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4.1: Biodiversity

Difficulty Level: At Grade Created by: CK-12

Understanding Biodiversity does not attempt to provide a complete review of biodiversity. For additional information about biodiversity, see the Communities and Populations chapter in the CK-12 Biology FlexBook® textbook at http://www.ck12.org/flexbook/book/2537 and the Ecology and Human Actions chapter in the CK-12 Biology I - Honors FlexBook® textbook at http://www.ck12.org/flexbook/book/829.

“If names are not correct, language will not be in accordance with the truth of things.” Confucius.

Biodiversity refers to the variety of life and its processes, including the variety of living organisms, the genetic differences among them, and the communities and ecosystems in which they occur. Scientists have identified about 1.9 million species alive today, each with their own unique scientific name. They are divided into the six kingdoms of life shown in the Figure below. Scientists are still discovering new species. Thus, they do not know for sure how many species really exist today. Most estimates range from 5 to 30 million species.

Diversity of life from Archaebacteria to Plants and Animals.

The Importance of Biodiversity

Human beings benefit in many ways from biodiversity. Biodiversity has direct economic benefits. It also provides services to entire ecosystems.

Economic Benefits of Biodiversity

The diversity of species provides humans with a wide range of economic benefits. Just a few of these are described below:

  • Wild plants and animals maintain a valuable pool of genetic variation. This is important because many domestic species are genetically uniform. This puts the domesticated species at great risk of dying out due to disease.
  • Other organisms provide humans with many different products, including timber, fibers, adhesives, dyes, and rubber.
  • Certain species may warn us of toxins in the environment. When the peregrine falcon nearly went extinct, for example, it warned us of the dangers of DDT.
  • More than half of the most important prescription drugs come from wild species. Only a fraction of species have yet been studied for their medical potential. Therefore, declining biodiversity can indirectly harm human health.
  • Other living things provide inspiration for engineering and technology. For example, the car design in the Figure below was based on the structure of a fish.

From flowers to fish, biodiversity benefits humans in many ways.

Ecosystem Services of Biodiversity

Biodiversity generally increases the productivity and stability of ecosystems. A large biodiversity helps ensure that at least some species will survive environmental change. It also provides many other ecosystem services. For example:

  • Plants and algae maintain the atmosphere. During photosynthesis, they add oxygen and remove carbon dioxide.
  • Plants help prevent soil erosion. They also improve soil quality when they decompose.
  • Microorganisms purify water in rivers and lakes. They also return nutrients to the soil.
  • Bacteria fix nitrogen as part of the nitrogen cycle and make the nitrogen available to plants. Other bacteria recycle the nitrogen from organic wastes and the remains of dead organisms.
  • Insects and birds pollinate flowering plants, including crop plants.
  • Natural predators control insect pests. They reduce the need for expensive pesticides, which may harm people and other organisms.

Why Study Biodiversity?

The economic services and benefits of biodiversity listed above are just a small sample of the reasons to study biodiversity. Every time a species goes extinct or an ecosystem is harmed, it can be argued that we are affected as well. So, as a species, we need to understand as much as we can about other species, especially the niche of other species and how they benefit their ecosystems. Benefits to humans are bound to result from the study of other species. See Biodiversity at http://vimeo.com/14105623 for additional information.

Millions of Unseen Species

A study released in August 2011 estimates that Earth has almost 8.8 million animal, plant, and fungi species, but we've only discovered less than a quarter of them. Recent newly discovered species have been very diverse: a psychedelic frogfish, a lizard the size of a dime, and even a blind hairy mini-lobster at the bottom of the ocean. There are potential benefits from these undiscovered species, which need to be found before they disappear from the planet. The study estimates that of the 8.8 million species, about 6.5 million would live on land and 2.2 million in the ocean. The research estimates there are 7.8 million animal species, followed by fungi with 611,000 and plants with just shy of 300,000 species. See http://news.yahoo.com/wild-world-millions-unseen-species-fill-earth-210051661.html for additional information.

If the 8.8 million estimate is correct, “those are brutal numbers,” said Encyclopedia of Life executive director Erick Mata. “We could spend the next 400 or 500 years trying to document the species that actually inhabit our planet.”

Biodiversity and Human Actions

Over 99 percent of all species that ever lived on Earth have gone extinct. Five mass extinctions are recorded in the fossil record. They were caused by major geologic and climatic events. Evidence shows that a sixth mass extinction is occurring now. Unlike previous mass extinctions, the sixth extinction is due to human actions.

Some scientists consider the sixth extinction to have begun with early hominids during the Pleistocene. They are blamed for over-killing big mammals such as mammoths. Since then, human actions have had an ever greater impact on other species. The present rate of extinction is between 100 and 100,000 species per year. In 100 years, we could lose more than half of Earth’s remaining species.

