2. Objective
Content: Describe how living
things use free energy to
maintain homeostasis
Skill: Connect and relate
knowledge across domains
3. Life exists in
all parts of the
world
Animals inhabit every part
of the Earth
Amazing diversity of
habitat, form, and function
Natural selection favors
individuals who can meet
the demands of their
particular environment
4. Physical Laws & the Environment Constrain
Animal Size & Shape
Flying animals can only get
so big…
Physics of flight would never
allow a flying dragon
Water is 1000x more dense
than air
Any bump on the body causes
drag
Fast swimmers all have
torpedo shaped bodies
An example of convergent
evolution
5. Another example is single-celled organisms
Surface area to volume ratio is important
Keeps single celled organisms very small and flat
In multicellular animals:
all the cells must have access to an aqueous
environment
branching and folding of internal parts help
accomplish this
11. Quick Think
How does a large surface area contribute to
the functioning of the small intestine?
How does a large surface area of organs
benefit larger organisms like blue whales
and humans?
12. Levels of
Organization in
complex animals
Cells - smallest functional unit
Tissues - groups of cells with a common structure and
function
4 types of tissue:
1. Epithelial - sheets of tightly packed cells; covers the body and lines the
organs
2. Connective tissue - supports & binds other tissues; made up of scattered
cells in the ECM; examples - cartilage, tendons, ligaments; bone; blood
3. Nervous tissue - made up of neurons; senses & transmits info
4. Muscle tissue - made up of long cells called muscle fibers; can contract
when stimulated; 3 types: cardiac, skeletal, smooth
13.
14. Organs - organized
groups of tissues
Organ systems -
groups of organs that
work for a common
purpose
Example: digestive
system
15. Animals use the chemical energy in food to
maintain homeostasis, grow, & reproduce
Metabolic rate - the amount of
energy an animal uses in a
given amount of time
Energy measured in calories or
kcal
2 basic “strategies”
Endotherms - animals bodies
warmed by heat generated
through metabolism
Ectotherms - animals bodies
warmed by environment -
metabolism does not produce
enough heat to warm the body
Lizard sunning itself on a
rock to warm up
16. Endotherms
Birds and mammals
Body temp maintained by
metabolism
Much energy required
Permits intense, long
duration activity
In general, the smaller the
endotherm, the higher the
metabolic rate
17. Ectotherms
Fish, amphibians, reptiles,
invertebrates
Body temp controlled by
environment
Less energy required
Move more slowly when cold
18. Quick Think
If a mouse and a small lizard of the same
mass were placed in a respirometer under
identical environmental conditions, which
animal would consume oxygen at a higher
rate? Explain.
19. Maintaining a constant internal environment
Homeostasis - the state of internal balance
2 main strategies:
Regulator - some animals are this type - they moderate
internal change in the face of external fluctuations
(keeping body temp constant by sweating, shivering)
Conformer - some animals are this type - allow their
internal conditions to vary with the environment
These are the 2 extremes - most animals use some of
both
Regulator or Conformer? - Can drop it’s
body temp 50 degrees at night to deal with
freezing overnight conditions
20. Mammals are endotherms - use metabolism to
adjust for fluctuations in environment
Fish & aquatic inverts. are conformers - they
live in stable environments and can adjust
bodies for slight changes in environment
21. Modes of heat
exchange
Conduction - the transfer of
heat between objects in
direct contact with each
other
Example - animal sitting in
cool water
Convection - transfer of heat
through the movement of air
or liquid past a surface
Example - a cool breeze
Radiation - the emission of
electromagnetic waves by warm
objects(anything warmer than absolute zero)
Evaporation - removal of heat
from the surface of a liquid as
molecules leave the surface as
gas
Example - as sweat evaporates off
skin it cools the skin
22. Thermoregulation
How animals maintain their internal temperature
Takes place through the following processes:
1. Adjustment of the rate of heat exchange between the animal
and its environment through hair, feathers, fats - is accomplished
through:
1. vasodilation (blood vessels expand near skin, cools the blood)
2. vasoconstriction (blood vessels contract away from skin, keeps blood
warm)
23. 2. Evaporation across the skin (panting or
sweating)
3. Behavioral responses like changing
location or body position
4. Alteration in the rate of metabolic heat
production in endotherms
2. 3.
24. Mechanisms of Homeostasis
Negative feedback - a change
in one variable (the output)
triggers a change in the control
center which turns the system
off
Example - human body
temperature
Positive feedback - a change
in one variable (the output)
triggers the control center to
amplify the output
Example - nursing by babies
(the more the baby nurses, the
more milk is produced by the
mother)
25. Quick Think
Describe the difference between positive
and negative feedback mechanisms.
