ACE Animal Anatomy & Physiology 2 — Questions and Answers
Question 1: Which insect organ system is primarily responsible for gas exchange, delivering oxygen directly to tissues?
- Circulatory system
- Tracheal system (Correct answer)
- Malpighian tubules
- Digestive system
Correct answer: Tracheal system
Insects use a tracheal system of tubes that deliver oxygen directly to cells, bypassing the circulatory system for gas transport.
Question 2: The insect hemolymph differs from vertebrate blood primarily because it:
- Contains hemoglobin for oxygen transport
- Lacks red blood cells and does not primarily transport oxygen (Correct answer)
- Flows through a closed circulatory system
- Is pumped by a multi-chambered heart
Correct answer: Lacks red blood cells and does not primarily transport oxygen
Insect hemolymph transports nutrients, hormones, and waste but relies on the tracheal system—not hemolymph—for oxygen delivery.
Question 3: In insects, the proventriculus functions primarily to:
- Absorb water from digested food
- Grind and filter food before it enters the midgut (Correct answer)
- Produce digestive enzymes
- Store lipids for energy reserves
Correct answer: Grind and filter food before it enters the midgut
The proventriculus acts as a gizzard-like valve that grinds food and controls passage of material into the midgut.
Question 4: Which structure in the insect nervous system acts as the primary processing center analogous to a vertebrate brain?
- Subesophageal ganglion
- Protocerebrum (Correct answer)
- Ventral nerve cord
- Corpora allata
Correct answer: Protocerebrum
The protocerebrum is the largest region of the insect brain and processes visual information and higher-order functions.
Question 5: Spiracles in insects are regulated by which mechanism to prevent desiccation?
- Continuous opening to maximize gas flow
- Discontinuous gas exchange cycles with valve-like closures (Correct answer)
- Pumping via abdominal contractions only during flight
- Passive diffusion with no muscular control
Correct answer: Discontinuous gas exchange cycles with valve-like closures
Discontinuous gas exchange cycles allow spiracles to remain closed most of the time, conserving water while still enabling CO₂ release.
Question 6: The fat body in insects serves a function most analogous to which vertebrate organs combined?
- Heart and lungs
- Liver and adipose tissue (Correct answer)
- Kidney and spleen
- Pancreas and thyroid
Correct answer: Liver and adipose tissue
The fat body stores lipids and glycogen, detoxifies compounds, and synthesizes proteins—roles divided between the liver and fat tissue in vertebrates.
Question 7: During insect metamorphosis, larval tissues are broken down and reorganized by which cell type in the pupa?
- Oenocytes
- Imaginal discs and histoblasts (Correct answer)
- Hemocytes
- Trichogen cells
Correct answer: Imaginal discs and histoblasts
Imaginal discs (in holometabolous insects) and histoblasts are clusters of undifferentiated cells that form adult structures from larval tissue breakdown.
ACE Animal Anatomy & Physiology 2
Which insect organ system is primarily responsible for gas exchange, delivering oxygen directly to tissues?