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.

45. During gene expression, which molecule carries the genetic code from the nucleus to the ribosomes in the cytoplasm for protein synthesis? (A) Ribosomal RNA (rRNA) (B) Transfer RNA (tRNA) (C) DNA polymerase (D) Amino acids (E) Messenger RNA (mRNA)

46. Which condition violates the assumptions of the Hardy-Weinberg principle? (A) Random mating occurs. (B) No gene flow into or out of the population.. (C) The population size is very large. (D) Natural selection favors certain genotypes. (E) No new mutations occur.

47. If a population is in Hardy-Weinberg equilibrium for a gene, its allele frequencies will: (A) remain constant across generations unless an evolutionary force acts. (B) be perfectly balanced by genetic drift and gene flow. (C) change due to active mate choice based on genotype. (D) significantly deviate from predicted genotypic frequencies. (E) always be significantly altered by new mutations in the short term.

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.

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

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

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.