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.

Verified step by step guidance

1. Understand the term 'cold-blooded': In biology, 'cold-blooded' refers to animals that do not regulate their body temperature internally. Instead, their body temperature changes with the environment. This term is often used to describe ectothermic animals, such as reptiles, amphibians, and fish.
2. Recognize the scientific term: The more accurate term for 'cold-blooded' is ectothermic. Ectotherms rely on external sources of heat to regulate their body temperature, unlike endotherms, which maintain a constant body temperature through internal metabolic processes.
3. Identify the classification of tortoises: Tortoises are reptiles, and like most reptiles, they are ectothermic. This means they rely on environmental heat sources to regulate their body temperature, rather than generating heat internally.
4. Explain the misconception: The term 'cold-blooded' can be misleading because it implies that these animals always have cold blood, which is not true. Their blood temperature varies with the environment, and they can be quite warm when basking in the sun.
5. Clarify the behavior of giant tortoises: Giant tortoises, like those on the Galápagos Islands, use behavioral adaptations to regulate their temperature. They bask in the sun to warm up and seek shade or burrow to cool down, demonstrating their ectothermic nature.

Key Concepts

Island Gigantism

Island gigantism is a biological 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 fully. The isolation of islands often leads to unique evolutionary paths, resulting in larger body sizes as a survival advantage.

Ectothermy

Ectothermy refers to organisms that rely on external sources of heat to regulate their body temperature, often inaccurately termed 'cold-blooded.' Giant tortoises are ectothermic, meaning they use environmental heat to maintain their physiological processes, rather than generating heat internally like endotherms (warm-blooded animals).

Adaptation to Island Environments

Adaptation to island environments involves evolutionary changes that enable species to thrive in isolated ecosystems. For tortoises, larger size may be an adaptation to exploit available resources and reduce vulnerability to predators. This adaptation is part of a broader pattern of island gigantism, where isolation leads to unique evolutionary traits.