What Makes Up a Cell?Cells, like organisms, have certain needs. Cells need to obtain nutrients, water, and oxygen. They also need to get rid of waste. The structures that make up a cell help it carry out these functions.

Click on the link below to watch the “Cells” BrainPOP® movie. As you watch the movie, answer the following questions in your science notebook:

1. What is a cell membrane, and what does it do?2. What do organelles do? How are organelles like organs? Give an example of an

organelle, and explain what it does.3. What is the difference between a eukaryotic cell and a prokaryotic cell? Give an

example of an organism with eukaryotic cells and an example of an organism with prokaryotic cells.

4. Which type of organism has cells with a cell wall? What does the cell wall do?

 Cells

Click on the Show Answer button to check your answers.

Answers:

1. The cell membrane surrounds the outside of a cell. It allows substances that

the cell needs to enter the cell and keeps things the cell does not need out of

the cell.

2. Organelles do all the work that a cell needs to do, such as making proteins,

turning food into energy, and getting rid of waste. Just as organs carry out

different functions in the body, organelles carry out different functions in a cell.

The nucleus, for example, is an organelle that controls the functions of a cell

—just as the brain controls the functions of the body.

3. In a eukaryotic cell, the genetic information, or DNA, is found in the nucleus.

Plants, animals, and humans have eukaryotic cells. Prokaryotic cells do not

Cells produce more cells by dividing. This is how you grow.

have a nucleus. Their DNA is found in the cytoplasm. Most prokaryotes are

bacteria.

4. Plants have cells with cell walls. Their cell walls help plant cells keep their

shape.

A cell membrane is a thin layer, primarily made up of lipids, that surrounds a cell and controls what substances enter and leave the cell. Inside the cell membrane is the cytoplasm and organelles that make up the cell. Cytoplasm is a gel-like mixture of water and chemicals that is constantly moving, carrying necessary chemicals and organelles from place to place within the cell. Organelles are tiny structures that carry out all the functions of the cell. The nucleus is an example of an organelle. In eukaryotic cells, the DNA is found in the nucleus. You may recall that DNA carries the instructions for all of the cell’s functions in the form of a chemical code. Because the nucleus contains these instructions, it is often called the control center of the cell. 

Click on the link below to access the Directed Virtual Lab: How Can You Observe Cells? activity from the Interactive Digital Path website. Record your answers to the questions on slides 5, 8, 10, 14, 17, and 18 in your science notebook. 

 Directed Virtual Lab: How Can You Observe Cells?

Click on the Show Answer button to check your answers.

Another scientist, Walther Flemming, discovered that cells reproduce by dividing. From Flemming’s work, as well as others, Rudolf Virchow, a German scientist, contributed to the understanding of cells by concluding that all cells develop from other cells. The idea that all living things are made up of cells, that cells are the building blocks of life, and that all cells are created from other cells through cell division is called the cell theory. The cell theory explains the relationship between cells and living things based on the observations of many scientists over time.

With the exception of chloroplasts and lysosomes, the organelles of plant and animal cells are basically the same. Click on the link below to watch the “Cell Structures” BrainPOP® movie. As you watch the movie, answer the following questions in your science notebook:

1. Which three activities do cells need to manage?2. How do the mitochondria, vacuoles, smooth endoplasmic reticulum, ribosomes, rough

endoplasmic reticulum, and Golgi bodies assist in the management of cell activities?3. How is a cell like a factory?

 Cell Structures

Click on the Show Answer button to check your answers.

Answers:

1. Cells need to manage energy consumption, protein production, and waste

management.

2.Mitochondria   break down food and release energy.   Vacuoles   store water, waste products, and food until they are needed.   Smooth endoplasmic

reticulum   creates and stores large molecules and charged particles.   Ribosomes   manufacture proteins, and the   rough endoplasmic

reticulum   transports them to other locations in the cell.   Golgi bodies   pack up proteins that are ready to be sent out to the body.

3.Like a factory, cells take in materials and send out products.

Plant PartsMost green plants have three major parts that work together to keep them alive. These three parts are the plant’s roots, stems, and leaves. How do these body systems function to keep the plant alive? Click on the links below to watch the “Roots,” “Stems,” and “Leaves” Discovery Education™ streaming movies. As you watch the movies, answer the following questions in your science notebook:

1. What are the functions of a plant’s roots? How does the structure of root hairs improve their function?

2. Describe the structure of xylem and phloem. What does each of these tissues do?3. What is the major function of leaves? How does their structure help them carry out their

function?

