ESSENTIALS OF ECOLOGY (Chapter 9)
1. Review the Key Questions and Concepts for this chapter on p. 184. What factors led to the premature extinction of the passenger pigeon in the United States?
Factors that led to the premature extinction of the passenger pigeon are uncontrolled commercial hunting and habitat loss. Passenger pigeon in the 1858 became a big hunting business. Weapons like shotguns, traps and artilleries were used and even the burning of sulfur in suffocating the birds. These threats imposed by humans are increasing every year which degrades the habitat of these passenger pigeons which cause premature extinction.
2. Distinguish between background extinction and mass extinction. What is the extinction rate of a species? Describe how scientists estimate extinction rates. Give four reasons why many extinction experts believe that human activities are now causing a sixth mass extinction. Distinguish between endangered species and threatened species. List some characteristics that make some species especially vulnerable to extinction.
Background extinction is defined as the continuous, low level of extinction of species over the 3.56 billion years life existed on Earth as for the mass extinction defined as the extinction of many species in a relatively short period of time. The extinction rate of species is expressed as a percentage or number of species that go extinct within a certain time period such as a year. One extinction per million species per year would be 1/1,000,000 0.000001 species per year.
This method describes how scientist estimates extinction rate: first, the extinction of a species typically takes such a long time that it is not easy to document. Second, we have identified only about 1.8 million of the world’s estimated 4 million to 100 million species. Third, scientists know little about the nature and ecological roles of most of the species that have been identified.
These are the reasons why extinction...
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