Regulating the Internal Environment -...
Transcript of Regulating the Internal Environment -...
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AP Biology
AP Biology 2006-2007
Homeostasis
Regulating the Internal
Environment
AP Biology
Diverse Forms, Common Challenges
▪ Anatomy: the study of
the biological form
(STRUCTURE) of an
organism
▪ Physiology: the study
of the biological
FUNCTIONS an
organism performs
▪ Structure dictates
function!
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Hierarchical Organization of Body Plans
Cells Tissues Organs Organ Systems
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Four main types of tissues:
1.Epithelial: covers the outside of the
body and lines the organs and cavities
within the body
2.Connective: binds and supports other
tissues (cartilage, tendons, ligaments,
bone, blood, adipose)
3.Muscle: controls body movement
(skeletal, smooth, cardiac)
4.Nervous: senses stimuli and transmits
signals throughout the animal
(neurons, glia)
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Coordination and control within a body
▪ Endocrine System: transmits chemical signals (hormones) to all locations in the body through the bloodstream
Slow acting, long-lasting effects
Info received by: cells with specific receptors for released hormone
▪ Nervous System: neurons transmit info between specific locations
Very fast!
Info received by: neurons, muscle cells, endocrine cells
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Homeostasis
▪ Keeping the balance
animal body needs to coordinate many systems all at once▪ temperature
▪ blood sugar levels
▪ energy production
▪ water balance & intracellular waste disposal
▪ nutrients
▪ ion balance
▪ cell growth
maintaining a “steady state” condition
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Conformers vs. Regulators
▪ Two evolutionary paths for organisms
regulate internal environment▪ maintain relatively constant internal conditions
conform to external environment▪ allow internal conditions to fluctuate along with external changes
conformer
thermoregulation
regulator
conformer
osmoregulation
regulator
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Homeostasis
▪ Fluctuations above/below a set point
serve as a stimulus; these are detected by
a sensor and trigger a response
▪ The response returns the variable to the
set point
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Negative Feedback
▪ “More gets you less.”
▪ Return changing
conditions back to set
point
▪ Examples:
Temperature
Blood glucose levels
Blood pH
Plants: response to
water limitations
Positive Feedback
▪ “More gets you more.”
▪ Response moves
variable further away
from set point
▪ Stimulus amplifies a
response
▪ Examples:
Lactation in
mammals
Onset of labor in
childbirth
Plants: ripening of fruit
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Temperature Regulation
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sensor
Negative Feedback Loop
high
low
hormone or nerve signal
lowersbody condition(return to set point)
hormone or nerve signal
gland or nervous system
raisesbody condition(return to set point)
gland or nervous system
sensor
specific body condition
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Thermoregulation• Maintain an internal
temperature within a
tolerable range
• Endothermic animals
generate heat by
metabolism (birds and
mammals)
• Ectothermic animals
gain heat from external
sources (invertebrates,
fishes, amphibians, and
nonavian reptiles)AP Biology
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• Metabolic rate: total amount of energy an animal uses in a unit of time
• Ectotherms have much lower metabolic rates than endotherms of a comparable size
Energy Use
Metabolic rate is inversely related to body size among similar animals
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Balancing Heat Loss and Gain•Organisms exchange heat by four
physical processes: radiation, evaporation, convection, and
conduction
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Five adaptations for thermoregulation:
• Insulation (skin, feather, fur, blubber)
• Circulatory adaptations (countercurrent exchange)
• Cooling by evaporative heat loss (sweat)
• Behavioral responses (shivering)
• Cellular adjustments (“antifreeze” proteins, membrane lipids, enzyme variants)
AP Biology
Countercurrent
heat exchange
A counterflow mechanism that
enables fluids at different
temperatures flowing in
channels in opposite directions
to exchange their heat content
without mixing.
An example of countercurrent heat
exchange occurs in the feet geese, in
which heat from blood in the arteries
supplying the feet is transferred to blood
returning to the body's core in veins that lie
close to these arteries.
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Controlling Body Temperature
high
low
nerve signals
sweat
nerve signals
brain
body temperature
shiver brain
dilates surfaceblood vessels
constricts surfaceblood vessels
Nervous System Control
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Torpor and Energy Conservation
▪ Torpor is a physiological state in which activity is low and metabolism decreases
▪ Save energy while avoiding difficult and dangerous conditions
▪ Hibernation: torpor during winter cold and food scarcity
▪ Estivation: summer torpor, survive long periods of high temperatures and scarce water
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Osmoregulation
Nitrogenous wastesMarine vs. Freshwater FishAP Biology
Osmoregulation
Mammalian Excretory System
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Osmoregulation
Why do all land animals have to conserve water?
