Identify sea urchin parts and the average size of the sea urchin's digestive tract, as well as the trend of how larger ones are getting smaller due to genetic drift and otters.

Understand the Problem

The question is asking for information on the anatomical structure of sea urchins, specifically their parts and the size of their digestive tract. It also inquires about the trend of larger sea urchins becoming smaller due to genetic drift and predation from otters, indicating a need for ecological context.

Answer

Sea urchins possess spines, a test, and a digestive system. Larger sea urchins are becoming smaller because of predation and genetic drift.

Sea urchins have various parts including spines, a hard shell called the test, and a complex digestive system. The sea urchin's digestive tract size isn't specifically mentioned, but shifts in urchin size structure are attributed to size-selective predation by sea otters. Larger sea urchins are getting smaller due to predation and genetic drift.

More Information

Sea urchins have spines for protection and locomotion, and their size can be affected by environmental factors as well as predation. Sea otters, being key predators of urchins, select larger urchins, influencing their size distribution over time.

Tips

Avoid assuming that all size changes in sea urchins are solely due to genetic drifts; ecological factors like predators also play a crucial role.

Sources

Accounting for size‐specific predation improves our ability to predict ... - ncbi.nlm.nih.gov
Enhydra lutris (Sea otter) - Society for Marine Mammalogy - marinemammalscience.org

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