Transcript Basic Principles of animal form & function

Campbell & Reece Chapter 40
BASIC PRINCIPLES OF ANIMAL
FORM & FUNCTION
Definitions
 Anatomy: structure of an organism
 Physiology: processes & functions of an
organism
Evolution of Animal Size & Shape
 Physical laws influence animal body plans
with regard to maximum size.
 As body sizes increase: thicker skeletons
required to maintain adequate support
 affects animals with exoskeletons as well as
endoskeletons
 also affects amt body mass that must be
allocated to muscle   @ some pt.
locomotion becomes impossible
Body Plans
 Physical requirements constrain what
natural selection can “invent”
 the mythical winged dragon could not
possibly exist (anything that large could not
generate enough lift to take off & fly)
Body Plans: Aquatic Animals
 Laws of hydrodynamics constrain the
shapes possible for aquatic organisms that
swim very fast
 All animals that swim fast have same
fusiform shape
 minimizes drag
 convergent evolution occurs because natural
selection shapes similar adaptations when
diverse organisms face the same environmental
challenges (resistance of water to fast travel)
Convergent Evolution
Exchange with the Environment
 Animals must exchange materials with
their environments which also imposes
limitations on their body plans
 rates of exchange for nutrients, wastes, &
gases is proportional to membrane surface
area
 amt material necessary to sustain life is
proportional to cell vol.
Exchange in Multicellular Animals
 works only if every cell has access to a
suitable aqueous environment (either in or
out of animal’s body)
Aqueous Environment Required
 exchange with environment occurs as
dissolved substances diffuse or are
transported across plasma membranes
 ex: unicellular protists living in water has
sufficient surface area to serve its entire
volume: surface area/vol ratio important
physical constraint on size of unicellular
organisms
Exchange with the Environment
 Interstitial Fluid: fluid that fills space
between cells in multicellular organisms;
allows all cells to have contact with aqueous
environment
 complex body systems can filter & adjust
composition of interstitial fluid
Interstitial Fluid
Exchange with the Environment
 Animals of diverse evolutionary histories &
varying complexity must solve how to
obtain energy, oxygen, how to get rid of
wastes & manage movement
 All animals must obtain food for nrg,
generate body heat, & regulate internal
temperature, sense & respond to external
stimuli
Hawk Moth
 Its probiscus extends
as a straw thru which
moth sucks nectar
from deep w/in tubeshaped flowers
Bioenergetics
 how organisms obtain, process, & use nrg
resources: a connecting theme in the
comparative study of animals
Organization of Body Plans
Definitions
 Cells: basic unit of structure & function in
living things; cells form a functional animal
body thru their emergent properties
 Tissues: groups of cells with similar
appearance & a common function
 Organs: different types of tissues grouped
together into functional units
 Organ Systems: groups of organs that work
together with a common function
Organization of Body Plans
 simplest animals lack true tissues & organs
Organ Systems in Mammals
Organ Systems in Mammals
Organ System
Main Components
Main Function
Digestive
Mouth, pharynx,
esophagus, stomach,
intestines, liver,
pancreas, anus
Food processing
(ingestion, digestion,
absorption, elimination)
Circulatory
Heart, blood vessels,
blood
Internal distribution of
materials
Respiratory
Lungs, trachea, other
breathing tubes
Gas exchange
Immune & Lymphatic
Bone marrow, lymph
nodes, thymus, spleen,
lymph vessels, WBCs
Body defense (fighting
infection & cancer)
Organ Systems in Mammals
Organ System
Main Components
Main Functions
Excretory
Kidneys, ureters, urinary
bladder, urethra
Disposal of metabolic
wastes; regulation of
osmotic balance of blood
Endocrine
Pituitary, thyroid,
pancreas, adrenal, &
other hormone-secreting
glands
Coordination of body
activities
Reproductive
Ovaries or testes & ass’c
organs
Reproduction
Muscular
Skeletal, Smooth &
Cardiac muscle
movement & locomotion
Organ Systems in Mammals
Organ System
Main Components
Main Function
Nervous
brain, spinal cord, nerves, coordination of body
sensory organs
activities, detection of
stimuli & formulation of
responses to them
Integumentary
skin & its derivatives
(nails, hair/fur claws, skin
glands)
protection against
mechanical injury,
infection, dehydration;
thermoregulation
Skeletal
bones, tendons,
ligaments, cartilage
body support, protection
of internal organs,
movement
Organ Systems in Animals
 built from a limited set of cell & tissue types
 4 tissue types:
1. Epithelial
2. Connective
3. Muscle
4. Nerve
Epithelial Tissue
 Epithelium (singular); Epithelia (plural)
 sheets of cells
 cover outside of body or line organs &
cavities w/in body
 closely packed cells often w/ tight jcts: so
can function as protection vs.. mechanical
injury, infection, fluid loss
 5 cell types
1. Cuboidal Epithelial Cells
 cubes, dice
 specialized for secretion
 found:
 renal tubules
 glands
2. Simple Columnar Epithelium
 large brick-shaped
 functions: secretion, absorption
 found: lines intestines
3. Simple Squamous Epithelium
 plate-like cells
 functions: diffusion
 found: lining blood vessels, air sacs in lungs
(alveoli)
4. Pseudostratified Columnar
Epithelium
 single layer that appears to be >1 layer
 cells are of different hts
 +/- ciliated
 form mucous membranes (lines cavities
that open to exterior of body)
 found: lining respiratory tract where
beating cilia move film of mucus with any
trapped material away from lungs
Pseudostratified Columnar
Epithelium
5. Stratified Squamous
Epithelium
 multiple layers of cells; top layer squamous
 regenerates rapidly/ new cells formed on
basement membrane…upper cells sloughed
off
 function: protection
 found: on surfaces subject to abrasion
Stratified Squamous Epithelium
Keratinized
Nonkeratinized
Connective Tissues
 tissue type with sparsest density of cells
 main cell: fibroblast: secrete fiber proteins
like collagen
 also macrophages (phagocytes)
 cells in extracellular matrix
 made up of web of fibers embedded in liquid,
jelly-like, or solid foundation
 functions:
 holds tissues together & in place
3 Connective Tissue Fibers
1. Collagenous

