1. Cells are organized into tissues, tissues into organs, organs into organ systems, and organ systems form an organism. 2. There are four main tissue types - epithelial, connective, muscular, and nervous tissue. Epithelial tissue lines body surfaces and cavities, while connective tissue connects and supports other tissues. 3. Homeostasis uses negative feedback loops to maintain stable internal conditions like temperature and blood glucose levels. Positive feedback increases a condition until an endpoint is reached, like childbirth.

1. Animal Systems
Organization and Homeostasis

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

6. Four tissue types
• Epithelial
• Connective
• Nervous
• Muscular

7. Epithelial tissue
• Epithelial cells form
the outer covering,
line the internal
cavities, and make
up the glands.
• Examples: Skin,
mucous
membranes.

9. Connective tissue
• Consists of living
cells in a secreted
matrix.
• Examples: bone,
cartilage, blood.

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.

20. Maintaining Temperature

21. Blood Glucose Regulation

22. Body systems maintain homeostasis
through:
1 2 3
33% 33%
33%
1. Positive feedback
systems.
2. Negative feedback
systems.
3. Uncontrolled
feedback systems.

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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