Obtaining Energy and Removing Waste Chapter Notes | Science for Grade 6 PDF Download

Introduction

In this chapter, we will learn how living things, like humans, animals, and plants, get the energy they need to live and grow. We will explore how our bodies break down food to get energy and how they remove waste. This process is called digestion for animals and photosynthesis for plants. We will also understand how different parts of the body work together to process food and get rid of waste. By studying this, we will see how important energy is for all living things and how their bodies handle waste to stay healthy.

Why do organisms eat?

• Organisms eat food to get energy to live and grow.
• Hunger is the body’s way of saying it needs food.
• Food gives energy, measured in Calories.
• A Calorie is the energy needed to raise the temperature of 1 kg of water by 1°C.
• Different foods have different amounts of energy; for example, one grape has 2 Calories, but a slice of cheese pizza has 220 Calories.
• All foods provide energy for the body to use for activities.

What does energy from food power?

• Energy from food powers every activity, like running, sleeping, or playing.
• The digestive system breaks down food to release energy for the body’s cells and activities.
• The amount of energy a person needs depends on their weight, age, activity level, and gender.
• Active tasks, like playing soccer, need more energy than less active ones, like playing video games.
• Nutrients in food provide the energy the body uses.

What nutrients are in food?

• Food contains nutrients, which are substances the body needs to grow and stay healthy.
• Each nutrient has a special job in the body.
• Proteins help build muscles.
• Calcium strengthens bones.
• Nutrients give the body energy and help it work properly.

How does a body get nutrients from food?

• Nutrients in food are needed for the body to work well.
• The body breaks down food to release nutrients so they can be used.
• Proteins from food help build and repair muscles.
• Calcium from food makes bones strong.
• The digestive system processes food to get these nutrients out.

How does digestion work?

Digestion is the process of breaking down food into small pieces and molecules the body can use.

Types of Digestion

There are two types of digestion: mechanical and chemical.

• Mechanical digestion physically breaks food into smaller pieces.
  • Chewing, mashing, and grinding food with teeth and tongue is mechanical digestion.
  • Smaller food pieces are easier to swallow and have more surface area for chemical digestion.
• Chemical digestion uses chemical reactions to break food into small molecules.
  • Chemical digestion makes nutrients easier for the body to absorb.

The Mouth

• Digestion starts in the mouth with mechanical digestion.
• Chewing food with jaw muscles breaks it into smaller pieces.
• Saliva in the mouth contains chemicals that start breaking down carbohydrates.
• Saliva also neutralizes acidic foods to protect the mouth.

The Esophagus

• After swallowing, food moves into the esophagus, a muscular tube.
• The esophagus connects the mouth to the stomach.
• Food moves through the esophagus by muscle contractions called peristalsis.
• Peristalsis is like squeezing a toothpaste tube, pushing food toward the stomach.

The Stomach

• Food enters the stomach, a large, hollow organ, after the esophagus.
• The stomach stores food temporarily.
• The stomach helps with chemical digestion using gastric juice, an acidic fluid.
• Gastric juice breaks down structures in food, like those in bread, to make it easier to digest.

The Small Intestine

• The small intestine is a long tube where most chemical digestion happens.
• Nutrients from food are absorbed in the small intestine.
• The small intestine has folds covered with tiny projections called villi.
• Villi have blood vessels that take in nutrients from digested food.
• Nutrients enter the blood through these blood vessels.

The Large Intestine

• Most water from food and drinks is absorbed in the small intestine.
• The large intestine absorbs even more water from the remaining material.
• Waste products from digestion become more solid as water is removed.
• The semisolid waste is then removed from the body.

Removing Waste

• The body gets rid of waste products through the excretory system.
• The excretory system collects and removes waste and controls the body’s fluid levels.
• Different body systems help remove waste, like the urinary system for liquid waste.
• The respiratory system removes carbon dioxide as a waste product.
• The skin removes excess salt and water through sweat glands.

Kidneys

• The kidneys are two bean-shaped organs that filter waste from the blood.
• They remove harmful substances to keep the body healthy.
• If waste builds up in the blood, it can become toxic and harm the body.

A Closer Look: Celiac Disease

• Celiac disease is a condition where people cannot eat gluten, a protein in wheat, rye, and barley.
• Gluten can also be in medicines, envelope adhesives, and lip balm.
• Eating gluten damages the small intestine in people with celiac disease.
• Symptoms include stomach pain, mouth ulcers, and bloating from gas or fluids.
• Some people with celiac disease have no symptoms.
• The damaged intestine can’t absorb nutrients properly, causing malabsorption.
• Malabsorption can lead to weight loss, fatigue, anemia (low iron), and osteoporosis (weak bones).
• Treatment for celiac disease is eating a gluten-free diet.
• Many stores sell gluten-free foods like bread and cereal.

How do plant bodies obtain energy and get rid of waste?

• Plants need food, water, and oxygen to survive, just like animals.
• Unlike animals, plants make their own food.
• Leaves are the main organs where plants make food through photosynthesis.
• Photosynthesis uses light energy, water, and carbon dioxide to make glucose, a food-energy molecule.
• Photosynthesis also produces oxygen as a waste product.
• Glucose moves through a tissue called phloem to all plant cells.
• Plant cells break down glucose to release energy.
• Water enters plants through roots and moves through a tissue called xylem to all parts.
• Plants produce water vapor as a waste product.
• Carbon dioxide, oxygen, and water vapor move in and out of plants through tiny openings in leaves.