Step outside and take a look around. What kinds of creatures do you see? Any insects flying through the air? Any dogs, cats, birds? What about flowers and other plants? Don’t forget the organisms you can’t see—there are plenty of living species that are visible only with microscopes.
Humans share the earth with millions of other species. Millions! This variety of life on Earth is called biodiversity. Biodiversity includes plants, animals, fungi, bacteria, and microorganisms of all shapes and sizes. Biodiversity includes you! It also refers to large species such as blue whales and polar bears and giant redwood trees. There are medium-sized species such as saguaro cacti, wolves, and dolphins, as well as small species—ladybugs and tree frogs and forget-me-not flowers.
ESSENTIAL QUESTION
How is everything on the planet related to everything else?
organism: a living plant, animal, or single-celled form of life.
species: a group of living things that are closely related and can produce offspring.
biodiversity: diversity is a range of different things. Biodiversity is the variety of life on Earth.
fungi: the plural of fungus, an organism that has no leaves, flowers, or roots and that lives on dead or rotting organic matter. Mushrooms are a fungus.
bacteria: microorganisms found in soil, water, plants, and animals that are often beneficial but sometimes harmful.
microorganism: a living thing so small that it can be seen only with a microscope.
ecosystem: an interdependent community of living and nonliving things and their environment.
biotic: of or relating to living things.
abiotic: of or relating to nonliving things such as temperature, wind, precipitation, soil type, and more.
kelp: a tall, brown seaweed that grows in forests in shallow ocean waters close to shore.
This National Geographic video is a photographic introduction to the wonders of the amazing biodiversity on Earth. Check it out!
Nat Geo biodiversity video
Biodiversity includes organisms so small they can be seen only with a microscope! In fact, in every square foot there are hundreds, sometimes thousands, of species growing, squirming, wiggling, flying, multiplying, eating, and thriving.
Why is this important? Why do we care that there are so many different species, especially when we can’t even see them?
Polar bears are part of our biodiverse world!
All life on Earth is interconnected. Organisms, together with their physical environment, form a community called an ecosystem. Within an ecosystem, both the biotic and abiotic—or living and nonliving—factors work together to maintain the balance of nature. If one part of the ecosystem changes or disappears, the whole system is out of balance. People call this the web of life because if one connection breaks, the whole web may be affected.
DID YOU KNOW?
The word biodiversity was first used in the mid-1980s as a shorter way to say “biological diversity.” Today, it is a common term.
The web of life is like a well-tuned machine. All the biotic and abiotic factors are the nuts, bolts, and gears that each play a role in keeping the machine in good working order.
For example, along the shorelines of California, sea otters eat sea urchins. Sea urchins eat giant kelp. When the number of sea otters drops, the number of sea urchins rises. All those sea urchins then destroy the giant kelp forests.
Kelp forests are also affected by changes in water temperature, light, and pollution.
A giant kelp forest
credit: Clinton Bauder (CC BY 2.0)
erosion: the gradual wearing away of the earth’s surface, usually by water or wind.
carbon dioxide (CO2): a colorless, odorless gas. Humans and animals exhale this gas while plants absorb it—it is also a byproduct of burning fossil fuels.
atmosphere: the mixture of gases that surround a planet.
Without the kelp forests, dozens of species that rely on the kelp for survival are at risk. Kelp helps protect shorelines from erosion and absorbs carbon dioxide (CO2) from the atmosphere.
Kelp forests are just one ecosystem. Other large ecosystems include deserts, forests, grasslands, wetlands, jungles, and oceans. Ecosystems can also be small, such as a cave or pond or tide pool, or even microscopic, including the ecosystem that exists under a rock. The parts within a single ecosystem are interconnected, and all the world’s ecosystems are connected to each other.
They are like pieces of a puzzle that make up planet Earth.
DID YOU KNOW?
John Muir (1838–1914), an American naturalist, author, and environmentalist, once commented, “Whenever we try to pick out anything by itself, we find it hitched to everything else in the universe.”
