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Do a 3-2-1 for Gravity

3 things you learned

2 vocabulary words

1 question you still have

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Draw a model of your roller coaster you built at the beginning of the year. Label it and explain how gravity plays a part.

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Virtual Roller Coaster Ride - Timber Wolf POV at Worlds of Fun

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Get a piece of white paper from the Art Cart, draw a visual to represent the solar system.

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Follow along to make some shadow puppets and learn more about shadows. You may use the flashlights from the science supplies.

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Summary

Introduction

Have you ever played with your own shadow? It is fascinating how it follows your every move. But why do you not see your shadow every day? Why is your shadow very long sometimes, and other times very short? In this activity, you will make your own shadow puppet and explore how you can change the shape or size of its shadow. If you like, you can even create your own shadow play!

This activity is not recommended for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.

Materials

Prep Work

1. Place a table right next to a light-colored wall.

2. Put the flashlight on a box on a table so it faces the wall. It should be located about 50 cm (about 20 inches) away from the wall.

3. Cut a circle (about 2-inch diameter) from the cardstock.

4. Dim the lights in the room so it is dark enough to see clear shadows on the wall.

Instructions

1. Cut a figure or puppet out of the cardstock.

2. Tape a wooden skewer or popsicle stick to the cardstock puppet.

3. Turn your knowledge about light and shadow into a shadow play. Make more shadow puppets and tell a story with them! You can also create scenes on the wall by making trees, buildings, or other figures from the cardstock.

Cleanup

What Happened?

Were you able to change the size and shape of your puppet's shadow? First you had to make the shadow by placing the puppet directly in front of the flashlight. You probably did not see a shadow when you placed the circle off to the side instead of directly in front of the flashlight. This happens because light travels in straight lines. In order to block the light, the circle needs to be in front of the flashlight. This created a shadow on the wall that was the same shape as the circle.

You probably noticed that the cardstock circle made the darkest shadow. This happens because cardstock blocks all the light that shines on it. The frosted plastic lets some light through, so it did not make a very good shadow. The clear plastic lets almost all the light through, so it barely casts any shadow at all.

You should have noticed that you could make the puppet's shadow bigger by moving it closer to the flashlight, and smaller by moving it farther away from the flashlight. When you move the puppet closer to the flashlight, you block more of the light, resulting in a bigger shadow. When you change the angle of the flashlight, you can change the shape of the shadow and even make it distorted and stretched out. A steeper angle will result in a longer shadow.

Digging Deeper

The saying "where there is a shadow there must be light" tells us that you need some kind of light source to generate a shadow. For example, your own shadow that constantly follows you around on a sunny day is generated by the sun. But shadows do not necessarily disappear with the sun. Other light sources like the headlights of a car, a table lamp, or a simple flashlight can cast shadows too. The brighter the light source, the sharper your shadows will be. All light sources emit light that travels away in a straight line called a ray.

To cast a shadow, you need an object that can block the light rays. Materials that are opaque, like the cardstock, block all light and make good shadows. Materials that are translucent, like the frosted plastic, let some light through, and might make blurry or lighter shadows. Materials that are transparent, like the clear plastic sheet, let almost all light through and barely cast any shadow at all. You also need a surface, like the wall in this activity, on which to cast the shadow and make it visible.

But how can you vary the size and shape of a shadow? This can be done by either moving the light source or moving the shadow puppet. The closer an object is to a light source, the more light it blocks, resulting in a larger shadow. Changing the angle of the light source can change the length and shape of the shadow. A steeper angle will result in a longer shadow. This is why your shadow is very long if you go outside near sunrise or sunset, but very short when the sun is directly overhead at noon.

Ask an Expert

For Further Exploration

Make more shadow puppets! Cut out different shapes or other figures from the cardstock and see how their shadows look. Can you make a puppet with moving parts?

What happens to your shadow if you use multiple light sources? Test it by using two or three light sources at the same time. Place them all at different positions and observe how your shadow(s) change.

Can you find a way to make colored shadows? Look at this "Colored Shadows" activity to find out how it works.

