Body Systems

Body Systems

Middle School

​

Learning Objectives

• Describe the levels of organization in the human body from cells to organ systems.

• Explain how the body is a system of interacting subsystems with specialized functions.

• Show how different organ systems work together to help us survive and grow.

• Analyze how body systems interact to maintain a stable internal environment.

Key Vocabulary

​

Cell

A cell is the most basic, fundamental building block of all living organisms.

​

Tissue

A tissue is a large group of specialized cells that work together to perform a specific function.

​

Organ

An organ is a distinct structure made up of different types of tissues that work together.

​

Organ System

An organ system is a group of organs that cooperate to perform major functions in the body.

​

Subsystem

A subsystem is a self-contained system that exists and operates within a much larger system.

​

Specialized Cell

A specialized cell is a unique cell that is adapted to perform a very specific function.

Key Vocabulary

​

Homeostasis

Homeostasis is the process by which the body maintains a stable and balanced internal environment.

​

Circulatory System

The circulatory system is responsible for transporting blood, oxygen, nutrients, and hormones throughout the body.

​

Respiratory System

The respiratory system manages gas exchange by taking in oxygen (O₂) and removing carbon dioxide (CO₂).

​

Digestive System

The digestive system's primary function is to break down food into nutrients for absorption.

​

Nervous System

The nervous system acts as the body's control center for communication and coordinating actions.

​

Excretory System

The excretory system is responsible for the elimination of metabolic wastes from the body.

​

​

Levels of Organization

• Specialized cells are the simplest level, adapted for a specific job.

• ​These cells group to form tissues like muscle, connective, nervous, and epithelial.

• Different tissues combine to form an organ, such as the heart.

• Organs and tissues work together in organ systems to keep organisms alive.

​

Multiple Choice

Which list shows the levels of organization in the correct order, from simplest to most complex?

• Cells, Tissues, Organs, Organ Systems

• Tissues, Organs, Cells, Organ Systems

• Organs, Organ Systems, Tissues, Cells

• Organ Systems, Cells, Tissues, Organs

Multiple Choice

What is the relationship between tissues and organs in a living organism?

• Different tissues combine to form an organ.

• An organ is a single type of specialized tissue.

• Tissues are more complex than organs.

• Organs are made of specialized cells, not tissues.

Multiple Choice

The heart is an organ made of different tissues that work together. If one of these tissues stops working correctly, what is the most likely outcome?

• The organ's ability to work within its organ system would be affected.

• The organ would break down into individual specialized cells.

• The other tissues in the organ would perform the muscle's job.

• The organ system would immediately replace the damaged tissue.

​

​

The Body as a System of Systems

• The human body is a complex system of many interacting subsystems.

• ​No subsystem works alone; they cooperate to perform all functions necessary for life.

• For example, your digestive, respiratory, and circulatory systems get energy to muscles.

• This interaction is essential for an organism’s survival and growth.

​

Multiple Choice

Which statement best describes the human body?

• A group of many subsystems that all work together.

• A collection of parts that each work alone.

• A simple system that is controlled by the muscles.

• A system that does not need energy to survive.

Multiple Choice

What is the main reason that body subsystems must cooperate with each other?

• To ensure each system can operate independently.

• To carry out the functions necessary for survival and growth.

• To allow different systems to compete for energy.

• To prevent the body from using too much energy.

Multiple Choice

Based on the way body systems interact, what would most likely happen if the digestive system failed to provide nutrients?

• The muscles would not get the energy they need to work.

• The circulatory system would stop moving blood.

• The respiratory system would take over the digestive system's job.

• The body would no longer need energy for survival.

Structure and Support in Animals

​

Skeletal System

• This system provides the body with a strong and sturdy framework.

• It supports the body and protects important internal organs from injury.

• It produces blood cells and stores important minerals like calcium.

• Joints are where bones meet, allowing for movement and flexibility.

​

Muscular System

• Muscles are tissues that contract and relax to create movement.

• They work together with the skeletal system to move the body.

• Skeletal muscles are voluntary, meaning you can control their movement.

• Cardiac and smooth muscles are involuntary and work automatically.

​

Alternative Support

• Not all animals have bones; some have different support structures.

• Earthworms use a fluid-filled cavity called a hydrostatic skeleton.

• Crabs have a hard outer shell called an exoskeleton for protection.

Multiple Choice

What is the primary role of the skeletal system in an animal's body?

• To provide the body with a strong framework and protection

• To contract and relax, creating all types of movement

• To form a hard outer shell for defense against predators

• To automatically control functions like digestion and heartbeat

Multiple Choice

Which statement best explains the difference between how a person's arm moves and how their heart beats?

