Introduction to the Topic

Welcome to NCERT Explained: Class VII Science, Chapter 11 - Transportation in Animals and Plants! Have you ever wondered how the food you eat reaches every single cell in your body? Or how water absorbed by plant roots travels all the way up to the highest leaves of a giant tree? Just like a bustling city needs a complex transport network of roads, railways, and delivery trucks to supply goods to every home and business, our bodies and plants have their own brilliant internal transport systems. In this chapter, we will dive deep into how living organisms transport vital substances like oxygen, food, water, and waste products from one part of their body to another. Understanding these biological highway systems helps us appreciate the intricate design of nature and how living things sustain life!

Key Concepts Explained

To understand transportation in living organisms, we need to break it down into two main parts: how it happens in animals (especially humans) and how it works in plants. Let us explore the key components step by step.

1. Transportation in Animals: The Circulatory System

In complex animals like humans, substances cannot simply move from cell to cell by diffusion because distances are too large. Instead, we have a specialized transport system called the circulatory system, which consists of the blood, blood vessels, and the heart.

  • Blood: Blood is the fluid that flows in our blood vessels. It transports substances like digested food from the small intestine to other parts of the body. It also carries oxygen from the lungs to the body cells and takes away waste products like carbon dioxide to be eliminated. Blood has a liquid part called plasma and solid components including Red Blood Cells (RBCs) containing hemoglobin (which binds to oxygen), White Blood Cells (WBCs) that fight germs, and Platelets that help in blood clotting.
  • Blood Vessels: There are three main types of blood vessels in our body:
    • Arteries: Carry oxygen-rich blood from the heart to all parts of the body. They have thick, elastic walls because blood flows under high pressure.
    • Veins: Carry carbon dioxide-rich blood from all parts of the body back to the heart. They have thin walls and valves that ensure blood flows only towards the heart.
    • Capillaries: Extremely thin vessels that connect arteries and veins. Through their walls, substances are exchanged between the blood and body cells.
  • The Heart: The heart is a muscular organ located in our chest cavity that beats continuously to act as a pump for the transport of blood. It has four chambers: two upper chambers called the atria (singular: atrium) and two lower chambers called the ventricles. Valves between the chambers prevent the mixing of oxygen-rich and carbon dioxide-rich blood.

2. Excretion in Animals

As our cells perform various activities, they produce waste products that are toxic and need to be removed. The process of removal of wastes produced in the cells of living organisms is called excretion. In humans, the excretory system includes two kidneys, two ureters, a urinary bladder, and a urethra. The kidneys filter the blood to remove urea and other wastes, which are dissolved in water to form urine. The urine goes into the urinary bladder through ureters and is eventually expelled out through the urinary opening.

3. Transportation in Plants

Plants may not have a pumping organ like a heart or blood vessels, but they still need water, minerals, and food. How do they move these substances? Let us look at the specialized tissues:

  • Transport of Water and Minerals: Plants absorb water and minerals from the soil through their roots. Root hairs increase the surface area for absorption. Plants have pipe-like vessels made of specialized cells called xylem to transport water and nutrients from the soil up to the leaves.
  • Transpiration: Plants absorb much more water than they actually need. The excess water evaporates into the atmosphere as water vapour through tiny pores called stomata present on the surface of leaves. This process is called transpiration. Transpiration creates a powerful suction pull—much like sipping juice through a straw—that draws water upward from the roots to great heights even in very tall trees!
  • Transport of Food: The leaves prepare food through photosynthesis. This food needs to be transported to all other parts of the plant, including the roots and stem. The tissue responsible for the transport of food in plants is called phloem.

Summary & Key Takeaways

Let us review the most important facts from this chapter to help you ace your exams:

  • The circulatory system in humans is composed of the heart, blood vessels, and blood.
  • Blood consists of plasma, RBCs, WBCs, and platelets. Hemoglobin in RBCs carries oxygen.
  • Arteries carry blood away from the heart, while veins bring blood back to the heart.
  • Capillaries allow the exchange of substances between blood and tissues.
  • The human heart has four chambers: two atria and two ventricles.
  • Excretion is the removal of metabolic waste products from the body; kidneys play the primary role in human excretion.
  • Plants use xylem tissue to transport water and minerals absorbed by roots.
  • Transpiration helps create a suction pull that lifts water up through the xylem.
  • Plants use phloem tissue to transport synthesized food from leaves to the rest of the plant body.