🧩 Subjective Questions and Answers (Chapter Review)

This section contains exam-style subjective questions and answers from the full chapter (Animal Tissues + Frog).

Q1. Differentiate between Simple Epithelium and Compound Epithelium.

Answer.

Epithelial tissue is the covering/lining tissue. The main difference is number of layers and main function.

  • Simple epithelium = single layer of cells.

  • Why single layer? Because it is meant for diffusion, filtration, absorption, secretion.

  • Examples/locations:

    • Simple squamous: alveoli, capillaries (easy diffusion)
    • Simple cuboidal: kidney tubules, ducts (absorption/secretion)
    • Simple columnar: intestine (absorption)

  • Compound epithelium = many layers (stratified) of cells.

  • Why many layers? Mainly for protection against friction, drying, chemicals.

  • Examples/locations:

    • Stratified squamous (non-keratinized): buccal cavity, pharynx, oesophagus
    • Stratified squamous (keratinized): skin

✅ Tip to remember:

  • SIMPLE = Single = “S” for Secretion/absorption
  • COMPOUND = Covering for protection (many layers = strong shield)

Q2. Differentiate between Bone and Cartilage.

Answer.

Both are skeletal connective tissues, but they differ mainly in hardness, matrix, blood supply, and function.

Bone

  • Nature: hard, rigid
  • Matrix: collagen fibres + calcium salts (mainly calcium phosphate) → makes it hard
  • Cells: osteocytes in lacunae
  • Vascularity: highly vascular (blood vessels present)
  • Functions: support, protection, movement (with muscles), mineral storage, blood cell formation (bone marrow)

Cartilage

  • Nature: firm but flexible (pliable)
  • Matrix: chondroitin sulphate/chondrin (not mineralized like bone)
  • Cells: chondrocytes in lacunae
  • Vascularity: avascular (no blood vessels; nutrition by diffusion)
  • Functions: flexibility + smooth surface at joints, shock absorption

✅ Tip to remember:

  • BONE = ‘B’ for “Builds rigid body frame” + “B” for Blood vessels present
  • CARTILAGE = “C” for Cushion + “C” for Cannot bleed (avascular)

Q3. Differentiate between Tendon and Ligament.

Answer.

Both are dense regular connective tissues, but they connect different structures and have different elasticity.

Tendon

  • Connects: muscle → bone
  • Fibres: mostly collagen (white fibres)
  • Property: very strong, less elastic
  • Why? It must transmit pulling force from muscle to bone.

Ligament

  • Connects: bone → bone
  • Fibres: collagen + more elastic fibres (yellow fibres)
  • Property: strong but more elastic
  • Why? It holds bones together but allows flexibility at joints.

✅ Super-easy memory trick:

  • Tendon = “T” → “To” bone (Muscle TO bone)
  • Ligament = “L” → “Link” bones (Bone to bone link)

Q4. Describe the three types of cell junctions found in epithelial tissue.

Answer.

Epithelial cells are tightly packed, so they need special junctions to seal, hold, and communicate.

1) Tight junctions (Occluding junctions)

  • Work: act like a seal/zip, so substances cannot leak between cells.
  • Where important? Lining of intestine, kidney tubules (prevents leakage).

2) Adhering junctions (Anchoring junctions / Desmosome-type in concept)

  • Work: act like cement/strong glue to keep cells attached and prevent tearing.
  • Where important? Skin epithelium (high friction area).

3) Gap junctions (Communicating junctions)

  • Work: make tiny channels between adjacent cells for transfer of ions/small molecules.
  • Importance: helps cells coordinate quickly (cell-to-cell communication).

✅ Tip to remember (T-A-G):

  • Tight = Tight seal
  • Adhering = Attachment
  • Gap = Goes (messages go across)

Q5. Differentiate between the three types of muscular tissue.

Answer.

Muscle tissue contracts because of actin and myosin, but different muscles are built differently for different jobs.

