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Animal Form & Function
Lecture 10
Winter 2014
Physical Constraints on Form & Function
1
• Anatomy &
physiology (define)
• Environmental
constraints on form
– Convergent evolution
• Larger organisms
– Need thicker
skeletons to maintain
support
– Larger muscles for
movement of larger
mass
Fig. 40.2
Physical Constraints on Form & Function
2
• Exchange with environment
– Substances dissolved in aqueous medium move across
plasma membranes of cells
– Plasma membranes must be kept moist to maintain
integrity
• What materials need to be exchanged with
environment?
• Limits with surface to volume ratios
– Rates of exchange (for nutrients, waste, gases) are
proportional to membrane surface area
– Amount of material that needs to be exchanged to
sustain life is proportional to volume
Physical Constraints on Form & Function
3
• Single-cell organism: entire surface area contacts
environment
• Simple organization in multicellular organisms
– Hydra: two cells thick with gastrovascular cavity allows for all cells to
have direct with the environment
– Tapeworm: Thin & flat - can keep most cells in contact with external
environment
• More challenging for
more multicellular
organisms
• As the number of cells
increase, the ratio of
outer surface area to
total volume
decreases
Fig. 40.3
Physical Constraints on Form & Function
4
• How to bathe every cell in fluid in order to have
exchange?
• Specialized surfaces that are extensively branched
or folded
– Most surfaces within body
– Example lungs, blood vessels, intestines of humans
• Interstitial fluid
– Fluid in spaces between cells
– exchanges nutrients, gases, waste, etc. with circulatory
fluid (e.g., blood in humans)
Physical Constraints on Form & Function
Fig. 40.4
5
Hierarchical Organization
6
• Tissue
– Integrated group of cell
with a common function,
structure or both
• Organ
– Specialized center of
body function composed
of several different types
of tissues
• Organ System
– Group of organs that
work together in
performing vital body
functions
See Fig. 1.4
7
Functions?
8
Tissue types
• Note: For tissue types, only focus on function (as
listed here)
• Epithelial
– Covers outside of body
– Lines organs and cavities in body
– Protection against mechanical injury, pathogens, fluid
loss
– Forms active interface with environment (e.g., nasal
cavity)
• Connective
– Bind and support other tissues in body
– Includes loose connective tissue, fibrous connective
tissue, cartilage, bone, adipose tissue, blood
Tissue types
• Muscle
– Body movement
– Actin & myosin filaments
– Skeletal, smooth & cardiac
• Nervous
– Sense stimuli, process
information and transmit signals
Fig. 40.5
9
Coordination & Control
• Endocrine System
– Signaling molecules released into
bloodstream reach all locations in
body
– Signaling molecule: hormones
– Cell must have receptor for hormone
– Slower acting
– Coordinates growth, development,
reproduction, metabolic processes,.
digestion
• Note: overview only – we will look
at details in later chapter
10
Coordination & Control
11
• Nervous System
– Neurons transmit signals
between specific locations in
body
– Fast actingCordinating
immediate & rapid response to
environment, locomotion &
behavior
– Both endocrine and nervous
system often work together
• Note: overview only – we will look
at details in later chapter
Fig. 40.6
Homeostasis
Homeostasis
• The maintenance of a relatively constant chemical
and physical environment within an organism
Examples of conditions in the body that need to be
maintained?
12
Homeostasis
13
• Regulator
– Uses internal control mechanisms to moderate internal
change in the face of external changes
• Conformer
– Allows its internal condition to vary with certain external
Fig. 40.7
changes
• An animal may be both
regulator and conformer
depending on the variable
• Example: Bass is a
conformer for temperature,
but a regulator for solute
concentration of blood and
interstitial fluid
Homeostasis
• Sensor/Receptor
• Integrator/Control
Center
• Effector/Response
Set point
• Normal or target
value/range for the
controlled variable
See Fig. 40.8
14
Homeostasis
Fig. 40.8
15
Homeostasis
Negative Feedback Loops
• Corrective response in
which effectors reduce
or oppose the change in
internal conditions
• Moves a system back
towards a set point or
normal range
Fig 40.16
16
Regulation of Systems
17
Positive Feedback loop
• Increased temperatures = increased melting
• Increased melting = less ice/snow cover
• Less ice/snow cover = less light reflection
• Less light reflection = more light absorption
• More light absorption = increased temperature
Positive feedback loops
• Moves a system further
away from a set point
• Amplifies the disturbance
E.g., Albedo Effect
• Ice & snow reflect
sunlight
• Rocks/soil absorb
sunlight
Thermoregulation
18
• Process which
organisms
maintain an
internal
temperature
within a
tolerable range
• Why is this
important?
• Heat transfer
always from
warmer
temperatures to
colder
temperatures
Fig. 40.11
Mechanisms of Thermoregulation
19
• Endotherm
– An organism that uses its metabolism
to generate heat for body
• Ectothermic
– An organism that uses external heat
sources for body heat
• Why aren’t all organisms
endothermic?
• Poikilotherm
– Organism whose body temperature
varies with its environment
• Homeotherm
– Organism whose body temperature is
relatively constant
Fig. 40.10
Mechanisms of Thermoregulation
• Insulation
– Reduces flow of heat
between animal and
environment
– Trap air layer under fur
or feathers
– Body fat
20
Mechanisms of Thermoregulation
Circulatory adaptations
• Vasodilation
– Widening of superficial blood
vessels, increases blood flow
• Warms skin & increases heat transfer
from body
• Vasoconstriction
– Decreases diameter of superficial
blood vessels, reduces blood flow
& heat transfer
• Conserves body heat to central core
– E.g., ears of jackrabbit in very hot
environment
• Prevents heat absorbed by ears from
being transferred to body
21
Mechanisms of Thermoregulation
Circulatory adaptations
• Countercurrent heat exchange
– Transfer of heat between adjacent fluids
flowing in opposite directions
– Maximizes transfer of heat (or solutes)
22
Fig. 40.12
Mechanisms of Thermoregulation
• Evaporative cooling
– Water absorbs heat
when it evaporates
– Water vapor carries
heat away from body
• Kangaroos lick their skin
to increase evaporative
cooling
23
Mechanisms of Thermoregulation
Behavioral responses
• Positional/postural
– Orientation to sun
• Social behavior
– Honeybees & penguins
huddle to keep warm &
rotate positions
24
Mechanisms of Thermoregulation
Behavioral responses
• Topor
– State of low physical and metabolic activity
– Short-term
– Anna’s hummingbird in Seattle winter – torpor state
overnight when too cold
• Hibernation
– Long-term
25
Mechanisms of Thermoregulation
• Thermogenesis
• Heat production
• Shivering
– E.g., chickadees, hawkmoth& bumblebee pre-flight
warm-up, python incubating eggs
• Non-shivering thermogenesis
– Increase metabolic activity to produce heat (rather
than ATP)
Fig. 40.15
26
27
Acclimatization
• A temporary adjustment to changes in an
organism’s external environment
– Change in altitude causes change in
production of red blood cells
– Seasonal changes
• Thicker fur, or shedding
• Proportion of saturated vs. unsaturated lipids in
cell membrane
• Acclimatization is not Adaptation
• Pgs 868-871 (Concept 40.4 Energy
requirements are related to animal size..)
will be covered with the next chapter
(Animal Nutrition)