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Biosc 41 Announcements 12/3 § Turn in research papers! § Evolution review § Quiz 10- chapters 22, 23 § Lecture: chapter 56, conservation biology § Lab- presentations § Review for final exam © 2014 Pearson Education, Inc. Evolution Review § What was Darwin’s original phrase for what we now know as “evolution”? § What are the two sources of genetic variation? § Can natural selection create new traits? § Darwinian snails example: what are two limitations on shell thickness in a population? § Does natural selection select for the same alleles regardless of environment? § Is natural selection based on equal or unequal reproduction? § Does natural selection act on genotypes or phenotypes? © 2014 Pearson Education, Inc. Evolution Review § Is speciation an example of microevolution or macroevolution? § Is Hardy-Weinberg equilibrium common in nature? § What are 5 conditions of non-evolving populations? § No mutations § Random mating § No natural selection § Very large population size § No gene flow © 2014 Pearson Education, Inc. Evolution Review § In the Darwinian snails lab, what conditions prevented evolution of the snail population? § No variation in shell thickness in the population (note- mutations can lead to evolution under these conditions!) § Shell thickness was not heritable § Crab was not selective of shell thickness § In the Darwinian snails lab, what conditions led to evolution of the snail population? § Variation in shell thickness in the population § Heritability of shell thickness § Crab was selective of shell thickness © 2014 Pearson Education, Inc. Evolution Review § In a population of 12,000, it is known that 12 individuals have sickle-cell anemia. § What percent of the population is homozygous recessive? § q2 = 0.001 = 0.1% § What percent of alleles in the gene pool are recessive? § q = √0.001 = 0.03 = 3% § What percent of alleles in the gene pool are dominant? § p = 1-q = 0.97 = 97% § What percent of the population is homozygous dominant? § p2 = 0.972 = 0.94 = 94% § What percent of the population is heterozygous? § 2pq = 2 x 0.97 x 0.03 = 0.06 = 6% © 2014 Pearson Education, Inc. Evolution Review § In the case of sickle-cell anemia, what factors influence whether the recessive sickle-cell allele remains in the population? § Presence of malaria leads to selection of heterozygotes § Wet climates = more mosquitos = more malaria § Is the sickle-cell allele likely to decrease and/or disappear in wet regions? § Is the sickle-cell allele likely to decrease and/or disappear in dry regions? © 2014 Pearson Education, Inc. Evolution Review § Describe 4 mechanisms of microevolution: § Mutations § Genetic drift: bottlenecks, founder effects- bigger influence in smaller populations § Gene flow: migration- reduces genetic variation between populations § Natural selection, including nonrandom mating § Directional § Disruptive § Stabilizing © 2014 Pearson Education, Inc. Imagine a species of bird in which females prefer to mate with brightly colored males. However, males with bright backs are more often preyed upon by hawks. Assuming that a wide variety of genetic variation exists in the species, which do you think is the most likely evolutionary outcome? a. Males will be selected to be brightly colored. b. Females will be selected to choose drab males. c. Males will be selected to have bright chests and dull backs. d. Females will not mate. e. The species will go extinct because the hawks catch all the males. © 2014 Pearson Education, Inc. Imagine a species of bird in which females prefer to mate with brightly colored males. However, males with bright backs are more often preyed upon by hawks. Assuming that a wide variety of genetic variation exists in the species, which do you think is the most likely evolutionary outcome? a. Males will be selected to be brightly colored. b. Females will be selected to choose drab males. c. Males will be selected to have bright chests and dull backs. d. Females will not mate. e. The species will go extinct because the hawks catch all the males. © 2014 Pearson Education, Inc. Using the Galápagos finches example from the book, which of the following best explains the Darwinian reason why the insect-eating finch has such a long, narrow beak? a. Variation existed in the finch population. Those that naturally had longer, narrower beaks could reach their food more easily, allowing finches with these features to survive and reproduce more often than those that did not. b. Every day, finches who needed to eat insects would squeeze their beaks into tiny holes to reach insects, eventually changing the shape of their beaks, which then got passed on to future generations. c. Those with longer, narrower beaks carried the dominant gene for that, which is how they evolved. © 2014 Pearson Education, Inc. Using the Galápagos finches example from the book, which of the following best explains the Darwinian reason why the insect-eating finch has such a long, narrow beak? a. Variation existed in the finch population. Those that naturally had longer, narrower beaks could reach their food more easily, allowing finches with these features to survive and reproduce more often than those that did not. b. Every day, finches who needed to eat insects would squeeze their beaks into tiny holes to reach insects, eventually changing the shape of their beaks, which then got passed on to future generations. c. Those