Download Chapter 11 Notes

Answers to Thinking Critically Questions
Mader: Inquiry into Life, Twelfth Edition
Chapter 11
1. In what way(s) is blood like a tissue?
Explanation/Answer: Blood is composed of specialized cells (red blood cells, white
blood cells, and platelets) with a similar function – to circulate throughout the body and
provide support in the form of oxygen, defenses, and clotting capabilities.
2. Think about what types of environmental conditions germs might favor. What are some
features of human skin that make it a good protection against most infectious agents, such
as bacteria and viruses?
Explanation/Answer: The epidermal surface contains keratin, a hard, waterproof protein
(germs like water). The outermost epidermal cells are dead, and many germs require that
live cells to infect. The production of sweat makes skin rather salty, and many germs are
inhibited by salt (think about how long olives or pickles last on the shelf).
3. Which of these homeostatic mechanisms in the body are examples of positive feedback,
and which are examples of negative feedback? Why?
a. The adrenal glands produce epinephrine in response to a hormone produced by the
pituitary gland in times of stress; the pituitary gland senses the epinephrine in the
blood and stops producing the hormone.
b. As the bladder fills with urine, pressure sensors send messages to the brain with
increasing frequency signaling that the bladder must be emptied. The more the
bladder fills, the more messages are sent.
c. When you drink an excess of water, by specialized cells in your brain as well as stretch
receptors in your heart detect the increase in blood volume. Both signals are
transmitted to the kidneys, which increase the production of urine.
Explanation/Answer: Positive feedback = b and c. Negative feedback = a
4. Homeostatic systems in the body can be categorized as transport systems, maintenance
systems, support systems and control systems. What organ systems (from section 11.3)
could be placed into more than one of these categories?
Explanation/Answer: Nervous system – involved in control, which in term affects
maintenance (respiration, body temperature). Immune system – maintenance of the body
by fighting infection, and transportation of lymphocytes within the lymphatic vessels.
Endocrine system – some hormones (from thyroid, adrenal glands) involved in overall
control of body processes, others involved in maintenance systems like urine production.
Cardiovascular system – transport of gases and nutrients, white blood cells, and platelets,
these functions also support other tissues.
5. What are one or two characteristics that all types of cancer have in common? Why do
they often have such different manifestations, such as leukemia vs. a melanoma?
Explanation/Answer: All cancers involve an unregulated increase in the division rate of
cells; but each type can have very different manifestations depending on what tissue(s)
are affected (skin or muscle vs. brain or heart)