AP Biology Unit Four Maintaining Homeostasis

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AP Biology Unit FourMaintaining Homeostasis
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Just bear with me
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• BIG IDEA 2 Biological systems utilize energy
  and molecular building blocks to grow, to
  reproduce, and to maintain homeostasis.
• BIG IDEA 3 Living systems store, retrieve,
  transmit, and respond to information essential to
  life processes.
• BIG IDEA 4 Biological systems interact, and
  these interactions possess complex properties.

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We will cover..

• Feedback control AGAIN!
• Evolutionary development of animal organ systems
  to control homeostasis with the environment
• Cellular signaling
• Specific systems endocrine, nervous, immune
• Plants homeostaticmechanisms and how they
  respond

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Organism Organization

• Cells
• Tissues
• Organs
• Organ Systems (not technically in plants)
• Organism
• The structure of a component of an organism
  underlies its function.

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Homeostasis

• occurs in ALL organisms
• Involves all levels (except unicellular
  organisms) cells, organs, organisms
• Reflects continuity and change
• Shaped by evolution
• Affected by disruptions
• Defenses evolved to maintain

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Remember.

• Body systems coordinate their activities to
  maintain homeostasis.

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• Boseman videos are helpful!
• bit.ly/homeoprezi

http//www.youtube.com/watch?vTeSKSPPZ6Ik
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HOMEOSTASIS
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behavior
Timing and control control
disruption
Feedback loops
response
environment
Shaped by evolution
HOMEOSTASIS
physiological
abiotic
biotic
development
defenses
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Regulator or conformer?

• Regulators control internal fluctuations (us)
• Conformers allow internal conditions to vary
  with environmental changes (temp in ectotherms)

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acclimatization

• An animals normal range of homeostasis may
  change as the animal adjusts to external
  environmental changes

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Video on Feedback Loops

• As you watch, take notes on the basic diagram of
  a negative feedback loop
• What are the component parts
• Use two biological examples

http//www.youtube.com/watch?vq_e6tNCW-uk
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Negative Feedback Loops
RECEPTOR
STIMULUS
EFFECTOR
RESPONSE
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• In mammals, a group of neurons in the
  hypothalamus functions as a thermostat
• Fever as a response to infection can reset the
  hypothalamus set point.

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Other circulatory adjustmentsCountercurrent
exchange in temp regulation

• Common in marine mammals and birds
• the heat in the arterial blood leaving the body
  core is transferred to the venous blood

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Other thermoregulatory mechanisms

• Insulation
• Evaporative heat loss
• Behavioral responses
• Regulation of metabolic heat
• - endotherms use metabolic heat to
• maintain their body temp
• - ectotherm gain heat mostly from
• environment

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Raising temp metabolically

• Mammals and birds regulate rate of metabolic heat
  production through activity and shivering.
• Some mammals generate heat through nonshivering
  thermogenesis, rise in metabolic rate produces
  heat instead of ATP.
• Some mammals have brown fat for rapid heat
  production.

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Negative feedback control of sugar in the blood
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Islets of Langerhans
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Positive feedbackoxytocin to induce childbirth
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Ethylene in fruit ripening
Has anyone told you to put a banana in the bag
with your apples or pears to help them ripen?
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Biological Examples of Negative Feedback Loops
Thermoregulation Blood Sugar Levels Blood
volume Respiratory Rate
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Negative Feedback Loops
RECEPTOR
STIMULUS
EFFECTOR
RESPONSE
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• Homeostatic mechanisms and organ systems are
  shaped by evolution.
• Excretory systems deal with osmoregulation
  (water balance) and excretion of nitrogenous
  wastes

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osmoregulation

• Prokaryotes respond via altered gene expression
  to changes in the osmotic environment
• Protists Many have contractile vacuoles

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• Freshwater Water will diffuse into the fish, so
  it excretes a very hypotonic (dilute) urine to
  expel all the excess water. Gills uptake lost
  salt.
• A marine fish has an internal osmotic
  concentration lower than that of the surrounding
  seawater, so it tends to lose water and gain
  salt. It actively excretes salt out from the
  gills.

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dealing with nitrogenous wastes

• The excretory system in vertebrates
• - maintains water, salt, and pH balance
• - removes nitrogenous wastes (from breakdown
  of protein and nucleic acids) by filtering the
  blood
• - nitrogenous waste type depends on
  environment

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Excretory system in flatworms
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Excretory system in earthworms
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In humans
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• The kidney works closely with the circulatory
  system in that the salt content, pH, and water
  balance of the blood is controlled by the
  kidneys.

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Within the kidney, fluid and dissolved substances
are filtered from the blood and pass through
nephrons where some of the water and dissolved
substances (nutrients) are reabsorbed. The
remaining liquid (including toxins) and wastes
form urine.
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What homeostatic mechanisms work here?

• Concentrated blood (too much salt, too little
  water) signal receptors in the hypothalamus to
  stimulate release of ADH (AntiDiuretic Hormone)
  by the pituitary gland which influences kidney to
  reabsorbs water, making blood more dilute.

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• Alcohol inhibits the release of ADH, causing the
  kidneys to produce dilute urine.

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• If, on the other hand, a person drinks an excess
  of water, the sodium in the blood becomes more
  dilute and the release of ADH is inhibited.
• The lack of ADH causes the nephrons to become
  practically impermeable to water, and little or
  no water is reabsorbed from them back into the
  blood.
• Consequently, the kidneys excrete more watery
  urine until the water concentration of the body
  fluids returns to normal.