▪ always lose water (breathing & waste)
▪ may lose life while searching for water
▪ Water balance
freshwater
▪ hypotonic
▪ water flow into cells & salt loss
saltwater
▪ hypertonic
▪ water loss from cells
land
▪ dry environment
▪ need to conserve water
▪ may also need to conserve salt
hypotonic
hypertonic
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Intracellular Waste
▪ What waste products?
what do we digest our food into…
▪ carbohydrates = CHO
▪ lipids = CHO
▪ proteins = CHON
▪ nucleic acids = CHOPN
CO2 + H2O
NH2 =
ammonia
CO2 + H2O
CO2 + H2O
CO2 + H2O + N
CO2 + H2O + P + N
|
| ||H
HN C–OH
O
R
H
–C–
Animalspoison themselvesfrom the insideby digestingproteins!
lots!verylittle
cellular digestion…cellular waste
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Nitrogenous waste disposal
▪ Ammonia (NH3)
very toxic
▪ carcinogenic
very soluble
▪ easily crosses membranes
must dilute it & get rid of it… fast!
▪ How you get rid of nitrogenous wastes depends on
who you are (evolutionary relationship)
where you live (habitat)
aquatic terrestrial terrestrial egg layer AP Biology
Nitrogen waste▪ Aquatic organisms
can afford to lose water
ammonia
▪ most toxic
▪ Terrestrial need to conserve
water
urea
▪ less toxic
▪ Terrestrial egglayers need to conserve water
need to protectembryo in egg
uric acid
▪ least toxic
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Freshwater animals
▪ Water removal & nitrogen waste disposal
remove surplus water
▪ use surplus water to dilute ammonia & excrete it
need to excrete a lot of water so dilute ammonia &
excrete it as very dilute urine
▪ also diffuse ammonia continuously through gills or
through any moist membrane
overcome loss of salts
▪ reabsorb in kidneys or active transport across gills
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Land animals
▪ Nitrogen waste disposal on land
need to conserve water
must process ammonia so less toxic▪ urea = larger molecule = less soluble = less toxic 2NH2 + CO2 = urea
produced in liver
kidney▪ filter solutes out of blood
▪ reabsorb H2O (+ any useful solutes)
▪ excrete waste urine = urea, salts, excess sugar & H2O
urine is very concentrated
concentrated NH3 would be too toxic
OC
HNH
HNH
Ureacosts energyto synthesize,
but it’s worth it!
mammals
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Egg-laying land animals
itty bittyliving space!
▪ Nitrogen waste disposal in egg
no place to get rid of waste in egg
need even less soluble molecule
▪ uric acid = BIGGER = less
soluble = less toxic
birds, reptiles, insects
Uric Acid = Polymerized urea
large molecule
precipitates out of solution
▪ doesn’t harm embryo in egg
white dust in egg
▪ adults still excrete N waste as white paste
no liquid waste
uric acid = white bird “poop”!
This is also why male birds don’t have penis
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Summary ▪ Not filtered out
cells proteins
remain in blood (too big)
▪ Reabsorbed: active transport
Na+ amino acids
Cl– glucose
▪ Reabsorbed: diffusion
Na+ Cl–
H2O
▪ Excreted
urea
excess H2O excess solutes (glucose, salts)
toxins, drugs, “unknowns”
whyselective reabsorption
& not selectivefiltration?
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Environmental Ques and
Homesostasis
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Daily and Seasonal Timing
Circadian and Circannual Clocks in Living
Things
Many Living Things Have a Internal Clocks
DAILY
Regulates daily cycle of
activitiesRegulates seasonal
changes in gene expression
and behavior
SEASONAL
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Circadian Rhythm are Endogenous
▪ Occur internally- do not require environmental cues
▪ BUT can be altered by environmental cuesAP Biology
Evolutionary Adaptations
▪ Daily and seasonal changes are genetic characteristics
that have evolved because their presence is
advantageous
▪ Natural selection has favored these traits
▪ We have genes that control these rhythms
▪ But environment can change gene expression (epigenetics)
▪ There are clear patterns of brain wave activity, hormone production,
cell regeneration and other biological activities linked to this daily
cycle.
Under Genetic Control
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Circadian Rhythms in Plants
▪ Change in leaf
orientation
▪ Opening of
stomata – pores in
the leaf
▪ Opening of flowers
and release of
fragrance
▪ Movement of Leaves happened at nearly same time
every day, even on cloudy days
▪ BUT artificial light at different times confuses the
plant’s internal clockAP Biology
Circadian Rhythm in Animals
Closely tied to sleep-wake cycle
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Why You’re Stressed in the Morning
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Light Might Inhibit Melatonin Release▪ Melatonin to controls sleep urges
▪ artificial lights can prevent melatonin release and keep people
awake
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Seasonal Clocks
Affect gene expression
Control things like:
Shedding of coats
Reproduction
Hibernation
Migration
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In Animals▪ Light absorption by the eye triggers change in gene
expression / Thought to be mediated by melatonin
Shedding of Coats or Changing of Color
Arctic Wolf in SummerArctic Wolf in Winter
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Seasonal
Reproduction
▪ Many species only
reproduce in
spring or summer
▪ When more food
(energy) is
abundant
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Ex. How Seasons Affect Reproduction
in Animals
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Hibernation/Estivation
▪ Helps conserve
energy when little
food available
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Migration▪ Changes in light trigger
hormone changes
As there’s less light
birds build up fat for
journey
▪ Also occurs in birds in
captivity with consistent
light sources
▪ BUT reducing light brings
about changes in behavior