Questions & explanations
1. Which of the following statements about cockroaches is correct?
- They belong to class Arachnida of phylum Arthropoda.
- Periplaneta americana is a common species of cockroach.
- Cockroaches are red or yellow bodied insects.
- Cockroaches are not insects but belong to class Crustacea.
Answer: Periplaneta americana is a common species of cockroach.
Cockroaches are insects belonging to class Insecta of phylum Arthropoda, and Periplaneta americana is indeed a common species. The other options are incorrect: they belong to Insecta, not Arachnida or Crustacea, and they are typically brown or black, not red or yellow.
2. In cockroach, at the junction of foregut and midgut, there are ring-like 6-8 blind tubules that secrete digestive juice. These are called:
- Hepatic or gastric caecae
- Malpighian tubules
- Salivary glands
- Gastric glands
Answer: Hepatic or gastric caecae
The hepatic or gastric caecae are present at the junction of foregut and midgut in cockroach and secrete digestive juice. Malpighian tubules are excretory, salivary glands are in the mouth, and gastric glands are not present in cockroach.
3. Which of the following correctly describes the wings of a cockroach?
- Both pairs of wings are membranous and used for flight
- The first pair arises from the mesothorax, is leathery and opaque, and is called tegmina
- The second pair arises from the prothorax and is membranous
- The first pair arises from the metathorax and is used for flight
Answer: The first pair arises from the mesothorax, is leathery and opaque, and is called tegmina
In cockroaches, the first pair of wings (tegmina) arises from the mesothorax and is leathery and opaque, serving as protective covers. The second pair arises from the metathorax and is membranous, used for flight.
4. The alimentary canal of a cockroach is divided into three regions. Which of the following is the correct order from mouth to anus?
- Foregut, hindgut, midgut
- Foregut, midgut, hindgut
- Midgut, foregut, hindgut
- Hindgut, midgut, foregut
Answer: Foregut, midgut, hindgut
The alimentary canal is divided into foregut, midgut, and hindgut in that order. The mouth opens into the pharynx, then oesophagus, crop, gizzard (foregut), followed by midgut and hindgut.
5. Exchange of gases in cockroach takes place at the tracheoles by:
- Diffusion
- Active transport
- Facilitated diffusion
- Osmosis
Answer: Diffusion
Gas exchange in tracheoles occurs by simple diffusion due to concentration gradients. Active transport and facilitated diffusion require energy or carriers; osmosis is for water.
6. In cockroach, the Malpighian tubules are present at the junction of midgut and hindgut. Their number is approximately:
- 6-8
- 10-20
- 100-150
- 200-250
Answer: 100-150
Cockroach has 100-150 yellow-coloured thread-like Malpighian tubules that remove excretory products from haemolymph. 6-8 is the number of hepatic caecae, not Malpighian tubules.
7. The heart of cockroach is:
- A tubular structure lying mid-dorsally with funnel-shaped chambers and ostia
- A two-chambered heart located in the thorax
- A single-chambered sac in the abdomen
- Absent; blood is pumped by body movements
Answer: A tubular structure lying mid-dorsally with funnel-shaped chambers and ostia
Cockroach heart is an elongated muscular tube along the mid-dorsal line, differentiated into funnel-shaped chambers with ostia. It is not two-chambered like in fish, nor absent.
8. How many pairs of walking legs are present on the thoracic segments of a cockroach?
- One pair
- Two pairs
- Three pairs
- Four pairs
Answer: Three pairs
Each thoracic segment bears one pair of walking legs, and there are three thoracic segments (prothorax, mesothorax, metathorax), so a total of three pairs of walking legs.
9. The blood vascular system of cockroach is characterized by:
- Closed type with well-developed blood vessels
- Open type with poorly developed blood vessels opening into haemocoel
- Absence of blood vessels
- Presence of a single dorsal vessel only
Answer: Open type with poorly developed blood vessels opening into haemocoel
Cockroach has an open circulatory system where blood vessels are poorly developed and open into the haemocoel. Closed type is found in annelids and vertebrates.
10. The exoskeleton of a cockroach is made of which material?
- Calcium carbonate
- Chitin
- Cellulose
- Keratin
Answer: Chitin
The cockroach exoskeleton is hard and chitinous. Calcium carbonate is found in crustaceans, cellulose in plants, and keratin in vertebrates like hair and nails.
11. In cockroach, the opening of spiracles is regulated by:
- Sphincters
- Valves
- Cilia
- Muscles attached to trachea
Answer: Sphincters
Spiracles in cockroach are regulated by sphincters. Valves are in heart, cilia are not involved, and muscles attached to trachea are not the primary regulators.
12. The head of a cockroach is connected to the thorax by which structure?
- A long extension of the abdomen
- A short extension of the prothorax called the neck
- A flexible joint called the arthrodial membrane
- Direct fusion without any connecting structure
Answer: A short extension of the prothorax called the neck
The head is connected to the thorax by a short extension of the prothorax known as the neck. The arthrodial membrane joins sclerites, not head to thorax.