The following information explains some of the basic science concepts contained in the Treemendous Science! unit. This background information will help teachers prepare and present the unit activities to their young learners. It is meant to support teachers’ comfort and competency and is not necessarily intended to be shared directly with students.
It is helpful to keep in mind that as children learn new concepts, they construct explanations for the things they observe that may be very different from the true scientific explanations. These so-called “misconceptions” play an important role in learning, especially for K–2 students, because they help learners make sense of the world around them.
For example, young children often:
- Believe that trees are not alive (because they do not move);
- Don’t consider trees to be plants (they think that only flowers or small, green vegetation can be plants);
- Deduce that seeds are produced by people (because they come from the store);
- Think that plants absorb food through their roots (whereas food is actually made in the plant’s leaves from carbon dioxide and water).
This background information can enable teachers to recognize where students’ thinking may be incomplete or not fully formed, and to help young learners to construct more accurate explanations based on evidence they observe.
The teacher information below applies to all Treemendous Science! activities and all three teaching levels (Level A, Level B, and Level C). It has been organized around the following Frequently Asked Questions to assist teachers in navigating to the specific content required.
Frequently Asked Questions
What is a tree?
What do trees need to live and grow?
What are the two main types of trees?
What are the parts of a tree?
What are tree rings?
How can you tell trees apart?
Why do some trees drop all their leaves in the fall?
How do some trees stay green all winter?
What are tree buds?
What is a tree’s habitat?
What other living things can live in a tree?
How do people use trees?
How can I help children find signs of animal life in trees?
Where can I get more information?
What is a tree?
A tree is a large, woody plant with a long trunk, roots, branches, and leaves.
What do trees need to live and grow?
Like all living things, trees and other plants need air, water, and food to grow. The most important difference between plants and animals is that plants make their own food using energy from the sun. Trees need:
Figure 1: Through the process of photosynthesis, plants use the sun’s energy to make food.
- Sunlight – All plants get their energy from the sun. The green pigment (chlorophyll) in leaves helps to turn the sun’s energy into food. In a process called photosynthesis, leaves use energy from the sun to convert carbon dioxide and water into oxygen and sugar (food).
- Air – Plants need the carbon dioxide in air to make their food. During photosynthesis, they take in carbon dioxide from air and give off oxygen.
- Water – Plants need water for several reasons. It is a crucial ingredient for photosynthesis. It also is the primary component of a plant’s structure. In addition, plants need water to transport nutrients from the soil to the plant’s roots.
- Nutrients – Just as people and animals need certain vitamins for growth, plants need mineral nutrients, such as nitrogen and phosphorus. They get these from the soil.
If trees don’t get enough sunlight, air, water, or nutrients, they may grow slowly or die.
What are the two main types of trees?
There are more than 50,000 kinds of trees in the world, which generally fall into two main types:
- Conifers – Conifers such as pines, spruces, hemlocks, and firs have seeds that develop inside cones. Most conifers also have needle-shaped leaves. And most also are evergreen, which means they don’t lose all their leaves at once, but instead stay green year-round.
- Broad-leaf Trees – Broad-leaf trees such as oaks, maples, beeches, and aspens have wide, flat leaves. Most broad-leaf trees are deciduous, which means they lose all of their leaves in one season each year. Their seeds develop inside fruits, nuts, or seed pods.
What are the parts of a tree?
A tree is made up of different parts that play a role in helping it to live and grow:
- Leaves – Leaves are the food factories of a tree. This is where photosynthesis takes place. Tiny holes called stomata , on the under surface of the leaves, let in carbon dioxide needed for photosynthesis and let out oxygen. Water vapor also exits through the stomata.
- Trunk and Branches – The trunk provides support for branches, which in turn support the tree’s leaves. The trunk and branches contain the tree’s “pipes”—the tubes that transport water and nutrients to the leaves and sugar to the rest of the tree. They also contain the growing layer of the tree that makes the trunk, branches, and roots of the tree thicker each year.
- Bark – Bark is a very important part of a tree. It acts as a protective coating, warding off insects and disease, and protecting the inner tissues against damage from storms or extreme temperatures. The bark of certain species also protects the tree from fire. Bark may be thin, thick, spongy, rough, smooth, or covered with spines, depending on the type of tree. The bark of some species changes significantly with age.
- Roots – A tree’s roots help anchor the tree in the ground. They also absorb water and nutrients from the soil. Trees have lateral roots that spread out from the tree and cover a broad area. Many trees have a taproot that grows straight into the ground.
- Seeds – Seeds are plant embryos with protective coverings. They contain all the materials necessary for plants to begin growing, including a small supply of food. Seeds come in many different forms and shapes and may be found in fruits, nuts, seed pods, or cones.
Figure 2: A tree’s growth rings can be used to tell how old it is.
What are tree rings?
A tree ring, or growth ring, is a layer of wood produced by a tree during one growing season. Looking at a cross-section of a tree, you can tell how old the tree is by counting the rings. You can also determine the growing conditions that the tree experienced. Wide rings indicate that the tree had plenty of sunshine, air, water, and nutrients, while narrow rings often indicate less favorable conditions for growth.
How can you tell trees apart?
You can tell one tree from another by looking at the trees’ leaves, bark, and tree shape.
- Leaf Shape – Different trees differ in the overall shape of their leaves. Some have long, slender leaves or needles, some have oval-shaped leaves, and some have triangular-shaped leaves. The bases of leaves may be heart-shaped, rounded, or squared, and the tips of leaves may be tapered, rounded, notched, or pointed.
