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Homeostasis
Lecture #6Ms. Day/ Honors Biology
Organization of Life &
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What are Cells?What are Cells?• Definition: basic unit of structure and function
of life• Although ALL living things are made of cells,
organisms may be:–Unicellular – composed of one cell–Multicellular- composed of many cells
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Multicellular OrganismsMulticellular Organisms• Cells in multicellular organisms often specialize
(take on different shapes & functions)
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Cell Specialization = DIFFERENTIATION
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Cell Differentiation• Do all cells look alike?
• NO!!!• Do all cells have the
same functions?• NO!!!
• Cell Differentiation –Process by which
unspecialized cells (stem cells) develop into different cell forms and functions
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How Do Cells Specialize Their How Do Cells Specialize Their Functions?Functions?
• Cells in multicellular organisms become specialized by turning ON or OFF different genes different parts of their DNA
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Levels of OrganizationHow are living
things organized?
1. Chemical2. Cells3. Tissues4. Organs5. Systems6. Organism
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Chemical Atoms, molecules, compounds
Cell Basic unit of living things
Tissue Similar cells doing specific function
Organ Similar tissues performing specific task
Organ System Organs working together
Organism All systems working together
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• Tissues• groups of cells similar in structure and
perform common or related functions•Epithelial Tissue
• Skin, lining of tissues•Connective Tissue
• Blood, bones, cartilage•Muscle Tissue
• Smooth, striated, cardiac•Nervous Tissue•Nerves and fibers
Four Basic Types of Tissues
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What is Homeostasis?• Process that occurs in ALL living
things• All organ systems work together
to achieve homeostasis• Definition:
– The ability of an organism to maintain its internal environment despite changes to its internal or external environment
http://balancewines.wordpress.com/2009/12/
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Homeostasis in Animals• What do animals need to keep
constant/healthy?• Body cells work best if they have the correct
– Temperature– Water balance– Blood Pressure– Blood pH level– Glucose (sugar) levels– Oxygen and Carbon Dioxide Levels
• How does an organism respond to these changes? • 2 different pathways
» Negative or Positive Feedback
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Negative Feedback1. Process that activates body to RESTORE
conditions to their ORIGINAL STATE2. Counteract further change in the same
direction–STOPS THE CHANGE!
3. It ensures that small changes don’t become too large
–MAINTAINS HOMEOSTASIS• EX: Thermoregulation, Blood sugar levels, Blood Calcium
level, O2/CO2 levels in blood
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Positive Feedback1. Process that activates body to AMPLIFIES
original change2. CONTINUES more change in the same
direction–INCREASES the change!
3. Allows for small changes to become too large
–DOES NOT MAINTAINS HOMEOSTASIS• EX: Uterine contractions, Lactation, blood clotting
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Homeostasis Control Systems• 3 components:
– Receptor– Control Center– Effector
• Receptor – detects a change in some
variable in the organism’s internal environment, such as a change in temperature
• control center – processes the information it
receives from the receptor and directs an appropriate response by the effector
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HomeostasisExample: household thermostat
Whole control system is called a negative feedback system
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Negative FeedbackExample #1: Thermoregulation in the body
What happens when you are too hot?
Sweat (liquid) turns to gas requires HEAT
Heat comes from your
body/skin skin cools
down
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Negative FeedbackExample #1: Thermoregulation in the body
What happens when you are too cold?
“Goose Bumps” hairs trap a layer of air
next to skin warms by body heat
Air becomes an insulating layer
Called piloerection
Shivering Muscle movements
use ATP (energy) Breaking ATP
releases HEAT
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Maintaining Body Temperature(Thermoregulation)
• Humans have a normal temperature of around 36.2 to 37.2 °C (98.6°F)
• If your body temperature goes above normal temperature likely suffering from infection– your body raises its
temperature to fight off the infection
• If your body goes below this range it indicates hypothermia.– could lead to cell damage
and possibly death.http://asimplebutimpossibletask.blogspot.com/
http://news.bbc.co.uk/2/shared/spl/hi/health/03/travel_health/diseases/html/sars.stm
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Negative FeedbackExample #2: Regulating Blood Sugar (Glucose) Levels
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Negative FeedbackExample #3: Regulating Calcium Levels in Blood
Why do you need calcium?
1)Carries messenges in body
1)Muscle contractions2)Nervous system homeostasis
1)Bone/teeth formation
2)Helps blood clotting
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Holding Holding breath, breath, COCO2 2 levels levels
riserise
Control system Control system forces exhale, forces exhale, inhaleinhale
OO2 2 // COCO2 2 level level
returns to normalreturns to normal
Negative FeedbackExample #4:Regulating Oxygen and Carbon
Dioxide Levels in Blood
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Positive FeedbackExample #1: Uterine Contractions
During childbirth…• Baby’s head PUSHES against sensors near opening of uterus •Oxytocin (hormone) is released stimulates uterine contractions• More contractions more oxytocin• ONLY STOPS when pushing STOPS
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Positive FeedbackExample #2: Lactation (making milk)
•Suckling by baby stimulates brain to release hormone (prolactin) •Prolactin makes milk•More suckling by offspring (baby) more milk production
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•Damaged blood vessel stimulates release of Damaged blood vessel stimulates release of clotting factors clotting factors Platelets build up at injured site •More chemicals released more platelets
•Platelets continue to pile up and until clot is formed•Finally, growth hormones stimulate cell Finally, growth hormones stimulate cell divisiondivision
platelets
fibrin
white blood cellred blood cell
blood vessel
clot
Positive Feedback Example #3: Blood Clotting
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Homeostasis in Plants• What do plants need to keep
constant/healthy?• Plant cells work best if they have the correct
–Water– Sunlight–Oxygen and Carbon Dioxide Levels
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Homeostasis in Plants
• What mechanisms for plants use to help maintain homeostasis? –Creates a waxy cuticle on leaves–Stores extra water–Opening/closing of stomata (pores in
leaves)–Bends towards light
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Stoma OpenStoma Closed
Guard Cells
Stoma
CO2
O2 H2O
What goes in?
What goes out?
•What do plants use to control gas exchange?
•Guard Cells & Stoma
•Why do plants need to OPEN stomata?
•Photosynthesis
•Making food
•If the plant needs water for photosynthesis, why is water coming out of the stomata?
•Losing H20 helps get
H20 up plant against
gravity!!
Homeostasis in Plants Using Stomata
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Stoma Open Stoma Closed
Guard Cells Guard Cells•Why would the plant close stomata using guard cells?
•Prevent excess water loss (conserve water)
•So what is the point of having stomata?
•Remove waste gas (O2)
•Take in gas (CO2) for photosynthesis
•Help move water up plant for photosynthesis
•Control water loss
Homeostasis in Plants Using Stomata
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More Homeostasis in Plants• Stems bend towards
sunlight to maintain the amount of photosynthesis. –Called phototrophism
• Stems store extra water in a huge “pool” inside their cells–Called a central vacuole