Q1. Gastrulation in a mammal would be most similar to gastrulation in
Correct Answer: (c)
Mammals and birds (such as eagles) share similar patterns of gastrulation involving the primitive streak, making avian gastrulation the closest comparison.
Q2. Somites
Correct Answer: (d)
Somites are mesodermal segments that give rise to multiple tissues (muscle, vertebrae, dermis) and their number varies among species, reflecting differences in body segmentation.
Q3. Which of the following plays the greatest role in determining how cytoplasmic division occurs during cleavage?
Correct Answer: (b)
The amount and distribution of yolk strongly influence cleavage patterns. Large yolk masses slow or restrict cell division, leading to unequal or incomplete cleavage in many species.
Q4. You have discovered a new organism living in tide pools at your favorite beach. Every so often, one of the creature’s appendages will break off and gradually grow into a whole new organism, identical to the first. This is an example of
Correct Answer: (c)
Budding is an asexual reproductive process in which a new individual develops from an outgrowth or fragment of the parent body. The detached appendage growing into a complete organism is characteristic of budding.
Q5. Your Aunt Ida thinks that babies can stimulate the onset of their own labor. You tell her that
Correct Answer: (d)
Fetal hormones, particularly cortisol, play an important role in signaling the onset of labor by influencing maternal hormonal pathways.
Q6. Of the following processes, which occurs last?
Correct Answer: (b)
Fertilization occurs first, followed by cleavage and gastrulation. Neurulation occurs later, when the nervous system begins to form from the ectoderm.
Q7. Which of the following would qualify as a secondary induction?
Correct Answer: (a)
Secondary induction occurs when tissues induced earlier go on to induce other tissues. The neural ectoderm inducing lens formation is a classic example of secondary induction.
Q8. In species with environmental sex determination,
Correct Answer: (d)
In environmental sex determination, factors such as temperature influence sex during embryonic development, making both statements (a) and (b) correct.
Q9. Which of the following structures is the site of spermatogenesis?
Correct Answer: (d)
Spermatogenesis occurs within the seminiferous tubules of the testes, where diploid germ cells undergo meiosis to form haploid sperm.
Q10. Which of the following terms describes your first stage as a diploid organism?
Correct Answer: (d)
A zygote is formed by the fusion of haploid sperm and egg during fertilization. It is the first diploid stage of a new organism.
Q11. Suppose that a burst of electromagnetic radiation were to strike the blastomeres of only the animal pole of a frog embryo. Which of the following would be most likely to occur?
Correct Answer: (a)
In frog embryos, the animal pole primarily gives rise to ectodermal tissues such as epidermis. Damage to this region would most likely affect skin development.
Q12. Axis formation in amniotic embryos could be affected by
Correct Answer: (c)
Axis formation depends on organizer regions. In amphibians this is the dorsal lip, while in amniotes it is the primitive streak. Mutations in either can disrupt body axis formation.
Q13. Your cousin just had twins. She tells you that twinning occurs when two sperm fertilize the same egg. You reply that
Correct Answer: (c)
Polyspermy is prevented by cortical granule reactions after fertilization. Twins typically arise from the splitting of a single fertilized egg, not from fertilization by two sperm.
Q14. In humans, fertilization occurs in the____, and implantation of the zygote occurs in the____.
Correct Answer: (c)
Fertilization typically occurs in the oviduct (fallopian tube), while implantation of the developing embryo takes place in the uterus.
Q15. Mutations that affect proteins in the acrosome would impede which of the following functions?
Correct Answer: (a)
The acrosome contains enzymes that help the sperm penetrate the egg’s protective layers. Defects in acrosomal proteins would prevent successful fertilization.
Q16. Which of the following is a major difference between spermatogenesis and oogenesis?
Correct Answer: (b)
Spermatogenesis occurs continuously after puberty, whereas oogenesis is discontinuous and includes long arrest phases, making their timing fundamentally different.
Q17. If you decided that the organism you discovered in question 1 used parthenogenesis, what would you also know about this species?
Correct Answer: (d)
Parthenogenesis is a form of asexual reproduction in which offspring develop from unfertilized eggs. Because no male gametes are involved, the population consists entirely of females, making all statements correct.
Q18. Internal and external fertilization differ in that all species that
Correct Answer: (a)
Amniotic eggs require internal fertilization to ensure protection and development of the embryo, making internal fertilization a defining feature of amniote reproduction.
Q19. Gametogenesis requires the conclusion of meiosis II. When does this occur in females?
Correct Answer: (c)
In human females, the secondary oocyte is arrested in metaphase II and completes meiosis II only after fertilization by a sperm.
Q20. The testicles of male mammals are suspended in the scrotum because
Correct Answer: (a)
Sperm production requires a temperature slightly lower than core body temperature. The scrotum maintains this cooler environment, ensuring normal spermatogenesis.
Q21. The major difference between an estrous cycle and a menstrual cycle is that
Correct Answer: (a)
In estrous cycles, females are sexually receptive only near ovulation, whereas in menstrual cycles (as in humans), sexual receptivity is not restricted to a specific phase.
Q22. FSH and LH are produced by the
Correct Answer: (c)
Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are gonadotropins secreted by the anterior pituitary gland and regulate reproductive processes in both males and females.
Q23. In the Spemann experiment, when the dorsal lip is transplanted, the recipient embryo then has a second source of molecules that
Correct Answer: (b)
The dorsal lip acts as an organizer by secreting molecules that inhibit ventralizing signals, allowing dorsal structures to form at a new location in the embryo.
Q24. Which of the following events occur immediately after fertilization?
Correct Answer: (d)
Fertilization triggers a cascade of immediate events including egg activation, cortical reactions that prevent polyspermy, and extensive cytoplasmic rearrangements. All these processes are essential to initiate normal embryonic development.
Q25. Drug or alcohol exposure during which stage is most likely to have a profound effect on neural development of the fetus?
Correct Answer: (b)
The first trimester is a critical period for organogenesis, including neural development. Exposure to toxins during this stage can cause severe developmental abnormalities.
Q26. Gastrulation is a critical event during development. Why?
Correct Answer: (d)
Gastrulation establishes the basic body plan by forming germ layers, creating the primitive gut, establishing body axes, and reorganizing the embryo from a simple blastula into a complex, structured organism.
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