Study of Animal Type : Cockroach
1. Choose correct option
A. Chemical nature of chitin is ………….
a. protein. b. carbohydrate.
c. lipid. d. glycoprotein.
Answer: b. carbohydrate
B. Cockroach has ……………. type of mouthparts.
a. sponging
b. chewing and biting
c. piercing and Sucking
d. lapping
Answer: b. chewing and biting
C. Spiracle is a part of ……………….. system of cockroach.
a. circulatory b. respiration
c. reproductive d. nervous
Answer: b. respiration
D. ………………. is a part of digestive system.
a. Trachea b. Hypopharynx
c. Haemocyte d. Seminal vesicle
Answer: b. Hypopharynx
E. ………………… is also called as brain of cockroach.
a. Supra-oesophageal ganglion
b. Sub-oesophageal ganglion
c. Hypo-cerebral ganglion
d. Thoracic ganglion
Answer: a. Supra-oesophageal ganglion
2. Answer the following questions
A. Describe the digestive system of cockroach.
Answer: The digestive system of a cockroach consists of mouthparts, an alimentary canal, and salivary glands. The alimentary canal is a 6-7 cm long tube divided into three regions:
- Foregut (Stomodaeum): Includes the pharynx, oesophagus, crop, and gizzard. The pharynx is a short muscular tube, the oesophagus is a narrow tube, the crop stores food, and the gizzard grinds food with chitinous teeth and bristles.
- Midgut (Mesenteron): Comprises the stomach and hepatic caeca. The stomach, lined with glandular epithelium, secretes digestive enzymes for digestion and absorption. Hepatic caeca produce enzymes to aid digestion.
- Hindgut (Proctodaeum): Consists of the ileum, colon, and rectum. The ileum receives nitrogenous wastes via Malpighian tubules, the colon reabsorbs water, and the rectum, with rectal pads, expels undigested food through the anus.
- Salivary glands secrete saliva via ducts opening at the hypopharynx, aiding in food processing. The cockroach is omnivorous, chewing food with mouthparts and digesting it in the alimentary canal.
B. Give an account on tracheal system of cockroach?
Answer: The tracheal system is the respiratory system of the cockroach, consisting of air tubes that deliver oxygen directly to tissues without blood involvement.
- Spiracles: Ten pairs of slit-like openings (2 thoracic, 8 abdominal) on the ventro-lateral body allow air entry and exit.
- Trachea: Branched tubes with chitinous linings to prevent collapse, forming a network arranged transversely and longitudinally.
- Tracheoles: Fine intracellular tubes penetrating tissues, ending blindly with fluid-filled tips where gas exchange occurs. During high activity, fluid is partially absorbed for rapid oxygen intake.
- Rhythmic movements of thoracic and abdominal muscles renew air in the system, and body fluid acts as a diffusion medium.
C. Describe nervous system of cockroach.
Answer: The nervous system of a cockroach is ventral, solid, and ganglionated, comprising:
- Central Nervous System (CNS): Includes a nerve ring and ventral nerve cord (VNC). The nerve ring consists of supra-oesophageal ganglia (brain, above the oesophagus), sub-oesophageal ganglion (below the oesophagus), and circum-oesophageal connectives. The VNC, arising from the sub-oesophageal ganglion, has nine paired ganglia: three thoracic and six abdominal, with the sixth abdominal ganglion being the largest.
- Peripheral Nervous System (PNS): Nerves from CNS ganglia innervate eyes, antennae, mouthparts, wings, legs, and visceral organs.
- Autonomous Nervous System (ANS): Includes four ganglia (frontal, hypocerebral, ingluvial, and ventricular) and a retrocerebral complex, regulating visceral functions.
The system coordinates sensory and motor functions, with compound eyes and antennae as key sense organs.
D. With help of neat labelled diagram, describe female reproductive system of cockroach.
Answer: The female reproductive system includes:
- Ovaries: Paired, located in the 2nd to 6th abdominal segments, each with eight ovarioles containing developing ova.
- Oviducts: Lateral oviducts from each ovary unite to form a common oviduct (vagina), opening into the genital chamber (bursa copulatrix).
- Spermatheca: A sperm-storing structure in the -necess to verify segment number, likely 6th- segment, opening into the genital chamber.
- Collateral Glands: Paired accessory glands opening into the genital chamber, secreting ootheca material.
- Gonapophyses: Six chitinous plates surrounding the genital pore.
- Diagram: (As text-based, describe key components): Label ovaries, oviducts, common oviduct, spermatheca, collateral glands, genital chamber, and gonapophyses.
E. With help of neat labelled diagram, describe the digestive system of cockroach.
Answer: The digestive system includes:
- Mouth/Pre-oral Chamber: Bounded by mouthparts (labrum, mandibles, maxillae, labium, hypopharynx), where food is received.
- Foregut: Pharynx (muscular, with taste sensillae), oesophagus (narrow tube), crop (food storage), gizzard (grinding with chitinous teeth).
- Midgut: Stomach (digestion/absorption with glandular epithelium), hepatic caeca (enzyme secretion).
- Hindgut: Ileum (receives wastes), colon (water reabsorption), rectum (with rectal pads, opens via anus).
- Salivary Glands: Paired, with glandular lobes and reservoirs, secreting saliva via ducts to the hypopharynx.
- Diagram: Label mouth, pharynx, oesophagus, crop, gizzard, hepatic caeca, stomach, ileum, colon, rectum, anus, salivary glands, and ducts.
