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Chapter 14

Chapter 14. Conserving Biodiversity Community and Ecosystem Ecology. 14.1 The Sixth Extinction. Terms Biodiversity – the entire diversity of living organisms in an area Extinction – the complete loss of a species Endangered Species Act (ESA)

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Chapter 14

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  1. Chapter 14 Conserving Biodiversity Community and Ecosystem Ecology

  2. 14.1 The Sixth Extinction Terms • Biodiversity – the entire diversity of living organisms in an area • Extinction – the complete loss of a species Endangered Species Act (ESA) • law passed in 1973 to protect and encourage population growth of threatened and endangered species

  3. 14.1 The Sixth Extinction Measuring Extinction Rates • History of life on earth has been punctuated with five mass extinctions Figure 14.2

  4. 14.1 The Sixth Extinction Causes of Previous Mass Extinctions • Climate changes • Changes in sea level • Continental drift that changed ocean to land • Asteroid impact Figure 14.2

  5. 14.1 The Sixth Extinction Measuring Extinction Rates • Is the sixth mass extinction event occurring now? • Need to know the background extinction rate • Fossils indicate that average species exists for ~1,000,000 years • Estimate of background extinction rate is 0.0001% per year

  6. 14.1 The Sixth Extinction Current rate of extinction • more bird and mammal species have disappeared in the last 150 years • Current Extinction Rate = 0.005% Figure 14.4

  7. 14.1 The Sixth Extinction Definition of Extinction of modern species • no individuals of a species must have been seen in the wild for 50 years However: • 44 of 68 shallow-water mussel species missing in Tennessee River • 144 of 266 fresh-water fish in Malaysia are missing • 200 of 300 fish from Africa’s Lake Victoria are gone Figure 14.4

  8. 14.1 The Sixth Extinction International Union for the Conservation of Nature (IUCN) • Highly respected organization of scientists, governments and organizations • Predicts that the following are endanger of extinction: • 11% of all plants • 12% of all birds • 24% of all mammals Figure 14.4

  9. 14.1 The Sixth Extinction Four Major Causes of Extinction • Loss or degradation of habitat • Most important cause • Introduction of non-native species • Overexploitation • Pollution • Most of these are due to human activities

  10. 14.1 The Sixth Extinction 1. Habitat Destruction • As human population increases, pressure on natural areas increases • Species area curve – the number of species that a natural area of a given size can support

  11. 14.1 The Sixth Extinction Tropical Rainforest Destruction • ~7722 square miles of So. American rainforest are cut each year. • This rate will reduce rainforest to 10% of original size within 35 years • Will mean extinction of about 50,000 species

  12. 14.1 The Sixth Extinction Habitat destruction not limited to rainforests • Freshwater lakes and streams, grasslands, and temperate forests are also threatened • If worldwide habitat destruction continues at present rate, as many as 25% of all world’s species could become extinct in 50 years • But other threats, such as habitat fragmentation, could push extinction rates even higher

  13. 14.1 The Sixth Extinction - Habitat Destruction PLAY Animation—Tropical deforestation and the species area curve

  14. 14.1 The Sixth Extinction Habitat Fragmentation = large natural areas subdivided into smaller areas • Large predators are threatened because they require large home ranges • Human activity usually results in habitat fragmentation Figure 14.5b

  15. 14.1 The Sixth Extinction - Habitat Fragmentation PLAY Animation—Habitat Destruction and Fragmentation

  16. 14.1 The Sixth Extinction 2. Introduced Species = non-native species introduced to a new area either purposely or accidentally by human activity • Often destructive because they have not evolved with local species • Brown tree snake, introduced to Guam, caused many local bird species to go extinct • Domestic cats in Wisconsin kill 39 million birds/year • Zebra mussels, accidentally released in the Great Lakes from Europe, are outcompeting native species. • Kudzu, a vine brought from Japan, is now called “the vine that ate the south” Figure 14.5c

  17. 14.1 The Sixth Extinction 3. Overexploitation = When human use of a natural resource exceeds its reproductive rate. • Can occur if species is highly prized by humans, which can spur illegal hunting. • 3 of 8 species of tigers are extinct, other extremely endangered • Partly due to ‘Traditional Chinese Medicine’ • Can also occur if species competes with humans • Gray wolves almost exterminated by ranchers

  18. 14.1 The Sixth Extinction 4. Pollution = The release of poisons, toxins, excess nutrients, and other waste products. • Excess fertilizer runoff leads to eutrophication of waterways • Eutrophication is the excess growth of bacteria that depletes oxygen from the water • Herbicide atrazine is killing amphibians • Carbon dioxide is another atmospheric pollutant, associated with climate change

  19. 14.2 Consequences of Extinction So Why Should We Care If Species Become Extinct? • Extinction is forever • It is unethical to kill entire species • Selfish Reasons • Causing extinction has negative impacts on us too! • Loss of Resources • Environmental instability • Disrupted energy & Chemical Flows Figure 14.11

