Lesson Notes By Weeks and Term v5 - Grade 10
Support and transport systems in plants and animals – Week 7 focus
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Support and transport systems in plants and animals – Week 7 focus
Download the Lessonotes Mobile South Africa app for faster lesson access on Android and iPhone.
Subject: Life Sciences
Class: Grade 10
Term: 2nd Term
Week: 7
Theme: General lesson support
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This week, we delve into the fascinating world of support and transport systems in plants and animals. These systems are vital for survival. Just as our bones give us structure and our blood carries nutrients, plants and animals have intricate mechanisms to stand tall, move, and distribute essential substances throughout their bodies. Understanding these systems allows us to appreciate the remarkable adaptations that enable life to thrive in diverse environments, from the towering baobab trees of Limpopo to the scurrying hadeda ibises in our gardens.
2.1 Support Systems in Plants Plants require support to stand upright and expose their leaves to sunlight for photosynthesis. There are three main types of support systems: Turgor Pressure: This is the pressure exerted by water inside plant cells against the cell wall. When plant cells are full of water (turgid), they become rigid, providing support to the plant. This is why plants wilt when they lose water. Think of a deflated bicycle tyre versus an inflated one. The water inside the cell acts like the air in the tyre, providing support.
Collenchyma: This is a type of plant tissue with thickened cell walls, providing flexible support, especially in young stems and leaves. You can find collenchyma in the outer layers of celery stalks, which allows them to bend without breaking. Imagine the flexible strength of a young tree branch bending in the wind – that's collenchyma at work.
Sclerenchyma: This tissue provides rigid support due to heavily thickened cell walls containing lignin, a complex polymer. Sclerenchyma cells are often dead at maturity, providing strength and support. Sclerenchyma is found in the shells of nuts and the hard outer layers of seeds. Think of the hard shell of a peanut – that’s sclerenchyma. 2.2 Transport Systems in Plants Plants have two main transport systems: xylem and phloem.
Xylem: Xylem transports water and dissolved mineral salts from the roots to the rest of the plant. Xylem vessels are dead cells arranged end-to-end, forming continuous tubes. The thick, lignified walls of xylem vessels provide support and prevent them from collapsing under pressure. The movement of water in xylem is primarily driven by transpiration, the evaporation of water from leaves.
Transpiration Pull: As water evaporates from the leaves through stomata (tiny pores), it creates a negative pressure or "pull" that draws water up the xylem from the roots. This pull is aided by cohesion (water molecules sticking together) and adhesion (water molecules sticking to the xylem walls).
Root Pressure: The roots absorb water and mineral salts from the soil through osmosis and active transport. The accumulation of these substances in the root cells creates a positive pressure that pushes water up the xylem.
However, root pressure is less significant than transpiration pull in most plants.
Root Hairs: These are tiny, hair-like extensions of root epidermal cells that greatly increase the surface area for water and mineral absorption from the soil.
Phloem: Phloem transports sugars (produced during photosynthesis) from the leaves to other parts of the plant, such as roots, stems, and fruits. Phloem consists of living cells called sieve tube elements and companion cells. Sugars are transported in the form of sucrose. The movement of sugars in phloem is called translocation.
Source-Sink Relationship: Sugars are produced in "source" tissues (e.g., leaves) and transported to "sink" tissues (e.g., roots, fruits, growing points) where they are needed for growth or storage. Translocation follows a pressure flow mechanism.
Example: Water Transport in a Maize Plant Root hairs absorb water from the soil by osmosis. Water moves from cell to cell across the cortex of the root to the xylem vessels. Transpiration in the leaves creates a pull that draws water up the xylem. Water travels up the xylem through the stem to the leaves. Water evaporates from the leaves through stomata (transpiration). 2.3 The Mammalian Circulatory System The mammalian circulatory system is a closed system, meaning blood circulates within vessels. It consists of the heart, blood vessels, and blood.
The Heart: The heart is a muscular organ that pumps blood throughout the body.
It has four chambers: two atria (receiving chambers) and two ventricles (pumping chambers). Valves prevent backflow of blood.
Atria: Receive blood from the body (right atrium) and lungs (left atrium).
Ventricles: Pump blood to the lungs (right ventricle) and the body (left ventricle). The left ventricle has thicker walls because it pumps blood over a longer distance.
Valves: Tricuspid valve (between the right atrium and right ventricle), bicuspid (mitral) valve (between the left atrium and left ventricle), pulmonary valve (between the right ventricle and the pulmonary artery), and aortic valve (between the left ventricle and the aorta).
Blood Vessels: Arteries: Carry blood away from the heart. They have thick, elastic walls to withstand the high pressure of blood pumped by the heart. The aorta is the largest artery, carrying blood from the left ventricle to the rest of the body.
Veins: Carry blood back to the heart. They have thinner walls than arteries and contain valves to prevent backflow of blood. The vena cava is the largest vein, carrying blood from the body back to the right atrium.
Capillaries: Tiny blood vessels with very thin walls that allow for the exchange of gases, nutrients, and waste products between the blood and body cells. Capillaries connect arteries and veins.