F. A student observed that the cockroaches are killed for dissection by simply putting them in soap water. He inquired whether soap is so poisonous. Teacher said it is due to its peculiar respiratory system. How?
Answer: Cockroaches breathe through spiracles connected to a tracheal system. Soap water reduces surface tension, allowing water to enter the spiracles and tracheae, blocking air entry. This causes suffocation, as oxygen cannot reach tissues, leading to death. The tracheal system’s open structure makes it vulnerable to such liquid infiltration, unlike the lung-based respiration in other animals.
G. Describe the cirulatory system of cockroach.
Answer: The cockroach has an open circulatory system with:
- Haemolymph: Colourless, pigment-free blood containing plasma and haemocytes, rich in nutrients and wastes like uric acid.
- Haemocoel: Body cavity divided into pericardial (dorsal, contains heart), perivisceral (middle, contains viscera), and perineural (ventral, contains nerve cord) sinuses by dorsal and ventral diaphragms.
- Dorsal Blood Vessel: Includes a heart (2.5 cm, 13 chambers, 10 abdominal, 3 thoracic) and dorsal aorta. The heart has ostia (12 pairs) with valves allowing blood entry from sinuses.
- Circulation: During diastole, alary muscles contract, flattening the dorsal diaphragm, drawing blood into the heart via ostia. During systole, heart contraction pushes blood to the dorsal aorta and head, then to perivisceral and perineural sinuses. Diastasis follows, with the heart expanded. Alary muscle relaxation during systole aids blood movement.
3. Answer the following questions
A. How will you identify male or female cockroach?
Answer:
- Male: Narrower, tapering abdomen; ninth sternum bears a pair of short, unjointed anal styles; male gonapophyses (phallomeres) surround the gonopore.
- Female: Broader abdomen; no anal styles; female gonapophyses (six chitinous plates) surround the genital pore; presence of spermatheca and collateral glands.
B. Write a note on : Gizzard of cockroach.
Answer: The gizzard (proventriculus) is a small, spherical organ in the foregut, following the crop. Internally, it has six chitinous teeth and backward-directed bristles. The teeth crush and grind food, while bristles filter it, preventing large particles from entering the midgut. The gizzard’s muscular action aids mechanical digestion, preparing food for enzymatic breakdown in the midgut.
C. Give the systematic position of cockroach.
Answer:
- Kingdom: Animalia (cell wall absent, heterotrophic)
- Phylum: Arthropoda (jointed appendages, segmented body, chitinous exoskeleton)
- Class: Insecta (two pairs of wings, three pairs of walking legs)
- Genus: Periplaneta (nocturnal, straight wings)
- Species: americana (origin in America)
D. What would have happened if cockroach did not had gizzard?
Answer: Without a gizzard, the cockroach would struggle to mechanically break down food. The gizzard’s chitinous teeth and bristles grind and filter food, preparing it for digestion in the midgut. Its absence would lead to inefficient digestion, reduced nutrient absorption, and potential blockages in the alimentary canal, impairing the cockroach’s survival and growth.
E. What is the functional difference between eyes of cockroach and human being?
Answer:
- Cockroach Eyes: Compound eyes with ~2000 ommatidia, each forming a small image, creating a mosaic or hazy vision. They excel at detecting motion with high sensitivity but low resolution, suitable for nocturnal environments.
- Human Eyes: Single-lens eyes with a retina, providing high-resolution, detailed vision and color perception. They focus light to form a single, clear image but are less sensitive to rapid motion in low light compared to cockroach eyes.
F. What is the functional difference between respiratory systems of cockroach and human being?
Answer:
- Cockroach: Tracheal system with spiracles, tracheae, and tracheoles delivers oxygen directly to tissues via diffusion, without blood involvement. It is efficient for small bodies but vulnerable to water infiltration (e.g., soap water).
- Human: Lung-based system with alveoli, where oxygen is absorbed into blood via the respiratory tract and circulated to tissues. It supports larger bodies and is protected from external liquids but requires a complex circulatory system for gas transport.
4. Explain the following in short
A. What are anal cerci?
Answer: Anal cerci are paired, many-jointed, sensory appendages on the tenth abdominal segment of the cockroach, projecting backward. They detect vibrations and air movements, aiding in predator avoidance.
B. What is the ganglion?
Answer: A ganglion is a mass of nerve cell bodies in the cockroach’s nervous system, acting as a local control center. Examples include supra-oesophageal (brain), sub-oesophageal, and segmental ganglia in the ventral nerve cord.
C. What is the role of hypopharynx?
Answer: The hypopharynx (lingua) is a tongue-like structure in the pre-oral cavity, bearing comb-like super-lingua plates. It mixes saliva with food, aids feeding, and directs chewed food into the alimentary canal.
D. What is mesenteron?
Answer: The mesenteron (midgut) is the middle part of the cockroach’s alimentary canal, comprising the stomach and hepatic caeca. It is the primary site for digestion and absorption, with glandular epithelium and caeca secreting digestive enzymes.
E. Location of tergum.
Answer: The tergum is the dorsal chitinous plate (sclerite) covering each body segment of the cockroach, providing protection and muscle attachment. It is present on the head, thorax (pro-, meso-, metathorax), and abdomen.
F. What is ootheca?
Answer: The ootheca is a dark reddish to blackish-brown egg case (8 mm long) formed by collateral gland secretions, containing 14-16 fertilized eggs in two rows. It is deposited in humid crevices for protection during development.
G. How many chambers are present in the heart of cockroach?
Answer: The cockroach’s heart has 13 chambers: 10 in the abdominal region and 3 in the thoracic region.
Leave a Reply