Everywhere you look, everywhere on Earth, you will find life. Biodiversity exists in every corner of the planet. Some examples of biodiversity you can see. A lot you cannot. Biodiversity is found in large biomes as well as microbiomes.
Life thrives in places you might expect, such as in rainforests or oceans. But it also thrives in unlikely places, including deserts and the Arctic. Biodiversity is even found in ice and volcanoes. Life is everywhere!
While biodiversity is found in every corner of the planet, it is not evenly distributed, or spread around. Colder ecosystems tend to have less species diversity than warmer ones. The study of the distribution of species, and the patterns of distribution across the planet, is called biogeography.
ESSENTIAL QUESTION
Where is biodiversity found?
WORDS TO KNOW
biome: a large natural area with a distinctive climate, geology, set of water resources, and group of plants and animals that are adapted for life there.
biogeography: the study of the distribution of biodiversity on Earth.
precipitation: the falling to Earth of rain, snow, or any form of water.
geography: the features of a place, such as mountains and rivers.
In biogeography, scientists look at species diversity in an area. They also look at the size of the population of each species, along with other factors. This helps scientists to better understand the factors that have shaped biodiversity in Earth’s history and to predict how biodiversity will respond to our changing planet.
Biodiversity is unevenly distributed because species rely on many different factors to survive. Abiotic factors such as temperature, precipitation, and geography all affect species diversity and species populations in different areas. Some species live in fresh water, while others live in salt water. Some species thrive in extremely cold climates, while others are adapted to living in hot climates. Still others live in very wet, humid climates, while others are adapted to dry climates.
The darker red places on the map have the highest human population density.
credit: daysleeperrr (CC0 1.0)
polar regions: the areas of the earth around the North and South Poles, within the Arctic and Antarctic Circles.
temperate zone: the area of the earth that lies between the tropics and the polar regions.
tropical zone: the area of the earth around the equator.
tundra: a treeless Arctic region that is permanently frozen below the top layer of soil.
lichen: a plant-like organism made of algae and fungus that grows on solid surfaces such as rocks or trees.
savanna: a dry, rolling grassland with scattered shrubs and trees.
Biotic factors also affect species diversity and species populations. In places with high biodiversity, more life can be supported than in places with low biodiversity. Life depends on other life to survive.
Even the distribution pattern of humans is uneven, affected by both abiotic and biotic factors. Few people live in the cold polar regions. The closer to the warmer temperate zone and even warmer tropical zone you look, however, the more people there are.
There are also few people who live in extreme desert climates or high mountain ecosystems. More people live in areas with ample rainfall and moderate temperatures suitable for farming. Humans tend to live in areas that have many resources, which include biodiversity. These biotic factors are important to people for food, shelter, fuel, and clothing.
DID YOU KNOW?
Rainforests cover less than 2 percent of the earth’s surface but host more than 50 percent of Earth’s biodiversity!
Arctic Adaptations
All organisms living in polar regions have adaptations that allow them to survive in the harsh climate. The polar bear has a thick fur coat and a layer of blubber to keep it warm. Snowshoe hares have fur coats as well, but they also cluster together for warmth. Plants in the polar region stay close together, too! They are low-lying plants and can photosynthesize under a layer of snow. Flowering plants have a brief seasonal cycle, so they can produce flowers quickly once warmer weather arrives. These plants are also drought-tolerant. Even the microorganisms must be adapted to withstand the cold in the polar regions. Some cyanobacteria, researchers have discovered, wrap themselves in a complex coating made of sugar that protects their cells from freezing.
If you visit the Arctic tundra, you would find low species diversity. You might see a large herd of caribou, a polar bear, or an Arctic fox in the Arctic region. In the Antarctic, you will find several species of penguins and seals. You will also see moss, lichen, and other small plants in these polar regions during their summer season.
Countless microorganisms also survive in the polar regions. Every species in these regions, from the largest polar bear to those tiny microbes, is well-adapted to the harsh environment and is an important part of those ecosystems.
