ENSP101 Chapter 11 Biodiversity 11 1 Diversity and the Species Concept 3 kinds of biodiversity are essential to preserve these ecological systems o 1 Genetic diversity is a measure of the variety of different versions of the same genes within individual species o 2 Species diversity describes the number of different kinds of organisms within individual communities or ecosystems o 3 Ecological diversity assess the richness and complexity of a biological community including the number of niches trophic levels and ecological processes that capture energy sustain food webs and recycle materials within this system Within species diversity we can distinguish between species richness the total number of species in a community and species evenness the relative abundance of individuals within each species Species are defined in terms of reproductive isolation all the organisms potentially able to breed in nature and produce fertile offspring o Another definition favored by many evolutionary biologist is the phylogenetic species concept PSC which emphasizes the branching or cladistic relationships among species or higher taxa regardless of whether organisms can breed successfully o A third definition favored by some conservation biologists is the evolutionary species concept ESC which defines species in evolutionary and historic terms rather than reproductive potential Increasingly DNA sequencing and other molecular techniques are giving us insights into taxonomic and evolutionary relationships This new technology can help resolve taxonomic uncertainties in conservation o In some cases an apparently widespread and low risk species may in reality comprise a complex of distinct species some rare of endangered o On the other hand in some cases genetic analysis shows that a protected population is closely related to another much more abundant one o In some cases molecular taxonomy is causing a revision of the basic phylogenetic ideas of how we think evolution proceeded The 1 6 million species presently known probably represent only a small fraction of the total number that exist o Based on the rate of new discoveries by research expeditions especially in the tropics taxonomists estimate that there may be somewhere between 3 million and 50 million different species alive today o About 76 of all known species are invertebrates o This group probably makes up the vast majority of organisms yet to be discovered and may constitute 95 of all species o Biodiversity hot spots areas with exceptionally high numbers of endemic species Although they occupy only 1 4 of the world s land area these hot spots house of the world s most threatened mammals birds and amphibians The hot spots also account for about half of all known higher plant species and 43 of all terrestrial vertebrate species 11 2 How Do We Benefit From Biodiversity All of our food comes from other organisms Living organisms provide us with many useful drugs and medicines Biodiversity provides ecological services Biodiversity also brings us many aesthetic and cultural benefits o Existence value the importance we place on just knowing that a particular species or a specific organism exists 11 3 What Threatens Biodiversity Extinction the irrevocable elimination of species can be a normal process of the natural world as species out compete or kill off others or an environmental conditions change o In undisturbed ecosystems the rate of extinction appears to be about one species lost every decade o In this century however human impacts on populations and ecosystems have accelerated that rate causing hundreds or perhaps even thousands of species subspecies and varieties to become extinct every year o Extinction is a natural process Studies of the fossil record suggest that more than 99 of all species that ever existed are now extinct o We are accelerating extinction rates o HIPPO habitat destruction invasive species pollution population human and overharvesting the lading causes of extinction Habitat destruction Invasive species The most important extinction threat for most species especially terrestrial ones is habitat loss Sometimes we destroy habitat as side effects of resource extraction such as mining dam building and indiscriminate fishing methods A major threat to native biodiversity in many places is from accidentally or deliberately introduced species Invasive species organisms that thrive in new territory where they are free of predators diseases or resource limitations that may have controlled their population in their native habitat A few important examples of invasive species include the following o Barred owl o Eurasian milfoil an exotic aquatic plant native to Europe o Kudzu vine o Purple loosestrife o Zebra mussels Island ecosystems are particularly susceptible to invasive species New Zealand is a prime example Pollution We have known for a long time that toxic pollutants can have disastrous effects on local populations of organisms Population Human population growth represents a threat to biodiversity in several ways If our consumption patterns remain constant with more people we will need to harvest more timber catch more fish plow more land for agriculture dig up more fossil fuels and minerals build more houses and use more water Overharvesting is responsible for depletion or extinction of many Overharvesting species Commercial products and live specimens Much of this represents sustainable harvest but some forms of commercial exploitation are highly destructive and present a serious threat to certain rare species Despite international bans on trade in products from endangered species smuggling of furs hides horns live specimens and folk medicines amounts to millions of dollars every year Plants are also threatened by overharvesting 11 4 Endangered Species Management Slowly we are adopting national legislation and international treaties to protect these irreplaceable assets o Parks wildlife refuges nature preserves zoos and restoration programs have been established to protect nature and rebuild depleted populations o Hunting and fishing laws have been effective o Legislation is key to biodiversity protection Endangered species those considered in imminent danger of extinction Threatened species those that are likely to become endangered Vulnerable species naturally rare or have been locally depleted by human Recovery plants rebuild populations of endangered species activities to a level that puts them at risk o The US currently