1) Skeletal muscle (Striated / Voluntary)

  • Striations: present
  • Control: voluntary (we can control)
  • Cells: long, cylindrical, unbranched
  • Nuclei: many (multinucleate)
  • Location: attached to bones
  • Function: movement, posture

2) Smooth muscle (Unstriated / Involuntary)

  • Striations: absent
  • Control: involuntary
  • Cells: spindle-shaped (fusiform)
  • Nuclei: one (uninucleate)
  • Location: walls of hollow organs (intestine, stomach, blood vessels, urinary bladder)
  • Function: movement of substances (peristalsis, vasoconstriction)

3) Cardiac muscle (Striated but Involuntary)

  • Striations: present
  • Control: involuntary
  • Cells: branched, interconnected
  • Special feature: intercalated discs (help fast impulse spread + strong connection)
  • Location: heart wall
  • Function: rhythmic pumping without fatigue

✅ Tip to remember:

  • Skeletal = “Skeleton” + “Self-control” (voluntary)
  • Smooth = “Stomach/Systems inside” (involuntary)
  • Cardiac = “Cardio” + “Connected” (intercalated discs)

Q6. Draw a neat diagram of a neuron and label its main parts.

Answer (how to write in exam + what to label): In exams, you must draw a clean neuron and label the standard parts.

✅ What to draw (step-by-step):

  1. Draw a cell body (cyton) with a nucleus.
  2. From the cyton, draw many short branches = dendrites.
  3. From one side, draw a long fibre = axon.
  4. Show myelin sheath as bead-like covering on axon (optional but good).
  5. End axon with branching = axon terminals / synaptic knobs.

✅ Labels to include (most important):

  • Cell body (cyton)
  • Nucleus
  • Dendrites
  • Axon
  • Myelin sheath (if shown)
  • Nodes of Ranvier (gaps in myelin; optional but impressive)
  • Axon terminals / Synaptic knobs

🧠 One-line concept (good for viva):

  • Dendrites receive impulses, axon sends impulses.

✅ Tip to remember:

  • D = Dendrite = Direction towards cell body
  • A = Axon = Away from cell body

Q7. Draw a neat diagram of the digestive system of a frog.

Answer (how to draw + labels): Draw the frog digestive tract from mouth to cloaca and show major accessory glands.

✅ Main parts to draw in order: Mouth → Buccal cavity → Oesophagus → Stomach → Small intestine (duodenum + ileum) → Large intestine/Rectum → Cloaca

✅ Accessory glands to show (very important):

  • Liver (3 lobes in frog) and gall bladder
  • Pancreas (near the duodenum)

✅ Key labelling points (NEET-style):

  • Stomach (with pyloric end)
  • Duodenum (first part of small intestine)
  • Ileum (coiled part)
  • Rectum
  • Cloaca
  • Liver, gall bladder, pancreas

🧠 Quick explanation line (to write below diagram): Food passes through the alimentary canal, while liver secretes bile (fat emulsification) and pancreas secretes enzymes for digestion.

✅ Tip to remember order:

  • M-B-O-S-I-R-C = Mouth, Buccal, Oesophagus, Stomach, Intestine, Rectum, Cloaca

Q8. Mention the function of the ureters in a frog.

Answer.

Ureters are tubes that carry urine from kidneys to the cloaca.

In male frog: ureters work as urinogenital ducts.

  • They carry urine + sperms to the cloaca.
  • Reason: in males, urinary and reproductive pathways partially share ducts.

In female frog: ureters are only urinary.

  • They carry only urine from kidneys to cloaca.
  • Eggs travel through oviducts, not ureters.

✅ Tip to remember:

  • Male = “Mixed” (urine + sperms in ureter)
  • Female = “Free/Separate” (oviduct separate from ureter)

Q9. Describe the heart of a frog.

Answer.

Frog has a three-chambered heart because it has 2 atria (auricles) + 1 ventricle.

  • Right atrium receives deoxygenated blood from the body.

  • It comes through major veins into a thin-walled chamber called sinus venosus, which opens into the right atrium.

  • Left atrium receives oxygenated blood from lungs/skin via pulmonary veins.

  • Both atria open into a single ventricle, so blood becomes partly mixed.

  • Blood leaves the ventricle into a vessel called truncus/conus arteriosus.