with longer, narrower beaks carried the dominant gene for that, which is how they evolved. © 2014 Pearson Education, Inc. MRSA infections are occurring at alarming rates. One reason for this could be that people do not finish their antibiotics. Which of the following is the most likely reason that this could lead to something like MRSA? a. Antibiotics take awhile to start working, giving the bacteria time to mount defenses against the antibiotics over a few days. b. Because antibiotics are often taken when there is no bacterial infection, the antibiotics aren’t using their medicinal/antibacterial properties and are losing them. c. The first few days of antibiotics kill off the weak bacteria, making people feel better. Then, when people stop taking the antibiotics, the strong bacteria that survived have been selected, breed with one another, and create a stronger population. © 2014 Pearson Education, Inc. MRSA infections are occurring at alarming rates. One reason for this could be that people do not finish their antibiotics. Which of the following is the most likely reason that this could lead to something like MRSA? a. Antibiotics take awhile to start working, giving the bacteria time to mount defenses against the antibiotics over a few days. b. Because antibiotics are often taken when there is no bacterial infection, the antibiotics aren’t using their medicinal/antibacterial properties and are losing them. c. The first few days of antibiotics kill off the weak bacteria, making people feel better. Then, when people stop taking the antibiotics, the strong bacteria that survived have been selected, breed with one another, and create a stronger population. © 2014 Pearson Education, Inc. In evolutionary terms, an organism's fitness is measured by its ________. a. stability in the face of environmental change b. contribution to the gene pool of the next generation c. genetic variability d. mutation rate e. health © 2014 Pearson Education, Inc. In evolutionary terms, an organism's fitness is measured by its ________. a. stability in the face of environmental change b. contribution to the gene pool of the next generation c. genetic variability d. mutation rate e. health © 2014 Pearson Education, Inc. Indicate what type of selection is occurring in the example here: Due to less snowfall in an area, white mice are predated on more than intermediateor dark-colored mice. a. directional selection b. disruptive selection c. stabilizing selection © 2014 Pearson Education, Inc. Indicate what type of selection is occurring in the example here: Due to less snowfall in an area, white mice are predated on more than intermediateor dark-colored mice. a. directional selection b. disruptive selection c. stabilizing selection © 2014 Pearson Education, Inc. Which of the following evolutionary mechanisms increases the amount of genetic variation in a population? a. genetic drift b. mutation c. sexual selection d. directional natural selection e. stabilizing natural selection © 2014 Pearson Education, Inc. Which of the following evolutionary mechanisms increases the amount of genetic variation in a population? a. genetic drift b. mutation c. sexual selection d. directional natural selection e. stabilizing natural selection © 2014 Pearson Education, Inc. A high proportion of the cats on Key West (a relatively isolated island) have extra toes (polydactyly). What is the most likely explanation? a. high rate of mutation b. founder effect c. bottleneck effect d. directional selection for extra toes © 2014 Pearson Education, Inc. A high proportion of the cats on Key West (a relatively isolated island) have extra toes (polydactyly). What is the most likely explanation? a. high rate of mutation b. founder effect c. bottleneck effect d. directional selection for extra toes © 2014 Pearson Education, Inc. Quiz 10 1. Describe two factors that led to evolution in Darwinian snail shell thickness. 2. Describe two factors that prevented evolution in Darwinian snail shell thickness. 3. Describe two factors that limit maximum shell thickness in Darwinian snails. 4. Would you expect the frequency of sickle-cell alleles to be higher in dry or wet regions of Africa? 5. Describe two mechanisms of microevolution. © 2014 Pearson Education, Inc. Conservation Biology and Global Change (chapter 56) © 2014 Pearson Education, Inc. HOW many species?? § Scientists have named and described 1.8 million species § Biologists estimate 10-100 million species exist on Earth § Tropical forests contain some of the greatest concentrations of species and are being destroyed at an alarming rate § Humans are rapidly pushing many species toward extinction © 2014 Pearson Education, Inc. § Conservation biology, which seeks to preserve biodiversity (the variety of life), integrates several fields: § Ecology § Physiology § Molecular biology § Genetics § Evolutionary biology © 2014 Pearson Education, Inc. Three Levels of Biodiversity Genetic diversity: source of variations that enable populations to adapt to environmental changes Species diversity: important in maintaining structure of communities and food webs © 2014 Pearson Education, Inc. Ecosystem diversity: provides life-sustaining services such as nutrient cycling and waste decomposition § The local extinction of one species can have a negative impact on other species in an ecosystem § For example, flying foxes (bats) are important pollinators and seed dispersers in the Pacific Islands © 