• Arm movement is voluntary using skeletal muscles, while the heartbeat is involuntary using cardiac muscle.

• Arm movement is involuntary, while the heartbeat is controlled by skeletal muscles.

• The skeleton moves the arm, while the heart moves on its own without any muscles.

• Both arm movement and heartbeat are voluntary actions controlled by joints.

Multiple Choice

An animal like an earthworm uses a fluid-filled hydrostatic skeleton for support. What is the most likely reason an earthworm cannot grow as large as an animal with an internal skeleton?

• A fluid-filled cavity does not provide the same strong, sturdy framework as bones.

• It does not have joints that allow for flexibility and movement.

• It cannot be protected by a hard outer shell like an exoskeleton.

• It is unable to produce its own blood cells or store important minerals.

​

​

Structure and Support in Plants

Roots

• ​Roots anchor the plant in the ground, providing stability and support.

• ​​They absorb the water and important nutrients that plants need to survive.

• ​Some roots are large taproots that also store food for the plant.

Stems

• ​Stems provide the main support for a plant’s leaves, flowers, and branches.

• ​​They transport water, minerals, and food throughout the entire plant.

• ​Stems can be hard and woody, or they can be soft and green.

Multiple Choice

What is the main structural job of a plant's roots and stems?

• To provide stability and support for the plant.

• To absorb sunlight to produce food.

• To create colorful flowers to attract insects.

• To produce seeds for plant reproduction.

Multiple Choice

Besides providing support, how do the roots and stems work together to help a plant survive?

• Roots absorb water and nutrients, which the stem transports to the rest of the plant.

• Stems absorb water from the air, and roots transport it to the leaves.

• Roots primarily store food, while stems are responsible for absorbing all nutrients.

• Stems make food for the plant, and the roots store it for later use.

Multiple Choice

If a healthy plant's stem were to be cut near the base, what would be the most likely result?

• The leaves would wilt because they could no longer receive water and nutrients from the roots.

• The roots would immediately stop growing because they would no longer be anchored.

• The plant would grow taller and stronger by sending out a new, harder stem.

• The plant would start storing food in its leaves instead of its roots.

​

​

Obtaining Energy and Removing Waste

Energy and Waste in Animals

• Animals eat food, which is broken down by mechanical digestion like chewing and chemical digestion using saliva and acid.

• Food travels from the mouth, through the stomach, to the small intestine where nutrients are absorbed into the body.

• The kidneys are organs that filter waste from the blood to produce urine, which is then removed from the body.

Energy in Plants

• Plants are producers, meaning they make their own food using a process called photosynthesis, which occurs in the leaves.

• Photosynthesis uses sunlight, water, and carbon dioxide to create glucose, which provides energy.

• As a part of this process, plants also release oxygen, which is essential for many living things to breathe.

Multiple Choice

What is the main difference in how animals and plants obtain the energy they need to survive?

• Animals get energy by eating food, while plants make their own food.

• Plants absorb energy through their roots, while animals absorb it through their skin.

• Animals use sunlight to create energy, while plants get energy from the air.

• Plants and animals both get energy by breaking down chemicals in the soil.

Multiple Choice

How do the processes of digestion in animals and photosynthesis in plants both help an organism get energy?

• Digestion breaks down food to be absorbed by the body, while photosynthesis uses sunlight to create food.

• Digestion releases oxygen into the air, while photosynthesis absorbs nutrients from the ground.

• Digestion uses carbon dioxide to make sugars, while photosynthesis uses saliva and acid to break down food.

• Digestion creates urine to remove waste, while photosynthesis creates glucose to build leaves.

Multiple Choice

What conclusion can be drawn by comparing the waste products of plants and animals as described in the text?

• The plant's waste product (oxygen) is essential for the animal, while the animal's waste must be removed to prevent harm.

• The animal's waste product (urine) is used by the plant to perform photosynthesis.

• Both organisms release waste gases that are harmful to the environment.

• The plant's waste is stored in its leaves, while the animal's waste is stored in its stomach.

​

​

Transporting Materials in Animals

Gas Exchange

• The respiratory system is how animals take in oxygen from the air and release carbon dioxide waste.

• In humans, air enters the lungs, which contain millions of tiny air sacs called alveoli.

• This is where oxygen moves into the blood and carbon dioxide moves out to be exhaled.

Circulatory Systems

• The circulatory system uses the heart to pump blood, transporting oxygen and nutrients throughout the body.

• Humans have a closed circulatory system, where blood is always contained within vessels like arteries and veins. This allows blood to be pumped efficiently, ensuring that all parts of the body receive oxygen.

• Insects have an open system, where blood flows freely in open spaces, surrounding the organs.