  20. 14.2 Consequences of Extinction Loss of Resources • Loss of species can lead to economic impacts for humans • Some biological resources harvested directly include wood (lumber and fuel), shellfish (protein), and algae (gelatin) • Wild species provide biological chemicals (medicines) • Wild species have alleles that are not present in domestic species, which can increase vigor of domesticated species • Wild species can contribute other means of combating pests (biological control) Figure 14.11

  21. 14.2 The Consequences of Extinction – Environmental Instability • Species interact with one another and their environment in complex ways, not just a simple food chain • Communities = all organisms living in a habitat • Niche = the role each species plays in the community Food Web Figure 14.12

  22. 14.2 The Consequences of Extinction – Environmental Instability: Terminology • Mutualism = organism that interact with each other in a mutually beneficial way Figure 14.12

  23. 14.2 The Consequences of Extinction – Mutualism: How Bees Feed the World • Mutualism – relationship in which both species benefit from their interaction • Many examples: • Cleaner fish • Fungal mycorrhizae • Ants and acacia trees • Bees are primary pollinators of many wild plants • Wild bees pollinate 80% of agricultural crops in U.S. • Bee populations are falling due to “colony collapse disorder” • Humans benefit from mutualism, and will lose if bees go extinct

  24. 14.2 The Consequences of Extinction – Environmental Instability: Terminology • Predation = survival of one species by feeding upon another Figure 14.12

  25. 14.2 The Consequences of Extinction – Predation: How Songbirds May Save Forests • Predator – species that survives by eating other species • Songbirds consume many insects • Most insects eaten by songbirds consume plants • Songbirds help to sustain forests • As songbird numbers decline, damage to forests increase

  26. 14.2 The Consequences of Extinction – Environmental Instability: Terminology • Competition = when two species both need the same resources (food, shelter, etc), they will be in competition if those resources are limited Figure 14.12

  27. 14.2 The Consequences of ExtinctionCompetition: How a Deliberately Infected Chicken Could Save a Life • A leading cause of food illness in the U.S. is caused by Salmonella enteritidis. • About 2 million Americans infected each year • About 400 die each year as a result of infection • Most common source of infection is eggs • S. enteritidis contaminates egg when it forms in the hen

  28. 14.2 The Consequences of Extinction Competition: How a Deliberately Infected Chicken Could Save a Life • Competitive exclusion is the use of food and space resources, making it impossible for another species to establish • On this principle, chickens are deliberately infected with harmless bacteria • Harmless bacteria establish and prevent S. enteritidis from living in chicken’s gut

  29. 14.2 The Consequences of Extinction - Competition: How a Deliberately Infected Chicken Could Save a Life Figure 14.16

  30. 14.2 The Consequences of Extinction Competition & Humans • Competition between species can have consequences for humans as well • Mosquitos, snails and tadpoles compete for same resources in ponds • When populations of snails and tadpoles decrease, mosquitoes increase • Potentially serious because mosquitoes can spread malaria, West Nile virus, and yellow fever

  31. 14.2 The Consequences of Extinction – Environmental Instability: Terminology • Keystone Species = the activities of a single species can play a dramatic role in the composition of a community Figure 14.12

  32. 14.2 The Consequences of Extinction Keystone Species: Wolves in Yellowstone • Keystone species are key figures in determining the food web of an ecosystem • Wolves were eradicated from Yellowstone Park in 1920s • With wolves gone, aspen, cottonwood, and willow trees declined • Trees declined due to predation by elk • Trees are crucial for beavers, songbirds, and fish • With reintroduction of wolves, trees and other species rebounded

  33. 14.2 The Consequences of Extinction – Ecosystem Energy and Chemical Flows • Ecosystem – includes: • all living organisms in an area • Plus nonbiological environment • Loss of some species can dramatically affect both of these ecosystem properties Figure 14.8

  34. 14.2 The Consequences of Extinction – Disrupted Energy Flows Biomassin mountain lions About 10% of energy takenin by deer is available tomountain lion. About 10% of energytaken in by grass isavailable to deer. Biomassin deerpopulation Biomass in grass population • Energy flow - only a small portion ( ~10%) of the energy in one level of a trophic pyramid can be converted to biomass at the next level • Diversity also affects energy flow, such as in more diverse grasslands, more biomass is produced Figure 14.8

  35. 14.2 The Consequences of Extinction – Disrupted Chemical Flows Nitrogen(N2) Animal protein Animal protein Plantprotein Dead organicmatter Free-living,nitrogen-fixingbacteria Nitrogen-fixingbacteria in plantroot nodules Decomposers(bacteria and fungi) Nitrate(NO3–) Nitrite (NO2–) Ammonia(NH3) • Nutrient cycling – nutrients that pass through a food web rarely leave the system Figure 14.18

  36. 14.2 The Consequences of Extinction – Disrupted Chemical Flows • The soil community has an important role in nutrient cycling • Introduction of non-native earthworms in NE U.S. had dramatic impact on forest plants • Non-native worms changed the soil community Figure 14.19

