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3.1.1 Explain why shark fossils that have been discovered are limited to denticles and teeth - NSC Marine Sciences - Question 3 - 2022 - Paper 2
Question 3
3.1.1 Explain why shark fossils that have been discovered are limited to denticles and teeth. 3.1.2 Turtles and snakes are examples of organisms that returned to th... show full transcript
Worked Solution & Example Answer:3.1.1 Explain why shark fossils that have been discovered are limited to denticles and teeth - NSC Marine Sciences - Question 3 - 2022 - Paper 2
Step 1
Explain why shark fossils that have been discovered are limited to denticles and teeth.
Answer
Shark fossils are primarily limited to teeth and denticles due to their cartilaginous skeletons, which do not preserve well over time. Unlike bone, cartilage is less durable and more likely to decompose, leading to a scarcity of fossilized remains. The robust nature of shark teeth, which are made of harder calcium compounds, aids in their preservation, making them the most frequent fossil finds.
Step 2
State possible reasons why these organisms returned to the ocean.
Answer
- Competition for food or space on land may have led some terrestrial vertebrates to migrate back to aquatic environments in search of abundant resources.
- To avoid terrestrial predators, returning to the ocean offered a refuge where they could thrive.
Step 3
Discuss which limitations these organisms overcame as they returned to the marine environment.
Answer
- Locomotion: Limbs that were used for walking required modification for swimming, leading to adaptations such as the development of paddle-like structures.
- Gaseous exchange: These organisms evolved mechanisms for efficient gas exchange to utilize oxygen effectively underwater.
- Osmoregulation: They had to address challenges related to maintaining proper hydration levels in a saline environment.
Step 4
Differentiate between the reproductive processes in amphibians and reptiles.
Answer
Amphibians typically exhibit external fertilization, laying eggs in water, which are soft and susceptible to environmental stressors. Their young undergo metamorphosis as they develop. In contrast, reptiles engage in internal fertilization, laying eggs with a hard, calcareous shell to protect against desiccation, thus allowing them to reproduce on land. This difference represents a significant evolutionary adaptation as reptiles have become less reliant on aquatic environments for reproduction.