Transportation in Animals and Plants

Overview

Transportation in living organisms is a fundamental life process that ensures the distribution of essential substances throughout the body. In animals, this involves the circulatory system carrying oxygen, nutrients, hormones, and waste products. In plants, it involves the movement of water and minerals (through xylem) and food (through phloem). This topic carries significant weight in Assam TET Paper II as it connects biology concepts across multiple chapters—nutrition, respiration, and excretion all depend on transport systems.

For the exam, you must understand the structural differences between plant and animal transport systems, the mechanisms driving movement (like transpiration pull and heart pumping), and be able to compare arteries, veins, and capillaries. Questions often test your ability to distinguish between xylem and phloem functions and to explain why the heart has four chambers in humans.

Key Concepts

• **Circulation in animals** is the movement of blood through a closed system of vessels, driven by the heart, to deliver oxygen and nutrients while removing carbon dioxide and wastes.

• **Double circulation** in humans means blood passes through the heart twice in one complete cycle—once through pulmonary circulation (heart to lungs) and once through systemic circulation (heart to body).

• **Xylem** transports water and dissolved minerals unidirectionally from roots to leaves; it consists of dead cells (tracheids and vessels) with thick lignified walls.

• **Phloem** transports prepared food (sucrose) bidirectionally from leaves to other plant parts; it consists of living cells (sieve tubes and companion cells).

• **Transpiration pull** is the main force driving water upward in plants—as water evaporates from leaves, it creates suction that pulls water up through xylem.

• **Blood components**—plasma (liquid matrix), RBCs (carry oxygen via haemoglobin), WBCs (immunity), and platelets (clotting)—each serve distinct transport and defence functions.

• **Root pressure** helps push water upward, especially at night or in small plants, when transpiration is minimal.

• **Translocation** is the movement of food from source (leaves) to sink (roots, fruits, growing tips) through phloem, requiring energy from companion cells.

Formulas / Key Facts

| Fact | Detail | |------|--------| | Normal human heart rate | 72 beats per minute (resting adult) | | Blood volume in adult human | Approximately 5–6 litres | | Chambers of human heart | 4 (2 atria + 2 ventricles) | | Haemoglobin location | Inside red blood cells | | Direction of xylem transport | Upward only (root to leaf) | | Direction of phloem transport | Bidirectional (source to sink) | | Main transpiration site | Stomata on leaf surface | | Pressure in arteries vs veins | Arteries = high pressure; Veins = low pressure | | Valves in veins | Present (prevent backflow); absent in arteries | | Function of root hairs | Increase surface area for water absorption |