 Roots

 Stems

 Leaves

Click on the Show Answer button to check your answers.

Answers:

1. Roots hold a plant in place and absorb water and minerals that the plant needs. Root

hairs are tiny projections that greatly increase the surface area of the roots, allowing

them to absorb more water. In some plants, the roots also store some of the food

made in the plant’s leaves.

2.Xylem and phloem are long, hollow tubes that connect a plant’s roots with its leaves.

Water and nutrients move from the plant’s roots up to its leaves through

the   xylem   tissue. Food made by the leaves moves down to its roots through

the   phloem   tissue.

The tiny hairs on plant roots increase the surface area of the roots, allowing them to take in more water.

3.Leaves make food for the plant. Leaves on a plant are arranged so that they can

capture as much sunlight as possible because they use the energy from sunlight to

turn water and carbon dioxide into sugars that the plant can use as food.

Xylem and phloem make up the vascular tissue of plants. Cambium is a specialized tissue in plants that divides to produce new phloem and xylem tissue as the plant grows.

Not all plants have vascular tissue. Because nonvascular plants have no xylem and phloem to transport material from one place to another, materials that the plant cells need must be passed from cell to cell. This is a very slow process. As a result, nonvascular plants tend to be low growing and small. Mosses, liverworts, and hornworts are examples of nonvascular plants.

Flowers and seeds are also important parts of some plants. These parts will be addressed in future lessons.

Plant PartsImagine a plant like a factory, or a system. All systems require input. They all have processes, or things that happen inside the system, and produce outputs, too. Click on the link below to watch “The Sun, Light, and Photosynthesis” Discovery Education™ streamingmovie. As you watch the movie, answer the following questions in your science notebook:

1. What are the inputs required for plants to make food? What plant structures gather these materials?

2. What is the process that plants use to make food called?3. What are the outputs of this process?

 The Sun, Light, and Photosynthesis 

Click on the Show Answer button to check your answers.

Answers:

1. Energy from the sun, carbon dioxide, and water are inputs required for plants to make

food. A plant’s leaves take in energy from the sun and carbon dioxide from the air.

The plant’s roots absorb water and minerals from the ground.

2.The process in which green plants make food is called   photosynthesis .

3.The outputs of photosynthesis are glucose and oxygen.

InvertebratesVertebrates may be the animals that most people think of, but invertebrates actually outnumber vertebrates by a large margin. The invertebrate group includes animals such as insects, spiders, snails, and worms. 

Click on the link below to watch the “Invertebrates” BrainPOP® movie. 

 Invertebrates

As you watch the movie, answer the following questions in your science notebook:

1. What percentage of animals are invertebrates?2. Which eight groups are invertebrates divided into? What are the characteristics of each

group? What is the largest group of invertebrates?3. How do scientists use body symmetry to classify invertebrates? Give an example of an

animal with each type of body symmetry.4. How does radial symmetry help cnidarians survive?

Click on the Show Answer button to check your answers.

Answers:

1. Ninety-five percent of animals are invertebrates.

2.Invertebrates are grouped into sponges, cnidarians, flatworms, segmented worms,

mollusks, roundworms, arthropods, and echinoderms. Sponge are the simplest

animals.   Cnidarians   have stinging cells that they use to capture prey. Flatworms

are worms with long, flat bodies and bilateral symmetry. Most are parasites. Round

worms are worms with round bodies.   Mollusks   are soft-bodied invertebrates, often

with a protective shell, that have a muscular foot that allows them to move around or

anchor themselves. Annelids are segmented worms, such as earthworms and

leeches.   Arthropods   are the largest group of invertebrates. They have jointed body

parts, such as claws, legs, and antenna; bilateral symmetry; and segmented

bodies.   Echinoderms   have spiny skin, water-filled veins, an internal skeleton, and

tube feet. They have radial symmetry.

Invertebrates are the most numerous and diverse group of animals on Earth.

3.Invertebrates that have body parts arranged around a central point are said to

have   radial symmetry . Sea stars and sand dollars have radial symmetry.

Invertebrates that have a body with two halves that are mirror images of each other

have   bilateral symmetry . Butterflies and lobsters have bilateral

symmetry.   Asymmetric   animals do not have any symmetry at all. Sponges are

asymmetric.

4.Radial symmetry helps cnidarians find food from any direction.

