidly through pioneer herbs and grasses.

Step-by-Step Solution

Identify the key environmental conditions present after the bushfire disturbance.

The fire destroyed vegetation but left intact soil, nutrients in ash, and dormant seeds.

Determining whether a substrate has pre-existing soil is the fundamental criterion for differentiating succession types.

Distinguish between primary and secondary succession based on substrate characteristics.

Primary succession starts on bare substrate (e.g., bare rock, volcanic lava, sand dunes) with no soil. Secondary succession starts on established soil after partial destruction.

Existing soil allows faster plant establishment and seed germination.

Select the statement that correctly accounts for secondary succession.

The presence of pre-existing soil containing organic matter and propagules defines secondary succession.

This directly aligns with ecological succession definitions.

Key Concept

Distinction between primary and secondary ecological succession based on pre-existing substrate and soil presence.

Estimated Time:1m 0s

Question 52Question →

An estuarine wetland ecosystem in a coastal industrial corridor experiences severe eutrophication due to untreated organic sewage and industrial runoff, leading to a critical decline in dissolved oxygen and widespread fish kills. Which integrated environmental management approach provides the most ecologically sustainable solution to restore the water quality and preserve biodiversity in the wetland?

Implementation of biological wastewater treatment and bioremediation using micro-organisms, combined with enforcing statutory effluent limits on industrial discharge.

Draining the entire wetland basin to completely remove organic matter and allowing primary succession to re-establish the ecological community on bare rock substrate.

Applying persistent chemical oxidants continuously to the entire estuarine basin to artificialize dissolved oxygen levels while ignoring upstream effluent sources.

Constructing aquatic physical barriers to invert the ecosystem's pyramid of energy, thereby reducing energy loss at decomposer trophic levels.

Show answer & explanation

Answer: Implementation of biological wastewater treatment and bioremediation using micro-organisms, combined with enforcing statutory effluent limits on industrial discharge.

Answer

Implementation of biological wastewater treatment and bioremediation using micro-organisms, combined with enforcing statutory effluent limits on industrial discharge.

Combining biological wastewater treatment and bioremediation directly neutralizes excess organic nutrients and pollutants. Enforcing effluent discharge limits prevents continuous influx of contaminants, offering a sustainable, long-term solution for wetland restoration.

Step-by-Step Solution

Identify the primary environmental problem

Eutrophication caused by excess organic nutrients in untreated sewage and industrial effluent.

Excess nutrients trigger algal blooms whose subsequent decomposition consumes dissolved oxygen, leading to hypoxia.

Evaluate sustainable restoration methods

Bioremediation and biological wastewater treatment degrade organic pollutants into harmless inorganic substances.

Biological treatment utilizes decomposers naturally without introducing toxic chemical residues.

Integrate regulatory management controls

Enforcing statutory effluent standards prevents ongoing nutrient input.

Sustainable conservation requires combining biological remediation techniques with legal and institutional enforcement.

Key Concept

Water pollution control and biological environmental management

Question 53Question →

Arrange the following ecological stages of primary succession on bare rock (xerosere) in correct sequential order from the pioneer stage to the climax community. Which sequence accurately reflects this ecological progression?

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct succession sequence begins with pioneer crustose lichens, followed by foliose lichens and mosses, then herbaceous grasses, followed by perennial shrubs, and culminates in a climax forest community.

Primary ecological succession on bare rock (xerosere) follows a predictable sequence of seral stages: crustose lichens pioneer soil formation, followed by foliose lichens and mosses deepening soil, herbaceous grasses colonizing, perennial shrubs establishing, and finally mature climax trees reaching ecological equilibrium.

Step-by-Step Solution

Identify the pioneer stage on bare substrate.

Crustose lichens colonize bare rock first due to their extreme xerophytic tolerance and ability to weather rock chemically.

Primary succession requires pioneer organisms capable of initiating soil formation on subaerial rock surfaces.

Determine the early seral invaders following initial weathering.

Foliose lichens and mosses invade the thin layer of weathered rock particles and organic dust.

Mosses require small amounts of accumulated moisture and organic debris to anchor their rhizoids.

Sequence the emergence of vascular herbaceous species.

Annual herbs and grasses establish as soil depth and humus content increase.

Vascular root systems need sufficient soil volume, which accumulates through the decay of mosses and foliose lichens.