As you move south from the Arctic, species diversity increases. You will see a greater variety of plants, animals, fungi, bacteria, and other microorganisms as you pass through forests, savannas, and grasslands in the temperate zone. As you get closer to the equator in the tropics, the biodiversity is even greater.
The blue poison dart frog lives in the rainforest.
credit: Michael Gäbler (CC BY 3.0)
Rainforests have the greatest biodiversity on Earth. The warm, tropical regions support millions of different species. If you stood in the middle of a rainforest, you might see howler monkeys, toucans, sloths, tree frogs, bromeliad plants, orchids, leafcutter ants, sharpshooter leafhoppers, and countless other species. In the Amazon rainforest alone, scientists have identified more than 40,000 plant species, 400 mammals, 1,300 birds, close to 400 reptiles, more than 400 amphibians, and approximately 3,000 species of fish. That doesn’t even include the microorganisms!
endemic: a plant or animal that is native to only a certain area.
producer: a part of a food chain that includes all plants that make their own food through photosynthesis.
food chain: a community of plants and animals where each is eaten by another higher up in the chain.
nutrients: substances in food and soil that living things need to live and grow.
salinity: the amount of salt in water.
Endemic Species
Some species are found in only one place on the planet—they are called endemic species. These species are usually limited to a certain ecosystem, small or large, because they are uniquely adapted to that environment. Because of this specialization, these species cannot move to other habitats. The wet-rock physa, a snail the size of a pinhead, is one endemic species living only in Zion National Park in Utah. The Texas blind salamander is found exclusively in water-filled caves in one part of Texas. And the flowering Holgrem’s buckwheat plant can be seen only in Great Basin National Park in Nevada.
One explanation for greater species diversity in the tropics is the abundance of both sunlight and rain, as well as warm temperatures. In that region, the sun is overhead for the same number of hours a day all year round. Therefore, the sun’s energy supports the continual growth of producers of the food chain—plants—all year round. Regular rainfall and moderate temperatures also help the producers to grow. This plant life then supports other life in the region.
Longer periods of tropical conditions over greater areas of the planet throughout Earth’s history are another reason biodiversity is unevenly distributed. Species have lived in tropical climates longer than in cooler ones. These tropical species have had longer to adapt and evolve into new species.
Bizarre Biodiversity
Archer Fish: The archer fish got its name because it takes aim at an insect above the water surface and shoots a mouthful of water at it to knock the insect into the water to eat it.
credit: James St. John (CC BY 2.0)
Life on Earth is not found just on land. Lakes, streams, wetlands, ponds, and oceans are full of biodiversity, too. In the ocean alone, during the Census for Marine Life in the early 2000s, scientists documented 250,000 known marine species, and that count doesn’t include microbes. Scientists estimate that another 750,000 species, plus more than a billion species of microbes, live in the ocean.
DID YOU KNOW?
Biodiversity is so great on some tropical reefs that there may be 1,000 different species within 1 square meter.
Just as on land, many different ecosystems exist within the ocean. And just as on land, life in the ocean is not evenly distributed among them. This distribution is affected by many factors, including temperature, sunlight, nutrients, salinity, and water pressure.
Some places in the ocean, such as coral reefs in the tropics, are full of life. In fact, because of their biodiversity, coral reefs are often called the rainforests of the sea.
Welcome to a rainforest of the sea—a coral reef!
estuary: a body of water where a river meets the ocean, with a mix of fresh water and salt water.
chemosynthesis: the process some organisms use to create energy from chemicals instead of the sun.
extremophile: an organism that thrives in environments that most other life forms cannot live in.
permafrost: permanently frozen subsoil and rock just beneath the surface of the ground.
global warming: an increase in the average temperature of the earth’s atmosphere, enough to cause climate change.
dormant: in a state of rest or inactivity.
infectious: illness that is spread by germs or viruses.
Check out this interactive site and find information about the biodiversity found in the earth’s oceans, as well as links to explore further.
marine shining sea
Estuaries are places where rivers meet the ocean. They are very productive ecosystems, providing food, nurseries, and migration stopovers for many marine species. In estuaries, you might find mangrove trees or marshes, sea otters and herons, or many other species such as fish, seahorses, crabs, and oysters.