The body symmetry of animals affects how they function. Animals with radial symmetry can take in information from any direction. Animals with bilateral symmetry, on the other hand, generally have sense organs, such as eyes, noses, and ears, concentrated at the head end. The head end of these animals also tends to contain a concentration of nervous tissue, which comprises a brain.

Animals Respond to Their EnvironmentA stimulus is a change in an organism’s environment that the organism responds to. The ability to respond to the environment—both internal and external—helps keep living things alive. 

Click on the link below to watch the “All Living Things Can Move and Respond to Their Surroundings” Discovery Education™ streaming movie. 

 All Living Things Can Move and Respond to Their Surroundings

As you watch the movie, answer the following questions in your science notebook:

1. Give three examples of the ways in which living things respond to their environment.2. What is the main difference between the way nonliving things move in response to

things in their environment and the way living things respond?3. Give an example of an involuntary response to changes in the environment.

Click on the Show Answer button to check your answers.

Answers:

A butterfly responds to the danger presented by a cat’s claws by flying away.

1. Plants move to position their leaves to receive the best light. A lizard moves into the

shade when it gets too hot. A thirsty bird moves to drink. A hungry prairie dog looks

for plants to eat. A frightened mouse hides from a cat. The rate of your heartbeat

increases when you exercise.

2.The main difference between the responses of living and nonliving things to changes

in their surroundings is that living things control their responses, either voluntarily or

involuntarily. Nonliving things do not control their responses.

3.How fast your heart beats changes involuntarily in response to changes in the

environment.

The Nervous SystemThe nervous system is the body system that receives information from an animal’s internal and external surroundings and coordinates a response. 

Click on the link below to read the “Messages in Motion” Discovery Education™ Science reading passage. 

 Messages in Motion

As you read the passage, answer the following questions in your science notebook:

1. What are senses and sense organs? What do sense organs do?2. How do the sense organs work together with nerves and the brain?3. What is a reflex?

Click on the Show Answer button to check your answers.

Answers:

1. The   senses   are sight, hearing, smell, taste, and touch. Sense organs include the

eyes, ears, nose, tongue, and skin. The sense organs gather information from the

environment.

The brain is the control center of the body.

2.Messages from the sense organs are sent along nerves to the brain. The brain

determines the appropriate response to these messages and sends new messages

to other parts of the body.

3.A   reflex   is an automatic response that allows you to move quickly away from danger.

The nervous system is made up of many parts that work together to allow an animal to sense and respond to its environment. Click on the link below to access the Key Concept Summary tutorial from the Interactive Digital Path website. Review the information in Key Concept 1. In your own words, define the following key words in your science notebook: neuron, impulse, sensory neuron, interneuron, and motor neuron.

 Key Concept 1

Click on the Show Answer button to check your answers.

Answers:

neuron   – a nerve cell that can receive and pass on information; the basic unit of the nervous system  

impulse   – an electrical message that travels along nerve cells

sensory neuron   – a neuron that detects stimuli  

interneuron   – a neuron that passes information from one neuron to another  

motor neuron   – a neuron that carries a response to muscles and other organs

Imagine you wanted to kick a soccer ball. Your sense organs gather information about the location of the ball. Impulses travel along your sensory neurons to your spinal cord and then to your brain. Scientists define the brain as an organized grouping of neurons in the head of an animal with bilateral symmetry. The information about the ball is processed in the brain, the control center of the body, and an impulse is transferred

through interneurons to the motor neurons. Motor neurons relay the impulse to the muscles in your leg, and you kick the ball.

The impulses in a reflex travel a slightly different path. For example, if you put your hand on a hot stove, you will reflexively jerk your hand back. Because you need to move your hand quickly, impulses travel down your sensory neurons to interneurons in your spinal cord, but do not keep on traveling to your brain. Instead, interneurons in the spinal cord pass the response impulse directly to motor neurons so the muscles in your arm get the message to move your hand away quickly.

Differences in Nervous SystemsMany animals have the same senses that humans do, but some have even more. Click on the link below to watch the “A Closer Look at Sharks and Rays” Discovery Education™ streaming movie. As you watch the movie, answer the following questions in your science notebook:

1. What senses do humans, sharks, and rays have in common?2. What senses do sharks and rays have that humans do not?

 A Closer Look at Sharks and Rays

Click on the Show Answer button to check your answers.

Answers:

1. Like humans, sharks and rays can see and smell. They also have a sense of touch.

2.Unlike humans, sharks and rays can detect electrical charges emitted by living

animals.

