Acids secreted by the stomach give the materials within it a pH level that can lie between that of lemon juice and battery acid. Yet our small intestines, which the stomach feeds into, have chemical buffers flowing into them that raise the pH level of the material coming from the stomach. Why should the stomach need such an extreme pH level while the small intestines do not?

Muscle fibers that are striated and voluntary are found in:

a. cardiac muscle.

b. skeletal muscle.

c. smooth muscle.

d. rough muscle.

e. all four types of muscle.

Hormones and the glands or cells that secrete them make up the:

a. cardiovascular system.

b. respiratory system.

c. lymphatic system.

d. urinary system.

e. endocrine system.

Surface epidermal cells of the skin:

a. rapidly divide and are filled mostly with keratin.

b. never divide and remain in place through adult life.

c. rapidly divide and are in place only a short time.

d. are dead and filled with keratin.

e. rapidly divide and are filled with fat.

Cells called _____ build bone tissue, _____ maintain it, and _____ break it down.

a. osteoblasts; osteoclasts; osteocytes

b. osteoclasts; osteons; osteoblasts

c. osteoblasts; osteocytes; osteoclasts

d. osteons; osteocytes; osteoclasts

e. osteocytes; osteoblasts; osteoclasts

The essence of muscle contraction is that thick and thin muscle proteins:

a. slide past each other.

b. link irreversibly with each other.

c. are short enough to respond quickly.

d. stay completely separate.

e. pull in opposite directions.

No skeletal muscle can contract without first:

a. receiving a hormone signal.

b. checking on the status of nearby skeletal muscles.

c. lining up its actin and myosin filaments.

d. receiving a nervous system signal.

e. linking to a bone.

In all angiosperms, a growing embryo is first surrounded by a _______, which will serve to _______ the embryo until it germinates in the ground.

Fruit can be defined as the mature _______ of an angiosperm. Fruit in this sense lies outside the _______ that surrounds the angiosperm embryo.

The plants with which we’re familiar, such as maple trees, do not produce gametes (eggs and sperm), but instead produce _______, making them the _______ generation of plants. This generation alternates with the _______ generation, which on the male side consists of _______ and on the female side consists of small collections of cells, each one of which is known as a(n) _______.

For a new generation of sporophyte plant to be produced, _______ from one plant must land on the _______ of a plant, a necessary step in allowing the fusion of ______ with _______ that will bring about reproduction.