Structural organization in Animals 🐸 - Biology Class 11th - Handwritten Notes 📖 [PDF]📚

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).

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:

1. Striated (skeletal, voluntary, multinucleated).
2. Unstriated (smooth, involuntary, spindle-shaped).
3. 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.

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.

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)