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A rocky shore is a dynamic zone - NSC Marine Sciences - Question 5 - 2022 - Paper 2
Question 5
A rocky shore is a dynamic zone. It is ever changing and the organisms living in this area have to be adapted to these environmental changes. During a large storm, ... show full transcript
Worked Solution & Example Answer:A rocky shore is a dynamic zone - NSC Marine Sciences - Question 5 - 2022 - Paper 2
Step 1
Compare the circulatory mechanism in marine Osteichthyes and Echinoderms.
Answer
Marine Osteichthyes, commonly known as bony fish, possess a closed circulatory system, characterized by a two-chambered heart. The heart comprises an atrium, which receives blood from the body, and a ventricle, which pumps the blood to the gills for oxygenation and then to the rest of the body.
In contrast, Echinoderms utilize a water-vascular system that does not rely on blood. This system consists of fluid-filled coelomic chambers and tube feet that facilitate movement and feeding. The cilia within these chambers circulate the fluid, assisting in the transport of substances throughout the organism.
Step 2
Discuss osmoregulation and excretion in both organisms.
Answer
In Osteichthyes, osmoregulation is managed through specialized kidneys that filter waste products from the blood, allowing for the excretion of excess salts and nitrogenous wastes. The gills also play a role in excreting small amounts of waste, contributing to overall osmotic balance.
Conversely, Echinoderms lack specific excretory organs. Their coelomocytes are responsible for engulfing foreign substances and waste, which then pass out of the body via tube feet. These organisms are largely stenohaline, meaning they cannot tolerate significant changes in salinity, leading to difficulties when encountering fresh water.
Step 3
Critique why the Echinoderms numbers were reduced and the fishes were not.
Answer
The reduction in Echinoderm numbers following the storm can be attributed to their sensitivity to changes in salinity. The sudden influx of rainwater likely diluted the salinity of their habitat beyond tolerable levels, causing osmotic stress.
In contrast, Osteichthyes are generally more adaptable to fluctuating water conditions. Their kidneys allow for better regulation of internal osmotic balance, enabling them to survive and thrive even with varying salinity levels. As a result, the fish populations remained stable, while the Echinoderms suffered.