Sra: Imagine It!, Themes, Taking a Stand, Ancient Civilizations Ecology, Great Expectations, Earth in Action, Art and Impact, Level 6

... and others

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Kingdom Protoctista 80,000 species

Are they plants? Animals? The answer is yes ... and no. The Kingdom Protoctista has a little bit of everything. Some species (the algae) are plantlike--they can make their own food. Others (the protozoa) are animal-like--they depend on other species for food.

Protoctista are found in water and other wet environments. In the ocean, they are a major food source known as plankton. Fish, shrimp, and other crustaceans eat plankton and in turn become food for other animals, both in water and on land. This is called a food chain. When many food chains are linked together, they form a food web. Without plankton, many species would starve, and the food webs that support the Tree of Life might break down.

Algae have another important role. They help maintain the balance of gases in Earth's atmosphere. How? Algae, like plants, absorb carbon dioxide and use sunlight to create food for themselves. (This process is called photosynthesis.) By doing so, they create the oxygen that all animals on the Tree of Life need to breathe.

(paramecia, amoebas ...)

(green algae, red algae, fire algae ...)

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Paramecia, a type of protozoa, have tiny hairlike structures called cilia. To help paramecia move in their watery habitats, the cilia move back and forth--a little like rowing a boat.

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Just about anywhere you look on land, you will find members of the plant kingdom. They range from the flowers in your window box, to the trees that give you shade in the summer, to the mosses you walk on in woods and the veggies you eat for dinner.

Plants provide valuable habitats for many animals. A habitat is an area where species can find the food, shelter, water and space they need to survive. Without habitats, animals could not survive.

Like protoctista, plants are also at the base of food chains. Plants make their own food--and become food for other living things. A rabbit nibbles on a clover plant. A snake eats the rabbit, then a hawk eats the snake. When the hawk dies, bacteria and fungi feed on its body. Without plants, food chains and webs on the Tree of Life would collapse, and species would become extinct.

As plants make food for themselves during photosynthesis, they create oxygen. Next time you take a deep breath (or even just a tiny one), remember that the oxygen plants produce makes life on Earth possible.

Plant species

235,000 flowering plants (maples, oaks, cacti, grasses, daisies ...)

12,000 ferns (maidenhair fern, Boston fern, staghorn fern ...)

10,000 mosses (peat moss, sphagnum moss, granite moss ...)

630 conifers (pine trees, cedars, junipers ...)

... and others

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High up in tropical rainforests, the bromeliad grows into a "bowl" of leaves attached to a tree. The bowl catches water and becomes a habitat for many species of frogs, insects, spiders and worms. The largest bromeliad is just a bit smaller than a backpack. It can hold nearly 7.5 L (2 U.S. gal.) of water.
Milkweed is an important plant for monarch butterflies--it's where they lay their eggs and it's the main food for young monarch caterpillars. Eating milkweed also makes the caterpillars and butterflies poisonous to other animals.
The bee orchid is an excellent mimic. Its flower looks so much like a female bee that male bees are tricked into landing on it. When they fly away, they carry pollen with them to the next flower.

Many plants are used in medicines. The rosy periwinkle of Madagascar is a vital ingredient in two medicines that treat cancer. Sadly, rosy periwinkles are at risk because their habitat is disappearing.

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Kingdom Animal 1,318,000 species

From lions, tigers and bears, to jellyfish, sponges and sea slugs-- the animal kingdom is by far the largest and most diverse of the five kingdoms. It accounts for about three-quarters of all leaves on the Tree of Life.

The species in this kingdom are further grouped into invertebrates (animals without backbones, such as spiders, insects, sponges and worms) and vertebrates (animals with backbones--fish, birds, reptiles, amphibians and mammals).

With or without backbones, all animals share some characteristics. Unlike plants, animals cannot create their own food. They rely on other life forms for food. Some animals (herbivores) eat plants, while others (carnivores) eat the animals that eat plants.

