Ichthyosaurs Were Aquatic Dinosaurs

question 21

Multiple Choice

Ichthyosaurs were aquatic dinosaurs. Fossils show us that they had dorsal fins and tails, as do fish, even though their closest relatives were terrestrial reptiles that had neither dorsal fins nor aquatic tails. The dorsal fins and tails of ichthyosaurs and fish are

• A) homologous.
• B) examples of convergent evolution.
• C) adaptations to a common environment.
• D) Three of the responses above are correct.
• E) Two of the responses above are correct.

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Definitions:

Double Helix

The structure of DNA, consisting of two strands that wind around each other like a twisted ladder.

PKU

stands for Phenylketonuria, a genetic disorder resulting from the body's inability to process the amino acid phenylalanine, leading to its accumulation and potential brain damage.

Recessive Gene

A gene that produces its characteristic phenotype only when its allele is identical and not masked by a dominant allele in a heterozygous condition.

Double Helix

The structure of DNA, characterized by two intertwined strands forming a spiral shape, discovered by Watson and Crick.