This fungus is growing on a tree. Take a magnifying glass outside to look at a tree. What do you see on the bark? On the leaves?
LIFE ON A TREE
To better understand biodiversity and how ecosystems are interconnected, let’s take a look at a tree. The tree itself is a living organism. What else lives there? A bird, maybe. Perhaps a squirrel. In some parts of the world, there might be a monkey or a sloth up there. Look closer. Is there a vine growing on the tree? There could be moss, too, or some other type of plant. Fungi can also grow on trees.
Look even closer! You might spot insects on the bark, such as ladybugs, aphids, spiders, caterpillars, or beetles. And, most likely, there are insects under the bark, too.
boreal forest: a forest of coniferous trees found in the cold temperatures of the Northern Hemisphere.
genetic diversity: the variety of genes within a species.
gene: instructions within cells that affect how an organism will look, grow, and act.
cell: the smallest unit, or building block, of an organism.
adapt: to make changes to survive in new or different conditions.
species diversity: the variety of species living in an area.
mammal: an animal that has a constant body temperature and is mostly covered with hair or fur. Humans, dogs, horses, and mice are mammals.
current: the steady flow of water or air in one direction.
equator: an imaginary line around the earth, halfway between the North and South Poles.
theory of evolution: a scientific theory that explains how species change through time and how all species have evolved from simple life forms.
DID YOU KNOW?
The largest organism on Earth is a fungus! This giant underground fungus covers almost 4 square miles of land in the Blue Mountains of Oregon.
There is also life in and on the tree that you can’t see. Bacteria, both helpful and harmful types, often grow in trees. There are many other microorganisms within the tree, all hidden from our sight.
There are an estimated 3 trillion trees on the planet. Not only are trees home to a huge number of species, they also give us oxygen, food, and shelter. They reduce the pollution in the air. Their roots help to hold soil in place. They provide shade on hot summer days. And, especially important today, they pull carbon dioxide out of the atmosphere.
Each tree is a miniature ecosystem for the species that depend on it and the tree is also part of a larger ecosystem, such as a rainforest or boreal forest. Trees play an important role in the overall health of the earth.
LEVELS OF BIODIVERSITY
Scientists study biodiversity on three levels: genetic, species, and ecosystem.
Genetic diversity is the variety of genes found within a species. Genes are the traits passed from parents to their offspring that affect behavior and looks. They are the instructions for the cells in an organism about how to grow and work. Your own genes were handed down to you from your biological parents. These genes determined your eye color, your height, and more.
Take dogs as an example. Some are large, some are small, some have floppy ears, others have pointy ears that stick up from their heads. There are hound dogs, retrievers, cattle dogs, lap dogs, guide dogs, and guard dogs. They all belong to the same species—dog. But the differences in behavior and appearance is because of the genetic diversity within the species.
When looking at biodiversity in an area, genetic diversity refers to the variety of genes in a population. And, the more genetic diversity there is, the more likely species will be able to adapt to changing environments. That’s because some individuals will have traits that make them better able to handle changes and fight off new diseases.
So, even when things change in an environment, genetic diversity allows some individuals of the species to survive.
Species diversity is the number of different species in an area. This includes plants, animals, fungi, bacteria, and microorganisms. Coral reef ecosystems have great species diversity. They are sometimes called the rainforests of the sea because of the amount of species diversity. Within a reef ecosystem, there are thousands of species of plants and animals, including fish, crabs, eels, turtles, sharks, shrimp, sponges, marine mammals, and more. These species interact with each other and the environment.
Galápagos Islands
The Galápagos Islands lie more than 600 miles off the west coast of Ecuador, in the Pacific Ocean. This area sits where three ocean currents meet and it straddles the equator. Because of this location and isolation, the collection of 19 islands is well-known for its biodiversity, much of which is found nowhere else in the world. The English naturalist Charles Darwin (1809–1882) visited the islands during a round-the-world tour in 1835. It was on the islands that Darwin developed his theory of evolution.
ecosystem diversity: the variety of ecosystems in a certain region.
habitat: a plant or animal’s home, which supplies it with food, water, and shelter.
