Chapter 9. Chapter 9: Biodiversity

What is the estimated total number of species on Earth...?

Interactive Study Guide

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Guiding Question 9.2

What is the estimated total number of species on Earth, and which taxonomic groups have the most species? How sure are we of these numbers? Why?

Why You Should Care

The estimated number of species on the planet varies quite a bit (from 3 to 100 million species). This disparity is basically due to the difficulty in knowing how little you know before you know it. There are several reasons to care about how many species there are. First, it gives us an indication of where scientific study needs to be directed. Second, knowing which groups have many species gives us an indication of which groups are likely to have species with narrow or specific niches or global importance. Lastly, knowing how many species there are out there gives you a new appreciation for the world around you.

Question 9.1

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999

Try again.

Correct.

Incorrect.

Question 9.2

Most of the known species on Earth are tnVLKK1KTQEQ0ZFwoTUx05q5h4f2/31W1+SVzuqn0cM2xgWiPUFPYV2AQBFMk0g22u2LE/PAFKOtnWsG3BJXEA==.

999

Try again.

Correct.

Incorrect.

Question 9.3

The second largest group of known species are D0MFjtL9Ul6Jjay7BQQrhS13ZpTmpkvGcbV++WJuiqakqQjty1ytOIE5W13lhuxmN3QByP8Cpf0lOdFS/Nf7NQ==.

999

Try again.

Correct.

Incorrect.

Question 9.4

The group with the smallest number of estimated species is the nlGYLhMbozBI/8+HMUrvQ4tdWlzZKiXjYV3gkXCL1TdIUgCsh8Hh6kzH2chlqcMoVvCtQqc/aXnVtDha0LU6Jg==.

999

Try again.

Correct.

Incorrect.

Question 9.5

Do the math: Which group has the fewest known species per estimated species? (To find your answer, divide the number of known species by the number of estimated species and find the lowest number.)

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999

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Correct. Bacteria have by far the lowest percentage of described species at less than 1 percent.

Incorrect. Bacteria have by far the lowest percentage of described species at less than 1 percent.

Question 9.6

Which two groups have the highest proportion of known species?

Plants 9PufMCe/gaVcshPB

Fungi s87TBEH0BM9yDZCI

Bacteria s87TBEH0BM9yDZCI

Roundworms s87TBEH0BM9yDZCI

Insects s87TBEH0BM9yDZCI

Vertebrates 9PufMCe/gaVcshPB

999

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Correct. Both plants and vertebrates have between 75 and 80% of their estimated number of species described.

Incorrect. Both plants and vertebrates have between 75 and 80% of their estimated number of species described.

Question 9.7

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A species that is known has been described by scientists, usually in an article published in a scientific journal. If possible, the described species also has a preserved specimen representing it in a natural-history collection.

Question 9.8

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There are many possible answers here. Examples: Plants are more-or-less stationary, so it should be easier to capture and describe them. Furthermore and unlike fungi, they are largely macroscopic. Insects aren't always easy to catch, but they are easy to handle after capture and often present in large numbers. Land vertebrates are large and often easy-to-spot organisms compared to roundworms. Roundworms are not very charismatic, compared to vertebrates, and most live in soil, making it very difficult to find new species.