All animals respond to their surroundings. However, not all of them have as complex a nervous system as vertebrates. Click on the link below to access the Key Concept Summary tutorial from the Interactive Digital Path website. Review the information in Key Concept 2, and answer the following questions in your science notebook:

1. Which two features are found in the complex nervous systems of humans and other vertebrates?

Sharks have the same senses that humans do, but they have an extra one, too.

2. Describe the nervous system of cnidarians. Do cnidarians have a brain? Do they have sensory and motor neurons?

3. Describe a planarian’s nervous system. Do planarians have a brain?4. Other than vertebrates, which other animal groups have a complex nervous system with

a brain and specialized neurons?

 Key Concept 2

Click on the Show Answer button to check your answers.

Answers:

1. Humans and other vertebrates with complex nervous systems have a nerve cord and

a brain.

2.Cnidarians have a net-like arrangement of neurons called a   nerve net . No,

cnidarians do not have a brain. No, a nerve net does not have specialized nerve

cells, such as sensory neurons, interneurons, and motor neurons. A stimulus to one

neuron sends impulses in all directions.

3.Planarians have a slightly more complex nervous system than that of cnidarians.

Planarians have a nerve cord and eye spots made up of groups of interneurons, but

they have no brain.

4.Along with vertebrates, arthropods and mollusks have a complex nervous system with

a brain and specialized neurons.

1. A stimulus is a signal that causes an animal to react in some way. A response is an animal’s reaction to that stimulus. 

2. Sensory neurons detect stimuli. Interneurons transfer information between neurons. Motor neurons carry response information. 

3. A nerve net is a net-like arrangement of neurons found in the simplest of animals, such as cnidarians. A nerve net has no specialized neurons. 

4. A brain receives information, interprets it, and controls an animal’s response. 

5. Animals with many sense organs can process many stimuli at the same time because different areas of the brain respond to different stimuli. 

Characteristics of Living Things ReviewClick on the link below to watch “The Characteristics of Life” Discovery Education™ streaming movie. As you watch the movie, answer the following question in your science notebook: Which characteristics do all living things share?

 The Characteristics of Life

Click on the Show Answer button to check your answer.

Answer:All living things, or organisms, can reproduce, or

produce new life that is very similar to themselves.

They grow and develop, respond to the outside world, and must use energy to stay

alive. All living things undergo change and move. In the end, all living things die. All

living things are made up of cells, which are the building blocks of life. Some

organisms are made up of only one cell. They are unicellular. Other organisms have

multiple cells and are multicellular. The cells of multicellular organisms are highly

organized and specialized.

Cell Structure ReviewCells are the smallest units of life that can function independently. To carry out the functions of life, cells contain structures, called organelles. 

Click on the link below to watch the “Cell Structure” Discovery Education™ streaming movie. 

 Cell Structure

As you watch the movie, answer the following questions in your science notebook:

All living things have certain characteristics and requirements.

Cells are made up of many parts that work together to keep the cell functioning. Multicellular organisms are made up of many cells that work together to keep the

organism functioning.

1. What is a cell? Which life processes do cells carry out?2. What are single-cell organisms called? Give an example. What are organisms with

multiple cells called? Give an example. How are the cells of organisms with multiple cells organized?

3. What are organelles? Describe the function of the cell membrane, cytoplasm, mitochondria, endoplasmic reticulum, ribosomes, Golgi bodies, lysosomes, and nucleus.

Click on the Show Answer button to check your answers.

Answers:

1. Cells are the smallest unit of life that can function independently. They are the

building blocks of life. Cells move, respond to their surroundings, reproduce, and

grow. They also need to carry out respiration, get the nutrition they need, and excrete

waste products.

2.Organisms that are made up of only one cell are unicellular. Bacteria are examples of

unicellular organisms. Organisms with multiple cells are called multicellular

organisms. Humans are multicellular. Multicelluar organisms are made up of many

organized parts. Cells are organized into tissues, which are groups of cells that work

together to carry out a specific function. Groups of tissues work together and make

up organs, and organs are organized into organ systems, which work together to

keep the entire organism functioning properly.

3.Organelles are structures within cells that carry out specific functions. All cells are

surrounded by a flexible, lipid-containing envelope called a cell membrane. The cell

membrane is selectively permeable, which means that it allows some substances to

enter and leave the cell while preventing others from getting in or out. The cytoplasm

is a mixture of water and chemicals inside the cell membrane where food molecules

are changed into materials needed for energy production and growth. Mitochondria

convert food energy into a form of energy that the cell can use to carry out its

functions. The endoplasmic reticulum stores and moves materials, such as proteins,

within the cell. Ribosomes manufacture proteins. The Golgi bodies package and

distribute proteins and other materials to other parts of the cell. Lysosomes contain

digestive enzymes that break down large food particles, waste, and worn-out cell

parts. The nucleus contains the cell’s DNA, which carries the instructions for how the

cells should function.

