Structural Organisation in Animals

The chapter "Structural Organisation in Animals" in NEET Biology focuses on understanding the levels of organization in animal bodies, including tissues, organs, and organ systems. It covers animal tissues, their classification, and their functions. It also provides a detailed study of the morphology and anatomy of common animals such as earthworm, cockroach, and frog.

Animal Tissues

Animals have four primary types of tissues that perform different functions.

1. Epithelial Tissue

• Forms the outer covering of the body and lines internal organs.

• Functions include protection, absorption, secretion, and excretion.

• Types: Squamous, Cuboidal, Columnar, Ciliated, and Glandular Epithelium.

2. Connective Tissue

• Connects, supports, and binds other tissues and organs.

• Types: Areolar, Adipose, Fibrous, Cartilage, Bone, and Blood.

3. Muscular Tissue

• Responsible for movement and locomotion.

• Types: Skeletal (voluntary), Smooth (involuntary), and Cardiac (heart muscles).

4. Nervous Tissue

• Composed of neurons that transmit impulses.

• Helps in coordination and response to stimuli.

Morphology and Anatomy of Animals

This section provides an in-depth study of the structure and functioning of selected animals.

1. Earthworm (Pheretima posthuma)

• Morphology: Cylindrical, segmented body with a clitellum.

• Digestive System: Complete digestive tract with a buccal cavity, pharynx, esophagus, gizzard, intestine, and anus.

• Circulatory System: Closed type with heart and blood vessels.

• Excretory System: Nephridia help in excretion.

• Nervous System: Consists of a nerve ring and paired ventral nerve cords.

• Reproductive System: Hermaphrodite with cross-fertilization.

2. Cockroach (Periplaneta americana)

• Morphology: Three body parts – Head, Thorax, and Abdomen. Brown, dorsoventrally flattened body.

• Digestive System: Mouthparts adapted for chewing; alimentary canal includes foregut, midgut, and hindgut.

• Circulatory System: Open type with a tubular heart and hemolymph.

• Excretory System: Malpighian tubules remove nitrogenous waste.

• Nervous System: Ventral nerve cord and paired ganglia.

• Reproductive System: Separate sexes, internal fertilization.

3. Frog (Rana tigrina)

• Morphology: Streamlined body with smooth, moist skin.

• Digestive System: Consists of the buccal cavity, esophagus, stomach, intestine, and cloaca.

• Circulatory System: Closed type, three-chambered heart.

• Respiratory System: Uses lungs and skin for respiration.

• Excretory System: Paired kidneys remove urea.

• Nervous System: Well-developed brain, spinal cord, and cranial nerves.

• Reproductive System: External fertilization in water.

This chapter is crucial for NEET as it helps students understand how different animals function, their structural adaptations, and their survival mechanisms.