Other places in the ocean, such as colder waters, places far from land, and the very deep parts of the ocean, have very low biodiversity. Yet, as you will learn, even though the biodiversity is low, there is still life in these extreme places.
Census of Marine Life
During a 10-year period, scientists from 80 different countries collaborated to record biodiversity in the oceans. They also looked at the distribution and populations of species. To collect this information, more than 2,700 scientists participated in 540 different marine expeditions. They explored coral reefs, shorelines, the deep-sea floor, open ocean, underwater mountains called seamounts, the Arctic and Antarctic regions, and more. Their work contributes to our understanding of oceans past and present, which can help with future planning to protect marine species. Despite the scope of the project, however, 95 percent of the ocean is still unexplored. Because of that, scientists estimate that 91 percent of all ocean biodiversity has not yet been formally identified and recorded!
Not All Life Needs Oxygen or Sunlight
Humans would certainly consider an environment without oxygen or sunlight extreme. So would most of the other species on Earth. However, not all life needs oxygen or sunlight to thrive. Some microorganisms living at the bottom of the deep ocean, for example, use a process called chemosynthesis to convert chemicals into energy instead of using sunlight for photosynthesis. These microbes are found living near hydrothermal vents that spew the chemicals the microorganisms use. Other microorganisms, such as some species of bacteria, are anaerobic. They survive in environments with little or no oxygen, soil, and water, and even inside living animals! Scientists also discovered microscopic multi-cellular animals called Loricifera living in the oxygen-free sediment at the bottom of the Mediterranean Sea.
EXTREMOPHILES
Of all the places on Earth you may not expect to find life, ice, volcanoes, and the deep, deep ocean might come to mind. But even in these extreme environments, scientists have discovered life—hardy organisms called extremophiles thrive in environments where most other species could not exist.
Some of these extremophiles are found in or under ice in the polar regions. In both the Arctic and Antarctic ice, researchers have found living bacteria. The populations are small, but they are there and alive despite the low-nutrient, low-temperature environment.
Some bacteria and viruses have been locked away in the ice for tens of thousands of years! As glaciers retreat and permafrost melts due to global warming, ancient bacteria and viruses that were dormant are making a comeback. Scientists are concerned that some of these life forms that have survived in this extreme environment for hundreds of thousands of years could become a source of deadly infectious diseases today.
antifreeze: a liquid that is added to a second liquid to lower the temperature at which the second liquid freezes.
terrestrial: related to land.
toxic: poisonous.
Lakes buried beneath the ice are another place that extremophiles live in the polar regions. Locked under more than 2 miles of ice in eastern Antarctica is Lake Vostok. The water in this lake—roughly the size of Lake Ontario on the U.S. and Canadian border— has been trapped underneath the ice for more than 15 million years. No light reaches the water. Yet scientists discovered a unique ecosystem in the water, based on minerals in the lake and rock instead of on sunlight. The biodiversity in this lake includes fungi, Archaea, thousands of bacteria, and other microbes.
DID YOU KNOW?
In 2005, scientists at NASA were able to revive bacteria that had been trapped for 32,000 years in a frozen pond in Alaska.
The vivid colors around the Grand Pragmatic Spring at Yellowstone Park are caused by the microbes that live there!
credit: Jim Peaco, National Park Service
Bizarre Biodiversity
Icefish: These Antarctic fish have blood that acts like antifreeze. They can withstand cold temperatures that would freeze other fish.
credit: Valerie Loeb, NOAA
On the other end of the temperature spectrum, very hot places have biodiversity, too. One such place is in Yellowstone National Park. The hot springs and mud pots there are home to a variety of microbes. The temperatures in the hot springs and mud pots are too hot for humans to touch. But the organisms living there survive in temperatures hotter than 175 degrees Fahrenheit (79 degrees Celsius). That’s almost boiling!
Researchers have also explored in and around volcanoes, which are hot and acidic with few nutrients. Despite the harsh environment, they have discovered bacteria, fungi, and other organisms living around volcanoes.
