Evolution of the platypus Flashcards
Describe the evolution of the three types of mammals.
An ancient group of reptiles called cynodonts were the earliest ancestor of mammals. Monotremes split off first (150mya), then marsupials (130mya), and then placentals (110mya).
What other animals evolved from cynodonts?
Birds, modern reptiles.
Describe the branching of monotremes from the other mammals in the evolutionary timeline.
Protherian mammals branch off from therian mammals around 148mya. Protherian mammals evolved into monotremes, while therian mammals evolved into marsupials and placentals.
Describe how a technology has helped our understanding of platypus evolution.
DNA analysis and molecular dating have identified that platypus and echidnas shared a common ancestor, splitting 19-48mya.
Describe how the platypus evolved to have venom in its hind spurs.
Although they are a reptilian feature, genome analysis suggests that this feature arose independently.
What led to monotremes surviving in Australia, but placentals dying out?
As Australia drifted north, the continent became drier and hotter. Monotremes had a lower resting metabolic rate than placentals, meaning they survived better. Monotremes also had a lack of predators, as there were not many carnivorous mammals in Australia.
What features of the modern platypus suggests it is more highly evolved than its ancestors?
They no longer have teeth, they have horny pads. They also have a sensitive electroreceptive system for detecting prey in murky water.
Is platypus evolution macro or microevolution?
The evolution of the platypus is considered an example of macroevolution. Took place over a long time, resulting in the emergence of new species.
What features of the platypus are reptilian?
Venom in spurs, lays leathery eggs.
What features of the platypus are bird-like?
Bill, webbed feet
What features of the platypus are related to mammals?
Hair, produce milk.
