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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 (bony fish) possess a closed circulatory system characterized by a two-chambered heart, which consists of an atrium and a ventricle. This design allows for efficient circulation, where blood travels from the heart to the gills for oxygenation before reaching the rest of the body.
In contrast, Echinoderms utilize a water-vascular system rather than a traditional circulatory system. This system comprises fluid-filled coelomic chambers and is lined with cilia, which facilitate the circulation of the fluid. While Echinoderms do not have blood, they perform essential functions such as transportation of nutrients and waste removal through this unique system.
Step 2
Discuss osmoregulation and excretion in both organisms.
Answer
Osmoregulation in Osteichthyes is managed primarily by kidneys, which filter waste products from the blood and regulate the balance of electrolytes. Additionally, fish have gills that perform excretory functions by exhaling carbon dioxide and managing ion concentrations.
Echinoderms, lacking specialized excretory organs, rely on their coelomocytes, which are cells capable of engulfing foreign substances. The waste products can diffuse through their body wall into the water-vascular system and be expelled through tube feet or other surfaces. Echinoderms are described as stenohaline, meaning they cannot tolerate significant changes in salinity, which is crucial for their survival in varying aquatic environments.
Step 3
Critique why the Echinoderms numbers were reduced and the fishes were not.
Answer
The decline in Echinoderm populations following the storm can be attributed to their sensitivity to changes in salinity. Heavy rain can dilute the seawater, creating a lower salinity environment that Echinoderms cannot endure, leading to osmotic stress and potential death.
In contrast, Osteichthyes are generally more tolerant of salinity changes due to their adaptive capabilities, including the functionality of kidneys that can manage excess water intake and an ability to migrate or adjust their osmotic pressure. This adaptability allows them to survive in fluctuating conditions that may significantly impact Echinoderms.