Many species of animals on islands are larger than related species on the mainland. Scientists hypothesize that this phenomenon, called island gigantism, evolved in response to the scarcity of competitors and predators on islands. Reduced competition and predation allow species to exploit more resources and free them from the need to hide in small refuges.
True or false: The body temperatures of island tortoises always closely match the temperatures in their environments.

Many species of animals on islands are larger than related species on the mainland. Scientists hypothesize that this phenomenon, called island gigantism, evolved in response to the scarcity of competitors and predators on islands. Reduced competition and predation allow species to exploit more resources and free them from the need to hide in small refuges. Which of the following might be a trade-off of gigantism experienced by giant island tortoises?

a. They cool very rapidly during cold weather.

b. It would be difficult to sustain their high mass-specific metabolic rates on a diet of plants alone.

c. It could be more difficult to avoid thermally unfavorable conditions.

d. They could hide from nonnative predators more easily.

Many species of animals on islands are larger than related species on the mainland. Scientists hypothesize that this phenomenon, called island gigantism, evolved in response to the scarcity of competitors and predators on islands. Reduced competition and predation allow species to exploit more resources and free them from the need to hide in small refuges.

Which tortoises, mainland or island, need to eat more food per gram of their body mass?

Many species of animals on islands are larger than related species on the mainland. Scientists hypothesize that this phenomenon, called island gigantism, evolved in response to the scarcity of competitors and predators on islands. Reduced competition and predation allow species to exploit more resources and free them from the need to hide in small refuges. On a trip to the Galápagos Islands, you overhear a group of tourists refer to tortoises as 'cold blooded.'

Explain why this word is not accurate to describe a giant tortoise.

Many species of animals on islands are larger than related species on the mainland. Scientists hypothesize that this phenomenon, called island gigantism, evolved in response to the scarcity of competitors and predators on islands. Reduced competition and predation allow species to exploit more resources and free them from the need to hide in small refuges. The graph shown here compares the average carapace (shell) length of mainland and island tortoises. Summarize the results, then use the data to predict whether the surface area to volume ratio is higher in mainland or island tortoises.

Many species of animals on islands are larger than related species on the mainland. Scientists hypothesize that this phenomenon, called island gigantism, evolved in response to the scarcity of competitors and predators on islands. Reduced competition and predation allow species to exploit more resources and free them from the need to hide in small refuges. Suppose that a small mainland tortoise and a large island tortoise are placed in the same pen at a zoo.

Which tortoise will be more poikilothermic, the small or large tortoise? Why?