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?

Verified step by step guidance

1. Understand the concept of island gigantism: Island gigantism is a biological phenomenon where species on islands grow larger than their mainland relatives due to factors like reduced competition and predation.
2. Consider the energy requirements of larger animals: Larger animals generally have lower metabolic rates per gram of body mass compared to smaller animals, meaning they require less food per gram of body mass.
3. Analyze the environmental factors: On islands, the scarcity of predators and competitors allows animals to grow larger, potentially reducing their need for frequent feeding compared to smaller mainland species.
4. Compare the tortoises: Island tortoises, being larger due to island gigantism, likely have lower metabolic rates per gram of body mass than mainland tortoises, which are smaller and may need more food per gram of body mass.
5. Conclude based on metabolic rates: Mainland tortoises, being smaller, need to eat more food per gram of their body mass compared to island tortoises, which are larger and have lower metabolic rates per gram.

Key Concepts

Island Gigantism

Island gigantism refers to the evolutionary phenomenon where species on islands grow larger than their mainland counterparts. This occurs due to reduced competition and predation, allowing species to exploit available resources more freely. The lack of predators and competitors means that animals can grow larger without the need to hide or escape quickly.

Metabolic Rate

Metabolic rate is the rate at which organisms convert food into energy. Larger animals typically have a lower metabolic rate per gram of body mass compared to smaller animals, meaning they require less food relative to their size. This concept is crucial in understanding why island tortoises might need less food per gram of body mass compared to mainland tortoises.

Resource Availability

Resource availability on islands can differ significantly from the mainland due to isolation and limited biodiversity. The abundance or scarcity of food resources influences the size and metabolic needs of island species. In the context of island gigantism, the availability of resources without competition allows species to grow larger, impacting their dietary requirements.