Project Ideas

Science Fair Project Idea

Have you ever looked up at the stars at night and wondered how fast they were moving or how far away they were? By studying how the brightness of a star changes with distance, you can answer those questions. In this astronomy science project, you'll create a model of starlight and use a sensor app with your smartphone to discover the key relationship between brightness and distance. Read more

Science Fair Project Idea

This is a good project for someone who is interested in both electronics and color vision. The equipment needed is on the expensive side, but if you continue studying electronics, you can use it again and again. Read more

Activities

Have you ever considered taking a nighttime nature walk? Would you wait until there is a full moon, so you could profit from sunlight reflected on the moon, or would you rather take a flashlight? Do you think trees would look black, green, or grey in the dark? Do this activity to examine your night vision and prepare for your next nighttime adventure! Read more

Lesson Plans

Lesson Plan Grade: 6th-8th

How does light interact with matter? In this fun hands-on lesson, your students explore how different materials transmit, absorb and/or reflect light. They create their own experiments to demonstrate these phenomena and use a phones' built-in light sensor and a sensor app to add quantitative data to their arguments. Read more

Links

Careers

Physicists have a big goal in mind-to understand the nature of the entire universe and everything in it! To reach that goal, they observe and measure natural events seen on Earth and in the universe, and then develop theories, using mathematics, to explain why those phenomena occur. Physicists take on the challenge of explaining events that happen on the grandest scale imaginable to those that happen at the level of the smallest atomic particles. Their theories are then applied to... Read more

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In this fun activity, you will create shadow puppets and find out how to change the size and shape of their shadows.

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Go to Blooket and play a solo game of Solar System Review

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Search and discover new sets from a large collection created by users.

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Go to GetEpic and search books on Photosynthesis. Read one or a few books and do a Z chart to show what you learned.

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Read The Cycle of Photosynthesis on Epic

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Epic reaches 75 million kids in class and after school.

Built on a collection of 40,000+ popular, high-quality books from 250+ of the world's best publishers, Epic safely fuels curiosity and reading confidence for kids 12 and under.

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online access fun thousands children great kids ebooks books

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Read The Cycle of Photosynthesis on Epic

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The Cycle of Photosynthesis kids' book from the leading digital reading platform with a collection of 40,000+ books from 250+ of the world's best publishers. Read now on Epic.

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Go to GetEpic and read Many Kinds of Matter: A Look at Solids, Liquids, and Gases, after you read take the built in quiz.

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Instantly access over 40,000 of the best books & videos for kids on Epic

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Get unlimited access to 40,000 of the best books, audiobooks, videos, & more for kids 12 and under. Try it free.

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Read the article and make a T Chart with Food Chains on one side and Food Webs on the other.

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How food chains and food webs represent the flow of energy and matter. Trophic levels and efficiency of energy transfer.

Producers, or autotrophs, make their own organic molecules. Consumers, or heterotrophs, get organic molecules by eating other organisms.

A food chain is a linear sequence of organisms through which nutrients and energy pass as one organism eats another.

In a food chain, each organism occupies a different trophic level, defined by how many energy transfers separate it from the basic input of the chain.

Food webs consist of many interconnected food chains and are more realistic representation of consumption relationships in ecosystems.

Energy transfer between trophic levels is inefficient-with a typical efficiency around 10%. This inefficiency limits the length of food chains.

Introduction

Organisms of different species can interact in many ways. They can compete, or they can be symbionts-longterm partners with a close association. Or, of course, they can do what we so often see in nature programs: one of them can eat the other-chomp! That is, they can form one of the links in a food chain.

In ecology, a food chain is a series of organisms that eat one another so that energy and nutrients flow from one to the next. For example, if you had a hamburger for lunch, you might be part of a food chain that looks like this: grass cow human. But what if you had lettuce on your hamburger? In that case, you're also part of a food chain that looks like this: lettuce human.

As this example illustrates, we can't always fully describe what an organism-such as a human-eats with one linear pathway. For situations like the one above, we may want to use a food web that consists of many intersecting food chains and represents the different things an organism can eat and be eaten by.

