Moving Materials Chapter Notes | Science for Grade 6 PDF Download

Introduction

The chapter "Moving Materials" explores how living things like plants, humans, and other animals move important materials such as water, nutrients, oxygen, and waste products within their bodies. It explains how plants use special tissues to transport water and food, how humans use their respiratory and circulatory systems to move oxygen and nutrients, and how other animals have different ways to carry out these processes. This chapter helps us understand the systems that keep living things alive by moving essential materials to where they are needed.

How do plants transport materials?

Moving Materials Inside Plants

For a plant to survive, water and nutrients must move throughout all its tissues.

• Osmosis and Diffusion:
  • In some plants, materials move from cell to cell using the processes of osmosis and diffusion.
  • These processes involve movement from an area of high concentration to low concentration.
• Vascular Tissue:
  • Most plants, such as grasses and trees, have specialized tissues in their stems called vascular tissue.
  • Vascular tissue is made of tubelike cells that transport water and nutrients.
• Xylem: Xylem is a type of vascular tissue that:
  • Carries water and dissolved nutrients from the roots to the stem and leaves.
  • Also supports the plant due to the thick walls of some xylem cells.
• Phloem:
  • Phloem is another type of vascular tissue that:
  • Carries dissolved sugars made by the plant to all cells.
• Path of Water and Sugar:
  • Water enters a plant through the roots, moves into the xylem, and then travels to all parts of the plant.
  • Liquid sugar, made in food-producing cells, moves into the phloem and is transported to all other cells.
• Stomata and Gas Exchange:
  • Small openings in the epidermis (the outer surface of a leaf) are called stomata (singular: stoma).
  • Carbon dioxide, oxygen, and water vapor move in and out of the plant through the stomata.
  • Plants use oxygen and carbon dioxide to make food, and release water vapor as a waste product.
  • This release of water vapor through the stomata is called transpiration.

How do humans transport materials?

The Respiratory System

The respiratory system exchanges gases between the body and the environment. Its parts work together to supply oxygen to the body and remove waste gases like carbon dioxide.

• Inhalation and Exhalation:
  • When you inhale (breathe in), oxygen enters your body.
  • When you exhale (breathe out), carbon dioxide leaves your body.
• Pathway of Air:
  • Air enters through the nostrils and then passes into the pharynx.
  • The pharynx is a tubelike passage at the top of the throat that receives air, food, and liquids from the mouth or nose.
  • Because the pharynx connects to both the digestive and respiratory systems, it allows:
    • Food to pass into the esophagus
    • Air to pass into the trachea
• Trachea and Bronchi:
  • The trachea, also known as the windpipe, is a long tube held open by C-shaped cartilage rings.
  • It connects the pharynx to the bronchi, which are two narrower tubes that lead into the lungs.
• Lungs and Bronchioles:
  • The lungs are the main organs of the respiratory system.
  • Inside the lungs, the bronchi branch into smaller tubes called bronchioles.
• Role of the Diaphragm:
  • The diaphragm is a large muscle located below the lungs.
  • When you inhale, the diaphragm contracts and moves down, causing air to rush in to balance pressure.
  • When you exhale, the diaphragm relaxes and moves up, and air moves out of the lungs.
  • Breathing happens due to these changes in air pressure inside the chest caused by the diaphragm's movement.

Did You Know?

Harry Houdini

• Harry Houdini was a famous magician and escape artist who lived from 1874 to 1926.
• He performed daring escapes, like being buried under sand or locked in a glass coffin underwater.
• Houdini survived these tricks by controlling his breathing to use oxygen slowly.
• By breathing calmly and slowly, he could make the oxygen in a confined space last longer (up to 35 minutes).
• Fast or panicked breathing would use up oxygen quickly, making survival difficult.
• His ability to control breathing required strong nerves and great self-control.

Did You Know?

When carbon dioxide builds up in the blood, the nervous system signals the body to breathe out. This helps remove excess carbon dioxide and maintain balance in the body.

What happens to oxygen after it enters the lungs?

• Oxygen in the lungs moves into the blood through the alveoli during gas exchange.
• Carbon dioxide in the blood moves into the alveoli to be exhaled.
• Alveoli are tiny, balloon-like sacs that expand when you inhale and contract when you exhale.
• Blood vessels surround the alveoli, allowing oxygen and carbon dioxide to move quickly.
• The thin walls and large surface area of alveoli help billions of oxygen and carbon dioxide molecules move with each breath.
• Blood plays a key role in breathing by carrying oxygen from the lungs to the body’s cells and bringing carbon dioxide back to the lungs.