provide strength & flexibility
2. Reticular

join CT to adjacent tissues
3. Elastic

make tissues elastic
Loose CT
 vertebrates:most




widespread of 3 types
binds epithelia to
underlying tissues
holds organs in place
has all 3 fiber types
higher % matrix than
others
Fibrous CT
 dense w/collagen
fibers
 found in tendons
(attach muscle to
bone) & ligaments
(attach bone to bone)
Bone
 mineralized CT
 Osteoblasts: boneforming cells lay down
matrix of collagen
then Ca++, Mg++, &
PO4-- combine into
hard mineral
 Osteons: repeating
microscopic units that
make up bone
Blood
 CT with liquid matrix
called plasma
 water , salts, dissolved
proteins
 cells suspended in
plasma
 RBCs: O2
 WBCs: fight infection
 Platelets: cell
fragments used for
clotting
Adipose Tissue
 specialized loose CT that
stores fat in adipose cells
 Function:
1. pads & insulates
2. stores fuel
Cartilage
 collagen in rubbery
protein-carbohydrate
complex called
chondroitin sulfate
secreted by cells
called chondrocytes
 makes cartilage strong
but flexible
 many vertebrate
skeletons start as
cartilage  replaced
by bone
Muscle Tissue
 responsible for nearly all types of body
movement
 made of filaments with actin & myosin
(contractile proteins)
 cells called muscle fibers
 3 types:
1. Skeletal
2. Smooth
3. cardiac
Skeletal Muscle
 attached to bones by




