Test Prep Test Prep Certifications OAT Questions & Answers

• Question 81:

  Darwin's idea that evolution occurs by the gradual accumulation of small changes can be summarized as:

  A. Convergent evolution

  B. Adaptive radiation

  C. Punctuated equilibrium

  D. Phyletic gradualism

  E. Sympatric speciation

  Correct Answer: D

  Phyletic gradualism is the view that evolution occurs at a more or less constant rate. Contrary to this view, punctuated equilibrium holds that evolutionary history consists of long periods of stasis punctuated by geologically short periods of evolution. This theory predicts that there will be few fossils revealing intermediate stages of evolution, whereas phyletic gradualism views the lack of intermediate-stage fossils as a deficit in the fossil record that will resolve when enough specimens are collected.

• Question 82:

  A population of 1000 individuals has 110 births and 10 deaths in a year. Its growth rate (r) is equal to:

  A. 0.01 per year

  B. 0.11 per year

  C. 0.1 per year

  D. 0.09 per year

  E. 0.009 per year

  Correct Answer: C

  The growth rate is equal to the difference between births and deaths divided by population size.

• Question 83:

  When a population reaches its carrying capacity?

  A. The population size begins to decrease.

  B. The population growth rate approaches zero.

  C. Other populations will be forced out of the habitat.

  D. Density-independent factors no longer play a role.

  E. Density-dependent factors no longer play a role.

  Correct Answer: B

  Within a habitat, there is a maximum number of individuals that can continue to thrive, known as the habitat's carrying capacity. When the population size approaches this number, population growth will stop.

• Question 84:

  In the food chain below, vultures represent grass ?gt; cow ?gt; wolf ?gt; vulture:

  A. Scavengers

  B. Primary carnivores

  C. Detritivores

  D. Secondary consumers

  E. Herbivores

  Correct Answer: A

  Vultures eat carrion, or dead animals, so they are considered scavengers. Detritivores are heterotrophs that eat decomposing organic matter such as leaf litter. They are usually small.

• Question 85:

  In which of the following stages of embryo development are the three primary germ layers first present?

  A. Blastula

  B. Zygote

  C. Gastrula

  D. Coelomate

  E. Morula

  Correct Answer: C

  The gastrula is formed from the blastocyst, which contains a bilayered embryonic disc. One layer of this disc's inner cell mass further subdivides into the epiblast and the hypoblast, resulting in the three primary germ layers (endoderm, mesoderm, ectoderm).

• Question 86:

  Which of the following processes is an example of positive feedback?

  A. High blood glucose levels stimulate insulin release, which makes muscle and liver cells take in glucose

  B. Low blood oxygen levels stimulate erythropoietin production which increases red blood cell production by bone marrow

  C. High CO2 blood levels stimulate respiration which decreases blood CO2 levels

  D. Low blood calcium levels stimulate parathyroid hormone release from the parathyroid gland. Parathyroid hormone stimulates calcium release from bones.

  E. Increased nursing stimulates increased milk production in mammary glands

  Correct Answer: E

  In a positive feedback loop, an action intensifies a chain of events that, in turn, intensify the conditions that caused the action beyond normal limits. Nursing stimulates lactation, which promotes nursing. Contractions during childbirth, psychological hysteria, and sexual orgasm are all examples of positive feedback.

• Question 87:

  The structures composed solely of diploid cells:

  

  A. 1, 2, and 3

  B. 3, 4, and 5

  C. 1, 4, and 5

  D. 2, 3, and 4

  E. 1, 2, and 4

  Correct Answer: B

  In flowering plants, the anthers house the male gametophytes (which produce sperm) and the pistils house the female gametophytes (which produce eggs). Eggs and sperm are haploid. All other tissues are solely diploid.

• Question 88:

  The structure in which microspores are produced: A. 3

  

  B. 1

  C. 5

  D. 4

  E. 2

  Correct Answer: E

  Anthers produce microspores (the male gametophytes of flowering plants), which undergo meiosis to produce pollen grains.

• Question 89:

  The synaptonemal complex is present in which of the following phases of the cell cycle?

  A. Telophase of meiosis I

  B. Metaphase of meiosis II

  C. Metaphase of meiosis I

  D. Metaphase of mitosis

  E. Telophase of meiosis II

  Correct Answer: A

  The synaptonemal complex is the point of contact between homologous chromatids. It is formed when nonsister chromatids exchange genetic material through crossing over. Once meiosis I has completed, crossovers have resolved and the synaptonemal complex no longer exists. Rather, sister chromatids are held together at their centromeres prior to separation in anaphase II.

• Question 90:

  Leaves have parallel veins:

  A. Monocots

  B. Nonvascular plants

  C. Gymnosperms

  D. Dicots

  E. Angiosperms

  Correct Answer: A

  Monocots differ from dicots in that they have one cotyledon, or embryonic leaf in their embryos. They also have parallel veination, fibrous roots, petals in multiples of three, and a random arrangement of vascular bundles in their stems.