Identify the transition to woody vegetation.

Perennial shrubs displace grasses due to superior light competition and deeper root structures.

Enriched soil supports larger perennial roots, allowing taller shrub canopy growth.

Determine the final equilibrium community.

A mature forest climax community establishes.

Climax trees represent the maximum biomass and biodiversity sustainable under the prevailing climate.

Key Concept

Sequential seral progression in primary lithosere/xerosere ecological succession

Question 54Question →

Match each ecological sampling instrument with its most appropriate application or target organism group during a field study in a Nigerian savanna ecosystem.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Pooter matches Minute insects found on tree bark or foliage collected via suction; Pitfall trap matches Small crawling invertebrates on the soil surface and leaf litter; Quadrat frame matches Sessile or slow-moving organisms such as herbaceous weed plants; Sweep net matches Flying insects residing within tall grass canopy or shrubs.

Each equipment item is designed specifically for an organism's mobility level and habitat position: pooters extract tiny delicate insects via suction, pitfall traps collect ground-surface crawlers falling into sunken containers, quadrats quantify immobile plant species across defined area units, and sweep nets intercept active canopy insects.

Step-by-Step Solution

Identify the primary mechanism and target organism type for each sampling equipment.

Pooter uses suction for minute insects; pitfall trap targets ground crawlers; quadrat measures non-motile plants/animals in sample areas; sweep net catches flying foliage insects.

Different organism mobility, size, and micro-habitat dictate the appropriate ecological sampling tool.

Pair each instrument from the left column with its unique matching description from the right column.

Four correct matches established between instrument and ecological application.

Ensures complete alignment with ecological sampling standards.

Key Concept

Selection and Application of Ecological Sampling Instruments

Question 55Question →

An ecology student investigated the population density of water hyacinth (*Eichhornia crassipes*) in a section of a freshwater creek in Bayelsa State. A quadrat frame measuring $0.5\text{ m} \times 0.5\text{ m}$ was randomly thrown $20$ times across the sampling site. The cumulative count of water hyacinth plants recorded across all $20$ quadrat throws was $150$ . What is the estimated population density of water hyacinth in $\text{plants/m}^2$ ?

7.5\text{ plants/m}^2

15\text{ plants/m}^2

30\text{ plants/m}^2

600\text{ plants/m}^2

Show answer & explanation

Answer: $30\text{ plants/m}^2$

Answer

The population density of water hyacinth is

30\text{ plants/m}^2

To find population density, the total number of organisms observed (

150

) must be divided by the total area sampled. Since one

0.5\text{ m} \times 0.5\text{ m}

quadrat has an area of

0.25\text{ m}^2

, twenty throws cover a total area of

20 \times 0.25\text{ m}^2 = 5.0\text{ m}^2

. Dividing

150

plants by

5.0\text{ m}^2

yields

30\text{ plants/m}^2

Step-by-Step Solution

Calculate the surface area of a single quadrat frame

\text{Area of one quadrat} = 0.5\text{ m} \times 0.5\text{ m} = 0.25\text{ m}^2

Population density must be expressed in units of area, so the quadrat dimensions must first be converted into area.

Calculate the total area sampled across all throws

\text{Total area sampled} = 20 \text{ throws} \times 0.25\text{ m}^2 = 5.0\text{ m}^2

The cumulative plant count represents the total organisms found across the entire combined sampled space.

Calculate the population density per square metre

\text{Population Density} = \frac{\text{Total organism count}}{\text{Total area sampled}} = \frac{150\text{ plants}}{5.0\text{ m}^2} = 30\text{ plants/m}^2

Population density is defined as the total number of individuals of a species per unit area.

Key Concept

Quadrat Population Density Calculation

Estimated Time:1m 30s

Question 56Question →

In ecosystem structure, the specific functional role and behavioral position that an organism occupies within its environment is defined as its

ecological niche

physical habitat

trophic pyramid level

population density

Show answer & explanation

Answer: ecological niche

Answer

The functional role and behavioral position of an organism in its ecosystem is its ecological niche.

The correct answer is ecological niche because it encompasses all activities, interactions, feeding relationships, and environmental responses that define how an organism fits into an ecosystem.

Step-by-Step Solution

Identify the core concept described in the stem.

The stem describes the functional role, activities, and interactions of an organism within its environment.

