Lesson Notes By Weeks and Term v5 - Grade 8

Lesson Video

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Performance objectives

• Define a 'transport system' in organisms.
• Explain why transport systems are necessary.
• Identify transport components in plants (xylem and phloem).
• Describe the functions of xylem and phloem.
• Identify transport components in animals (heart, blood vessels, blood).

Lesson summary

This week, we embark on an exciting journey into the hidden world of transport systems in plants and animals! Think about how you get your food. It starts as something outside your body and needs to get inside to provide you with energy to play soccer, learn in class, or help your family. Similarly, think about a tall tree in your yard, a mealie plant in a field, or the flowers you see growing along the roadside. How do these plants get water and nutrients from the soil all the way to their leaves and flowers? The answer lies in specialized transport systems that move essential substances around the body.

Lesson notes

What is a Transport System? A transport system is a network of specialized structures and processes that moves essential substances (like nutrients, water, oxygen, and waste products) throughout a living organism. Think of it like a delivery network for a town or city. Trucks and trains transport goods from factories to shops, and then to people’s homes. Without this delivery network, the town would starve, and waste would pile up. The same is true for living organisms. Why are Transport Systems Necessary? Single-celled organisms, like bacteria, can directly absorb nutrients and eliminate waste across their cell membranes.

However, multicellular organisms (like plants and animals) are much larger and more complex. Their cells are often located far from the external environment. Diffusion alone (the movement of substances from high concentration to low concentration) is too slow to efficiently transport substances over long distances in multicellular organisms.

Therefore, specialized transport systems are crucial for survival. They ensure that every cell receives the resources it needs and that waste products are removed efficiently.

Transport Systems in Plants: Xylem and Phloem Plants have two main types of transport tissue: Xylem: Xylem transports water and dissolved minerals (nutrients) from the roots to the rest of the plant (leaves, stems, and flowers). Think of xylem as tiny pipes running up the stem of the plant. The water moves upwards due to transpiration (evaporation of water from the leaves), creating a "pull" from the top, and root pressure pushing from below. Xylem cells are dead at maturity, forming hollow tubes.

Phloem: Phloem transports sugars (produced during photosynthesis in the leaves) from the leaves to other parts of the plant, where they are needed for growth or storage. Think of phloem as the delivery system for food the plant produces. The movement of sugars in the phloem is called translocation. Phloem cells are alive, although they have companion cells that help them function.