In this article, we'll take a closer look at food chains and food webs to see how they represent the flow of energy and nutrients through ecosystems.

Autotrophs vs. heterotrophs

What basic strategies do organisms use to get food? Some organisms, called autotrophs, also known as self-feeders, can make their own food-that is, their own organic compounds-out of simple molecules like carbon dioxide. There are two basic types of autotrophs:

Photoautotrophs, such as plants, use energy from sunlight to make organic compounds-sugars-out of carbon dioxide in photosynthesis. Other examples of photoautotrophs include algae and cyanobacteria.

Chemoautotrophs use energy from chemicals to build organic compounds out of carbon dioxide or similar molecules. This is called chemosynthesis. For instance, there are hydrogen sulfide-oxidizing chemoautotrophic bacteria found in undersea vent communities where no light can reach.

Autotrophs are the foundation of every ecosystem on the planet. That may sound dramatic, but it's no exaggeration! Autotrophs form the base of food chains and food webs, and the energy they capture from light or chemicals sustains all the other organisms in the community. When we're talking about their role in food chains, we can call autotrophs producers.

Heterotrophs, also known as other-feeders, can't capture light or chemical energy to make their own food out of carbon dioxide. Humans are heterotrophs. Instead, heterotrophs get organic molecules by eating other organisms or their byproducts. Animals, fungi, and many bacteria are heterotrophs. When we talk about heterotrophs' role in food chains, we can call them consumers. As we'll see shortly, there are many different kinds of consumers with different ecological roles, from plant-eating insects to meat-eating animals to fungi that feed on debris and wastes.

Food chains

Now, we can take a look at how energy and nutrients move through a ecological community. Let's start by considering just a few who-eats-who relationships by looking at a food chain.

A food chain is a linear sequence of organisms through which nutrients and energy pass as one organism eats another. Let's look at the parts of a typical food chain, starting from the bottom-the producers-and moving upward.

At the base of the food chain lie the primary producers. The primary producers are autotrophs and are most often photosynthetic organisms such as plants, algae, or cyanobacteria.

The organisms that eat the primary producers are called primary consumers. Primary consumers are usually herbivores, plant-eaters, though they may be algae eaters or bacteria eaters.

The organisms that eat the primary consumers are called secondary consumers. Secondary consumers are generally meat-eaters- carnivores.

The organisms that eat the secondary consumers are called tertiary consumers. These are carnivore-eating carnivores, like eagles or big fish.

Some food chains have additional levels, such as quaternary consumers-carnivores that eat tertiary consumers. Organisms at the very top of a food chain are called apex consumers.

We can see examples of these levels in the diagram below. The green algae are primary producers that get eaten by mollusks-the primary consumers. The mollusks then become lunch for the slimy sculpin fish, a secondary consumer, which is itself eaten by a larger fish, the Chinook salmon-a tertiary consumer.

Each of the categories above is called a trophic level, and it reflects how many transfers of energy and nutrients-how many consumption steps-separate an organism from the food chain's original energy source, such as light. As we'll explore further below, assigning organisms to trophic levels isn't always clear-cut. For instance, humans are omnivores that can eat both plants and animals.

Decomposers

One other group of consumers deserves mention, although it does not always appear in drawings of food chains. This group consists of decomposers, organisms that break down dead organic material and wastes.

Decomposers are sometimes considered their own trophic level. As a group, they eat dead matter and waste products that come from organisms at various other trophic levels; for instance, they would happily consume decaying plant matter, the body of a half-eaten squirrel, or the remains of a deceased eagle. In a sense, the decomposer level runs parallel to the standard hierarchy of primary, secondary, and tertiary consumers.

Fungi and bacteria are the key decomposers in many ecosystems; they use the chemical energy in dead matter and wastes to fuel their metabolic processes. Other decomposers are detritivores -detritus eaters or debris eaters. These are usually multicellular animals such as earthworms, crabs, slugs, or vultures. They not only feed on dead organic matter but often fragment it as well, making it more available for bacterial or fungal decomposers.

