Class 11 Biology

Structural Organization

NCERT Solution

Question 1: Answer in one word or one line.

  1. Give the common name of Periplanata americana.
  2. How many spermathecae are found in earthworm?
  3. What is the position of ovaries in cockroach?
  4. How many segments are present in the abdomen of cockroach?
  5. Where do you find Malpighian tubules?

Answer: (i) Cockroach (ii) 2 spermathecae (iii) 2nd to 6th abdominal segment (iv) 10 segments (v) Malpighian tubules are the main excretory organs of the cockroach

Question 2: Answer the following:

(i) What is the function of nephridia?

Answer: Excretion

(ii) How many types of nephridia are found in earthworm based on their location?

Answer: There are of three types of nephridia in the earthworm, viz. septal nephridia, integumentary nephridia and pharyngeal nephridia.

Question 3: Distinguish between the followings

(a) Prostomium and peristomium

Answer: Prostomium is the frontmost part of the earthworm. This is not called a true segment as it doesn’t contain typical organs of an annelida. The true segment of the earthworm’s body begins from the peristomium.

(b) Septal nephridium and pharyngeal nephridium

Answer: Septal nephridia are present on both sides of intersegmental septa of earthworm, while pharyngeal nephridia are present in the 4th, 5th and 6th segments. They are same; in terms of structure and function.

Question 4: What are the cellular components of blood?

Answer: Red Blood Cells and White Blood Cells.

Question 5: What are the following and where do you find them in animal body.

(a) Chondrocytes

Answer: The cells of cartilage are called chondrocytes.

(b) Axons:

Answer: The tail like portion of the neuron is called axon.

(c) Ciliated epithelium:

Answer: Ciliated epithelium are present in the inner surface of hollow organs; like bronchioles and fallopian tubes.

Question 6: Describe various types of epithelial tissues with the help of labelled diagrams.

Answer: The epithelial tissues are further divided into two main types, viz. simple epithelium and compound epithelium.

Simple Epithelium: The simple epithelium is composed of a single layer of cells. It is present in the lining of body cavities, ducts and tubes.

Compound Epithelium: The compound epithelium is composed of more than one layer of cells. The compound epithelium serves the protective function. Compound epithelium is present in skin, in the lining of buccal cavity, pharynx, ducts of salivary glands and pancreatic ducts.

The simple epithelium can be further divided into three types, viz. squamous, cuboidal and columnar.

Squamous Epithelium: The squamous epithelium is made up of flattened cells with irregular boundaries. Squamous epithelium is present in the walls of blood vessels and air sacs of lungs. They form a diffusion boundary.

Cuboidal Epithelium: The cuboidal epithelium is composed of cube-like cells. The cuboidal epithelium is usually found in ducts of glands and tubular parts of nephrons. The main functions of cuboidal epithelium are secretion and absorption.

Columnar Epithelium: The columnar epithelium is composed of tall and slender cells. The nuclei of the columnar cells are located at the base. Microvilli may be present on the free surface. Columnar epithelium is present in the lining of stomach and intestine. They help in secretion and absorption.

Question 7: Distinguish between

(a) Simple epithelium and compound epithelium

Answer: Simple epithelium is composed of one layer of cells, while compound epithelium is composed of more than one layer of cells.

(b) Cardiac muscle and striated muscle

Answer: Cardiac muscles are present in the heart, while striated muscles are present in articulatory joints. Cardiac muscle fibres are branched, while striated muscle fibres are unbranched. Cardiac muscles continuously contract and relax throughout the life, while striated muscles show movement as and when required.

(c) Dense regular and dense irregular connective tissues

Answer: The cells and fibres are loosely arranged in a semi-fluid matrix; in loose connective tissue. The cells and fibres are compactly packed in dense connective tissue. Areolar tissue is an example of loose connective tissue, while tendon and ligament are examples of dense connective tissue.

(d) Adipose and blood tissue

Answer: Adipose tissue is an example of loose connective tissue, while blood tissue is a specialized connective tissue. Adipose tissue is usually located beneath the skin. The cells of the adipose tissue are specialized to store fat. Blood facilitates transportation of various materials in the body.

(e) Simple gland and compound gland

Answer: Simple gland is composed of single cell, while compound gland is composed of multiple cells.

Question 8: Mark the odd one in each series:

(a) Areolar tissue; blood; neuron; tendon

Answer: Neuron is not a connective tissue

(b) RBC, WBC, platelets, cartilage

Answer: Cartilage is not part of blood

(c) Exocrine, endocrime, salivary gland, ligament

Answer: Ligament is not part of gland

(d) Maxilla, mandible, labrum, antennae

Answer: Antennae is not a masticating part of cockroach

Question 9: Match the terms in column I with those in column II:

Column IColumn II
(a) Compound epithelium(1) Alimentary canal
(b) Compound eye(2) Cockroach
(c) Septal nephridia(3) Skin
(d) Open circulatory system(4) Mosaic vision
(e) Typhlosole(5) Earthworm
(f) Osteocytes(6) Phallomere
(g) Genitalia(7) Bone

Answer: (1) 3, (b) 4, (c) 5, (d) 2, (e) 1, (f) 7, (g) 6

Question 10: Mention briefly about the circulatory system of earthworm

Answer: Closed type blood vascular system is present in earthworm. The blood vascular system is composed of a heart, blood vessels and capillaries. Smaller blood vessels supply the gut, nerve cord and body wall. Blood glands are present on the 4th, 5th and 6th segments. The blood glands produce blood cells and haemoglobin. Blood cells are phagocytic in nature. Exchange of gases occurs through moist body surface into the blood stream.

Question 11: Mention the function of the following

(a) Ureters in frog

Answer: The ureters act as urinogenital duct male frogs. In females, the ureter is separate from the oviduct and only carries urine.

(b) Malpighian tubules

Answer: Excretion is performed by Malpighian tubules in cockroaches.

(c) Body wall in earthworm

Answer: The body wall of the earthworm facilitates exchange of gases.