Smaller molecules can diffuse across the cell membrane through tiny openings called pores. Diffusion is the spreading of molecules from an area of high concentration to an area of low concentration. The diffusion of water, specifically, is called osmosis. Diffusion and osmosis are both forms of passive transport. Passive transport is the movement of materials across a cell membrane without the use of cellular energy. 

Larger molecules move into the cell after being surrounded and engulfed by the cell membrane in a process called endocytosis. They are released to the outside of the cell when pouches, called vesicles, fuse with the cell membrane in a process called exocytosis. Endocytosis and exocytosis require cellular energy to move materials across the cell membrane and are, therefore, 

Plant ReviewLike all multicellular organisms, plants have parts that work together to keep the plant alive. Click on the link below to watch the “Photosynthesis” BrainPOP® movie. As you watch the movie, answer the following question in your science notebook: Explain how a plant’s body systems allow it to carry out photosynthesis.

 Photosynthesis

Click on the Show Answer button to check your answer.

Answer:A plant’s roots absorb water and nutrients from the soil. Xylem carries the water and nutrients

up to the leaves. The plant’s leaves take in carbon dioxide from the air. Organelles in the

plant’s cells, called chloroplasts, trap energy from the sun and use the energy to make food

from the water and carbon dioxide.

Green plants convert inorganic molecules and energyfrom the sun into a food source that all organisms rely

on.

Phloem is another part of a plant’s vascular system. It transports food made in the leaves to other parts of the plant. Cambium is a special tissue that produces more xylem and phloem cells as a plant grows.

Animal ReviewAnimals are multicellular organisms that feed on other living things, move in some way, and have the ability to maintain homeostasis. 

Click on the link below to watch the “Cellular Respiration” BrainPOP® movie.

 Cellular Respiration

As you watch the movie, answer the following questions in your science notebook:

1. What is the function of the respiratory system?2. Describe how cells get the materials they need to carry out cellular respiration. Explain

how waste products produced by this process are removed.3. What are some of the organic compounds cells use from cellular respiration to create?

Click on the Show Answer button to check your answers.

Answers:

1. The function of the respiratory system is to exchange gases, primarily oxygen and

carbon dioxide, with the surroundings.

2.The digestive system breaks down food in a process called digestion. Nutrients from

this process and oxygen from the respiratory system are delivered to the cells by the

circulatory system. In the mitochondria, or the power plant of the cell, these

substances undergo chemical reactions that release energy. Carbon dioxide, a waste

product of cellular respiration, is removed from cells by the circulatory system and

delivered to the respiratory system, where it is exhaled.

3.Cells use the energy from cellular respiration to synthesize complex molecules such

as DNA, RNA, and proteins.

The animal kingdom is incredibly diverse. Arthropods, a group that includes insects, 

like this moth, make up a vast majority of the animals on earth.

How do photosynthesis and cellular respiration work together to sustain life? Identify the inputs, outputs, and processes involved. Write a response in your science notebook. 

Click on the Show Answer button to check your answer. 

Answer:Plants use energy from the sun, carbon dioxide from the air, and water from the soil to

make food. Oxygen is a waste product of photosynthesis and is released by green

plants. Animals breathe in the oxygen and eat plants and other animals as food. Their

digestive systems break down the food, and their circulatory systems deliver the

nutrients and oxygen to their cells. Cells use glucose and oxygen to make the energy

that sustains life. Carbon dioxide is a waste product of cellular respiration. In animals,

the circulatory system removes carbon dioxide from the cells and delivers it to the

respiratory system, where it is exhaled. Plants use this carbon dioxide in

photosynthesis.

The inputs of the process of photosynthesis are carbon dioxide, water, and energy from the sun. The outputs are food and oxygen. The inputs for the process of cellular respiration are oxygen and food. The outputs are energy and carbon dioxide.

Scientists classify animals into different groups based on shared traits. Below are the characteristics of several animal groups. Identify the name of the group described in each case. Write your responses in your science notebook.

1. This group of animals all begin life with a rod of stiffened tissue that may develop into a backbone as the animal grows.