Scientists have named and recorded approximately 2 million different species on Earth. But, there are millions of species out there that have not yet been discovered! Scientists don’t agree on the total number of species on Earth, but they estimate that there are between 2 million and 12 million. Some studies have even suggested that there could be a trillion species sharing the planet with us!
Within an ecosystem, species diversity contributes to the overall stability of the ecosystem. In other words, as species diversity increases, so does the health of the ecosystem. This also means that the ecosystem will be better able to handle changes within it.
Ecosystem diversity is the variety of ecosystems, habitats, and biological communities that exist in an area. This includes both biotic and abiotic factors. One important thing to keep in mind is that ecosystems come in all sizes. They also don’t have definite borders. Therefore, different ecosystems are interrelated, so the loss of one ecosystem and the species within it will affect other ecosystems around it.
The greater the ecosystem diversity in an area, the healthier the entire area will be, and the better able it is to adapt to changes in the environment.
To keep the levels of biodiversity straight, think of it this way: genetic diversity is the variety of genes within a species, species diversity is the variety of species within an ecosystem, and ecosystem diversity is the variety of ecosystems within an area.
In Biodiversity, you’ll learn more about these three different types of biodiversity and what they all have to do with you, a human! You’ll discover some of the ways that biodiversity on Earth is threatened and what every individual can do to help protect the amazing variety of organisms that share our planet. Let’s go!
DID YOU KNOW?
Biodiversity is not evenly distributed among ecosystems. Colder ecosystems tend to have less species diversity than warmer ones.
Good Science Practices
Every good scientist keeps a science journal!
Scientists use the scientific method to keep their experiments organized. Choose a notebook to use as your science journal. As you read through this book and do the activities, keep track of your observations and record each step in a scientific method worksheet, like the one shown here.
Question: What are we trying to find out? What problem are we trying to solve? |
Research: What is already known about the problem? |
HypothesisAPrediction: What do we think the answer will be? |
Equipment: What supplies are we using? |
Method: What procedure are we following? |
Results: What happened? Why? |
Each chapter of this book begins with an essential question to help guide your exploration of biodiversity and the environment. Keep the question in your mind as you read the chapter. At the end of each chapter, use your science journal to record your thoughts and answers.
ESSENTIAL QUESTION
How is everything on the planet related to everything else?
DISCOVER THE THREE LEVELS OF BIODIVERSITY
The three levels of biodiversity are all around you. Take a closer look and find samples in a nearby ecosystem! Use your senses to see, hear, smell, and touch the variety of life around you.
Caution: Do not taste anything you find outdoors unless you have an expert adult with you who can identify it as something safe to eat!
›Take a walk near your home or school. After you’ve been out for a while, find a spot to comfortably sit.
›Start by observing the genetic diversity around you. Pick one species to observe, without touching. If you are in a forest, you might look at a stand of ponderosa pine trees, a family of ducks, or a group of mushrooms. How are the individuals different from one another? In your science journal, record how the different individuals of the same species look and act differently. This is genetic diversity.
›Now look further. How many different species can you see from where you are sitting? Record everything you notice. If you are on a beach, you might see different types of beach grass, shore birds, and sand crabs. This is species diversity.
›Finally, can you identify ecosystem diversity from where you sit? In the forest, that itself is an ecosystem. But there may also be a rotting log that is its own ecosystem, or a stream or pond. At the shore, there are ecosystems both in the water and on land. There may also be tide pools that are their own ecosystems.
Consider This
How might your observations change in a nearby natural area or different season? How about in an entirely different area? Each time you visit a natural area, take the time to observe what you see. Try to identify the levels of biodiversity there.
