BOA LAB
Surface Area and Volume of Animal Bodies
Among animals, there is a tremendous range in …
* body size
* shape
* temperature
Cylindrical Bodies
Pika
Grizzly
bear
Chunky Bodies
Walrus
Saw-whet owl
VOCABULARY
Homeotherms – animals with a high stable core
temperature
Endotherms – animals that generate much body heat
through their fast metabolism
“warm-blooded animals”
“cold-blooded animals”
Poikilotherms – animals with unstable core temperatures
that vary with environmental temperatures
Ectotherms – animals that gain body heat from the
environment
Poikilotherm
Homeotherm
Body
Temperature
Environmental Temperature
Homeotherms are usually Endotherms
Poikilotherms are Ectotherms
ALL ANIMALS:
Poikilotherms
Ectotherms
Reptiles
Amphibians
Fish
All Invertebrates
(insects, worms,
molluscs, jellyfish, etc.)
Homeotherms
Endotherms
Mammals
Birds
Marsupial
Mammal
C
O
R
E
S
34-35o C
40-41
37-38
Assume both animals have the same volume.
Which shape is better for an endothermic homeotherm?
Why?
Surface Area
Volume
(1)
Low
(2)
High
Which size is “better” for an endothermic homeotherm?
Why?
(1)
High SA:VOL
(2)
Low
SA:VOL
Body “Wall” Adaptations of Endothermic Homeotherms
40o C
Muskoxen
Huge Bodies
Thick Fur
Huddling Together
WALRUS
body wall
Skin
Blubber
Small Body
High Surface Area:Volume
Rapid loss of precious body heat
Heart Rate: 250 - 1200 min-1
Oxygen
Consumption
Hummingbirds have
a problem………
!
NOON
3 Endothermic Homeotherms
47
beats/min
HORSE
CAT
580
MOUSE
Weekly
requirements
of two grazers …
Oxygen
Consumption
LIZARD: An ectothermic poikilotherm
behaviorally thermoregulating
Benefit
Ectothermic Poikilotherms can have radical shapes
Benefit
Ectothermic Poikilotherms can be small
Smallest Poikilotherm??
Smallest Homeotherm??
Least shrew
Microscopic ciliate
Bee
hummingbird
LEGS: High SA:VOL
In cold weather, legs
won’t be kept warm
Today’s Work
• Make measurements of snake and tiger bodies
• Calculate body surface areas and body volumes
• Calculate body surface area:volume ratios
6
5
Animal surface areas and volumes can be difficult to estimate
unless some simplifying is done. For a four-legged animal, the
body can be seen as a collection of six cylinders. Total surface
area and volume is the sum of the six individual surface areas and
volumes.
1
2
3
4
For a snake, similar simplifying can be done. Even though a
snake is very cylinder-like, the diameter of the snake’s body is
not the same from end to end. Dividing the body into two or
more cylinders might yield a more accurate estimate of snake
surface area and volume.
1
2
3
……………… on facdata
BOA LAB
The BOA lab on September 9 involved making estimates of
surface area and volume for a homeotherm/endotherm and a
poikilotherm/ectotherm across three body sizes.
All students should submit a lab report of this work. This report
is due on September 17 at 10:00 am.
Remember that the written lab report is a solo effort, not
to be done in collaboration with your lab partner or
anyone else in class.
For this report, do the following.
1) Convert class data to means (averages) and then plot them
on one or more graphs. Excel or other software will do this
quite well.
2) In a separate paragraph, interpret the data on your graphs in a
way that is relevant to thermoregulation in endothermic
homeotherms and ectothermic poikilotherms.
3) Answer the questions listed below. Write answers that reflect
the depth of your understanding (1 sentence answers will not get
the job done).
4 Questions
1) Why are homeotherms not shaped like snakes?
2) The smallest homeotherms might be hummingbirds. Why
haven’t any homeotherms evolved that are smaller than
hummingbirds?
3) Why do humans that are native to far northern latitudes have
“chunky” bodies (torso, arms, and legs that are short and thick)?
4) Why is SA:VOL important in understanding animal thermal
regulation?
Metabolic rate is particularly important to
1) birds
2) mammals
o
37-41
C
……… why??
Because they are endotherms and homeotherms.
Fast metabolism generates body HEAT!!
All animals exhibit metabolism … some use it to keep
warm
Metabolic rate is particularly important to
1) birds
2) mammals
……… why??
o
37-41
C
1
3
2
4
7
5
6
10
8
9
11
Why can’t homeotherms be
small?
Homeotherm: Stable Core Temperature
… what does “core” mean?
Heat Conservation: BODY SHAPE
Chunky vs Linear
QUESTION: Why haven’t homeotherm/endotherms
evolved to be smaller than these 2 species?
Hummingbird
Shrew
WALL