Basic ecological concepts distinguish between where an organism lives (habitat) and what it does (niche).

Evaluate the option defining functional role.

The term 'ecological niche' specifically describes the full functional role, including feeding habits, microhabitat use, and ecological interactions.

This matches the exact definition of an ecological niche.

Key Concept

Distinction between Ecological Niche and Habitat

Question 57Question →

During a field study of an intertidal mangrove swamp in Cross River State, a student used a $0.5\text{ m} \times 0.5\text{ m}$ quadrat frame to sample the periwinkle (*Tympanotonus fuscatus*) population. Across $10$ randomly placed quadrat throws, a total count of $180$ periwinkles was recorded. What is the estimated population density of *Tympanotonus fuscatus* per square metre in this habitat?

18\text{ periwinkles/m}^2

45\text{ periwinkles/m}^2

72\text{ periwinkles/m}^2

720\text{ periwinkles/m}^2

Show answer & explanation

Answer: $72\text{ periwinkles/m}^2$

Answer

The estimated population density is

72\text{ periwinkles/m}^2

The correct option correctly evaluates population density by calculating the total sampled area (

10 \times 0.25\text{ m}^2 = 2.5\text{ m}^2

) and dividing the total counted organisms (

180

) by that area, yielding

72\text{ periwinkles/m}^2

Step-by-Step Solution

Calculate the area of a single quadrat frame

Area of 1 quadrat =

0.5\text{ m} \times 0.5\text{ m} = 0.25\text{ m}^2

Determines the surface area enclosed by one sampling unit.

Determine the total area sampled across all throws

Total sampled area =

10 \text{ throws} \times 0.25\text{ m}^2 = 2.5\text{ m}^2

Accounts for the cumulative ground area surveyed during the 10 quadrat throws.

Calculate the population density per square metre

Population density =

\frac{\text{Total number of organisms}}{\text{Total sampled area}} = \frac{180}{2.5\text{ m}^2} = 72\text{ periwinkles/m}^2

Population density is expressed as the total number of individuals per unit area.

Key Concept

Quadrat Population Density Calculation

Question 58Question →

Match each Nigerian biome or habitat on the left with its corresponding vegetative characteristic or indicator adaptation on the right.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Tropical Rainforest matches dense multi-layered canopy, buttress roots, and abundant epiphytes; Mangrove Swamp matches respiratory pneumatophores, stilt roots, and high salt tolerance; Southern Guinea Savanna matches tall grasses interspersed with deciduous broad-leaved trees; Sahel Savanna matches sparse vegetation dominated by thorny acacias and short grasses.

Each biome matches its characteristic indicator flora and physical adaptation to local environmental factors such as rainfall, soil aeration, and salinity.

Step-by-Step Solution

Analyze coastal and forested biome structural adaptations.

Mangrove habitats require aeration and anchoring in muddy saline water (pneumatophores and stilt roots), whereas tropical rainforest plants compete for light in dense, multi-layered forest canopies.

Environmental stressors like soil anoxia dictate specialized root modifications in intertidal biomes.

Compare vegetation profiles along the savanna moisture gradient in Nigeria.

Southern Guinea Savanna has higher annual rainfall supporting tall grass and deciduous trees, whereas Sahel Savanna experiences severe dry conditions favoring xerophytic thorny plants.

Precipitation steadily decreases moving northward across West Africa, altering plant morphology and community structure.

Key Concept

Biome Characteristics and Morphological Adaptations

Question 59Question →

An ecological survey of a protected forest reserve recorded four distinct ecological observations:

Observation	Description
I	All individuals of the mahogany tree (Khaya senegalensis) inhabiting a designated $15\text{--hectare}$ plot.
II	The combined populations of green plants, fruit bats, soil fungi, and earthworms interacting within the forest floor layer.
III	The physical soil minerals, ambient humidity, temperature, and solar radiation combined with all living organisms in the reserve.
IV	The specific micro-habitat conditions and nutritional role occupied by the pangolin (Phataginus tricuspis) as an ant-eating nocturnal mammal.

Which of the following correctly matches observations I, II, III, and IV to their corresponding levels of ecological organization and concepts?

