2. Which of these is the correct sequence
of levels of organization?
1 2 3
33% 33%
33%
1. Organs -> cells ->
tissues -> organs
2. Cells -> organs ->
organ systems ->
tissues
3. Cells -> tissues ->
organs -> organ
systems
3. • Of all human body systems, which do
you think is most important. Discuss. Try
to explain your answer.
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4. Organization in Living Things
• Cells are organized into tissues
• Tissues are organized into organs
• Organs are organized into systems
• Systems form an organism
7. Epithelial tissue
• Epithelial cells form
the outer covering,
line the internal
cavities, and make
up the glands.
• Examples: Skin,
mucous
membranes.
10. Muscular tissue
• Specialized protein
fibers allow these
cells to contract.
• Examples: skeletal
muscle, smooth
muscle, cardiac
muscle.
11. Nervous tissue
• Neurons have the
ability to pass an
“electrical” signal
from one cell to
another, or to target
cells (muscles,
glands, organs).
12. Tissues form organs
• The skin is an
example of an
organ made up of
multiple tissues:
epithelial, muscular,
nervous, and
connective tissues.
13. A group of cells that perform a
similar function is know as:
1 2 3 4
25% 25%
25%
25%
1. Tissue
2. Organ
3. Organ system
4. Organism
14. One cell type that must undergo
continual loss and replacement is:
1 2 3 4
25% 25%
25%
25%
1. Epithelial tissue
2. Connective tissue
3. Muscle tissue
4. Nervous tissue
15. Which tissue type is in direct
contact with the environment?
1 2 3 4
25% 25%
25%
25%
1. Epithelial
2. Muscle
3. Nervous
4. Connective
16. Homeostasis
• Homeostasis is the act of keeping the
internal environment of a living organism
within an acceptable range of conditions.
• Homeostasis controls temperature, pH,
blood volume, oxygen levels, blood sugar
levels, and other conditions.
• Negative feedback maintains
homeostasis.
17. Negative Feedback
• Negative feedback keeps
conditions within an ideal
range.
• As conditions exceed the
limits of the ideal range,
chemical signals
(hormones) regulate
conditions. Most often this
is controlled by the
hypothalamus in the brain.
18. Positive Feedback
• Positive feedback
takes a condition out of
the normal range,
often to some end
point.
• During labor, oxytocin
increases contractions,
which stimulate more
oxytocin production,
until birth occurs.
19. Maintaining Temperature
• Ectotherms are animals
that derive body heat from
the environment. Their
body temperature may
vary widely.
• Endotherms rely on
metabolic reactions and
physiological systems to
maintain a steady body
temperature.
23. True or false: “cold blooded” animals always
have a lower body temperature than “warm-
blooded” animals.
1 2
50%
50%
1. True
2. False
24. • Why is positive feedback not a good way
to maintain homeostasis?
• What are some other examples of
positive feedback loops in the human
body?
• Why do young animals often have more
body fat than adults? How does this
maintain homeostasis?
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25. • Draw a negative feedback loop for blood
calcium regulation.
• Falling calcium level signals release of
parathyroid hormone from the
parathyroid glands. Calcium is
released from bones, increased uptake
by digestive system.
• Rising calcium level signals release of
calcitonin from the thyroid. Blood
calcium is taken up into bone tissue.
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