CBSE Class 11 Biology Chapter 9: Structural Organisation in Animals NCERT Solutions

(i) The common name of Periplaneta americana is the American cockroach.

(ii) Earthworms possess four pairs of spermathecae, which are situated in the inter-segmental grooves between the 6th and 9th segments. These structures are vital for receiving and storing spermatozoa during the process of copulation.

(iii) In a cockroach, the pair of ovaries is located ventrolaterally within the 12th and 13th abdominal segments.

(iv) The abdomen of a cockroach, in both male and female individuals, is comprised of ten segments.

(v) Malpighian tubules are the principal excretory organs found in cockroaches. They are integrated as part of the cockroach's alimentary canal.

(i) Nephridia are specialized, segmentally arranged organs responsible for excretion in earthworms. They function to remove metabolic wastes and excess fluid from the body, maintaining internal osmotic balance.

(ii) Based on their anatomical position and structure, three distinct types of nephridia are found in earthworms:

• Septal nephridia: These are found on both sides of the inter-segmental septa, starting from behind the 15th segment. Their ducts open into the lumen of the intestine, contributing to waste removal from the gut contents.
• Integumentary nephridia: These nephridia are attached to the body wall, extending from the third segment all the way to the terminal segment. Their external openings are located on the body surface, facilitating excretion directly to the exterior.
• Pharyngeal nephridia: These occur in three paired tufts located in the pharyngeal region, specifically within the fourth, fifth, and sixth segments of the earthworm.

The reproductive system of an earthworm is complex, involving both male and female organs. A labelled diagram illustrating these organs is essential for understanding their arrangement and function. Key structures include:

• Testis sacs with testes: Located ventrally, these produce sperm.
• Spermiducal funnels: These capture sperm released from the testes.
• Vasa deferentia: Ducts that carry sperm away from the funnels.
• Seminal vesicles: Paired structures that store sperm.
• Spermathecae: Found in pairs between segments 6-9, these receive and store sperm from a partner during mating.
• Ovary and Ovarian funnel: Located ventrally in the 12th segment, these are the female reproductive organs producing ova.
• Prostate Gland and Accessory glands: These glands contribute secretions that aid in reproduction.
• Common prostatic and spermatic duct: A combined duct system for the passage of sperm and prostatic secretions.

(Note: A visual diagram is required here, as described by the question. The text above lists the components typically labelled in such a diagram.)

The alimentary canal of a cockroach is a complete tube extending from the mouth to the anus, adapted for processing food. It can be divided into three main regions: the foregut, midgut, and hindgut. A labelled diagram would typically show the following parts in sequence:

• Mouth: The entry point for food.
• Pharynx and Oesophagus: Part of the foregut, involved in swallowing and transport.
• Salivary Gland and Salivary Reservoir: Secrete saliva to aid digestion.
• Crop: A storage sac for food.
• Gizzard: A muscular part of the foregut that grinds food.
• Midgut (Mesenteron): The primary site for digestion and absorption, often with hepatic caeca (anteriorly) secreting digestive enzymes.
• Malpighian tubules: Located at the junction of the midgut and hindgut, these are the excretory organs.
• Hindgut: Consists of the ileum, colon, and rectum, responsible for water absorption and formation of faeces.
• Rectum and Anus: The final section for elimination of undigested waste.

(Note: A visual diagram is required here, as described by the question. The text above lists the components typically labelled in such a diagram.)