Along the shoreline of Lake
Michigan in Michigan, fruit trees are grown in abundance. These plants are not found 20 or 30 miles inland from the lake.
Why?

Objectives:
1. Identify where heat comes from and where is goes!!!
2. Describe how organisms compensate for variations in environmental temperatures
3. List similarities and differences between ectotherm and endotherm
4. Define resting stages and their applications

H s
= H m
+ H cd
+ H cv
+ H r
+ H e
Where:
H s
= Total heat stored in body
H m
= Heat gained from metabolism
H cd
= Heat gained or lost from conduction
H cv
= Heat gained or lost from convection

H s
= H m
+ H cd
+ H cv
+ H r
+ H e
Where:
H r
= Heat gained or lost through electromagnetic radiation
H e
= Heat lost through evaporation

Fig. 4.13

Organisms can control body temperature by:
• Amount of surface area exposed to sun
• Amount of body surface exposed to cooler/warmer surfaces
• Thermal conductivity of body surface (fluff fur or feathers

• Amount of stored chemical energy released by metabolism
• Amount of water evaporated from the body
• Amount of sunlight reflected from their surface

Organisms whose body temperature varies in directly with environmental temperatures -

Poikilotherms
Animals--- many aquatic: clams, worms, insect larvae, barnacles,
Plants--- aquatic: phytoplankton,
Others--- bacteria, fungi

Poikilotherms
Advantages:
Can allocate more energy to growth and reproduction
Can colonize areas of limited food and water
Expending no energy maintaining a temperature different than the environment

Poikilotherms
Disadvantages:
Activities restricted to warmer days and seasons
Limited ability to colonize colder regions

Ectotherms
Organisms that rely on external sources of heat to regulate body temperature, usually a combination of behavior, and anatomy

Ectotherms
How does this happen?
Plants:
• Orientation to or away from the sun, pigmentation (radiation)
• Loss of water through leaves (evaporation)
• Altering wind patterns using growth forms
(convection)

Fig. 4.14

Fig. 4.15

Fig. 4.16

Ectotherms
Animals:
Similar to plants-body size, shape, and pigmentation
One big advantage-
Animals can move to find different microclimates to best suite their needs

Fig. 4.17

Endotherms
• Similar to ectotherms; that is, they use the environment to warm and cool the body.
• But-- Rely extensively on metabolic heat to regulate the body temperature.

Endotherms
Below what temperature do you need to put on a coat?
Above what temperature would you like to have air conditioning?

Thermal neutral zone:
Range of temperature over which metabolic rate of endotherm does not change
“
”

Fig. 4-21

Advantages:
Can maintain activity over a wide range of temperatures
Efficient respiration enables long periods of activity
Can colonize a wide range of environments, including e.g., polar regions

Disadvantages:
Must expend energy to maintain body temperature
May require large amounts of water to maintain body temperature in hot environments

Regulate their body temperature within a narrow range, independent of the environment -
Homeotherms e.g., mammals and birds ~ 35-40 C
Warm-blooded????

Organisms that control their body temperature some of the time, while allowing it to be controlled by the environment other times-
Heterotherms e.g., animals that hibernate - bats, marmots, hummingbirds, But Not Bears

What is it?
A state of low metabolic rate and low body temperature. Organisms rely on stored energy reserves.

Daily or for several hours at a time:
“Torpor” e.g., hummingbirds
Extended period of time in winter
“Hibernation” e.g., marmots
Extended period of time in summer:
“Estivation” e.g., turtles

Fig. 4.29

For Thursday
Read Chapter 5 - Water Relations

1. Identified how some organisms compensate for variations in environmental temperatures
2. Know what the terms ectotherm, endotherm, homeotherm, heterotherm mean
3. Understand hibernation and torpor