Question
Modern, aquatic toothed whales evolved from a terrestrial ancestor Present day whales are best linked to their terrestrial ancestors by: analogous structures embryological evidence transitional fossils biogeography
Solution
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Vivienne
Master ยท Tutor for 5 years
Answer
The best link between modern whales and their terrestrial ancestors is **transitional fossils**.Here's why:* **Transitional fossils:** These fossils document the intermediate stages of evolution. In the case of whales, transitional fossils show a gradual progression from land-dwelling mammals with legs to fully aquatic whales with flippers. Key features like the gradual reduction of hind limbs and the shifting of the nasal opening to the top of the head are clearly preserved in these fossils. This provides direct evidence of the evolutionary pathway.* **Analogous structures:** These are structures that have similar functions but different evolutionary origins. For example, the wings of a bat and the wings of an insect are analogous. While they both allow flight, they developed independently. Analogous structures don't demonstrate evolutionary relationships between groups.* **Embryological evidence:** While embryological similarities can hint at common ancestry, they don't provide the concrete, step-by-step evidence that fossils do. Embryos of whales do show temporary hind limb buds, which suggest a terrestrial ancestor, but this is less conclusive than fossil evidence.* **Biogeography:** This is the study of the distribution of species across the globe. While the current distribution of whales doesn't directly link them to their terrestrial past, the locations where some key transitional fossils have been found can support the evolutionary story. However, the fossils themselves are the primary evidence.