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Structural Organisation in Animals – Class 11 Biology notes, important questions and MCQs

NCERT Class 11 Biology, chapter 7. Notes, key terms, important questions with answers and MCQs.

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Chapter overview

Animal bodies are built from four basic tissues. The frog (Rana tigrina) is studied as an example of organ systems in a vertebrate.

Animal tissues

  • Epithelial: covers and lines (squamous, cuboidal, columnar, ciliated; glands).
  • Connective: loose, dense, specialised (cartilage, bone, blood); collagen and elastin fibres.
  • Muscular (skeletal, smooth, cardiac) and neural tissue (neurons and neuroglia).

Frog

  • Frogs are cold-blooded and show aestivation and hibernation; skin helps in respiration.
  • Three-chambered heart (two atria, one ventricle); ureters and sperm ducts open into the cloaca.
  • Frogs are ureotelic; fertilisation is external; development includes a tadpole stage (metamorphosis).

Key terms

Epithelium
tissue covering body surfaces and lining cavities
Metamorphosis
change from larva (tadpole) to adult frog
Areolar tissue
loose connective tissue beneath the skin that supports and binds other tissues

Important questions with answers

Name the three types of cell junctions and their functions.2 marks

Tight junctions stop substances leaking across a tissue; adhering junctions (desmosomes) cement cells together; gap junctions connect the cytoplasm of neighbouring cells for communication.

Describe the digestive system of the frog in brief.3 marks

Mouth → buccal cavity (with teeth on the upper jaw and a bilobed tongue to catch insects) → pharynx → oesophagus → stomach → intestine → rectum → cloaca. The liver secretes bile stored in the gall bladder; the pancreas secretes pancreatic juice. Digested food is absorbed through villi and microvilli in the intestine.

Classify connective tissues with their components and functions, giving one example of each.5 marks

Loose connective tissue: areolar (fibroblasts, macrophages, mast cells; supports under the skin) and adipose (stores fat, insulates). Dense connective tissue: regular (tendons attach muscle to bone; ligaments join bones) and irregular (skin dermis). Specialised: cartilage (chondrocytes in a firm, flexible matrix; nose tip, ear pinna, between vertebrae), bone (osteocytes in a hard matrix of calcium salts and collagen; support and protection, bone marrow makes blood cells), and blood (fluid plasma with RBCs, WBCs and platelets; transport).

Quick revision

  • Blood is a fluid connective tissue.
  • Frog heart has 3 chambers.
  • Frogs are ureotelic.

Exam tips

  • Cardiac muscle is striated but involuntary.
  • Match each tissue with one location: squamous epithelium – alveoli; ciliated – trachea and fallopian tubes; cartilage – nose tip and ear pinna; adipose – under the skin.

Practice MCQs

  1. Blood is a type of

    1. epithelial tissue
    2. muscular tissue
    3. connective tissue
    4. neural tissue
    Show answer

    Answer: (c) connective tissue. Fluid connective tissue.

  2. Frog's heart has

    1. 3 chambers
    2. 2 chambers
    3. 4 chambers
    4. 1 chamber
    Show answer

    Answer: (a) 3 chambers. Two atria, one ventricle.

  3. Cardiac muscle is

    1. striated and voluntary
    2. smooth and involuntary
    3. smooth and voluntary
    4. striated and involuntary
    Show answer

    Answer: (d) striated and involuntary. Heart.

  4. Frogs excrete mainly

    1. ammonia
    2. creatinine
    3. uric acid
    4. urea
    Show answer

    Answer: (d) urea. Ureotelic.

  5. The tissue that joins skeletal muscle to bone is

    1. ligament
    2. cartilage
    3. tendon
    4. adipose tissue
    Show answer

    Answer: (c) tendon. Dense regular tissue.

  6. Cartilage and bone are examples of

    1. specialised connective tissue
    2. loose connective tissue
    3. epithelial tissue
    4. muscle
    Show answer

    Answer: (a) specialised connective tissue. Specialised.

  7. Tadpole changing into a frog is called

    1. aestivation
    2. regeneration
    3. hibernation
    4. metamorphosis
    Show answer

    Answer: (d) metamorphosis. Metamorphosis.

  8. Cells connected by gap junctions in tissues mainly allow

    1. quick passage of ions and small molecules between cells
    2. blocking of leaks
    3. cell division
    4. attachment to bone
    Show answer

    Answer: (a) quick passage of ions and small molecules between cells. Communication junction.

All chapters of Class 11 Biology

Written by Kundali IQ from standard, well-established facts to help with revision. This is not an official NCERT publication; always read your textbook too.