TAMU Biology 112 Lab Practical 2 Exam
Questions and Answers 100% Pass
2025/2026.
Section 1: Porifera & Cnidaria (Body Plans & Early Evolution)
1. A student observes a specimen under a dissecting scope. It has no visible tissues,
appears asymmetrical, and possesses small spicules. What structure would indicate the
flow of water exiting the organism?
A. Spongocoel
B. Osculum
C. Choanocyte
D. Nematocyst
Answer: B. Osculum
Rationale: In Phylum Porifera (sponges), water enters through small pores but exits through
the large opening called the osculum. The spongocoel is the central cavity .
2. How do choanocytes and amoebocytes collaborate in sponge digestion?
A. Choanocytes capture food via flagella; amoebocytes distribute nutrients.
B. Amoebocytes filter water; choanocytes secrete the skeleton.
C. Choanocytes create spicules; amoebocytes create the osculum.
D. They both only reproduce sexually.
Answer: A. Choanocytes capture food via flagella; amoebocytes distribute nutrients.
Rationale: Choanocytes (collar cells) generate water flow and trap particles via phagocytosis.
Amoebocytes pick up these food vacuoles and transport nutrients to the rest of the body .
3. A marine biologist finds an organism with two tissue layers (diploblastic), a
gastrovascular cavity, and stinging cells. Which class lacks a medusa stage entirely and
exists only as polyps?
A. Hydrozoa
B. Scyphozoa
C. Cubozoa
D. Anthozoa
, Answer: D. Anthozoa
Rationale: Anthozoa (corals and sea anemones) are the only class of Cnidarians that do not
have a medusa stage; they exist solely as polyps .
4. In Cnidarians, the gastrovascular cavity serves multiple functions. Which of the
following is NOT one of them?
A. Digestion of prey
B. Hydrostatic skeleton
C. Gas exchange via diffusion
D. Separate exit for undigested waste
Answer: D. Separate exit for undigested waste
Rationale: Cnidarians have a single opening that serves as both mouth and anus. The
gastrovascular cavity aids in digestion and acts as a hydrostatic skeleton, but waste exits
through the same opening it entered .
5. The Portuguese Man O' War (Physalia) is a colonial organism often mistaken for a
jellyfish. It belongs to Class Hydrozoa. Which statement best describes this group?
A. Dominant medusa stage, no polyp stage.
B. Dominant polyp stage, reduced medusa stage.
C. Exists only as a sessile polyp.
D. Exists only as a floating medusa.
Answer: B. Dominant polyp stage, reduced medusa stage.
Rationale: Class Hydrozoa typically exhibit a life cycle where the polyp stage is dominant and
the medusa stage is reduced or absent in some species .
Section 2: Lophotrochozoa (Platyhelminthes, Annelida, Mollusca)
6. A flatworm is observed with a digestive system that branches throughout the body but
lacks an anus. It has eyespots but is free-living. Which class does it belong to?
A. Trematoda
B. Cestoda
C. Turbellaria
D. Monogenea
Answer: C. Turbellaria
Rationale: Planarians (Turbellaria) are free-living flatworms with a branched gastrovascular
cavity but no anus. Trematodes and Cestodes are parasitic .
7. Why are tapeworms (Class Cestoda) able to survive without a digestive system?
A. They photosynthesize using their cuticle.
B. They absorb nutrients directly through their tegument (skin) from the host's intestine.
Questions and Answers 100% Pass
2025/2026.
Section 1: Porifera & Cnidaria (Body Plans & Early Evolution)
1. A student observes a specimen under a dissecting scope. It has no visible tissues,
appears asymmetrical, and possesses small spicules. What structure would indicate the
flow of water exiting the organism?
A. Spongocoel
B. Osculum
C. Choanocyte
D. Nematocyst
Answer: B. Osculum
Rationale: In Phylum Porifera (sponges), water enters through small pores but exits through
the large opening called the osculum. The spongocoel is the central cavity .
2. How do choanocytes and amoebocytes collaborate in sponge digestion?
A. Choanocytes capture food via flagella; amoebocytes distribute nutrients.
B. Amoebocytes filter water; choanocytes secrete the skeleton.
C. Choanocytes create spicules; amoebocytes create the osculum.
D. They both only reproduce sexually.
Answer: A. Choanocytes capture food via flagella; amoebocytes distribute nutrients.
Rationale: Choanocytes (collar cells) generate water flow and trap particles via phagocytosis.
Amoebocytes pick up these food vacuoles and transport nutrients to the rest of the body .
3. A marine biologist finds an organism with two tissue layers (diploblastic), a
gastrovascular cavity, and stinging cells. Which class lacks a medusa stage entirely and
exists only as polyps?
A. Hydrozoa
B. Scyphozoa
C. Cubozoa
D. Anthozoa
, Answer: D. Anthozoa
Rationale: Anthozoa (corals and sea anemones) are the only class of Cnidarians that do not
have a medusa stage; they exist solely as polyps .
4. In Cnidarians, the gastrovascular cavity serves multiple functions. Which of the
following is NOT one of them?
A. Digestion of prey
B. Hydrostatic skeleton
C. Gas exchange via diffusion
D. Separate exit for undigested waste
Answer: D. Separate exit for undigested waste
Rationale: Cnidarians have a single opening that serves as both mouth and anus. The
gastrovascular cavity aids in digestion and acts as a hydrostatic skeleton, but waste exits
through the same opening it entered .
5. The Portuguese Man O' War (Physalia) is a colonial organism often mistaken for a
jellyfish. It belongs to Class Hydrozoa. Which statement best describes this group?
A. Dominant medusa stage, no polyp stage.
B. Dominant polyp stage, reduced medusa stage.
C. Exists only as a sessile polyp.
D. Exists only as a floating medusa.
Answer: B. Dominant polyp stage, reduced medusa stage.
Rationale: Class Hydrozoa typically exhibit a life cycle where the polyp stage is dominant and
the medusa stage is reduced or absent in some species .
Section 2: Lophotrochozoa (Platyhelminthes, Annelida, Mollusca)
6. A flatworm is observed with a digestive system that branches throughout the body but
lacks an anus. It has eyespots but is free-living. Which class does it belong to?
A. Trematoda
B. Cestoda
C. Turbellaria
D. Monogenea
Answer: C. Turbellaria
Rationale: Planarians (Turbellaria) are free-living flatworms with a branched gastrovascular
cavity but no anus. Trematodes and Cestodes are parasitic .
7. Why are tapeworms (Class Cestoda) able to survive without a digestive system?
A. They photosynthesize using their cuticle.
B. They absorb nutrients directly through their tegument (skin) from the host's intestine.
