Lesson Notes By Weeks and Term v5 - Grade 8

Lesson Video

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Performance objectives

• Define a transport system and its importance.
• Describe the vascular system in plants (xylem and phloem).
• Identify the main parts of the circulatory system in animals.
• Explain the functions of blood.
• Compare the transport systems in plants and animals.

Lesson summary

This week, we're diving into the fascinating world of transport systems in plants and animals. Just like our buses, taxis, and trains move people and goods around South Africa, plants and animals need systems to move essential substances like water, nutrients, and oxygen throughout their bodies. This is crucial for their survival, growth, and overall health. Understanding these systems helps us appreciate the complexity and efficiency of living organisms, and it also provides a foundation for understanding human health and how diseases can disrupt these vital transport processes.

Lesson notes

What is a Transport System? A transport system is a network of structures and processes that work together to move substances from one part of an organism to another. These substances include water, nutrients, gases (like oxygen and carbon dioxide), and waste products. Without a transport system, cells would not receive the materials they need to function properly, and harmful waste products would accumulate, leading to cell death and ultimately, the death of the organism.

Transport Systems in Plants: The Vascular System Plants have a vascular system, which is like a system of pipes, that transports water, minerals, and sugars throughout the plant.

The two main types of vascular tissue are: Xylem: Xylem is responsible for transporting water and dissolved minerals from the roots to the rest of the plant, including the leaves. Think of it as a one-way street from the roots upwards. Xylem cells are dead and hollow, forming long, continuous tubes. They are strengthened with a substance called lignin, which provides structural support to the plant. The movement of water in xylem is driven by transpiration – the evaporation of water from the leaves. As water evaporates from the leaves, it creates a "pull" that draws water up the xylem from the roots. This process is called the transpiration stream.

Example: Imagine a tall mielie plant growing in a field. The roots absorb water from the soil. This water is then drawn up the xylem to the leaves, where it's used for photosynthesis and eventually evaporates.

Phloem: Phloem transports sugars (produced during photosynthesis in the leaves) to all parts of the plant, including the roots, stems, and fruits. This is a two-way street; sugars can move both up and down the plant. Phloem cells are living cells that are connected by sieve plates, which allow the flow of sugars. The movement of sugars in phloem is driven by a process called translocation. Sugars are actively transported into the phloem, which increases the concentration of sugars in that area. This causes water to move into the phloem from the xylem, increasing the pressure. The pressure pushes the sugary solution to areas where it is needed, such as the roots or developing fruits.

Example: Consider a mango tree. The leaves produce sugars through photosynthesis. These sugars are then transported via the phloem to the developing mango fruits, providing them with the energy they need to grow.

Transport Systems in Animals: The Circulatory System Animals, including humans, have a circulatory system, which is responsible for transporting blood throughout the body.

The circulatory system consists of: Blood: Blood is a fluid that carries oxygen, nutrients, hormones, and waste products. It also contains cells that fight infection and help with blood clotting.

The main components of blood are: Red blood cells: Carry oxygen (contain hemoglobin).

White blood cells: Fight infection.

Platelets: Help with blood clotting.

Plasma: The liquid part of blood, which carries dissolved substances.

Blood Vessels: Blood vessels are tubes that carry blood throughout the body. There are three main types of blood vessels: Arteries: Carry blood away from the heart. They have thick, elastic walls to withstand the high pressure of the blood being pumped from the heart.

Veins: Carry blood back to the heart. They have thinner walls than arteries and contain valves to prevent blood from flowing backwards.

Capillaries: Tiny, thin-walled vessels that connect arteries and veins. They are the site of exchange of oxygen, nutrients, and waste products between the blood and the body's cells.

Heart: The heart is a muscular organ that pumps blood throughout the body.

It has four chambers: two atria (upper chambers) and two ventricles (lower chambers). The heart contracts and relaxes rhythmically, pushing blood through the blood vessels. The Function of Blood Blood performs many important functions, including: Transporting oxygen: Red blood cells carry oxygen from the lungs to the body's cells. Oxygen is essential for cellular respiration, which provides energy for the cells.

Transporting nutrients: Blood carries nutrients, such as glucose, amino acids, and fatty acids, from the digestive system to the body's cells. These nutrients provide the building blocks and energy for cell growth and repair.

Transporting waste products: Blood carries waste products, such as carbon dioxide and urea, from the body's cells to the lungs and kidneys for excretion.

Transporting hormones: Blood carries hormones from endocrine glands to target organs. Hormones regulate many body functions, such as growth, metabolism, and reproduction.

Protecting the body: White blood cells fight infection by attacking pathogens (disease-causing organisms).

Regulating body temperature: Blood helps to regulate body temperature by distributing heat throughout the body. Guided Practice (With Solutions)

Question 1: Explain why plants need xylem and phloem.