2014 Pearson Education, Inc. Philippine eagle Yangtze River dolphin Benefits of Species and Genetic Diversity § Species related to agricultural crops can have important genetic qualities § Ex: plant breeders bred virusresistant commercial rice by crossing it with a wild population § In the U.S., 25% of prescriptions contain substances originally derived from plants § For example, the rosy periwinkle contains alkaloids that inhibit cancer growth © 2014 Pearson Education, Inc. § The loss of species also means loss of unique genes and genetic diversity § The enormous genetic diversity of organisms has potential for great human benefit © 2014 Pearson Education, Inc. Ecosystem Services § Ecosystem services encompass all the processes through which natural ecosystems and their species help sustain human life § Some examples of ecosystem services: § Purification of air and water § Detoxification and decomposition of wastes § Cycling of nutrients § Moderation of weather extremes © 2014 Pearson Education, Inc. Threats to Biodiversity § Most species loss can be traced to four major threats: § Habitat loss § Introduced species § Overharvesting § Global change © 2014 Pearson Education, Inc. Introduced Species § Introduced species are those that humans move from native locations to new geographic regions § Without their native predators, parasites, and pathogens, introduced species may spread rapidly § Introduced species that gain a foothold in a new habitat usually disrupt their adopted community § Ex: Lionfish © 2014 Pearson Education, Inc. Invasive lionfish in the Atlantic § Likely introduced by aquarists § Very few predators § They are voracious predators!! © 2014 Pearson Education, Inc. Overharvesting § DNA analysis can help conservation biologists identify the source of illegally obtained animal products § For example, DNA from illegally harvested ivory can be used to trace the original population of elephants to within a few hundred kilometers © 2014 Pearson Education, Inc. Can Extinct Species Be Resurrected? § Species recovery may be possible through cloning technology if frozen tissue is available § Current research is underway to determine if ancient extinct species frozen in Arctic ice can be successfully cloned § Resurrection of extinct species raises ethical questions © 2014 Pearson Education, Inc. Population conservation focuses on population size, genetic diversity, and critical habitat § Biologists focusing on conservation at the population and species levels follow two main approaches § The small-population approach § The declining-population approach © 2014 Pearson Education, Inc. Small-Population Approach § The small-population approach studies processes that can make small populations become extinct § A small population is prone to inbreeding and genetic drift, which draw it down an extinction vortex § The key factor driving the extinction vortex is loss of the genetic variation necessary to enable evolutionary responses to environmental change § Small populations and low genetic diversity do not always lead to extinction © 2014 Pearson Education, Inc. Figure 56.13 Small population Inbreeding, genetic drift Lower reproduction, higher mortality Loss of genetic variability Lower individual fitness and population adaptability Smaller population © 2014 Pearson Education, Inc. Case Study: The Greater Prairie Chicken and the Extinction Vortex Results § To test the extinction vortex hypothesis, scientists imported birds from larger populations § The declining population rebounded, confirming that low genetic variation had been causing an extinction vortex 150 100 Translocation 50 0 1975 1980 1995 Year (a) Population dynamics 1985 1970 1980 1985 Years 1990 90 80 70 60 50 40 30 © 2014 Pearson Education, Inc. 1970 100 Eggs hatched (%) § Populations were fragmented by agriculture and found to have decreased fertility Number of male birds 200 1975 1995 (b) Hatching rate 1990 Minimum Viable Population Size § Minimum viable population (MVP) is the minimum population size at which a species can survive § The MVP depends on factors that affect a population’s chances for survival over a particular time © 2014 Pearson Education, Inc. Declining-Population Approach § The declining-population approach § Focuses on threatened and endangered populations that show a downward trend, regardless of population size § Emphasizes the environmental factors that caused a population to decline © 2014 Pearson Education, Inc. Case Study: Decline of the Red-cockaded Woodpecker § Red-cockaded woodpeckers require living trees in mature pine forests § These woodpeckers require forests with little undergrowth § Logging, agriculture, and fire suppression have reduced suitable habitat Red-cockaded woodpecker Forests with © 2014(a) Pearson Education, Inc. low undergrowth (b) Forests with high, dense undergrowth § Red-cockaded woodpeckers take months to excavate new nesting cavities § In a study where breeding cavities were constructed, new breeding groups formed only in these sites § Based on this experiment, a combination of habitat maintenance and excavation of breeding cavities enabled this endangered species to rebound © 2014 Pearson Education, Inc. Weighing Conflicting Demands § Conserving species often requires resolving conflicts between habitat needs of endangered species and human demands § For example, in the U.S. Pacific Northwest, habitat preservation for many species is at odds with timber