Structural Organisation in Animals 🐸 | Class 11 Notes | NEET

Structural Organisation in Animals 🐸 | Class 11 Notes | NEET | NCERT

Animals have four basic types of tissues: epithelial, connective, muscular, and nervous.

1. Epithelial Tissue

Definition: Continuous sheet of cells covering body surface, organs, and cavities.

Characteristics: No intercellular spaces, basement membrane present, avascular (no blood supply).

Types:

1. Simple epitgelium (single layer)

Squamous (flat, thin; e.g., alveoli).
Cuboidal (cube-shaped; e.g., kidney tubules).
Columnar (tall, cylindrical; e.g., intestine).
Ciliated epithelium (movement of mucus/ova).
Glandular epithelium (secretes enzymes, hormones).

2. Compound epithelium (multi-layered; protective; e.g., skin).

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2. Connective Tissue

Definition: Binds, supports, protects body structures.

Matrix present.

Types:

1. Connective tissue proper

Loose (areolar, adipose).
Dense (regular – tendon, irregular – dermis).

2. Skeletal tissue

Cartilage (chondrocytes in lacunae).
Bone (osteocytes in lacunae, hard matrix with Ca salts).

3. Fluid connective tissue

Blood (RBC, WBC, platelets, plasma).
Lymph (defense, transport).

3. Muscular Tissue

Made of elongated cells (muscle fibres), contractile proteins actin + myosin.

Types:

Striated (skeletal, voluntary, multinucleated).
Unstriated (smooth, involuntary, spindle-shaped).
Cardiac (branched, striated, involuntary, intercalated discs).

4. Nervous Tissue

Structural + functional unit: Neuron.
Parts: Cell body (perikaryon), dendrites (receive impulses), axon (transmit impulse).
Functions: Communication, coordination, reflex actions.

Anatomy of Flowering Plants 🌿 - Biology Class 11th - Handwritten Notes 📖 [PDF]📚

Morphology & Anatomy of Earthworm (Pheretima posthuma)

Morphology

Long, cylindrical, segmented, bilaterally symmetrical, coelomate.
Length: 80–150 mm.
Body colour: Brown with cuticle.
Segmentation: 100–120 metameres.
First segment: peristomium (mouth).
14–16th segment: clitellum (reproductive band).
Nephridiopores: excretion.
Female genital pores: 14th segment.
Male genital pores: 18th segment.

Anatomy

Digestive system:

Mouth → Buccal cavity → Pharynx → Oesophagus → Gizzard (grinds food) → Stomach → Intestine (with typhlosole for absorption) → Anus.

Circulatory system:

Closed type.
Blood vessels: dorsal, ventral, lateral oesophageal, sub-neural.
Respiratory exchange: skin (cutaneous).

Nervous system:

Nerve ring around pharynx.
Ventral nerve cord with ganglia.

Excretory system:

Nephridia (3 types: septal, integumentary, pharyngeal).

Reproductive system:

Hermaphrodite.
Testes: 10th and 11th segments.
Ovaries: 13th segment.
Fertilization: external, in cocoons.

Morphology & Anatomy of Cockroach (Periplaneta americana)

Morphology

Body length: 34–53 mm, reddish-brown.

Segments: Head, thorax, abdomen.

Head: Triangular, antennae, compound eyes, biting & chewing mouthparts (labrum, mandibles, maxillae, labium, hypopharynx).

Thorax: Prothorax, mesothorax, metathorax; each bears a pair of walking legs; wings from meso- & metathorax.

Abdomen: 10 segments, anal cerci.

Sexual dimorphism: Males have anal styles, females do not.

Anatomy

Digestive system:

Mouth → pharynx → oesophagus → crop (storage) → gizzard (grinds food) → midgut (digestion) → hindgut (absorption, excretion).

Circulatory system:

Open type.
Heart: elongated, 13 chambers.

Respiratory system:

Tracheal system with spiracles.
Exchange of gases through spiracles → trachea → tracheoles.

Nervous system:

Brain (supra-oesophageal ganglion).
Double ventral nerve cord with ganglia.

Excretory system:

Malpighian tubules.

Reproductive system:

Male: Testes (4th–6th segment).
Female: Ovaries (in 4th–6th segment).
Fertilized eggs → ootheca → young cockroaches.

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Morphology & Anatomy of Frog (Rana tigrina / Rana hexadactyla)

Morphology

Amphibian, bilaterally symmetrical, streamlined body.
Divided into head and trunk (no neck or tail).
Hindlimbs long (jumping/swimming), forelimbs short.
Feet: webbed (swimming).
Eyes: large, protruding, nictitating membrane for protection.
Cloacal aperture: posterior opening for excretion and reproduction.

Anatomy

Digestive system:

Alimentary canal: mouth → buccal cavity → oesophagus → stomach → small intestine (duodenum + ileum) → large intestine → cloaca → cloacal aperture.
Digestive glands: liver, pancreas.

Circulatory system:

Closed, double circulation.
3-chambered heart (2 atria + 1 ventricle).
RBCs: nucleated.

Respiratory system:

Skin (cutaneous respiration).
Lungs (pulmonary).
Buccopharyngeal respiration.

Nervous system:

CNS: brain + spinal cord.
PNS: cranial + spinal nerves.
Sense organs: eyes, tympanum (hearing), olfactory organs, taste buds.

Excretory system:

Kidneys: mesonephric, ureters open into cloaca.
Ammonotelic (excretes ammonia).

Reproductive system:

Dioecious (separate sexes).
Fertilization: external (in water).
Development: indirect, with larval stage (tadpole).

Quick Revision Table

Feature	Earthworm	Cockroach	Frog
Body symmetry	Bilateral	Bilateral	Bilateral
Segmentation	Metameric (100–120)	3 regions (head, thorax, abdomen)	Head + trunk (no tail)
Circulation	Closed	Open	Closed, double
Respiration	Cutaneous	Tracheal	Skin, lungs, buccal cavity
Excretion	Nephridia	Malpighian tubules	Kidneys (mesonephric)
Reproduction	Hermaphrodite	Dioecious (ootheca)	Dioecious (external)