BIOL 1108 Exam 2 Guide 2026 [Latest
Update] | Principles of Biology II | 100%
Verified Q&A | Grade A
Question 1: Which embryonic tissue layer gives rise to the notochord in chordates?
A) Ectoderm
B) Endoderm
C) Mesoderm (dorsal)
D) Neural crest
Correct Answer: C) Mesoderm (dorsal)
Explanation: The dorsal mesoderm differentiates into the notochord, the defining chordate
structure that induces neural tube formation.
Question 2: The first vertebrates to evolve a true jaw were members of which group?
A) Agnatha
B) Placodermi
C) Chondrichthyes
,D) Osteichthyes
Correct Answer: B) Placodermi
Explanation: Extinct armored fishes (placoderms) possessed the earliest mineralized jaws derived
from gill-arch cartilages.
Question 3: Which of the following is a derived trait of all gnathostomes?
A) Single semicircular canal
B) Jaws and paired appendages
C) Bony endoskeleton
D) Lungs
Correct Answer: B) Jaws and paired appendages
Explanation: Jaws and paired fins/flippers are synapomorphies that improved feeding efficiency and
locomotion in vertebrates.
Question 4: In which group is the spiral valve intestine a key adaptation for nutrient absorption?
A) Teleostei
B) Chondrichthyes
C) Amphibia
D) Aves
,Correct Answer: B) Chondrichthyes
Explanation: The spiral valve increases surface area without lengthening the gut, important in
sharks with short digestive tracts.
Question 5: Which extra-embryonic membrane forms the fetal portion of the placenta in eutherian
mammals?
A) Amnion
B) Chorion
C) Allantois
D) Yolk sac
Correct Answer: B) Chorion
Explanation: The chorionic villi invade the endometrium to create the placenta, allowing
nutrient/waste exchange between maternal and fetal blood.
Question 6: The evolution of the amniotic egg freed vertebrates from dependence on
A) internal fertilization
B) aquatic environments for reproduction
C) endothermy
D) lungs
, Correct Answer: B) aquatic environments for reproduction
Explanation: Extra-embryonic membranes enclosed the embryo in a watery environment, permitting
development on land.
Question 7: Which cranial nerve innervates the diaphragm in mammals?
A) Vagus (CN X) via phrenic branches
B) Hypoglossal (CN XII)
C) Accessory (CN XI)
D) Facial (CN VII)
Correct Answer: A) Vagus (CN X) via phrenic branches
Explanation: Although the phrenic nerve arises from cervical spinal nerves (C3-C5), it carries vagal
fibers that modulate respiratory rhythm.
Question 8: Which of the following is a synapomorphy of Mammalia?
A) Three middle-ear ossicles (malleus, incus, stapes)
B) Keratinized scales
C) Four-chambered heart in all species
D) Nictitating membrane
Correct Answer: A) Three middle-ear ossicles (malleus, incus, stapes)
Update] | Principles of Biology II | 100%
Verified Q&A | Grade A
Question 1: Which embryonic tissue layer gives rise to the notochord in chordates?
A) Ectoderm
B) Endoderm
C) Mesoderm (dorsal)
D) Neural crest
Correct Answer: C) Mesoderm (dorsal)
Explanation: The dorsal mesoderm differentiates into the notochord, the defining chordate
structure that induces neural tube formation.
Question 2: The first vertebrates to evolve a true jaw were members of which group?
A) Agnatha
B) Placodermi
C) Chondrichthyes
,D) Osteichthyes
Correct Answer: B) Placodermi
Explanation: Extinct armored fishes (placoderms) possessed the earliest mineralized jaws derived
from gill-arch cartilages.
Question 3: Which of the following is a derived trait of all gnathostomes?
A) Single semicircular canal
B) Jaws and paired appendages
C) Bony endoskeleton
D) Lungs
Correct Answer: B) Jaws and paired appendages
Explanation: Jaws and paired fins/flippers are synapomorphies that improved feeding efficiency and
locomotion in vertebrates.
Question 4: In which group is the spiral valve intestine a key adaptation for nutrient absorption?
A) Teleostei
B) Chondrichthyes
C) Amphibia
D) Aves
,Correct Answer: B) Chondrichthyes
Explanation: The spiral valve increases surface area without lengthening the gut, important in
sharks with short digestive tracts.
Question 5: Which extra-embryonic membrane forms the fetal portion of the placenta in eutherian
mammals?
A) Amnion
B) Chorion
C) Allantois
D) Yolk sac
Correct Answer: B) Chorion
Explanation: The chorionic villi invade the endometrium to create the placenta, allowing
nutrient/waste exchange between maternal and fetal blood.
Question 6: The evolution of the amniotic egg freed vertebrates from dependence on
A) internal fertilization
B) aquatic environments for reproduction
C) endothermy
D) lungs
, Correct Answer: B) aquatic environments for reproduction
Explanation: Extra-embryonic membranes enclosed the embryo in a watery environment, permitting
development on land.
Question 7: Which cranial nerve innervates the diaphragm in mammals?
A) Vagus (CN X) via phrenic branches
B) Hypoglossal (CN XII)
C) Accessory (CN XI)
D) Facial (CN VII)
Correct Answer: A) Vagus (CN X) via phrenic branches
Explanation: Although the phrenic nerve arises from cervical spinal nerves (C3-C5), it carries vagal
fibers that modulate respiratory rhythm.
Question 8: Which of the following is a synapomorphy of Mammalia?
A) Three middle-ear ossicles (malleus, incus, stapes)
B) Keratinized scales
C) Four-chambered heart in all species
D) Nictitating membrane
Correct Answer: A) Three middle-ear ossicles (malleus, incus, stapes)