tendons
striated
voluntary
muscle fibers form by
fusion of several cells
so appear
multinucleated
sarcomere: contractile
units (actin/myosin)
Smooth Muscle
 nonstriated
 involuntary
 spindle-shaped cells
 in walls of organs
 Esophagus/Stomach
 Intestines
 Bladder
 Arteries & Veins
Cardiac Muscle
 striated
 involuntary
 found only in heart
 intercalated disc:
connections between
cardiac fibers which
relay signals from cell
to cell  synchronizes
heart contractions
Nervous Tissue
 receives , processes, & transmits
information
 cells: neurons: transmit action potentials
 supportive cells: glial cells
 many animals have a concentration of
nervous tissue = a brain (information
processing center)
Neurons
 basic unit of nervous
system
 receive nerve impulses
(action potentials)
from other neurons or
sensory organs via
dendrites or cell body
 impulse to next
neuron (muscle fiber,
gland) via axon
 nerve: bundle of
axons
Glia
 various types: all help
nourish, insulate, &
replenish neurons
 some modulate
neuron function
Coordination & Control
 The endocrine & nervous systems are the 2
means of communication between different
locations in body.
 Endocrine system releases signaling
molecules called hormones via blood 
target cells (have the correct receptors)
 Nervous system uses cellular circuits
involving electrical & chemical signals to
send information to specific locations
Feedback Loops
Homeostatic Mechanisms
 usually based on negative feedback in which
the response reduces the stimulus
Homeostatic Mechanisms
 positive feedback: involves amplification of
a stimulus by the response & often brings
about a change in state
Alterations in Homeostasis
 Circadian Rhythm: physiologic cycle of ~24
hrs that persists even in the absence of
external cues
Acclimatization
 1 way normal range of homeostasis can
change
 gradual process by which animal adjusts to
changes in its external environment
 Example: moving from Charleston, SC to
Denver CO: physiological changes over
several days will facilitate living at higher
altitude: lower O2 in air will stimulate
increase in rate & depth of respirations 
raises blood pH by exhaling more CO2
kidneys release more erythropoietin which
stimulates RBC formation in bone marrow
Thermoregulation
 process by which animals maintain an




internal temperature w/in a tolerable range
most biochemical & physiological processes
are very sensitive to changes in temperature
for every 10°C drop most enzyme-mediated
reactions decrease 2 – 3 fold
increasing temps speed up reactions but
only to a pt…. proteins denature (unfold)
fluidity of membranes changes (+/-) with
temp changes
Endothermy
 animals that are warmed mostly by heat
generated by metabolism are endothermic
 also a few nonavian reptiles, some fishes, &
many insects
Exothermic
 animals that gain heat from their external
environment
 reptiles, amphibians, many fishes
Thermoregulation
 endothermy requires greater expenditure of
nrg
 able to maintain stable body temp even when
there’s a large fluctuation in environmental
temp
 able to increase temp when its very cold & have
adaptations for staying cooler than environment
when it is hot
 extremes usually intolerable to most ectotherms
Ectotherms
 because they do not have to generate heat
by metabolism to stay warm they usually
get by on far fewer calories than
endotherms of similar size
 many adjust body temps by behavioral
means: basking in sun for warmth; digging
burrow to stay cool in heat
Variation in Body Temp
 animals can have either constant or variable
body temp
 Poikilotherm: body temp varies with its
environment
 largemouth bass
 Homeotherm: body temp remains relatively
constant
 river otter
Variation in Body Temp
 there is no fixed relationship between
source of heat & stability of body temp
 not all poikilotherm are ectotherms & not all
homotherms are endotherms
 ex: some fish live in waters of very stable temps
so their body temps do not really vary
 bats & hummingbirds can enter an inactive
state where they maintain a very low body temp
 Remember!
 Terms cold-blooded & warm-blooded are
misleading & are avoided in scientific
communication.
Which 1 is a poikilotherm?
Which is a homotherm?
Balancing Heat Loss & Gain
 Thermoregulation depends on animal’s
ability to control the exchange of heat with
their environment.
 Heat exchange occurs in 4 ways (same as
inanimate objects)
1. Radiation
2. Evaporation
3. Convection
4. Conduction
Heat Exchange
Thermoregulation
 animals must maintain rates of heat gain
that = rates of heat loss
 have adaptations that either reduce heat
exchange overall or favor heat exchange in 1
direction
 mammals utilize integumentary system
Integumentary System
1. Insulation


