Download Homeostasis and Evolution

Homeostasis and Evolution
AP Biology
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Homeostasis
 Homeostasis is the way an organism
maintains a stable internal environment
within itself
 Body systems coordinate their
activities to maintain homeostasis.
 This is done through the use of positive
and negative feedback loops
 These finely tune the internal workings of
the organism
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Remember Feedback Loops?
 Negative Feedback Loops:
 organism responds to a stimulus by decreasing the occurrence of the
stimulus or is opposite of the stimulus so that the “change” comes to
an end and balance is restored
 Examples:



Lac operon
Shivering to raise body temperature
Releasing insulin to lower blood sugar levels
 Animation of how lac operon works:
 http://www.sumanasinc.com/webcontent/animations/content/la
coperon.html
 http://vcell.ndsu.edu/animations/lacOperon/movie-flash.htm
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Negative Feedback Loops
RECEPTOR
STIMULUS
EFFECTOR
RESPONSE
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 Positive Feedback Loops:
 Control mechanism in which an organism adjusts to a change in
internal environment by further stimulating (propagating) the
change
 Examples:

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Release of oxytocine during childbirth to accelerate the rate of contractions
resulting (eventually) in birth
How Does Homeostasis Relate to
Evolution?
 We need to compare several species of organisms together to
find similarities and differences within one another to answer
that question…
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Circulatory Systems of Fish, Amphibian,
and Mammals
 Similarities suggests the existence of a common ancestor millions
of years ago
 All three circulatory systems are composed of blood, veins,
arteries, capillaries, and a heart.
 The purpose of the blood in all 3 is to carry oxygen and other
nutrients to locations throughout the organism.
 The major difference comes from the method through which the
3 systems carry out their blood flow.
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Circulatory systems
 Basic structures needed:
 circulatory fluid = “blood”
 tubes = blood vessels
 muscular pump = heart
open
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hemolymph
closed
blood
Two
chamber
heart
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Three
chamber
heart
Four
chamber
heart
 The mammal circulatory system is the “most advanced” because of
its ability to maximize the amount of oxygen and nutrients in the
organisms blood flow.
 The evolution of the chambered heart suggests the gradual fine
tuning that is associated with homeostasis.
 As organisms moved from water to land, in order to maintain the
stable internal environment, their circulatory system had to better
evolve in order to efficiently regulate the oxygen and nutrients
carried by the blood.
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Respiratory Systems of Aquatic and
Terrestrial Animals
 Both aquatic and terrestrial animals have specialized organs
to absorb oxygen from their surroundings, which travels
their blood to provide oxygen throughout their whole body.
Blobfish (Psychrolutes
marcidus) about a 1 foot
long and just floats along
bottom of ocean floor..in
danger of extinction
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Evolution of gas exchange structures
Aquatic organisms
external systems with
lots of surface area
exposed to aquatic
environment
Terrestrial
moist internal
respiratory tissues
with lots of surface area
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 Evolutionary evidence suggests that life originated in oceans and
eventually moved on to land.
 It is assumed that gills are primitive and evolved into lungs once
organisms moved out of the ocean
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Osmoregulation in Bacteria, Fish,
Protists, Aquatic and Terrestrial Plants
 Osmoregulation is the control of solute concentration and
balance between water gain and water loss
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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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In Fish
 Freshwater Fish: 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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Osmoregulation in Plants
 Occurs via stomata
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Nitrogenous Waste Production –
Aquatic and Terrestrial
 removes nitrogenous wastes (from breakdown of
protein and nucleic acids) by filtering the blood
 nitrogenous waste type depends on environment
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Nitrogen waste
 Aquatic organisms


can afford to lose water
ammonia
 most toxic
 Terrestrial


need to conserve
water
urea
 less toxic
 Terrestrial egg
layers



need to conserve water
need to protect
embryo in egg
uric acid
 least toxic
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One Way Digestion vs
Complete Digestion
 Digestion is the process of changing food into a form that the
body can absorb and use as energy or as the raw materials to
repair and build new tissue.
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One Way Digestion
 Some animals have a digestive system with only one opening
which is the mouth. These include jellyfish, sea anemone, and
planaria.
 They take in food through the mouth, digest the food and absorb
digested material. Then the undigested parts are pushed back out
through the mouth.
 This is also called an incomplete digestive system.
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Complete
Digestion
 Most animals have a digestive system with two openings which
are the mouth and the anus. These include worms, arthropods,
chordates.
 Take in food through the mouth, then digest and absorb it over
stages as it passes through the organs of the digestive system. The
undigested material passes out of the body through the anus.
 More efficient. An animal does not have to be finished digesting
and absorbing one meal before the animal takes in the next meal.
The animal can have food in all stages of digestion.
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Case Study
 The story of Evans Monsignac and his miraculous
homeostatic mechanisms!
http://www.telegraph.co.uk/news/worldnews/centralamericaandthecaribbean/haiti/7530686/Buri
ed-for-27-days-Haiti-earthquake-survivors-amazing-story.html
http://www.liveleak.com/view?i=34f_1265701618
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Other Earthquake
survival stories.....
http://news.bbc.co.uk/2/hi/americas/8459090.stm
https://www.youtube.com/watch?v=YlSENbUCRGM
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