Multiple Choice

What is the main purpose of an animal's respiratory and circulatory systems working together?

• To transport essential materials like oxygen and nutrients throughout the body.

• To break down food and absorb it into the bloodstream.

• To create a protective barrier against the outside environment.

• To provide structural support and allow for movement.

Multiple Choice

What is the relationship between the respiratory and circulatory systems in a human?

• The respiratory system takes in oxygen, which then moves into the blood to be transported by the circulatory system.

• The circulatory system delivers carbon dioxide to the lungs to be converted into oxygen.

• The respiratory system uses the heart to pump air directly into all the body's organs.

• The circulatory system filters waste from the air before it enters the lungs.

Multiple Choice

Why is a closed circulatory system, like the one in humans, better suited for a large, active animal than an open system, like the one in insects?

• A closed system allows blood to be pumped more efficiently, ensuring all parts of a larger body receive oxygen.

• An open system is better because blood can surround the organs directly.

• A closed system requires less energy because blood is contained in smaller spaces.

• An open system is more effective at removing carbon dioxide waste from the blood.

​

​

Transporting Materials in Plants

Vascular Tissues

• Plants have a transport system called vascular tissues to move essential materials where they are needed.

• Xylem is the tissue that transports water and dissolved nutrients from the roots to the leaves.

• Phloem is the tissue that carries food, made during photosynthesis, from the leaves to all other parts.

Gas Exchange

• Plants exchange gases with the atmosphere through tiny openings on their leaves known as stomata.

• They take in carbon dioxide (CO₂) and release the oxygen that is produced during photosynthesis.

• Plants also release water vapor through the stomata in a process which is called transpiration.

Multiple Choice

What is the primary function of a plant's vascular tissues?

• To move essential materials like water, nutrients, and food.

• To absorb sunlight for the plant to make energy.

• To release pollen into the air for reproduction.

• To protect the plant from insects and other animals.

Multiple Choice

What is the difference between the roles of xylem and phloem?

• Xylem transports food from the roots, while phloem transports water from the leaves.

• Xylem transports water from the roots, while phloem transports food from the leaves.

• Xylem takes in carbon dioxide, while phloem releases oxygen.

• Xylem releases water vapor, while phloem absorbs nutrients.

Multiple Choice

If a plant's stomata were unable to open, what would be the most likely consequence?

• The plant would not be able to take in carbon dioxide to perform photosynthesis.

• The xylem would stop transporting water from the roots.

• The phloem would carry too much food to the roots.

• The roots would be unable to absorb nutrients from the soil.

​

​

Control and Information Processing

Human Nervous System

• The nervous system is the body's control center, processing information and creating responses.

• It includes the Central Nervous System (brain and spinal cord) and the Peripheral Nervous System (nerves).

• Information is sent by specialized cells called neurons and is gathered through sensory receptors.

Plant Responses

• Plants do not have a nervous system but can still sense and respond to their environment.

• A plant's directional growth in response to a stimulus like light or gravity is called a tropism.

• Plants grow toward light (phototropism), and their roots grow in response to gravity (gravitropism).

Multiple Choice

What is the main role of the human nervous system?

• To act as the control center that processes information.

• To grow toward a light source.

• To transport water from the roots to the leaves.

• To create energy for the body to use.

Multiple Choice

What is a key difference in how humans and plants respond to their environment?

• Humans use a nervous system, while plants use directional growth called tropism.

• Humans respond to light, while plants only respond to gravity.

• Plants can create their own responses, while humans cannot.

• Plants use a brain and spinal cord, while humans use nerves.

Multiple Choice

A potted plant on a windowsill is knocked onto its side but remains in the light. What is the most likely outcome for the plant?

• The stem will bend and grow upward toward the light, while the roots will bend and grow downward.

• The entire plant will stop growing until it is turned upright again.

• The roots will start to grow upward toward the light, and the stem will grow downward.

• Both the stem and the roots will continue to grow straight out to the side.

​

Common Misconceptions

Misconception	Correction
Body systems work independently.	Body systems are interconnected and work together.
The skeleton is a non-living frame.	Bones are living organs that produce blood cells and store minerals.
Plants do not react to their surroundings.	Plants actively respond to stimuli like light, gravity, and touch.

​

Summary

• The body has levels of organization: cells, tissues, organs, and organ systems.

• Organ systems work together to maintain a stable internal state (homeostasis).

• Muscular and skeletal systems provide support, while others handle energy and transport.

• The nervous system controls functions, and the excretory system removes waste.

Poll

On a scale of 1-4, how confident are you about how body systems interact to keep an organism alive?

• 1

• 2

• 3

• 4