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AP Biology
• During development an organisms cells differentiate from
Stem cells
• Stem cell – any unspecialized cell that can produce,
during a single division one identical daughter cell and
one more specialized daughter cell
• This occurs via structural and functional divergence of cells
Cell Specialization
1.
2.
3.
4.
5.
6.
Molecular level (chemicals)
Cell
Tissue
Organ
Organ system
Organism
Cellular organization
Feedback
Disruption
Physiological
Homeostasis
• Defense
• Development
Response
Environment
Behavioral
• Timing and
coordination of
events
Biotic
Form and Function
Abiotic
• Negative – Reduces frequency, regulates physiological
processes back to a target set point (long term)
• Positive – Increase frequency or amplify processes (short
term)
Positive and Negative feedback
Target set point
Negative
feedback
Stabilization
Temperature
regulation
Plant responses
to water
Positive
feedback
Amplification
Fruit ripening
Child birth
Lactation in
mammals
Regulator
Vs
Conformer
Temp. regulation
To become attractive plants produce fruit, this
makes them desirable so animals will take and
carry off their seeds.
Plants communicate via ethylene – a gas
• Lactation in mammals – When baby drinks milk,
hormones prolactin and oxytocin are released, this causes
milk to be released and produced.
• Child birth – pressure on cervix causes contractions.
Contractions cause more pressure
• Blood clotting – vascular spasms
Decrease blood flow, plug
formation, coagulation
Other Positives
• Some changes to homeostasis are regulated and many are
controlled by hormones.
• Examples:
• Women’s menstrual cycle
• Circadian rhythm (changes that occur every 24 hours)
• Acclimation- gradual process in which animal adjusts to
external environment
Alteration of feedback 
Normal alterations
• Thermoregulation – process
by which animals maintain
an internal temperature
• Endothermic – warmed by
heat they generate via
metabolism
• Ectothermic – gain heat via
external sources
Maintaining homeostasis physiological
• Balancing Heat Loss and gain
•
•
•
•
Integumentary system
Insulation
Circulatory adaptations
Cooling via evaporative heat loss
Maintaining homeostasis
• Increases blood flow
to help keep warm
• Decreases blood flow
to help keep cool
Maintaining homeostasis
• Countercurrent
exchange- exchange
of heat via fluids or
between fluids that
are moving in the
opposite direction
Maintaining homeostasis
•
•
•
•
•
Maximize sunlight absorption
Postures
Huddling together
Torpor
Hibernation
Maintaining homeostasis behavioral
Feedback
Disruption
Physiological
Homeostasis
• Defense
• Development
Response
Environment
Behavioral
• Timing and
coordination of
events
Biotic
Form and Function
Abiotic
• Homeostatic disruptions are anything that affects the
individual or the environment in which the individual
lives in
• Can be:
• Molecular level
• Ecosystem level
Disruptions In Homeostasis
• Problem in feedback loops
• Can be
• Type I (juvenile or child onset)
• Type II
• Both cases cells are not communicating in the feedback
loop dealing with blood sugar
Diabetes
Diabetes
Insulin
Blood glucose
glucagon
Alteration of feedback 
Dehydration:
Molecular disruption
1-2% loss
increase in body temperature, thirst,
discomfort, loss of appetite, dry skin,
constipation
5% loss
All above and: headaches, increased
heart rate, nausea, tingling limbs
6% loss
All of the above and: muscle spasms,
cramping
10% loss
All above and: susceptibility to heat
stroke, circulatory collapse, vision
dims, urination stops
50% loss
death
Molecular disruption
• Invasive species: A species, often introduced by humans,
that takes hold outside its native range
Ecosystem disruptions
Feedback
Disruption
Physiological
Homeostasis
• Defense
• Development
Response
Environment
Behavioral
• Timing and
coordination of
events
Biotic
Form and Function
Abiotic
• Response: Anything an organism does as a result of its
surroundings
• Can be:
• Behavioral
• Physiological
Form and Function
• Occurs as a population or a group of organisms
• Examples:
1. Hibernation
2. Migration
Can be learned or inherited
Behavioral Responses
• Changes within the organism
• Examples:
1. Shivering
2. Sweating- evaporative cooling
Physiological responses
Feedback
Disruption
Physiological
Homeostasis
• Defense
• Development
Responses
General
Environment
Behavioral
• Timing and
coordination of
events
Biotic
Form and Function
Abiotic
• Plants and animals defend themselves from pathogens
• Pathogens- invaders
• 2 major forms of defense:
1. Nonspecific
2. Specific
Physiological-Defense
• Kills anything that invades (skin, saliva, normal bacteria,
swelling, inflammation etc.)