However, the inside of an active, terrestrial volcano is another story. The lava is simply too hot to support life. Remember how the earth didn’t have life at first because the entire planet was covered in molten rock? It had to cool for millions of years before the first life forms appeared.
Many volcanoes are found on the sea floor as well. Near the deep-sea volcanoes and hydrothermal vents, the water spewing out can be as hot as 660 degrees Fahrenheit (316 degrees Celsius). It is also full of toxic chemicals. Yet scientists have discovered bacteria, shrimp, worms, crabs, barnacles, and more thriving in this extreme environment. In some ways, these volcanoes and vents are oases for life in the ocean.
Caves are another extreme environment that contain fragile ecosystems and sustain rich biodiversity. Go on a cave exploration by watching this National Geographic video.
Nat Geo inside caves
bioluminescent: when living things give off light by hosting a chemical reaction in their bodies.
The deep, deep ocean is another extreme environment on Earth where life can be found. The Mariana Trench is the deepest part of the ocean in the world—it is 7 miles below the surface of the ocean. No light or oxygen exists down there, it is very cold, and the water pressure is tremendous. However, researchers have discovered bizarre creatures thriving there, including the bioluminescent anglerfish, crabs, and hundreds of types of microorganisms. Even the mud on the sea floor contains more than 200 different microorganisms.
DID YOU KNOW?
More than 17,000 species live in the deep ocean, where there is no light.
As you will learn, all this biodiversity found everywhere on the planet has a part in keeping Earth’s ecosystems healthy. Biodiversity matters!
A striped anglerfish
credit: SEFSC Pascagoula Laboratory; Collection of Brandi Noble, NOAA/NMFS/SEFSC
Beaches are a bit of an extreme environment. There isn’t much space. Sometimes there’s water, other times the tide goes out and there’s none. And waves are constantly pounding on the ecosystem. But, as in any ecosystem, the species that live there are well adapted to the environment. Microscopic organisms are small enough to move around between the grains of sand. They have other adaptations to protect them from pounding waves and to keep them from washing away.
Want to see what lurks in the sand? Check out this video to see the magnified microorganisms living at the beach.
Nat Geo inside caves
Sand is also home to billions of bacteria. A 2017 study revealed that on one grain of sand there may be between 10,000 and 100,000 microorganisms. To get a better idea of what that means, a grain of sand has more microorganisms than Helena, Montana, has residents!
Now that we’ve explored some of the places where biodiversity can be found, let’s turn our attention to why this is important. In the next chapter, we’ll find out why biodiversity matters so much to all life on Earth!
ESSENTIAL QUESTION
Where is biodiversity found?
MAKE BIOGAS
Every organism in an ecosystem plays an important role. Even when an organism dies, it helps the ecosystem function because it provides food for other organisms. Some of the organisms to benefit are microorganisms, which occasionally feed on dead or decaying matter. We can’t see these tiny organisms, but you can see the results of their work.
›Fill a plastic bottle with organic matter, such as dead leaves and compost.
›Stretch an uninflated balloon over the opening of the bottle. Make sure there is a tight seal between the bottle and the balloon. Place the bottle near heat or in the sun.
›What do you think will happen? Why? Start a scientific method worksheet in you science journal. Include your predictions. During the next week or so, observe the bottle and balloon. Record your observations in your journal.
Consider This
Reproduce the experiment using different organic materials and different light and temperature conditions. What happens? How are the results different from your original experiment?
Why do you think you got the results you did? What was going on in the bottle? What were the microorganisms doing? Do some research to see how scientists apply this knowledge to solve real-world problems.
Wetlands are found all over the world. Once thought of as wastelands to be drained, dredged, and filled, wetlands are now recognized for the important ecosystem services they provide, including purifying water and protecting against flooding and erosion. There are many kinds of wetlands—swamps, lagoons, bogs, tidal marshes, and more. They can be enormous, such as the Prairie Pothole Region in the northern Great Plains, or as tiny as a puddle. No matter their size or location, these wetlands are home to great biodiversity.
›Do some research to find a wetland near you. Take along your science journal, binoculars, a camera, and a friend.
›How many different species do you see? List them in your journal. Look for plants, birds, mammals, fish, reptiles, amphibians, and insects.