Decomposers as a group play a critical role in keeping ecosystems healthy. When they break down dead material and wastes, they release nutrients that can be recycled and used as building blocks by primary producers.

Food chains give us a clear-cut picture of who eats whom. However, some problems come up when we try and use them to describe whole ecological communities.

For instance, an organism can sometimes eat multiple types of prey or be eaten by multiple predators, including ones at different trophic levels. This is what happens when you eat a hamburger patty! The cow is a primary consumer, and the lettuce leaf on the patty is a primary producer.

To represent these relationships more accurately, we can use a food web, a graph that shows all the trophic-eating-related-interactions between various species in an ecosystem. The diagram below shows an example of a food web from Lake Ontario. Primary producers are marked in green, primary consumers in orange, secondary consumers in blue, and tertiary consumers in purple.

In food webs, arrows point from an organism that is eaten to the organism that eats it. As the food web above shows, some species can eat organisms from more than one trophic level. For example, opossum shrimp eat both primary producers and primary consumers.

Bonus question: This food web contains the food chain we saw earlier in the article-green algae mollusks slimy sculpin salmon. Can you find it?

Grazing vs. detrital food webs

Food webs don't usually show decomposers-you might have noticed that the Lake Ontario food web above does not. Yet, all ecosystems need ways to recycle dead material and wastes. That means decomposers are indeed present, even if they don't get much air time.

For example, in the meadow ecosystem shown below, there is a grazing food web of plants and animals that provides inputs for a detrital food web of bacteria, fungi, and detritovores. The detrital web is shown in simplified form in the brown band across the bottom of the diagram. In reality, it would consist of various species linked by specific feeding interactions-that is, connected by arrows, as in the grazing food web aboveground. Detrital food webs can contribute energy to grazing food webs, as when a robin eats an earthworm.

Energy transfer efficiency limits food chain lengths

Energy is transferred between trophic levels when one organism eats another and gets the energy-rich molecules from its prey's body. However, these transfers are inefficient, and this inefficiency limits the length of food chains.

When energy enters a trophic level, some of it is stored as biomass, as part of organisms' bodies. This is the energy that's available to the next trophic level since only energy stored as biomass can get eaten. As a rule of thumb, only about 10% of the energy that's stored as biomass in one trophic level-per unit time-ends up stored as biomass in the next trophic level-per the same unit time. This 10% rule of energy transfer is a good thing to commit to memory.

As an example, let's suppose the primary producers of an ecosystem store 20,000 kcal/m/year of energy as biomass. This is also the amount of energy per year that's made available to the primary consumers, which eat the primary producers. The 10% rule would predict that the primary consumers store only 2,000 kcal/m/year of energy in their own bodies, making energy available to their predators-secondary consumers-at a lower rate.

This pattern of fractional transfer limits the length of food chains; after a certain number of trophic levels-generally three to six, there is too little energy flow to support a population at a higher level.

In each trophic level, a significant amount of energy is dissipated as heat as organisms carry out cellular respiration and go about their daily lives.

Some of the organic molecules an organism eats cannot be digested and leave the body as feces, poop, rather than being used.

Not all of the individual organisms in a trophic level will get eaten by organisms in the next level up. Some instead die without being eaten.

The feces and uneaten, dead organisms become food for decomposers, who metabolize them and convert their energy to heat through cellular respiration. So, none of the energy actually disappears-it all winds up as heat in the end.

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Food chains & food webs (article) | Ecology | Khan Academy

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Learn for free about math, art, computer programming, economics, physics, chemistry, biology, medicine, finance, history, and more. Khan Academy is a nonprofit with the mission of providing a free, world-class education for anyone, anywhere.

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Get a starburst from Mrs. Johnson. Measure it in cm to find it's volume, recording it on a sticky note. Record its state of matter and what qualitative observations you made. Put your name on the back and stick it on the Matter poster hanging on the wall.

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Do some research and find out what plants can grow with hydroponics that produce something we can eat. Once you find something Label a notecard (from the Art Cart), with the type of plant, why you chose it, and how you could use the food it produces.