• Plants sense pathogens using Hypersensitive Responses
Nonspecific
• R gene in chromosomes –
senses invading proteins
• R gene will initiate a
hypersensitive response
• Oxidative burst – apoptosis
• Proteins sent to adjacent cells
will change cell wall
• Memory does not occur
Nonspecific - hypersensitive
• Specific responses identify pathogens and attack them
• Occurs in 2 forms:
1. Humoral – occurs in humor/liquid/blood/lymphatic
2. Cell mediated – target infected cells
Specific
•
•
•
•
Humoral responses are governed by B cells
B cells produce memory Antibodies
Antibodies target invaders
Invaders are called antigens -
Humoral
• Antibodies have antigenbinding sites
• Antigen- is an antibody
generating organism
• fungus, bacteria, virus etc.
Humoral
1. Antigen present – invader
2. Antigen is engulfed (eaten) by a WBC or macrophage
3. WBC will take some of the antigen and put it on the
surface of its cell (Antigen Presenting Cell)
4. Helper T cells- recognize the shape of the antigen
5. Helper T cells- activate B cells to make antibodies
a. plasma B – makes antibodies
b. memory B
6. B cells invade antigens
Humoral
• This response targets infected cells
• Called cytotoxic T cells – kills own cells that are infected
Cell-mediated
Feedback
Disruption
Physiological
Homeostasis
• Defense
• Development
Responses
General
Environment
Behavioral
• Timing and
coordination of
events
Biotic
Form and Function
Abiotic
How does this happen?
Physiological- Development
• Seed Germination –
• When planting seeds it needs 2 things to survive (water and
temperature) must be in correct combination
• Germinating cells will appear different
Physiological
• First step in development is cellular differentiation
• DNA will express specific proteins that determine each
tissue – called tissue specific proteins
• Cells will eventually specialize
Physiological
• Zygote makes a copies of itself
• Forms a sphere (blastula)
• Blastula folds in on itself (gastrula) forms ectoderm,
mesoderm and endoderm
• Transcription factors give off proteins that help to
determine what should happen
Physiological - differentiation
• Step 2 is embryonic induction:
• Cells induce other cells to become like them, give off
proteins
• Cells induce adjacent cells next to it
Physiological - induction
•
•
•
•
Just as important as cell growth
Hid, Grim, Reaper Genes
These genes are needed between fingers and toes etc.
microRNA genes – control hid, grim, reaper genes
Physiological – cell death
• How do cells “know” the body plan of organisms?
• Homeotic genes – are a series of genes that “tell”
drosophila where to put the organs/appendages etc.
• Famous ones are HOX genes
We learned from the
mutants
Ultrabithroax will
duplicate the thorax
Antp- one leg will
grow of the head
Series of genes that
codes for body plan
Physiological- Homeotic genes
Feedback
Disruption
Physiological
Homeostasis
• Defense
• Development
Responses
General
Environment
Behavioral
• Timing and
coordination of
events
Biotic
Form and Function
Abiotic
When traveling –
especially across time
zones jet-lag occurs
Timing and control
1. Phototrophism – how plants grow toward or away from
light
Toward light +
Away from light –
Hormone: Auxin
Timing and control - plants
2. Photoperiodism – how plants respond to changing
amounts of light during the season
Phytochrome – light receptor- when absorb light, will
change shape to let plant know what time of day and season
it is (regulates cellular activities)
Timing and control - plants
• Circadian rhythms –
• Animals sense light• Sent to pineal gland
• Releases melatonin which sets internal clock
Timing and control - animals
• Bacteria use Quorum Sensing
• How bacteria talk or communicate with each other
• Can be among species or between species
• Bacteria give off autoinducers
Timing and control – bacteria
Where does evolution fit?