  • It helps direct blood towards pulmonary (lungs/skin) and systemic (body) circulation.

✅ Why frog has “incomplete double circulation”?

  • There are two circuits (pulmonary + systemic), but because there is only one ventricle, complete separation of oxygenated and deoxygenated blood is not possible.

✅ Tip to memorize:

  • 2A + 1V = Amphibian heart (Amphibians: 3 chambers)
  • Sinus venosus = “S” for “Systemic blood entry”

Q10. How does a frog respire?

Answer.

Frog can breathe by three methods depending on environment:

1) Cutaneous respiration (through skin)

  • Skin is thin, moist, and highly vascular.
  • In water and during rest, oxygen diffuses through skin into blood.

2) Buccopharyngeal respiration (through buccal cavity lining)

  • When frog is on land (especially at rest), the lining of mouth and pharynx helps in gas exchange.
  • You can see rhythmic movement of the throat region.

3) Pulmonary respiration (through lungs)

  • Mainly on land, frog uses lungs.
  • Frog uses positive pressure breathing (pushes air into lungs by buccal pumping).

✅ Exam-ready line: Frog breathes through skin + buccopharyngeal cavity + lungs, so it is well adapted for both aquatic and terrestrial life.

✅ Tip to remember:

  • S-B-L = Skin, Buccal, Lungs

Q11. Differences between a male and a female frog (sexual dimorphism).

Answer.

Male and female frogs look similar, but males have some extra features for reproduction.

Male frog (commonly seen points):

1) Vocal sacs (usually paired or single depending on species)

  • Help produce loud croaking to attract female.

2) Nuptial (copulatory) pads on first digit (thumb) of forelimb

  • Rough pad helps the male hold/grip the female during amplexus.

Female frog:

  • Generally larger and heavier than male.
  • No vocal sacs and no nuptial pads.

✅ Tip to remember:

  • Male = “V + N” → Vocal sac + Nuptial pad

Q12. What is metamorphosis in a frog and which hormone controls it?

Answer.

Metamorphosis is the transformation of a frog’s larva (tadpole) into an adult frog.

Major changes during metamorphosis:

  • Tadpole has gills → adult develops lungs
  • Tail is resorbed/disappears
  • Limbs develop (hindlimbs first, then forelimbs)
  • Digestive system changes according to diet (tadpole mostly herbivorous; adult carnivorous/insectivorous)

Hormone controlling metamorphosis: Thyroxine (from thyroid gland).

✅ Tip to remember:

  • “Thyroxine Turns Tadpole to adult” (T-T-T)

Q13. Differentiate between the RBCs of a frog and a human.

Answer.

Both frog and human RBCs carry oxygen using haemoglobin, but their structure differs.

Frog RBCs

  • Nucleated (nucleus present)
  • Oval/elliptical and usually larger

Human RBCs (mammalian)

  • Enucleated (no nucleus at maturity)
  • Biconcave, circular discs (helps more surface area and flexibility)

✅ Tip to remember:

  • A-B-R (Amphibian, Bird, Reptile) RBCs = nucleated
  • Mammals = enucleated RBCs

Q14. What is the principal nitrogenous waste of a frog?

Answer.

  • Adult frog is ureotelic, so its main nitrogenous waste is urea.
  • This is suitable for land life because urea is less toxic than ammonia and needs less water to excrete.

Extra NEET point (very important):

  • Tadpole (larva) is mostly aquatic and is ammonotelic, excreting ammonia.

✅ Tip to remember:

  • Adult frog = Urea (Ureotelic)
  • Tadpole = Ammonia (Aquatic life → ammonia easy to diffuse in water)

Q15. What is a cloaca?

Answer.

A cloaca is a common chamber at the posterior end of the body where multiple systems open.

In frogs, three systems open into the cloaca:

1) Digestive system → faeces (via rectum)

2) Excretory system → urine (via ureters)

3) Reproductive system → sperms/eggs (via urinogenital ducts/oviduct openings)

So, the cloaca acts like a common exit for waste and gametes.

✅ Tip to remember:

  • Cloaca = “Common outlet of 3 systems” (D-E-R) → Digestive, Excretory, Reproductive