Causes of Extinction

This is one of the most powerful birds in the world. Could it go extinct? The Philippine Eagle, also known as the Monkey-eating Eagle, is among the rarest, largest, and most powerful birds in the world. It is critically endangered, mainly due to massive loss of habitat due to deforestation in most of its range. Killing a Philippine Eagle is punishable under Philippine law by twelve years in jail and heavy fines.

The single biggest cause of extinction today is habitat loss. Agriculture, forestry, mining, and urbanization have disturbed or destroyed more than half of Earth’s land area. In the U.S., for example, more than 99 percent of tall-grass prairies have been lost. Other causes of extinction today include:

  • Exotic species introduced by humans into new habitats. They may carry disease, prey on native species, and disrupt food webs. Often, they can out-compete native species because they lack local predators. An example is described in the Brown Tree Snake Figure below.
  • Over-harvesting of fish, trees, and other organisms. This threatens their survival and the survival of species that depend on them.
  • Global climate change, largely due to the burning of fossil fuels. This is raising Earth’s air and ocean temperatures. It is also raising sea levels. These changes threaten many species.
  • Pollution, which adds chemicals, heat, and noise to the environment beyond its capacity to absorb them. This causes widespread harm to organisms.
  • Human overpopulation, which is crowding out other species. It also makes all the other causes of extinction more severe.

Brown Tree Snake. The brown tree snake is an exotic species that has caused many extinctions on Pacific islands such as Guam.

Effects of Extinction

The results of a study released in the summer of 2011 have shown that the decline in the numbers of large predators like sharks, lions, and wolves is disrupting Earth's ecosystem in all kinds of unusual ways. The study, conducted by scientists from 22 different institutions in six countries, confirmed the sixth mass extinction. The study states that this mass extinction differs from previous ones because it is entirely driven by human activity through changes in land use, climate, pollution, hunting, fishing, and poaching. The effects of the loss of these large predators can be seen in the oceans and on land.

  • Fewer cougars in the western US state of Utah led to an explosion of the deer population. The deer ate more vegetation, which altered the path of local streams and lowered overall biodiversity.
  • In Africa, where lions and leopard are being lost to poachers, there is a surge in the numbers of olive baboons who are transferring intestinal parasites to human who live nearby.
  • In the oceans, industrial whaling led a change in the diets of killer whales, who eat more sea lion, seals, and otters and dramatically lowered those population counts.

The study concludes that the loss of big predators has likely driven many of the pandemics, population collapses, and ecosystem shifts the Earth has seen in recent centuries. See http://news.yahoo.com/loss-big-predators-disrupts-earth-ecosystem-study-181200945.html for additional information.

Disappearing Frogs

Around the world, frogs are declining at an alarming rate due to threats like pollution, disease and climate change. Frogs bridge the gap between water and land habitats, making them the first indicators of ecosystem changes. Meet the California researchers working to protect frogs across the state and across the world at http://www.kqed.org/quest/television/disappearing-frogs. Learn about the plight of the yellow-legged frog at http://www.kqed.org/quest/radio/plight-of-the-yellowlegged-frog.

Nonnative Species

Scoop a handful of critters out of the San Francisco Bay and you'll find many organisms from far away shores. Invasive kinds of mussels, fish and more are choking out native species, challenging experts around the state to change the human behavior that brings them here. See http://www.kqed.org/quest/television/san-francisco-bay-invaders for more information.

How You Can Help Protect Biodiversity

There are many steps you can take to help protect biodiversity. For example:

  • Consume wisely. Reduce your consumption wherever possible. Re-use or recycle materials rather than throwing out and buying new. When you do buy something new, choose products that are energy efficient and durable.
  • Avoid plastics. Plastics are made from petroleum and produce toxic waste.
  • Go organic. Organically grown food is better for your health. It also protects the environment from pesticides and excessive nutrients in fertilizers.
  • Save energy. Unplug electronic equipment and turn off lights when not in use. Take mass transit instead of driving.

Lost Salmon

Because of a sharp decline in their numbers, the entire salmon fishing season in the ocean off California and Oregon was canceled in both 2008 and 2009. At no other time in history has this salmon fishery been closed. The species in the most danger is the California coho salmon. Examine efforts to protect the coho in Northern California and explores the important role salmon play in the native ecosystem at http://www.kqed.org/quest/television/californias-lost-salmon and http://www.kqed.org/quest/television/coho-salmon-in-muir-woods.

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Date Created:
Feb 23, 2012
Last Modified:
Jan 30, 2016
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