Name two ecological factors that differentiate marine and freshwater stickleback habitats and influence morphology.

Name two ecological factors that differentiate marine and freshwater stickleback habitats and influence morphology.

• A. Predator communities and dietary resources.
• B. Altitude and soil moisture.
• C. Moon phase and tides.
• D. Pollination patterns.

Answer: (A)

Ecological factors that distinguish marine from freshwater environments drive the kinds of selective pressures that shape stickleback morphology. Predator communities differ between these habitats, so the need for protection varies. In marine settings with a broader and sometimes stronger set of predators, sticklebacks tend to retain more armor and longer spines as defense, and their body shape can reflect adaptations to avoid predation. In many freshwater systems, predator pressure is different—often with fewer large piscivores—leading to reduced armor and shorter spines over generations, a pattern seen in lake populations. Dietary resources also differ between these habitats, influencing feeding-related traits. The types and abundance of prey in marine versus freshwater environments select for different mouth structures and gill raker configurations, shaping how efficiently fish can capture and process their food. Increased or altered demands for processing certain prey types in one habitat versus the other help drive changes in jaw morphology, gill raker length and spacing, and related features. Other options don’t directly capture the main ecological differences that link habitat type to stickleback morphology. Altitude and soil moisture are terrestrial factors; moon phase and tides are not the primary drivers of the enduring morphological divergence seen between these aquatic habitats; pollination patterns are irrelevant to fish morphology.

Ecological factors that distinguish marine from freshwater environments drive the kinds of selective pressures that shape stickleback morphology. Predator communities differ between these habitats, so the need for protection varies. In marine settings with a broader and sometimes stronger set of predators, sticklebacks tend to retain more armor and longer spines as defense, and their body shape can reflect adaptations to avoid predation. In many freshwater systems, predator pressure is different—often with fewer large piscivores—leading to reduced armor and shorter spines over generations, a pattern seen in lake populations.

Dietary resources also differ between these habitats, influencing feeding-related traits. The types and abundance of prey in marine versus freshwater environments select for different mouth structures and gill raker configurations, shaping how efficiently fish can capture and process their food. Increased or altered demands for processing certain prey types in one habitat versus the other help drive changes in jaw morphology, gill raker length and spacing, and related features.

Other options don’t directly capture the main ecological differences that link habitat type to stickleback morphology. Altitude and soil moisture are terrestrial factors; moon phase and tides are not the primary drivers of the enduring morphological divergence seen between these aquatic habitats; pollination patterns are irrelevant to fish morphology.