Which one is more common in living
things?
26. Energy Budgets
For most animals – the majority of food
energy goes to making ATP
Very little goes toward growth or reproduction
There is great variety in how animals “spend”
their energy budget
27. Reproduction and the rearing of
offspring are “expensive”
These activities require extra energy
Animals use different strategies depending
on energy availability
Seasonal reproduction when food is available
28. Quick Think
Can ectotherms have stable body
temperatures? Explain.
29. So in summary…
What did you learn today about the main
mechanisms for how living things use free
energy to maintain homeostasis?
31. 4 main feeding mechanisms
Suspension feeders: sift small food
particles from water - ex: humpback
whales, clams
Substrate feeders: live on or in their
food source - ex: maggots, many
insect larvae
Fluid feeders: take nutrient rich fluid
from a living host - ex: mosquitos
Bulk feeders: eat relatively large
pieces of food - ex: humans, most
animals
32. Homeostatic mechanisms manage an
animal’s energy budget
Example: glucose
regulation
Animals store excess calories
as glycogen in the liver &
muscles & as fat
Animal can tap into these
energy stores when it needs
ATP
Blood glucose levels
maintained within a narrow
range by negative feedback Fat cells
33. Diet must supply carbon skeletons &
essential nutrients
Essential nutrients - must be
obtained in preassembled
organic form because animal
cannot produce them
About 1/2 of the amino acids
needed for protein synthesis are
essential amino acids - must be
taken in through food
Vitamins (B, E, C (in humans,
birds, snakes))
Minerals (Ca, P)
Caribou eating shed
antlers to get needed
phosphorus
34. Processing Food
4 main stages:
Ingestion - taking food
in
Digestion - breaking
down food into small
molecules that cells
can absorb (by
enzymatic hydrolysis)
Absorption - body cells
take up nutrients from
digestive tract
Elimination -
undigested material
passes out of digestive
tract
35. 2 main types of digestion
Intracellular - occurs within cells
enclosed by a protective
membrane - sponges do this
Extracellular - food is broken
down outside of cells - most
animals do this
Simple animals have a
gastrovascular cavity for digestion
with a single opening for food &
waste
Complex animals have complete
digestive tracts (alimentary
canals), one way flow, 2 openings
One way flow
36. The organs of the mammalian
digestive system
Mouth - food in the mouth
triggers the secretion of saliva
Saliva lubricates the food to aid
in swallowing
Saliva contains amylase -
breaks down carbs
Chewed food called a bolus
Swallowed food enters the
pharynx - tube that opens into
esophagus & trachea
Epiglottis (flap of cartilage)
covers the opening to the trachea
so food goes down the esophagus
37. Esophagus - uses peristalsis
(wave like contractions) to
move food to stomach
Stomach - stores food, secretes
very acidic (pH 2) gastric juices
Juices break down the ECM of
meat and plants; kills most
bacteria
Pepsin -enzyme in gastric juices;
secreted as pepsinogen (inactive
form) then activated by HCl
Esophagus - uses peristalsis
(wave like contractions) to
move food to stomach
Stomach - stores food, secretes
very acidic (pH 2) gastric juices
Juices break down the ECM of
meat and plants; kills most
bacteria
Pepsin -enzyme in gastric juices;
secreted as pepsinogen (inactive
form) then activated by HCl
Result of stomach
digestion is a substance
called acid chyme
This is moved into the
small intestine via the
pyloric sphincter
38. Small intestine - first section called duodenum
Here the acid chyme mixed with secretions from
pancreas, gallbladder
Rest of small intestine responsible for absorbing nutrients
Lining of small intestine has lots of little folds called villi
Villi has folds called microvilli
These greatly increase SA for absorption
39. Large intestine - AKA colon
Connected to small intestine by
a sphincter where the cecum is
found
Cecum is a small pouch with the
appendix
Main function of colon is to
absorb water & compact waste
Colon ends at rectum - feces
stored here until eliminated
40. Dentition
We can tell what
an organism eats
based on its teeth
(dentition)
Herbivores
usually have
longer digestive
tracts - since
vegetation takes
longer to digest
Editor's Notes
hummingbirds – 1260 beats per minute blue throated consume more than their weight in nectar per day can go into torpor when less food available heart down to 50-180 bpm
Eurasion pygmy shrew must eat every two hours1500 bpm