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Development of respiratory systems
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The Respiratory System

• The respiratory system
• - delivers oxygen to and removes CO2 from the
  circulatory system and eventually the tissues
• - in humans, this occurs in the alveoli of the
  lungs which are covered in capillaries
• The respiratory system works closely with the
  circulatory system.

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Fish respiratory system
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Countercurrent exchange
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How are lungs perfected for terrestrial living?
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lungfish
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How does structure correlate with the function of
the parts?
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What homeostatic mechanisms are at work here?

• Breathing is controlled by the medulla of the
  brainstem. It repeatedly triggers contraction of
  the diaphragm initiating inspiration.
• The rate of breathing changes with activity level
  in response to carbon dioxide levels, and to a
  lesser extent, oxygen levels, in the blood.
  Carbon dioxide lowers the pH of the blood (water
  and CO2 make carbonic acid H2CO3).
• Hemoglobin carries oxygen and also can carry
  bicarbonate ions (form of CO2)..

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• There are chemosensors in the carotid artery
  and the arch of the aorta . The sensors of the
  aortal are sensitive to the level of oxygen in
  the blood. Sensors near the medulla are sensitive
  to the level of carbon dioxide in the blood.
• If oxygen level falls or carbon dioxide levels
  vary too greatly from the set point, a negative
  feedback mechanism increases respiratory rate.

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• Mammals are most sensitive to carbon dioxide
  levels because the amount of CO2 varies most in
  respiration in response to different metabolic
  and environmental conditions.

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Circulatory System

• Function moving substances around nutrients
  (from digestion), wastes (from excretion), O2 and
  CO2 (from respiration), hormones (endocrine),
  immune substances, and lymph fluid.
• Closely tied to the digestive, excretory,
  respiratory, endocrine, immune, and lymphatic
  system.

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Types

• Open blood mixes with internal organs directly
  (insects, arthropods, mollusks)
• Closed blood stays in vessels (earthworms, some
  mollusks such as octopi, vertebrates

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Structures vary for types of animals

• Fish one ventricle, one atrium, gill
  capillaries, single loop
• Amphibian one v, 2 a, lung and skin
  capillaries, double circulation (one to body, one
  to lungs)
• Reptiles partially divided v, 2 a, other same
  as amphibs
• Mammal, Birds 2 v, 2 a, lung capillaries,
  double circulation

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• Flow of blood in Mammalian Heart
• right, right, lungs, left, left, body (right
  side unoxygenated traveling to lungs
• the pulmonary artery (arteries away, veins
  toward heart).
• R R lungs L L body

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Beating of the heart controlled when cardiac
muscles transfers an electrical signal via the SA
(sinoatrial) node or pacemaker (in top right
atrium) to the AV (atrioventricular) node between
the right a and v.
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Blood Pressure

• Force of blood against an artery. Measured as
  Systolic (Super Top Most.when ventricles are
  contracting) over Diastolic (down, minimum, when
  ventricles fill with blood) normal 120/80
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How does negative feedback loops work here?For
regulating heart beat

• Receptor
• Stimulus
• Effector
• response

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Development of Digestive Systems

• Intracellular Digestion ex amoeba
• Extracellular Digestion bacteria, us

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Digestive Systems in Animals

• One opening sac (cnidarians, flatworms)
• Tube roundworms and on
• Why more advantageous?

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The Digestive System in Humans

• Ingestion, mechanical and chemical breakdown of
  food, absorption of nutrients, elimination of
  wastes

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Pathway

• Oral Cavity only carbs broken down here!
  Mechanical digestion - teeth
• Esophagus just a muscular tube, peristalsis
  pushed food down
• Stomach only protein broken down here! (low pH
  due to secretion of gastric juice), lots of
  churning in another muscular organ

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The Big Boys..small intestines and accessory
glands

• Carbs, proteins, and lipids broken down here.
• Most digestion and absorption here!
• Pancreatic enzymes and bile (for fat) from the
  liver via the gallbladder released in this area.
• Microvilli extend the surface area.

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Microvilli in the small intestine
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Finishing up

• Large intestine (colon)- no digestion, just
  reabsorbs water and creates feces

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Can you live without yourHow?

• Stomach?
• Small Intestine?
• Large intestine?

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• How does the homeostatic evolution of these
  systems reflect
• Continuity
• Divergence

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Case Study

• The story of Darlene Etienne and her miraculous
  homeostatic mechanisms!

http//www.reuters.com/article/video/idUSTRE60O29A
20100128?videoId34511738
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• "We cannot really explain this because that's
  just (against) biological facts," Lambert told a
  news conference. "We are very surprised by the
  fact that she's alive. ... She's saying that she
  has been under the ground since the very
  beginning on the 12th of January so it may have
  really happened but we cannot explain that."
• Authorities say it is rare for anyone to survive
  more than 72 hours without water, let alone 15
  days. But Etienne may have had some access to
  water from a bathroom of the wrecked house, and
  rescuers said she mumbled something about having
  a little Coca-Cola with her in the rubble.
• Fuilla said Etienne did not suffer a broken leg,
  as first reported, but that both legs were
  trapped under debris. "Both legs are very sore,"
  he said.

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Rescuers said the 16-year-old, who was severely
dehydrated and covered in dust, possibly survived
by drinking bathwater but could not have lasted
much longer. Earthquake survival
stories
http//news.bbc.co.uk/2/hi/americas/8459090.stm