  37. 14.2 The Consequences of Extinction Psychological Effects • Our experience with nature has strong psychological effects • Instinctive desire to commune with nature is called biophilia • Pets can improve mental well-being • Dental patients viewing landscapes showed a decrease in blood pressure • Hospital patients who could view trees recovered from surgery more quickly • Loss of biodiversity could make human experience less pleasant

  38. 14.2 The Consequences of Extinction Replacing Extinction • 5-10 million years to recover species lost from a mass extinction • Species that replace those lost are different • After mass extinction of dinosaurs, mammals replaced them as dominant large animals • We can not predict what biodiversity will look like after another mass extinction • The mass extinction we are witnessing today will have consequences for thousands of human generations (if humans survive)

  39. 14.3 Saving Species - Protecting Habitat Caucasus Philippines MediterraneanBasin MediterraneanBasin South CentralChina CaliforniaFloristicProvince India-Burma Caribbean Polynesia/Micronesia Polynesia/Micronesia Mesoamerica Brazil’sCerrado TropicalAndes WesternGhats andSri Lanka Choco/DarienWesternEcuador W. AfricanForests TanzaniaandKenya TanzaniaandKenya Polynesia/Micronesia Polynesia/Micronesia Wallacea Sundaland NewCaledonia Brazil’sAtlanticCoast SucculentKaroo CentralChile Madagascar SouthwestAustralia Cape FloristicProvince Diversity hot spots New Zealand • Biodiversity hotspots = less than 2% of the earth’s surface contain up to 50% of the earth’s mammal, bird, reptile, and plant species. These areas are. Figure 14.21

  40. 14.3 Saving Species Protecting Habitat • Converting wild areas to agricultural production is a major cause of habitat destruction. • Altering our consumption patterns can help decrease habitat destruction. • Eating low on the food chain (less meat and dairy) makes a difference. • Reduce consumption of wood and paper • Support conservation organizations • Ultimately, slowing human population growth rate must occur

  41. 14.3 Saving Species – Population Size & Environmental Disasters • A large population provides group protection from environmental disaster. • A species with a slow growth rate is at greater risk if its numbers diminish. • The longer a population remains small, the greater its risk. Figure 14.22

  42. 14.3 Saving Species – Population Size & Environmental Disasters • The Heath Hen • Lived in New England & numbered in 100,000s • Declined due to habitat loss to 50 hens • Reserve created on Martha’s Vineyard in 1908 • Rebounded to 2000 hens by 1915 • 1916, fire destroyed much of reserve • 1917 cold winter brought hungry Goshawks • Then disease from domestic turkeys • 1927, only 14 remained, mostly males • 1932 last survivor seen Figure 14.22

  43. 14.3 Saving Species – Population Size & Environmental Disasters • Lessons from the Heath Hen • Large populations can survive better • EXP: population of 100,000 can loss 90%, but pop. of 1,000 can not. • Don’t put all members of species in same reserve • Whooping crane preserves are in Maryland, Wisconsin, Calgary Canada, and Louisiana Figure 14.22

  44. 14.3 Saving Species Conservation Genetics • Loss of genetic variability is a two-fold problem. • Low genetic variability leads to low fitness, and is more likely to express harmful mutant alleles. • Loss of genetic variability can lead to extinction due to the low fitness of individuals.

  45. 14.3 Saving Species - A Closer Look: Conservation Genetics Being heterozygous may confer higher fitness for responding to a changing environment. Homozygote 1: Relatively low fitness(only one type of jacket in wardrobe) Homozygote 2: Relatively low fitness(only one type of jacket in wardrobe) Heterozygote: Relatively high fitness(two types of jackets in wardrobe) The Importance of Genetic Variability • When individuals are heterozygotic for many genes, the overall effect is greater fitness. Figure 14.23

  46. 14.3 Saving Species - A Closer Look: Conservation Genetics Being heterozygous may confer higher fitness by masking deleterious recessive alleles. Homozygote 2: Relatively low fitness(two nonfunctional jackets in wardrobe) Homozygote 1: Relatively high fitness(two functional jackets in wardrobe) Heterozygote: Relatively high fitness(one functional jacket in wardrobe) • Heterozygotes can avoid deleterious effects of recessive alleles. Figure 14.24

  47. 14.3 Saving Species - A Closer Look: Conservation Genetics • In a small population, individuals are more likely to be related to their mates (inbreeding) • Result can be inbreeding depression, a decline in heterzygotes • Because of this, cheetahs have poor quality sperm and low rate of cub survival • In humans, children of first cousins have lower rates of heterozygosity and higher rates of infant mortality

  48. 14.3 Saving Species - A Closer Look: Conservation Genetics The Extinction Vortex • The Consequences of Low Genetic Variability in a Population • A small population can become stuck in a cycle that leads to extinction. Figure 14.26

  49. 14.3 Saving Species - A Closer Look: Conservation Genetics Irish potato famine • a human example of the potentially disastrous effects of low genetic diversity • In 1840s, Irish potato crop had very low genetic diversity • Fungus that causes potato blight arrived in Ireland; plants rotted in fields • Because of crop failure, nearly 1 million Irish died of starvation and disease

  50. 14.4 Protecting Biodiversity Table 14.3

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