I = Population, II = Community, III = Ecosystem, IV = Niche

I = Community, II = Ecosystem, III = Biome, IV = Habitat

I = Population, II = Ecosystem, III = Biosphere, IV = Habitat

I = Species, II = Community, III = Ecosystem, IV = Habitat

Show answer & explanation

Answer: I = Population, II = Community, III = Ecosystem, IV = Niche

Answer

Observation I corresponds to a Population, II to a Community, III to an Ecosystem, and IV to a Niche.

The correct option accurately distinguishes between the hierarchical tiers of ecological organization. A single species group in a defined region represents a population (I); the assembly of all living species forms a community (II); the combined biotic community and abiotic physical factors constitute an ecosystem (III); and the specific functional role and feeding behavior of an organism defines its ecological niche (IV).

Step-by-Step Solution

Analyze Observation I

Observation I describes a group of organisms belonging to the same species (*Khaya senegalensis*) inhabiting a specific geographic area at the same time.

By definition, a group of individuals of one species in a given area constitutes a Population.

Analyze Observation II

Observation II includes plants, animals, fungi, and earthworms (multiple species populations) interacting in one area without specifying non-living physical factors.

An assemblage of different interacting populations of organisms in a given habitat forms a Ecological Community.

Analyze Observation III

Observation III combines both living organisms (biotic factors) and non-living physical/chemical elements (abiotic factors such as soil minerals, humidity, temperature, solar radiation).

A community interacting with its non-living physical environment forms an Ecosystem.

Analyze Observation IV

Observation IV describes the functional position, feeding habits, and specific environmental adaptations of the ant-eating pangolin.

The complete functional role, position, and behavioral lifestyle of an organism within its environment defines its Ecological Niche.

Key Concept

Levels of Ecological Organization and Functional Differentiation

Question 60Question →

Plants growing in the Tropical Rainforest biome face intense competition for light in the dense canopy layer, whereas plants in the Sahel Savanna face extreme water scarcity and high evapotranspiration rates. Which combination of structural adaptations correctly distinguishes tropical rainforest trees from Sahel savanna shrubs?

Broad leaves with drip tips and buttress roots in rainforest plants; reduced needle-like or thorny leaves and deep taproot systems in savanna plants.

Pneumatophores and salt-excreting glands in rainforest plants; succulent stems with broad deciduous leaves in savanna plants.

Deep taproot systems with needle-like leaves in rainforest plants; buttress roots with broad leaves in savanna plants.

Broad leaves with prop roots in rainforest plants; pioneer mosses and lichen crusts lacking vascular tissue in savanna plants.

Show answer & explanation

Answer: Broad leaves with drip tips and buttress roots in rainforest plants; reduced needle-like or thorny leaves and deep taproot systems in savanna plants.

Answer

Broad leaves with drip tips and buttress roots in rainforest plants; reduced needle-like or thorny leaves and deep taproot systems in savanna plants.

Tropical rainforest trees inhabit humid, high-rainfall environments where light is limiting near the forest floor and soils are shallow; thus, they possess broad leaves with drip tips (to prevent leaf rotting and fungal growth) and massive buttress roots for physical support. Conversely, Sahel savanna vegetation faces severe drought and intense evapotranspiration, favoring xerophytic adaptations like reduced leaf surface area (thorns/spines) to minimize water loss and long taproots to draw water from deep subterranean layers.

Step-by-Step Solution

Analyze the environmental constraints of the Tropical Rainforest biome.

High rainfall, high humidity, and dense canopy require structural adaptations such as broad photosynthetic leaves to capture low light under the canopy, drip tips to quickly shed water off leaf surfaces, and tall trunks supported by buttress roots in nutrient-poor shallow soils.

Rainforest plants prioritize light capture, rapid water drainage from leaves, and physical stability.

Analyze the environmental constraints of the Sahel Savanna biome.

Low rainfall, prolonged dry seasons, and high temperatures require xeromorphic adaptations such as reduced leaf surface area (spines/thorns/thickets) to restrict transpiration losses, thick cuticles, and extensive deep taproot systems to access deep groundwater reserves.

Savanna plants prioritize water conservation and deep moisture absorption.

Select the option that correctly contrasts these two distinct biome profiles.

The option specifying broad leaves with drip tips and buttress roots for rainforest plants paired with reduced/thorny leaves and deep taproots for savanna plants is correct.

This accurately reflects the morphological adaptations demanded by the respective abiotic conditions of each biome.

Key Concept

Morphological Adaptations to Terrestrial Biomes

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