Study of Animal Type — Cockroach
Easy Overview
You probably hate cockroaches. But here's the thing — they're perfect for learning animal anatomy. They're big enough to see easily, and they have all the basic systems we have. Plus, they've survived for 300 million years, so they're clearly doing something right.
External Morphology — What You See
Cockroaches have three body parts: head, thorax, and abdomen. They have six legs (three pairs), two pairs of wings, and a pair of antennae. The exoskeleton is their hard outer shell — made of chitin. It protects them and prevents water loss.
Body Systems — Digestive System
The digestive system runs from mouth to anus. Food goes: mouth → esophagus → crop (storage) → gizzard (grinding) → midgut (digestion and absorption) → hindgut (water absorption) → anus. The crop is like a lunchbox. The gizzard has teeth made of chitin to grind food.
Circulatory System — Open Heart
Cockroaches have an open circulatory system. Blood (hemolymph) isn't confined to vessels. It just bathes the organs directly. The heart is a tube on the back with openings called ostia. It pumps hemolymph forward, and it seeps back through the body cavity.
Respiratory System — Air Tubes
No lungs needed. Cockroaches have a network of tubes called tracheae. Air enters through spiracles (holes on the sides) and travels directly to every cell. It's way more efficient than our system. That's why they can run so fast.
Nervous System and Sense Organs
They have a nerve cord running along the belly (opposite of us — ours is on the back). The brain is small but they have ganglia (nerve clusters) in each segment. Their antennae sense touch and smell. Compound eyes give them a wide field of view — they can see you coming from any direction.
Reproduction — Why There's So Many
Cockroaches lay eggs in a case called ootheca. A single ootheca can hold 16 eggs. Females can produce several. Nymphs hatch and look like mini adults — no caterpillar stage. They molt (shed their exoskeleton) several times before becoming adults. That's why they're everywhere.
Key Points
- •Body divided into head, thorax, abdomen. Six legs, two pairs of wings.
- •Exoskeleton of chitin — waterproof and protective.
- •Open circulatory system — heart pumps hemolymph into body cavity.
- •Respiratory system: tracheae and spiracles — direct oxygen delivery.
- •Digestive system: mouth → crop → gizzard → midgut → hindgut → anus.
- •Nervous system: nerve cord on ventral side, ganglia in segments.
- •Compound eyes provide wide vision; antennae sense touch/smell.
- •Reproduction: ootheca contains eggs; nymphs develop through molting.
Practice Questions
- Describe the digestive system of a cockroach.
- How does respiration occur in a cockroach?
- Draw a labeled diagram of the external features of a cockroach.
- Explain the circulatory system of a cockroach.
- What is an ootheca? What is its significance?