What happens at the synapse between two neurons?

Why are sponges classified as animals? ______________

$__________________$ : animals without backbones

Animals that are chordates but not vertebrates include _______, ______, and ______ Crania te s are animals that have a(n) ______Animals that are craniates but not vertebrates include _________.

The 2-propenyl cation appears to be a primary carbocation, and yet it is considerably more stable than a $1^{\circ}$carbocation such as the 1-propyl cation. $\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{CH}_{2}^{+}$ 2-Propenyl cation, $\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}^{+}$ 1-Propyl cation. How would you account for the differences in the stability of the two carbocations?

Simplify each expression to a single primary trigonometric function.

$$\begin{array}{l}{\text { a) } \frac{\sin 2 \theta}{2 \cos \theta}} \\ {\text { b) } \cos 2 x \cos x+\sin 2 x \sin x} \\ {\text { c) } \frac{\cos 2 \theta+1}{2 \cos \theta}} \\ {\text { d) } \frac{\cos ^{3} x}{\cos 2 x+\sin ^{2} x}}\end{array}$$

Two animals out of seven believed Chicken Little. If 85 animals did not believe Chicken Little, how many animals were there in all?

Why do large animals generally produce sounds that are lower in frequency than the sounds produced by smaller animals?

Simplify each expression to one of the three primary trigonometric functions.

$$\begin{array}{l}{\text { a) } \frac{\sin x}{\tan x}} \\ {\text { b) } \frac{\sec x}{\csc x}} \\ {\text { c) } \frac{\sin x+\tan x}{1+\cos x}} \\ {\text { d) } \frac{\csc x-\sin x}{\cot x}}\end{array}$$

Why animals use echolocation ?

The molecule in the next column is 2,2-dimethyl propane-1-ol, a primary alcohol. Because no $\mathrm{H}$ atoms are bonded to the $\beta$ carbon atom in this molecule, dehydration seems unlikely. However, when 2,2-dimethylpropan-1-ol is heated with an acid catalyst, 2-methylbut-2-ene is obtained. Suggest a mechanism that shows how 2-methylbut-2-ene is formed.

Most animals do not have a backbone. They are called invertebrates. What are some advantages that invertebrate animals might have over vertebrate animals?

Which of the following best describes hearing receptor "hair cells"? a. They are neurons. b. They lack ion channels. c. They are epithelial, but function like neurons. d. They are made of keratin.

The table gives the ages of a sample of householders in primary families. Use this table.

Age of Householder (years)	Number (thousands)
$15-24$	$3395$
$25-34$	$13,347$
$35-44$	$17,547$
$45-54$	$18,119$
$55-64$	$13,462$
$65+$	$12,978$

Source: U.S. Bureau of the Census

Construct a histogram of the data.