AP Biology Animal Form and Function Ch. 33

The Basics of Animal Form and
Function
Ch. 33

Objective
 Content: Describe how living
things use free energy to
maintain homeostasis
 Skill: Connect and relate
knowledge across domains

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

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

 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

Example 1: Microvilli in
intestinal cells

Example 2:
Root hairs in
plants

Example 3: branching
and folding of cell
membrane in amoeba

Example 4:
long flat body
of a tapeworm

Example 5: flat
body of
Platyhelminthes

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?

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

 Organs - organized
groups of tissues
 Organ systems -
groups of organs that
work for a common
purpose
 Example: digestive
system

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

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

Ectotherms
 Fish, amphibians, reptiles,
invertebrates
 Body temp controlled by
environment
 Less energy required
 Move more slowly when cold

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.

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

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

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

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)

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.

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)

Quick Think
 Describe the difference between positive
and negative feedback mechanisms.
 Which one is more common in living
things?

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

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

Quick Think
 Can ectotherms have stable body
temperatures? Explain.

So in summary…
 What did you learn today about the main
mechanisms for how living things use free
energy to maintain homeostasis?

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

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

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

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

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

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

 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

 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

 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

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

AP Biology Animal Form and Function Ch. 33

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AP Biology Animal Form and Function Ch. 33

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