Understanding Thermoregulation in Animals: Ectotherms vs. Endotherms, Study Guides, Projects, Research of Biology

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ECTOTHERM OR ENDOTHERM?

Objective

To explore the concept of thermoregulation and the different ways animals (including turtles!) maintain their body temperature.

ECTOTHERM OR ENDOTHERM?

Included in this Lesson Plan

Next Generation Science Standards (NGSS) Lesson Background Activities

1. Exploring with Graphs 2 ) Thermoregulation Scavenger Hunt Discussion Questions

Related Materials Available

Ectotherm or Endotherm? Exploring with Graphs Worksheet Ectotherm or Endotherm? Thermoregulation Scavenger Hunt Worksheet Ectotherm or Endotherm? Discussion Question Worksheet Ectotherm or Endotherm? PowerPoint Presentation

Lesson Background

Thermoregulation is the process by which animals maintain their body temperature. There are a few different ways this has evolved in different groups of animals, but they mostly fall into two categories: endotherms and ectotherms. Endotherm bodies have internal metabolic processes that maintain a constant temperature—like humans! Endotherms must eat constantly and regularly to make enough heat to keep their bodies warm. Most mammals are endotherms. They don’t have to do anything special to maintain their body temperatures, but the food they eat is converted to energy and warmth. Even if endotherms are in very cold or very hot weather, their internal body systems are constantly operating to maintain an even temperature. Ectotherms, on the other hand, rely on the environment to alter their temperatures. For the most part, they do not have internal processes that regulate temperature, so they have to move into the sun to warm up, or to the shade to cool down. They need to eat of course, but most do not need to eat as often or regularly as endotherms. Amphibians, reptiles and most fish are ectotherms, while most insects and invertebrates are largely ectothermic as well (although they’re a bit more complicated). The figure below plots how environmental temperature affects body temperature in mammals (a mouse) and reptiles (a lizard).

Figure from Wikimedia Commons Endotherms and ectotherms used to be referred to as “warm-blooded” and “cold- blooded,” but those terms have fallen out of favor because they are misleading. Cold- blooded creatures do not always have cold blood. Turtles and tortoises are ectotherms. That’s why you’ll often see them basking on a tree limb in a lake or pond; they’re trying to warm up after being in the cold water. Desert tortoises get hot in the desert sun and will lay in the shade of plants or deep in soil burrows with all of their limbs extended to cool down. The more surface area of their body that’s exposed to the sun or shade, the better they can offload or absorb heat. Case Study: Leatherback Sea Turtles Leatherbacks are anomalous among turtles in many ways. They don’t have a typical carapace; instead they have loosely interlocked bone covered by three centimeters of rubbery/oily skin and fibrous cartilage that is then covered by membrane bone called, “osteoderm.” This structure allows the large turtles to dive deep for food and withstand the pressure of the ocean. They can go as deep as 400 meters! Leatherbacks are

Activity

Activity 1: Exploring with Graphs Good for: Classroom activity or homework Materials: Exploring with Graphs Worksheet Give the students the “Ectotherm or Endotherm? Exploring with Graphs Worksheet.” Have them draw in the lines for endotherms (humans) and ectotherms. You could do one together as a class, and then have the students infer the other one based on their knowledge of how each operates. Activity 2: Thermoregulation Scavenger Hunt Good for: Outside activity or homework (class discussion can happen the following class). Materials: Scavenger Hunt Worksheet Each student should bring a “Ectotherm or Endotherm? Scavenger Hunt Worksheet” outside with a pen and clipboard, or something to write on. Instruct the students to wander around in some defined area (a school yard, a park, etc.) and search for animals. Any animals works, including birds, reptiles, insects, mammals, or even house pets! When they find an animal, they will observe it for 1 - 2 minutes and fill out the worksheet which has spaces for the animal’s name, a description of the animal’s activity, and whether they think it’s an endotherm or ectotherm and why. Ectotherm examples they

might find: a butterfly spreading its wings in the sun, ants warming up around their nest, a bird spreading its wings in the sun, a lizard on a warm rock. When you return to class, have the students make one long list of every animal they found, categorized by endotherms and ectotherms, and answer the following discussion questions.

Discussion Questions

These questions are the same as those listed on the “Ectotherm or Endotherm? Discussion Question Worksheet”.

1. Name three examples of endothermic animals.
2. Name three examples of ectothermic animals.
3. Name three ways that ectotherms can alter their body temperature.
4. What are the benefits and detriments of being an ectotherm?
5. What are the benefits and detriments of being an endotherm?
6. How does being an ectotherm affect a turtle’s ability to survive?