Plants rely on animals, too. Most flowering plants need animals, especially insects, to take pollen from one flower to another so that new seeds can form. Without animals, many plants could not produce seeds.

Animals also help spread plant seeds. Birds and bats eat the fruit the plants produce. The fruit is digested and the seeds are dropped in the animal's waste, away from the adult plant. This gives the new plants room to grow. Even squirrels and chipmunks get into the act. They collect seeds and bury them to eat later. The seeds that are forgotten grow into new plants.

Animals even help plants grow by providing much-needed nutrients. Animal poop is a rich fertilizer.

Animal species

1,265,500 invertebrates

52,500 vertebrates

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Stony corals are one of many coral species that build coral reefs. These reefs are the rainforests of the ocean--they provide a habitat for a huge diversity of animals.

A fruit-eating fish? The tambaqui of the Amazon River eats fruits that fall into the water. The seeds are dispersed in the animal's waste.
Ants and acacia trees have a special relationship. Ants protect acacia trees from plant-eating insects, such as beetles and aphids. In return, the acacia tree provides nectar for the ants to eat and hollow thorns for shelter.
The Jamaican leaf-nosed bat helps spread fig seeds. The bat eats the figs, then the seeds are dispersed in the bat's droppings.

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The Tree of Life is constantly changing. New species are discovered every day, and known species are sometimes reclassified. Scientists think there may be as many as twenty million species on the Tree of Life.

Species are also being lost at an alarming rate. As many as 27,000 species may be lost each year--that's 74 species per day, 3 species per hour.

Every species, from fire algae to mangrove trees to zebras, needs a habitat that provides food, water and shelter. But cutting down forests, draining wetlands and plowing grasslands to build highways, roads, farms, towns and cities reduces habitat. And air, soil and water pollution threatens the quality of the habitats that remain.

The equivalent of two football fields worth of tropical rainforest are cut or burned every second to make room for pastures and farmland. Without the habitat that tropical forests provide, more than half of the world's plant and animal species may be lost.

Almost half of mangrove forests are gone--cut down for lumber or damaged by pollution, aggressive fishing and urban growth. Without mangrove forests, coastlines may slip into the ocean. Animals will lose vital habitat.

Almost a third of coral reefs have been lost due to development, overfishing and pollution. At this rate, scientists estimate that half will be gone by 2010.

Half of wetlands in the United States have been lost. Many of Canada's wetlands are also gone. Though home to an incredible diversity of species, wetlands are being drained or filled to make room for farms, houses and factories.

The extinction of even one species weakens the chain of connections among all species on the Tree of Life. Lose too many sea otters, and sea urchins will destroy the kelp forests. Lose the milkweed, and monarch caterpillars will starve. Lose plankton, and entire marine food webs will collapse.

The math is simple. The loss of habitat equals the loss of species. And the loss of even one species on the Tree of Life affects all species.

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At risk
25,971 plants	555 insects
1,192 birds	408 species of crustaceans
1,137 mammals	296 species of reptiles
938 mollusks	157 species of amphibians
752 fish

Becoming Guardians of the Tree of Life

The Tree of Life is not here for us to prune--cut off a branch, trim a twig. It's not something we can dig up and plant somewhere else. We must learn to live our lives within the tree--as 1 leaf among 1,750,000. We are part of the Tree of Life. We are its guardians, not its gardeners.