Feedback
How does change support
homeostasis???
Disruption
Physiological
Homeostasis
• Defense
• Development
Responses
General
Environment
Behavioral
• Timing and
coordination of
events
Biotic
Form and Function
Abiotic
• Homeostasis reflects BOTH common ancestry and
divergence!!!
• Continuity
• Change
Homeostatic evolution
• Excretory system – All serve same purpose (get rid of
waste)
• Flatworms
• Earthworms
• Vertebrates
Continuity - Example
• Excretory system called Protonephridia
• Protonephridia forms networks of tubes connected to
external openings
• Flame bulbs (cells) is how waste moves out of the
platyhelminthes
• Rotifers, some annelids, mollusc larvae, and lancelets
flatworms
• Earthworms contain segments have Metanephridia
• Metanephridia are excretory organs that collect fluid
directly from the coelom
• Each segment has one
• Cilia funnel surrounds the opening which excretes waste
out of earthworm
Annelids
• Kidneys are present, function in osmoregulation and
excretion
• Kidney tubules – nephron
Vertebrates
Continuity –
Each phylum of organisms has a way
to get rid of waste.
Each are similar but with
modification “descent with
modification”
Common ancestry
• Homeostatic mechanisms also support change in response
to changing environments
• Vertebrates must have oxygen in their environment, must
have water in their environments
Change
• Example – Respiratory systems
• Aquatic
• Terrestrial
change
Where does evolution fit?
Feedback
How does change support
homeostasis???
Disruption
Physiological
Homeostasis
• Defense
• Development
Responses
General
Environment
Behavioral
• Timing and
coordination of
events
Biotic
Form and Function
Abiotic
• Organisms exhibit complex properties between organs
and systems
• Example: Respiratory and Circulatory systems 
Homeostasis contd.
Homeostasis
Homeostasis
Homeostasis
Nervous System works with all systems 
How does nervous system
function??
Relay system
1.
2.
3.
4.
5.
6.
7.
Homeostasis
Stimulus
Receptor
Afferent pathway
Integration center
Efferent pathway
Effector organ
Response
N.S
Peripheral
Somatic
Central
Autonomic
Parasympathetic
Sympathetic
Divisions of nervous System
Nerve impulses
Nerve impulses
Steps:
1. Resting (polarized)
Na+
Na+
Na+
Na+
K+
K+
Na+
Na+
K+
Na+
Na+
Nerve impulses
Na+
• Step 2 Depolarization (polarity is reversed)
Nerve impulses
• Step 3 Repolarization
• initiation of sodium potassium pumps
• Restores initial electrical configuration
Nerve impulses
Feedback
Disruption
Physiological
Homeostasis
• Defense
• Development
Responses
General
Environment
Behavioral
• Timing and
coordination of
events
Biotic
Form and Function
Abiotic
• Fixed action pattern
Ex: sticklebacks
Behaviors
• Migration – using
environmental cues to
guide regular, longdistance change in
location
Behaviors
• Courtship – fixed behaviors
1. Visual communication
2. Chemical communication
3. Tactile communication
Behaviors
• Cortship
Behaviors
• Honey bee Dances
Behaviors
Behaviors
Behaviors
• Innate behavior – developmentally fixed within an
organism
• Learning- the modification of behavior based on specific
experiences
Behaviors
• Imprinting – formation at
a specific stage in life a
long-lasting behavioral
response to a particular
individual or object
Behaviors
• Associative learning – associate environmental features
with another
Behaviors
Classical Conditioning – Pavlov’s dog
Operant conditioning – trial and error
• Social Learning:
Behaviors
• Foraging – food-obtaining behaviors
Behaviors
Behaviors
• Mating Systems and
Mate Choice
• Promiscuous mating
– no strong pair
bond
• Monogamous –
mates remain
together for a longer
period
• Polygamous – one
male and several
females or visa
versa
Behaviors
• Altruism – selflessness, reduces an animal’s individual
fitness, but increases the fitness of the others in the
population
Behaviors