2. Many of the animals in this group are supported by an external skeleton.3. The animals in this group have the simplest body plan. They have no symmetry.4. This group of animals has body parts arranged around a central point and stinging cells.5. This group of animals has radial symmetry, spiny skin, an internal skeleton, and a

system of water-filled veins.6. This group of animals has a muscular foot that allows them to move around or anchor

themselves. Snails and clams belong to this group.7. This group of animals is the most numerous and diverse.

Click on the Show Answer button to check your answers.

Answers:

1. Chordates are animals that have a backbone. All chordates, or vertebrates, begin life

with a rod of stiffened tissue called a notochord that can develop into vertebrae as

the animal grows. Vertebrae are the bones in the spinal column. Along with a spinal

column, vertebrates also have an internal skeleton, or endoskeleton. Birds,

mammals, fish, amphibians, and reptiles are vertebrates.

2.Most invertebrates do not have internal skeletons. Their bodies are supported by an

external skeleton, or exoskeleton. Invertebrates do not have backbones.

3.Sponges are the simplest of all animals. They are asymmetrical, or have no definite

shape.

4.Cnidarians are radially symmetrical invertebrates that use stinging cells to capture

prey and defend themselves. Jellyfish and corals are cnidarians.

5.Echinoderms have spiny skin, an internal skeleton, and a system of water-filled veins.

Sea stars and sea urchins are echinoderms. Echinoderms have body parts arranged

around a central point, which means they have radial symmetry.

6.Mollusks are soft-bodied invertebrates, often with a protective shell, that have a

muscular foot that allows them to move around or anchor themselves. Snails,

mussels, and clams are mollusks.

7.Arthropods are the most numerous and diverse animals on earth. Insects,

crustaceans, and arachnids are arthropods. They all have segmented bodies and

jointed appendages.

Mollusks, arthropods, flatworms, segmented worms, roundworms, and vertebrates have bilateral symmetry, or a body with two halves that are mirror images of each other. Animals with bilateral symmetry generally have a distinct head end, where their sense organs are concentrated

Information Processing ReviewAll organisms respond to stimuli, or changes, in their environment. An organism’s reaction to stimuli is called its response.  The brain of complex animals is a network

 of connected nerve cells, or neurons.

Plants exhibit growth responses called tropisms. A plant exhibits phototropism when it grows toward a light source. A chemical messenger, or hormone, in plants called auxin causes plant cells to grow faster. Auxin builds up on the shady side of plants, making the cells on that side grow faster and longer, which causes the plant to lean toward the light. 

Plants exhibit other types of tropisms, too. In your own words, explain the meaning of geotropism, thigmotropism, photoperiodism, and dormancy in your science notebook. 

Click on the Show Answer button to check your answers. 

Answers:Plant roots grow toward the ground in response to gravity, a process called geotropism. Some

plants, especially vines, respond to touch with a tropism called thigmotropism. Plants also

respond to the seasonal change in the number of hours of darkness, a response called

photoperiodism. When the nights get longer and the temperatures get colder, some plants

enter a state of dormancy, or inactivity.

In animals, information gathered by the senses, such as seeing, hearing, smelling, tasting, or feeling, moves along groups of nerve cells, called sensory neurons, as electrical impulses. These impulses are transmitted to the spinal cord or brain, where a response is determined. If the response requires the movement of muscles, the impulse travels down motor neurons to the muscles that need to move. Nerve cells that pass information from neuron to neuron are called interneurons. 

A reflex is an automatic response that allows an animal to move quickly away from danger. When an animal needs to move quickly to prevent injury, impulses travel from sensory neurons to the spinal column, and instructions to move are relayed directly to motor neurons without going through the brain first. 

Review the differences in the nervous systems of different animals. Click on the link below to access the interactive SCIENCE activity from the Interactive Digital Path website. Complete the Art in Motion activity by writing your answers to the questions on slides 3 and 4 in your science notebook. 

 Art in Motion: Nervous Systems at Work

Click on the Show Answer button to check your answers.

Answers:Slide 3: A sea anemone is a cnidarian. Cnidarians do not have brains. They have nerve

nets.

Slide 4: A hydra is a cnidarian. Cnidarians have nerve nets. Nerve nets do not have

specialized neurons, such as sensory neurons, interneurons, and motor neurons.

Cnidarians also do not have brains. An octopus is a mollusk. Mollusks have a more

complex nervous system than cnidarians, including specialized neurons, a nerve

cord, and a brain.