When we forget we are part of the Tree of Life, our impact can be damaging. But when we remember, it can be incredibly powerful. It doesn't take much to become a guardian of the Tree of Life. You don't need a lot of money or even a lot of time. All you need is desire, determination and the courage to think a little differently.
Some Species at Risk

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Rochelle Strauss

Strauss's passion is environmental education. She works as an author and as an educational consultant--a field in which she has helped to create museum exhibits and designs for a nature park. During college, Strauss's favorite class was a course on children's literature. While taking the class, she realized she wanted to become a children's book author. Her dream came true when she used her interest in environmental education to publish her first book for children, Tree of Life. Some of Strauss's favorite species are dolphins, bromeliads, and penguins.
Meet the Illustrator

Margot Thompson

Creating artwork for Tree of Life gave Thompson a chance to combine her knowledge of organisms and habitats (she has a degree in biology) with her skill as an artist. In addition to illustrating books and working as a graphic designer for the Royal Ontario Museum in Canada, Thompson also teaches children about art. She offers the following helpful advice to young artists: "Practice a lot, and don't be afraid to create your own style."
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Ecology: Theme Connections

Within the Selection

Beyond the Selection

Write about It!

Imagine you are a congressperson working on a conservation bill. What are some of the suggestions you would list in the bill? What opposition would you face getting the bill passed?

Remember to look for information about animals and their habitats for the

Genre

Feature

All living things described in "Tree of Life" are made up of cells. Some living things are made up of a single cell. Many of these are in the Monera and Protoctista kingdoms.

Most large plants and animals are multicellular. They contain billions of cells. A human body is made up of more than 75 trillion cells.

Some cells are fairly large, but most are so tiny you need a microscope to see them. Cells may be round, cube-shaped, coin-shaped, or flat.

Most living things have different types of cells. Groups of cells form body parts. For example, you have different types of cells in your skin, muscles, eyes, teeth, and brain. They also have unique jobs. They can digest their own nutrients and create energy from them. They can also make copies of themselves.

In one living thing, all cells must work together. Groups of similar cells form tissues. Tissues form organs such as your heart or lungs. A group of organs form a system that does a job for the body. The digestive system, for example, breaks down food into substances that can be delivered to all cells in the body. To work together cells must communicate with one another.

All cells have three main parts. They are the cell membrane, cytoplasm, and nucleus. Each part has different functions.

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Cell Part	Function of Cell Part
Cell membrane	Holds cell together, keeps harmful substances out, lets good ones in, gets rid of waste
Cytoplasm	Digests, makes energy and proteins, makes special substances
Nucleus	Controls growth and division, contains material to pass on traits

The cell membrane is the outer, skinlike wall of the cell. The membrane holds the cell together. It also keeps harmful substances out of the cell while allowing nutrients and other necessary substances to enter. Waste products leave the cell through the membrane.

The cytoplasm is mostly made up of water. It contains some solids. Most of the cell's functions take place in the cytoplasm. Food particles are digested and changed into energy and substances for growth and repair.

Most cells have a nucleus near the center. The nucleus has its own membrane. It contains a liquid called nucleoplasm. It also contains the material that passes on the cell's traits when it divides. The nucleus controls functions in other parts of the cell.

You have seen and read about the diversity of living things--from yeast to an elephant. Yet in their basic building blocks, they are all very similar.

How does the chart help you learn about cells?

What are the three main parts of most cells?

If all living things are made of cells, how can the world have so many different living things?

Try It!

As you work on your investigation, think about how you can use charts to organize your information.

* currents

* minerals

* deposits

* thrive

* lush

* delicate

* encased

* transforms

* perched

Vocabulary Strategy

Word Structure

Greek and Latin roots can often help you when you encounter an unfamiliar word. For example, the Latin root form means "shape." If you add the prefix trans- ("across") to this root, you have the word transform, which means "to change."

Dear Diary,

I always want to remember this day. So I am describing it now before I go home and forget any of the details. I hope to read this entry in years to come and smile as I recall this special day.

Some of my favorite moments are spent at the very spot where I am currently writing--a large, flat stone near Newtown Creek. The creek is in the forest close to my house.

The creek flows over and around huge, curved, water-worn stones. Leaves swirl and dance in the currents of the creek. A variety of minerals show up as spots of color in the stones.