reduces heat loss from animal  environment
hair, feathers, layer of subcutaneous adipose
(esp. important for marine mammals)
2. Circulatory alterations


major role in heat exchange from internal to
external body
nerve signals relax/constrict smooth muscle in
blood vessels depending on need to loose or
retain body heat
Countercurrent Exchange
 transfer of heat (or
solutes) between
fluids that are flowing
in opposite directions
Countercurrent Exchange
 used by birds, mammals, certain sharks,
fish, & insects
 Great white sharks, bluefin tuna &
swordfish all use it to keep main swimming
muscles several degrees warmer than
tissues near animal’s surface
 bumblebees, honeybees, & some moths use
it to maintain higher temps in their thorax
(flight muscles located there)
Cooling by Evaporative Heat Loss
 if environment’s temp > animal’s body temp
they will gain heat from their surroundings
+ metabolism: evaporation is only way to
keep body temp from rising
 terrestrial animals lose water by
evaporation from their skin & respiratory
surfaces
Cooling by Evaporation
 water absorbs considerable heat when it
evaporates: removing heat from body in
process
 some animals have adaptations that greatly
augment this cooling effect:
 panting important for many mammals & birds
 some birds have pouch rich in blood vessels in
mouth…fluttering the pouch increases
evaporation
Behavioral Responses
 used by both
endotherms : &
ectotherms: change
position to increase or
decrease amt
radiation from sun
Behavioral Responses
 Honeybees: response depends on social
behavior:
 cold weather: huddle, bees move from outer
edge of huddle to inside to keep everyone warm
enough, use honey as nrg source
 in heat: bring water in hive & fan over it with
wings promoting evaporation & convection
Adjusting Metabolic Heat
Production
 endotherms can vary thermogenesis to
match changing rates of heat loss
 increase thermogenesis: (as much as 5-10x)
 shivering
 chickadees use it to maintain 40°C even if-40°C
 mammals:
 some can switch mitochondria from making ATP
 heat
 others use brown fat (specialized for rapid heat
production)
Adjusting Heat Loss
 increasing thermogenesis:
 Burmese pythons become endothermic when
incubating eggs (were some dinosaurs
endothermic?)
 smallest endotherms are bees & moths
use flight muscles, shivering, to generate heat
Acclimatization in
Thermoregulation
 often involves changes in amts of insulation
in endotherms (thicker coat in winter/ shed
in warmer weather)
 ectotherms: make adjustments on the
cellular level:
 make variants of enzymes that have same
function but different optimal temps
 sat./unsat lipids in membranes changes
 produce antifreeze cpds
Hypothalamus (Mammals)
 contains sensors that function as a
thermostat
 when sense body temp outside normal range 
responses that activate mechanisms that
promote heat loss or gain
Energy Requirements
 Animals obtain chemical nrg from food,
storing it for short time in ATP
 Total amt of nrg used in a unit of time
defines an animal’s metabolic rate
 Generally, metabolic rates higher for
endotherms than ectotherms
Basal Metabolic Rate
 BMR: the metabolic rate of a resting,
fasting, & nonstressed endotherm at a
comfortable temperature.
 BMR for endotherms substantially higher
than the Standard Metabolic Rate (SMR) of
ectotherms (the metabolic rate of a resting,
fasting, and nonstressed ectotherm at a
particular temperature
BMRs in Humans
BMR
 minimum metabolic rate/g is inversely
related to body size among similar animals
 animals allocate nrg for basal (or standard)
metabolism, activity, homeostasis, growth,
& reproduction
Torpor
 a state of decreased activity & metabolism,
conserves nrg during environmental
extremes
 animals may enter torpor during sleep
periods (daily torpor), in winter
(hibernation) or in summer (estivation)
Hibernation
 most hibernating animals are small
 metabolic rates drop 20x so nrg savings
huge