Outcomes: Gradients 1Explain what a gradient is and the role of gradients in: A) Homeostasis B) Thermoregulation C) Osmoregulation D) Chemical reactions associated with metabolism, Gradients 2Identify whether a chemical or energy gradient exists in new situations, Gradients 3Indicate the direction of energy or material movement under different conditions such as: A) Chemical concentrations B) Temperature C) Permeability of membranes, Gradients 4Indicate the relative rate of energy or material movement under different conditions including: A) chemical concentrations B) temperature C) permeability of membranes D) varied shape (surface-to-volume ratio); Thermoregulation 1Apply the terms endotherm, ectotherm, poikilotherm/heterotherm, and homeotherm to organisms, Thermoregulation 2Identify organisms as endotherms, ectotherms, poikilotherms/heterotherms, and homeotherms based on: A) physical characteristics B) behavior C) metabolic changes D) membership in taxonomic groups (birds, mammals, etc.) E) changes in body temperature measurements, Thermoregulation 3Predict the effect of varying environmental temperatures on an organism's behavioral or metabolic responses including: A) enzyme activity B) locomotion C) body temperature, Thermoregulation 4Interpret data/graphs as they relate to the effect of varying environmental temperatures on an organism's behavioral or metabolic responses including: enzyme activity
locomotion
body temperature
, Thermoregulation 5Design or critique simple experiments to test the effect of varying environmental temperatures on an organism's behavioral or metabolic responses including: A) enzyme activity B) locomotion C) body temperature, Thermoregulation 6Explain how various temperature regulation methods serve to heat or cool an organism including: A) avoidance B) altering metabolic rate C) behaviorally adjusting posture, ratio of surface area-to-volume, and location D) explain how ratio of surface area-to-volume is involved in heat retention or loss, Thermoregulation 7Explain why organisms thermoregulate., Thermoregulation 8Explain mechanisms of heat generation at the cellular level.

1. The purpose of this activity is to illustrate the important role of SA/V in maintaining gradients. Students compare how life has evolved in extreme biomes namely by comparing images of the ear size of desert and tundra dwelling animals and connecting this structure with an animal’s ability to maintain homeostasis (i.e. temperature gradients and thermoregulation).  

Engage students by showing a photo of a desert biome and a tundra biome (see below). It is important that some plants be visible in each photo (not photos of sand dunes or snowpack) to illustrate that life can exist here. Ask students to make observations and compare and contrast each biome with their neighbors/teams. Ask students “What do you think might be an obstacle to life in these biomes?” and they usually respond with “temperature extremes and lack of liquid water.” Tell students, “Let’s look at the living things that have evolved to live in these extreme biomes.”

Prepare presentation slides with images of similar tundra and desert animals side by side for comparison by students (see below). Select images that prominently display the ears and legs of each animal so that students can eventually recognize the role of the ratio of surface area-to-volume in thermoregulation. Ask students to compare and contrast the body shapes of the following animals: Arctic Hare v. Jackrabbit, Lemming v. Kangaroo rat, Arctic fox v. Kit fox. It may help to show these images repeatedly as students discuss how the body shapes differ. Students will initially describe the animals as “chunky,” “skinny,” “fluffy,” etc. You may want to point out to students that it is difficult to measure how “fluffy” an animal is, so they should try describe the animals using surface area and volume.

Students soon realize that these two measurements are linked; as volume increases so does surface area. Although some students will start referring to these measurements as a ratio, many students will need prompting to make this connection.

2. Ask students to work in groups to research and find organisms to complete this table:

(Thermoregulation 1Apply the terms endotherm, ectotherm, poikilotherm/heterotherm, and homeotherm to organisms, Thermoregulation 2Identify organisms as endotherms, ectotherms, poikilotherms/heterotherms, and homeotherms based on: A) physical characteristics B) behavior C) metabolic changes D) membership in taxonomic groups (birds, mammals, etc.) E) changes in body temperature measurements)

3. After students work with the concepts of gradients and membrane transport, you may want to engage them this following case study:
   • Gradients and Thermoregulation: Left out in the cold! – While backpacking in the Canadian Rockies, Joel loses his way and finds that his experience hiking and camping in his home state of Florida hasn’t prepared him for springtime weather conditions in the mountains. This case study allows students to review and integrate physiological responses to cold exposure. (Gradients 1Explain what a gradient is and the role of gradients in: A) Homeostasis B) Thermoregulation C) Osmoregulation D) Chemical reactions associated with metabolism, Gradients 2Identify whether a chemical or energy gradient exists in new situations, Gradients 3Indicate the direction of energy or material movement under different conditions such as: A) Chemical concentrations B) Temperature C) Permeability of membranes, Gradients 4Indicate the relative rate of energy or material movement under different conditions including: A) chemical concentrations B) temperature C) permeability of membranes D) varied shape (surface-to-volume ratio))