6 Consider a pair of snail species that live on either side of a deep and wide c

Question

6 Consider a pair of snail species that live on either side of a deep and wide canyon. Snail species A occurs west of the canyon and snail species B occurs east of the canyon. Phylogenetic analysis reveals that the snails are sister species. Geologists estimate that the canyon formed over a relatively short time period, around 20 million years ago.

If these snails initially diverged due to vicariance, the age of their most recent common ancestor would be ___________. If they initially diverged due to dispersal across the canyon, the age of their most recent common ancestor would be __________.

more than 20 million years old; 20 million years old

20 million years old; less than 20 million years old

20 million years old; more than 20 million years old

less than 20 million years old; 20 million years old

7 The group Cetacea, shown on the phylogeny to the right, includes whales and dolphins. They possess stream-lined bodies and fins that they use to swim in the water. These same traits are present in fish such as sharks. The similarity in traits between Cetaceans and sharks is an example of _________.

Homoplasy

Homology

Synapomorphy

Genetic Drift

Return to the base of the tree Camelidae Suidae Tayassuidae CETACEA Hippopotamidae Tragulidae - TYLOPODA SUIFORMES CETANCODONTA ?Moschidae Cervidae Bovidae Antilocapridae RUMINANTIA _ Giraffidae

Explanation / Answer

7. The similarity in traits between Cetaceans and the sharks is an example of Homoplasy.

Homoplasy is defined as similar characters shared between different species but this character is not present in the common ancestor.

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