How is blood transported throughout the body?

All cells in the body need oxygen to turn nutrients into energy for survival. Oxygen from the lungs enters the blood and is carried to all parts of the body.

The Circulatory System

• The circulatory system is made up of the heart, blood, and blood vessels.
• Its main role is to transport nutrients, gases, wastes, and other substances throughout the body.
• The heart is made of muscle cells that are constantly contracting and relaxing.
• Heart contractions pump blood out to the rest of the body.
• When the heart muscles relax, blood from the body flows into the heart.
• The heart has four chambers — two upper chambers and two lower chambers.
• The upper chambers are called atria (singular: atrium), where blood enters the heart.
• The lower chambers are called ventricles, where blood exits the heart.
• Blood travels through the body in small tubes known as blood vessels.
• There are three main types of blood vessels:
  • Arteries: carry blood away from the heart.
  • Veins: carry carbon dioxide-rich blood back to the heart (except veins from the lungs, which carry oxygen-rich blood).
  • Capillaries: tiny vessels that allow oxygen, carbon dioxide, and nutrients to move between the circulatory system and body tissues.

Lower Heart Disease Risk

• Coronary heart disease is a condition where blood vessels in the heart get damaged, which can lead to a heart attack.
• A heart attack happens when an artery gets blocked, stopping oxygen and nutrients from reaching the heart.
• Heart disease is a lifelong condition, and damaged arteries increase the risk of heart attacks.
• Other cardiovascular diseases include stroke, high blood pressure, angina (chest pain), and rheumatic heart disease.
• Procedures like bypass surgery or percutaneous coronary intervention can help blood and oxygen flow better, but arteries stay damaged.
• Making healthy daily habits is important to prevent and control heart disease.

How do other animals take in oxygen and get rid of carbon dioxide?

• All animals need oxygen for their cells and tissues to survive.
• Some animals have lungs and breathe like humans.
• Other animals use different structures for gas exchange, such as diffusion, gills, or tracheal tubes.
• Diffusion allows oxygen and carbon dioxide to move directly through an animal’s body surface.
• Gills are used by animals like fish to take in oxygen from water.
• Tracheal tubes are used by insects to carry oxygen directly to their tissues.

How do other animals transport blood throughout their bodies?

Different animals have different circulatory systems that affect how fast blood moves.

Open Circulatory Systems

• An open circulatory system is found in many invertebrates, like bees.
• In an open circulatory system, blood and fluids flow into open spaces around organs, allowing oxygen and nutrients to reach tissues directly.

Closed Circulatory Systems

• A closed circulatory system uses blood vessels to transport blood and materials faster.
• In a closed circulatory system, capillaries (small blood vessels) surround organs to deliver oxygen and nutrients to cells.

Chambered Hearts

• Different animals have hearts with different numbers of chambers (compartments):
  • Fish have two-chambered hearts.
  • Amphibians have three-chambered hearts.
  • Birds and mammals (like cats, dogs, and humans) have four-chambered hearts.
• Almost all animals with three or four chambers in their hearts also have lungs.

Very Special: Blood Cells

• Horseshoe crabs are living relatives of extinct trilobites.
• They have been gathering on beaches for 350 million years.
• They usually become food for fish and birds.
• Yet someday your life might depend on horseshoe crabs—or at least on their blood.
• Unlike human blood, horseshoe crab blood contains only one type of blood cell.
• If bacteria enter the crab’s bloodstream from an open wound, blood cells secrete a clotting factor.
• This secretion closes the wound, and the blood cells engulf the bacteria.
• Scientists saw that horseshoe crab blood turned to a gel in the presence of harmful bacteria.
• They realized its value.
• Today, medical professionals use an extract made from horseshoe crab blood to screen all intravenous medicines for bacteria.
• A quart of this special blood costs about $15,000!
• The horseshoe crab blood can do even more.
• Another component of the blood can stop the human immunodeficiency virus (HIV) from replicating, or making copies of itself.
• Part of horseshoe crab blood can act as an antibiotic.
• Scientists are also using horseshoe crab blood in the development of a handheld instrument that helps diagnose human illnesses.
• The instrument uses enzymes from the blood as illness detectors.
• Technicians remove only a small portion of the crabs’ blood.
• After this procedure, the crabs are returned to the ocean.
• Their blood cell levels return to normal in a couple of weeks.