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Difficulty: MediumBiomes and Aquatic/Terrestrial Habitats

An ecological study of aquatic habitats in West Africa compares the physical conditions and organismal adaptations between lotic (swiftly flowing streams) and lentic (standing water bodies like ponds) environments. Which of the following structural adaptations is specifically characteristic of benthic invertebrates inhabiting lotic freshwater environments to survive strong currents?

  1. Dorsoventrally flattened body shapes and muscular ventral suction discsAnswer
  2. B
    Expanded internal gas bladders to maximize hydrostatic buoyancy
  3. C
    Pneumatophores with prominent lenticels for atmospheric gas exchange
  4. D
    Feathery external appendages designed primarily to trap airborne pollen grains

Answer

Dorsoventrally flattened body shapes and muscular ventral suction discs
Inhabitants of lotic (fast-running water) habitats face constant hydrodynamic drag. Flattened body profiles minimize surface area exposed to flowing water by keeping the organism low within the slow-moving boundary layer along rock surfaces, while ventral suckers or hooks provide firm attachment.

Step-by-Step Solution

1
Identify the primary physical stressor in lotic freshwater habitats
Lotic habitats (running waters such as streams and rivers) are defined by continuous, unidirectional water movement and strong hydrodynamic shear forces.
Organisms living in lotic environments must overcome the mechanical threat of being dislodged and swept downstream.
2
Evaluate morphological adaptations suited to overcome stream velocity
Dorsoventral flattening keeps the organism within the boundary layer near substrate surfaces, and adhesive suction mechanisms provide secure mechanical attachment.
These physical features directly counteract drag forces exerted by flowing water.

Key Concept

Structural Adaptations to Lotic Aquatic Habitats
Estimated Time:1m 0s
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Topics

Biomes and Aquatic/Terrestrial Habitats

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