2. Light reflecting off an object in the environment is detected by photoreceptors after following which path?
(A) lens ＞ cornea ＞ retina ＞ ganglion cell layer ＞ iris
(B) cornea ＞ lens ＞ iris ＞ ganglion cell layer ＞ retina
(C) retina ＞ ganglion cell layer ＞ lens ＞ iris ＞ cornea
(D) cornea ＞ iris ＞ lens ＞ ganglion cell layer ＞ retina

48. Microevolution refers to: (A) small-scale evolutionary changes within a population, observable over short periods, like allele frequency changes. (B) large-scale evolutionary changes that never lead to new species. (C) mechanisms entirely different from those causing macroevolution. (D) changes that cannot lead to macroevolutionary patterns. (E) speciation, as an exclusively macroevolutionary event.

49. Which of the following is a direct cause of microevolution within a population? (A) The formation of a new species over millions of years. (B) A change in the frequency of an allele due to random chance (genetic drift). (C) The large-scale extinction of a taxonomic group. (D) The diversification of life forms into new phyla. (E) The development of complex multicellular organisms from single-celled ancestors.

50. An example of microevolution is: (A) the appearance of the first flowering plants. (B) the diversification of mammals after the dinosaur extinction. (C) the evolution of birds from reptilian ancestors. (D) the formation of a new genus through accumulated genetic changes. (E) an increase in antibiotic resistance in a bacterial population over several generations.

1. The operation of the sodium-potassium "pump" moves _____.(A) sodium and potassium ions into the cell (B) sodium and potassium ions out of the cell (C) sodium ions into the cell and potassium ions out of the cell (D) sodium ions out of the cell and potassium ions into the cell (E) sodium and potassium ions into the mitochondria

3. How do myelin sheaths increase the speed with which action potentials are propagated along an axon? (A) They increase the permeability of Na+ ions in the plasma membrane. (B) They amplify the action potential by increasing sodium influx along the entire distance of the neuron. (C) They insulate the axon, preventing K+ ions from exiting the neuron. (D) They cause action potentials to "jump" down the axon rather than travel in a continuous path along every site on the axon.

4. A newborn who is accidentally given a drug that destroys the thymus would most likely _____ (A) lack class I major histocompatability (MHC) molecules on cell surfaces (B) lack innate immunity (C) be unable to genetically rearrange antigen receptors (D) be unable to differentiate and mature T cells (E) have a reduced number of B cells and be unable to form antibodies

5. Suppose a person's AV node in their heart suddenly stopped sending signals to the rest of the heart. How would this person's EKG differ from normal? (A) The EKG would have a taller P region. (B) The EKG would not have a QRS region. (C) The EKG would have a shorter T region (D) The EKG would not have a gap between the S and T regions.

6. Oxygen-poor blood is carried from the heart of a mammal to the lungs via the (A) pulmonary arteries. (B) pulmonary veins. (C) superior vena cava. (D) inferior vena cava.

7. Which of the following hormones is made by the hypothalamus and released by the posterior pituitary? (A) estrogen. (B) anti-diuretic hormone (ADH). (C) insulin. (D) calcitonin.

8. During ventricular systole, the semilunar valves _____ and the AV valves _____ (A) open; open. (B) close; open (C) open; close. (D) close; close