- Leaf Margin – Some leaves have teeth (are serrated) along their edges or margins, some leaves are lobed, and some leaf margins are smooth.
- Leaf Texture – Some leaves are completely hairy, others have hairs on only one side, and others are completely smooth. Leaves may also be thick or thin, rough or waxy.
- Simple or Compound – Simple leaves have only one piece to them. When most people think of leaves, they think of simple leaves. Compound leaves, on the other hand, are made up of several leaflets.
- Leaf Arrangement – Some leaves grow in whorls around the twig. Other trees have alternate leaves that are staggered along the twig or opposite leaves that grow in pairs along the twig. The leaves on needle-leaved trees also grow in different arrangements; they may grow in clusters of two, three, or more.
- Fruit and Flowers – Different trees produce different kinds of fruit, such as berries, winged seeds, nuts, or pods. Different conifers produce different kinds of cones. Different trees also have different flowers. The shape, color, texture, size, and other characteristics of the fruit, cones, and flowers can be used to identify trees.
- Bark – A tree’s bark may be shaggy, smooth, or rough; it may have deep furrows or markings. It may also be white, brown, gray, or other color.
- Tree Shape – Different kinds of trees have a different shape or habit. Some have branches that spread out to form a wide crown, while others may rise narrowly like a column.
Why do some trees drop all their leaves in the fall?
In temperate regions, many trees lose all their leaves in the fall, which helps protect the tree from winter’s freezing temperatures. Trees that drop their leaves in one season are called deciduous trees. As winter approaches, colder temperatures and shorter days trigger responses within the tree. The cells at the base of each leaf stem begin to die, forming a barrier that keeps water and nutrients from traveling to the leaf.
Chlorophyll, the green pigment in the leaves, starts to break down, and other leaf pigments begin to show through or accumulate. These changes bring about the yellow, orange, and red colors of fall. As the cells at the base of the leaf stem die, they also weaken the leaf’s attachment to the twig. When the attachment breaks, the leaf falls to the ground.
With the leaves gone, the tree is less likely to suffer damage from freezing. However, the tree cannot photosynthesize without leaves. So, deciduous trees remain dormant in the winter until the longer days and warmer weather of spring trigger their new leaves to grow.
How do some trees stay green all winter?
In contrast with deciduous trees, evergreen trees keep their leaves throughout winter. This enables them to photosynthesize later in the fall and start earlier in the spring than deciduous trees.
Evergreens have several different features that help them survive cold, wind, and snow. First, the trees themselves are narrow, which makes them less vulnerable to heavy loads of snow that would otherwise break a tree’s branches. Their narrow leaves are also covered by a thick layer of wax, which keeps them from drying out through the long winter. In addition, the leaves contain chemicals that act as an antifreeze, preventing ice from forming inside the leaves; these chemicals are what give evergreens their characteristic scent.
What are tree buds?
In deciduous trees, tiny leaves, stems, and flowers are located on the twigs in packages called buds, which you can see in winter.
These buds are made of tough scales that form a waterproof case around the miniature tree parts. In spring, as the temperature warms and days become longer, sap rises from the roots to the branches; the scales fall off the buds; and the tree’s leaves, stems, and flowers begin to unfurl and grow. During the summer, the tree begins to develop new buds for the following year.
For many animals, tree buds are a concentrated food source. During the winter, animals such as grouse, deer, squirrels, and rabbits feast on buds.
What is a tree’s habitat?
Habitat refers to the place where an organism lives. A plant’s or animal’s habitat provides it with everything it needs to survive and reproduce, including its specific needs for food, water, shelter, and space.
Trees can be found in a wide range of habitats—from a city lot to a country wood to a mountain meadow. The trees that thrive in a given habitat are suited to the special conditions found there, including the particular climate, topography, and soil.
What other living things can live in a tree?
Trees provide shade, shelter, and sources of food for animals and plants. A tree may serve as part of an organism’s habitat, or it may be the organism’s entire habitat. For example, an oak tree may provide food for squirrels and nest sites for crows. But lichens and moss get everything they need right on the tree.
Snags, or standing dead trees, also provide habitat for a number of different species. Tree frogs and beetles live under a snag’s bark. Woodpeckers and other birds feed on the insects that live in snags. Chickadees nest in cavities created by woodpeckers. Squirrels and deer mice store food in them.
How do people use trees?
People use trees in many different ways. They clean our air, hold soil in place, and help to filter our water. Trees also beautify our homes and cities and are a source of inspiration and reflection. For children, they provide a structure for climbing and branches for swinging. For everyone, trees provide shade for resting. Trees also beautify our homes and cities, and are a source of inspiration and reflection. In addition, they clean our air, hold soil in place, and help to filter our water.
Trees also provide us with many different products, including paper, which is made from wood fiber. Here are just a few of these products:
- Wood – Lumber for building, wood furniture, baseball bats, wood blocks, toothpicks
- Food – Apples, cinnamon, chocolate, maple syrup, oranges, walnuts
- Paper – Books, newspapers, paper towels, packages, toilet paper
How can I help children find signs of animal life in trees?
Even in the most sterile-looking environment, you can usually find some signs of animal life in or around a tree. Most of the animals and animal signs your students find will likely be insects and other small creatures. In an urban schoolyard, for example, students can find things such as spider webs, ants among the branches or on the trunk or exposed roots, or insects buzzing around. Remind students that people are animals, too. Around the schoolyard, they’ll find plenty of signs of “people life.”
Where can I get more information?
For more information about trees, their role in habitats, and their importance to people, please check out one or more of the books listed in the Literature Connections section of each lesson.