and mining industries § Managing habitat for one species might have positive or negative effects on other species © 2014 Pearson Education, Inc. Landscape and regional conservation help sustain biodiversity § The structure of a landscape can strongly influence biodiversity © 2014 Pearson Education, Inc. Fragmentation and Edges § The boundaries, or edges, between ecosystems are defining features of landscapes § An edge has its own set of physical conditions, which differ from those on either side of it § Some species take advantage of edge communities to access resources from both adjacent areas © 2014 Pearson Education, Inc. Corridors That Connect Habitat Fragments § A movement corridor is a narrow strip of habitat connecting otherwise isolated patches to promote dispersal and help sustain populations § In areas of heavy human use, artificial corridors are sometimes constructed § Corridors can also be harmful by facilitating the spread of disease between populations © 2014 Pearson Education, Inc. Preserving Biodiversity Hot Spots § A biodiversity hot spot is a relatively small area with a great concentration of endemic species and many endangered and threatened species § Biodiversity hot spots are good choices for nature reserves, but identifying them is not always easy- and they may change over time/ with climate Equator © 2014 Pearson Education, Inc. Earth’s terrestrial (■) and marine (▲) biodiversity hot spots Urban Ecology § The field of urban ecology examines organisms and their environment in urban settings § A critical area of research centers on urban streams, which experience rapid water fluctuations after rainfall § Restoration of Guichon Creek, near Vancouver, British Columbia, has allowed for the successful reestablishment of cutthroat trout © 2014 Pearson Education, Inc. Earth is changing rapidly as a result of human actions § Human-caused changes in the environment include § Nutrient enrichment § Accumulation of toxins § Climate change § Ozone depletion © 2014 Pearson Education, Inc. Nutrient Enrichment § Human activity often removes nutrients from one part of the biosphere and adds them to another § Harvest of agricultural crops exports nutrients from the agricultural ecosystem § Agriculture leads to the depletion of nutrients in the soil § Fertilizers add nitrogen and other nutrients to the agricultural ecosystem © 2014 Pearson Education, Inc. § Critical load is the amount of added nutrient that can be absorbed by plants without damaging ecosystem integrity § Nutrients that exceed the critical load leach into groundwater or run off into aquatic ecosystems § Agricultural runoff and sewage lead to phytoplankton blooms in the Atlantic Ocean § Decomposition of phytoplankton blooms causes “dead zones” due to low oxygen levels © 2014 Pearson Education, Inc. Toxins in the Environment § Humans release many toxic chemicals, including synthetics previously unknown to nature § In some cases, harmful substances persist for long periods in an ecosystem § One reason toxins are harmful is that they become more concentrated in successive trophic levels § Biological magnification concentrates toxins at higher trophic levels, where biomass is lower © 2014 Pearson Education, Inc. § Pharmaceutical drugs enter freshwater ecosystems through human sewage and agricultural runoff § Estrogen used in birth control pills can cause feminization of males in some species of fish Pharmaceuticals Farm animals Toilet Humans Manure Sludge Farms Treated effluent Sewage treatment plant © 2014 Pearson Education, Inc. Lakes and rivers Agricultural runoff Greenhouse Gases and Climate Change § One pressing problem caused by human activities is the rising level of CO2 and other greenhouse gases in the atmosphere 390 380 370 Temperature 360 350 340 CO2 330 320 310 300 © 2014 Pearson Education, Inc. 1960 1965 1970 1975 1980 Year 1985 1990 1995 14.9 14.8 14.7 14.6 14.5 14.4 14.3 14.2 14.1 14.0 13.9 13.8 13.7 13.6 2000 Average global temperature (°C) CO2 concentration (ppm) § Due to burning of fossil fuels and other human activities, the concentration of atmospheric CO2 has been steadily 15.0 increasing 400 § Climatologists can make inferences about past environments and climates § Pollen and fossil plant records reveal past vegetation § CO2 levels are inferred from bubbles in glacial ice § Chemical isotope analysis is used to infer past temp © 2014 Pearson Education, Inc. § Many organisms may not be able to survive rapid climate change § Some ecologists support assisted migration, the translocation of a species to a favorable habitat beyond its native range © 2014 Pearson Education, Inc. Climate Change Solutions § Global warming can be slowed by reducing energy needs and converting to renewable sources of energy § Stabilizing CO2 emissions will require an international effort § International negotiations have yet to reach a consensus on a global strategy to reduce greenhouse gas emissions § Reduced deforestation would also decrease greenhouse gas emissions © 2014 Pearson Education, Inc. Sustainable Development § Sustainable development can improve human lives while conserving biodiversity § Sustainable development is development that meets the needs of people today without limiting the ability of future generations to meet their needs § Sustainable development requires connections between life sciences, social sciences, economics, and humanities (interdisciplinary) © 2014 Pearson Education, Inc.