Ch 13 BIOL 100. Biodiversity: sum total of all organisms in an area. Split into three specific levels: Ecosystem diversity.

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1 Ch 13 BIOL 100 Biodiversity: sum total of all organisms in an area Split into three specific levels: Ecosystem diversity Species diversity GeneBc diversity Species diversity Number or variety of species in the world or in a parbcular region Species richness Number of species Evenness or rela4ve abundance Extent to which numbers of individuals of different species are equal or skewed SpeciaBon generates new species and adds to species richness ExBncBon reduces species richness 1

2 Taxonomists ScienBsts who classify species Common ancestry, ability to interbreed Genera Related species are grouped together Families Groups of genera Every species has a two-part scienbfic name Binomial nomenclature Genus and species Subspecies PopulaBons of species that occur in different areas and differ slightly from each other Divergence stops short of separabng the species Or sbll potenbally speciabng Subspecies are denoted with a third part of the scienbfic name Bengal Bger = Panthera )gris )gris Siberian Bger = Panthera )gris altaica All subspecies of )gers have disappeared from 93% of their historic range Gene4c diversity encompasses differences in DNA Among individuals within species and populabons Is the raw material for adaptabon to local condibons PopulaBons with higher genebc diversity More likely to survive Can cope with environmental change PopulaBons with low genebc diversity More vulnerable to Environmental change Disease Inbreeding depression: genebcally similar parents mate and produce less fit offspring 2

3 Ecosystem diversity Number and variety of ecosystems Also encompasses differing communibes and habitats Sizes, shapes, and interconnectedness of patches within habitats, communibes, or ecosystems Species not evenly distributed among taxonomic groups Many more insects ~80% of all species 40% of all insects are beetles Groups accumulate species by: AdapBve radiabon Allopatric speciabon Low rates of exbncbon Species richness EsBmates of 5 30 million species on Good gauge for overall biodiversity Earth Only million species Have been idenbfied and described Very difficult to idenbfy species Small organisms are easily overlooked Many species look idenbcal unbl closely examined Many remote spots on Earth remain unexplored 3

4 Living things Distributed unevenly across Earth La4tudinal gradient Species richness increases toward the equator Equatorial regions Have higher plant producbvity Stable climates No glaciabon Diverse habitats increase niches Increases species diversity Ecotone Areas where habitats intermix Have higher diversity of niches Therefore higher species diversity Ex4nc4on Occurs when the last member of a species dies Species ceases to exist Ex4rpa4on Disappearance of a parbcular populabon locally Not the enbre species globally Can lead to exbncbon 99% of all species ever existed are now exbnct 4

5 Past 440 million years Dinosaurs exbnct at end of the Cretaceous period Mass exbncbons eliminated at least 50% of all species 65 million years ago Made way for mammals Ex)nc)ons followed human arrival on islands and con)nents 5

6 The Red List Updated list of species facing high risks of exbncbons 22% of mammal species 12% of bird species 16 86% of all other species Since fish species, 9 bird species, and 2 mammal species have gone exbnct West African black rhinoceros, Baiji white dolphin (both last decade) U.S. in the last 500 years 236 animal and 17 plant species are confirmed exbnct Actual numbers are undoubtedly higher PopulaBons are declining With shrinking geographic ranges GeneBc, ecosystem, and species diversity are being lost Living Planet Index summarizes trends in populabons Between 1970 and 2003, the Index fell by 30% Reasons for biodiversity losses MulBfaceted, complex, and hard to determine Four primary causes 1. Habitat alterabon 2. Invasive species 3. PolluBon 4. OverharvesBng Global climate change now is the fihh cause 6

7 Greatest cause of biodiversity loss Farming Grazing Clearing forests Hydroelectric dams UrbanizaBon and suburban sprawl A few species (i.e., pigeons, rats) benefit from changing habitats generalists Less than 1% of North America s Great Plains remains, and grassland bird populabons have declined 82 99% Forests Fragmented by roads and logging Small forest fragments Lose diversity fastest StarBng with large species Equilibrium theory of island biogeography DistribuBon of species on oceanic islands Results from an equilibrium between immigrabon and exbrpabon Predicts an island s species richness Based on the island s size and distance from the mainland Also applies to habitat islands Patches of one habitat type isolated within a sea of others 7

8 Fewer species Colonize an island far from the mainland Large islands Have higher immigrabon rates Large islands Have lower exbncbon rates 8