›Find a comfortable place to sit quietly for 10 to 15 minutes. Observe what happens when you are quiet. Add the additional species you spot to your list. Take pictures or draw sketches of the biodiversity you find in the wetland. Also note the abiotic factors that influence the ecosystem.
Consider This
What species do you think might be in the wetland that you cannot see? Consider taking a water sample home to look at more closely under a microscope. (NOTE: Ask an adult for permission and use caution around water.) Using your notes, consider how all the biotic and abiotic factors in this habitat are interconnected. This may require more research or another visit , the area to talk to a park ranger, scientist, or other expert. Determine the ecosystem services provided by the wetland you visited and predict what might happen if that wetland was damaged or destroyed.
WORDS TO KNOW
wetlands: low areas filled with water, such as a marsh or swamp.
ecosystem services: the important benefits provided by ecosystems to keep the earth’s air, water, and soil healthy.
Even the human body is home to millions of microbes. The community of microbes varies depending on where they live in your body, just as species vary within different ecosystems on the planet. Microbial communities also vary from person to person. While this may sound a bit disgusting at first, these microbes are very important to your health. Just as they do in other ecosystems, microbes help keep your body in balance. You are healthier with them than without them!
Watch this short video for an introduction to the human gut biome.
TED-Ed You Are Microbes
›One of the most important and complex microbiomes in the human body is in the gut. Research the human microbiome in your own gut. Find out what factors influence the different types of microbes there. Some factors are out of our control, such as genetics, but other factors we can control. Learn what you can do to promote a healthy gut microbiome and to keep it balanced.
›Make a chart of the things you do that are good for your gut microbiome and things that need work. Based on your findings, make a plan to promote a healthier gut. Consider, for example, focusing on what you eat, how much water you drink, and the time you spend outdoors. Think about getting friends or family members to join you.
›Before you change your routine or your diet, take notes about how you feel most of the time, morning, midday, and in the evening. Also make note of how you feel after a meal. Full? Energized? Sluggish? Do you have a stomachache? Cramps? Follow your plan of action faithfully for a full week.
Sand
When you look at a sandy beach, it may seem like it has little biodiversity. You may come across a crab or shore birds, but not much else. But if you magnify a handful of sand, you will discover millions of organisms. Just as in soil, these microorganisms in the sand live in their own unique ecosystem. And the organisms you find will vary between beaches and will also vary depending on their location on a single beach.
This cluster of E. Coli bacteria is an example of a microbe that thrives in beach sand.
credit: U.S. Department of Agriculture
Consider This
How do you feel since you’ve focused on promoting healthy gut microbes? Better? Worse? Explain. Was making changes in your routine easy or difficult? Can you keep it up? Sometimes it takes a few weeks to develop new habits. Keep following your plan of action for a full month. How do you feel after that much time? Is it hard not to cheat?
How much do you know about your own microbiome? This online quiz will test your knowledge and present valuable facts about the microbes in your body.
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Water is alive with microbes! The types of microbes you find in water will, of course, vary depending on where you take the water sample from.
Caution: Be careful around water—always have an adult with you!
›Collect water from five different places near you. Each time you collect a sample, carefully label each with the location the sample was taken from, the time of day, and the date.
›At home, predict what you will see when you observe the samples closely. Start a scientific method worksheet in your science journal.
›First, look at the sample with just your eyes. Can you see anything in the water? Now, look at each sample separately under the microscope. What microorganisms are in the water sample? Make a chart to record your findings, including a quick sketch. Note the behavior of the different organisms.
Consider This
How are the five samples the same? Different? Is this surprising? Why or why not? You could repeat the experiment, taking samples from the same places but at different times of the year. Compare the differences. Alternatively, you could take different samples from the same water source in different areas of that source. For example, in a pond, take samples from different places near the shore, from deeper in the water, or even, if possible, from the center of the pond. Ask an adult before heading out to deeper water, and always wear a life vest.
DID YOU KNOW?
Of all the water on Earth, less than 1 percent is accessible freshwater and suitable for filtering to use as drinking water.
American Museum human biome quiz