Many different trees hug the banks of the creek. Their branches shut out most of the sunlight. It is spring, and the leaves on the trees are new and bright green. Dead leaves from last fall carpet the ground and crunch under my feet.
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The heavy smell of wet earth and leaves fills the air. Near the water, deposits of fertile, rich soil allow the plants to thrive and grow lush and strong.

On this spring day, I sit on my large stone and try to take in everything.

Flowering bushes crowd densely into a small clearing near my stone. I touch the delicate petals of a small, white bud.

On a nearby branch is a cocoon. Encased in this cocoon, a caterpillar transforms into a butterfly. I wonder what kind of butterfly it will be.

Birds of all kinds are perched on branches above my head. The notes of their calls fill the air. The adult birds probably have eggs or even young birds in their nests. I toss some scraps from my lunch. The birds group around them, squabbling over the larger chunks.

It is time to go. Tomorrow I will visit this spot again, and I will write more about what I see.

Concept Vocabulary

The concept word for this lesson is transfer. Transfer means "to move from one thing or place to another." Energy needs to transfer from one living thing to another in an ecosystem. How does transfer connect with the theme?

Game

Genre

Comprehension Strategy: Summarizing

As you read the selection, summarize the sections of the text to gain a clear understanding of how the pieces of the text fit together. This strategy will help you focus on the important items in each section and in the selection as a whole.

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Production note: this image crosses the gutter to appear both on page 288 and page 289 in the print version.

Focus Questions

What can the study of underwater life add to our understanding of ecology? How would your life be different if there were no phytoplankton?

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Imagine that you are setting out on an undersea voyage to meet the most important creatures on earth. You step into your own personal submarine. A flick of a switch magically shrinks you and your ship smaller than the period at the end of this sentence. Because of your tiny size, the water around you flows by as thick as chowder. You look outside your porthole and come face-to-face with the strange, amazing life forms that are responsible for all the other life in the sea--and for the oxygen we breathe and the atmosphere that surrounds the earth like a warm blanket.

Phytoplankton are incredibly small. Each one is a single cell or a chain of identical cells. One teaspoon of sea water can hold a million phytoplankton. Most of the photos in this book were taken through a microscope that made the phytoplankton appear hundreds of times larger than they actually are.

There are thousands of different phytoplankton. Scientists are reluctant to guess how many kinds there are because new ones are being discovered all the time. A few years ago, after researchers built even more powerful microscopes, they discovered new kinds of phytoplankton that until then they had thought were just dust specks on their slides.

Phytoplankton don't just live at the surface of the ocean. They are also found on mud flats along the seashore and in freshwater ponds. If you collect a jar of pond water and keep it on the windowsill for a few days, the water will turn pea-soup green as the phytoplankton bloom in the sunlight.

But for now, let's continue our journey through sea soup--
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Are they plants or are they animals?
It's not always easy to tell.

Normally, plants make their own food from sunlight, and animals hunt and capture their food. But a visit to our microscopic world shows us, like Alice in Wonderland, that nothing is quite what it seems. Some phytoplankton behave like plants, some like animals, and some like both.

Phytoplankton live at the surface of the sea, or as far under the water as the sun's light can reach. If you dive deeper into the ocean in your miniature submarine, you will see that light fades quickly after the first 30 feet or so until it disappears completely by the time you sink to about 600 feet.

You can think of the thin layer of water at the surface of the ocean as "plankton soup." Here there is sunlight, water, and carbon dioxide for phytoplankton to make their own food. Mixed with nutrients like phosphorus and nitrogen (which are the same fertilizers we put on our gardens), phytoplankton can bloom in huge numbers. Sometimes these blooms become so thick they change the color of the water to red, green, or brown.

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Phytoplankton and other plants have a chemical called chlorophyll that captures the sunlight and changes it into food--sugars and starches-- faster than the blink of an eye. This chemical reaction takes just a hundred-millionth of a minute and is called photosynthesis. It also makes oxygen, which humans and other animals need to breathe.