Ch 6_Evolution_lecture slides.pdf

6 Evolution and Ecology 1 What does Cecil the lion have to do with evolution? 2 1  Trophy Hunting Trophy Hunting: selective hunting of wild game with the primary motivation to seek the oldest a...

6 Evolution and Ecology 1 What does Cecil the lion have to do with evolution? 2 1  Trophy Hunting Trophy Hunting: selective hunting of wild game with the primary motivation to seek the oldest and most mature animal from a given population, which is typically a male with the largest body size or largest antlers or horns. 3 Trophy Hunting Case Study- Botswana Community Based Natural Resource Management (CBNRM)- pursuing conservation, while also providing income for residents of the land 4 2  Trophy Hunting Case Study- Botswana Ecotourism can alleviate poverty for local communities and promote conservation of resources Trophy hunting has historically been a big funder of conservation  10-d leopard hunting safari- $40,000  Avg. hunter spends >$100,000/trip 5 Hunting and Fishing Regulations Hunting and fishing regulations often target older, large males, the same organisms that would likely sire the largest number of healthy offspring. 6 3  Hunting and Rapid Evolution Selective poaching caused significant decline in tusk size from 1960s to 2005-2013  Encompasses 2 generations of elephants  Gene encoding for size maternally inherited  Tusk size decrease despite shoulder height increase Is this decrease in tusk size beneficial or harmful for elephants? 7 Introduction Big Horn Sheep- Hunting Effects Evolution is changes in organisms over time. Natural selection, genetic drift, and gene flow cause change. What about humans? 8 4  What Is Evolution? Genes are composed of DNA. They specify (encode) proteins. Genes can have two or more forms called alleles. The genotype is the genetic makeup, and is represented by letters, one for each allele. Example: for two alleles, A and a; individuals could be AA, Aa, or aa. 9 What Is Evolution? Evolution is change in allele frequency (proportion) over time. Example: population of 1,000 individuals: 360 are AA, 480 are Aa, 160 are aa Frequency of a = 800/2,000 = 0.4 (40%) Frequency of A = 1,200/2,000 = 0.6 (60%) If the frequency of A increased to 75%, we can use statistical analysis to see if that change was meaningful. If so, the population evolved at that gene. 10 5  What is Evolution? Change in allele frequency indicates a genetic change in a population, meaning a trait must be heritable. A broader definition is descent with modification– populations accumulate differences over time.  As a population accumulates differences over time a new species may form, different from its ancestors, but with many of the same characteristics. 12 Canis familiaris Species are groups of organisms whose members have similar characteristics and can interbreed. Dogs are all one species, with different breeds. 13 6  Mechanisms for Evolutions Mechanisms for evolutions 1)Natural selection 2)Genetic drift 3)Gene flow (4) Artificial selection)  Mutation is the source of new alleles; recombination is a re-arranging of existing alleles 14 Mechanisms of Evolution: Mutation Phenotypic differences in individuals are the result of: 1. Mutations- a change in the DNA of a gene  Errors during cell division  Damage to DNA  Mutation is central to evolution, it provides the raw materials for change.  In each generation, mutations occur at a rate of 1 every 10,000 to 100,000 copies of a gene 15 7  Mechanisms of Evolution: Mutation Mutations cause evolution of antibiotic resistance in E. coli https://www.youtube.com/watch?v=plVk4N VIUh8 16 Mechanisms of Evolution: Mutation In just 10 days, the E.coli colonies grow resistant to stronger and stronger antibiotics across several generations How? E. coli replicate every 20 minutes You can see evolution occurring in real time, it is not something that only happened in the past! 17 8  Mechanisms of Evolution: Recombination 2. Recombinations- offspring with combinations of alleles that differ from either of their parents 18 Charles Darwin Charles Darwin used the phrase “descent with modification.” He proposed that populations become different over time through natural selection: Individuals with certain heritable characteristics survive and reproduce more successfully than individuals with other heritable characteristics. 19 9  Charles Darwin Served on Voyage of HMS Beagle 1831-1836 Over the next 20 years wrote his masterpiece The Origin of Species by Means of Natural Selection Independently, A. R. Wallace arrived at same conclusions Gave a joint paper July 1, 1858 Darwin’s seminal book was published in 1859 20 Galapagos Tortoise Common descent Modifications that improve the match between the organism and its’ environment http://statedclearly.com/videos/what-is-natural-selection/ 21 10 Figure 6.4 Natural Selection Can Result In Differences Between Populations Natural selection can cause populations to diverge genetically over time Populations evolve, not individuals 22 Mechanisms of Evolution: Natural Selection Natural selection occurs when individuals with particular heritable traits consistently leave more offspring than individuals with other heritable traits. In other words, their fitness (an individuals’ contribution to future generations) is improved. 24 11  Case Study- Beak Morphology in Darwin’s Finches Medium ground finch inhabits Daphne Major (Galapagos Islands) Wide range of beak depths, follows normal distribution 25 Case Study- Beak Morphology in Darwin’s Finches Beak depth is Heritable Significant climate variability on Daphne Major ENSO caused extreme drought in 1977- 80% of finches died 26 12  Case Study- Beak Morphology in Darwin’s Finches Finches with deep beaks survived better because Caltrop was one of the only food sources remaining after the drought 27 Case Study- Beak Morphology in Darwin’s Finches Because the trait is heritable, the next generation of offspring also had deeper beaks However, 1983 was very wet favoring soft seeds, and beak depth then decreased * Evolution can be rapid * Traits can be advantageous in one environment, can be disadvantageous in another 28 13  Mechanisms of Evolution: Natural Selection Natural selection can be categorized into three types: Directional selection Stabilizing selection Disruptive selection 29 Directional: Individuals with one extreme of a heritable phenotypic trait are favored 30 14  Directional Selection Antibiotic resistance is Wild population often direction selection Ex) a small percent of Mycobacterium After rifampicin treatment tuberculosis (the bacteria that causes Tuberculosis) contain a rpoB gene that prevents rifampicin (antibiotic) from stopping Subsequent generations RNA transcription 31 Stabilizing: Individuals 2 predators- one prefers large with an intermediate galls, one prefers small galls phenotype are favored 32 15  Disruptive: Individuals at both phenotypic extremes are favored. 2 food sources favor 2 sizes of jaws- individuals that had either extreme survived best 33 Review Evolution is change in allele frequency (proportion) over time. Or “decent with modification.” Sources of genetic variation?  Mutations  Recombinations Natural selection (adaptive evolution)  Trait must be heritable  Trait must increase fitness  Types:  directional, stabilizing, disruptive 37 16  What about human lifestyles? Modification of our environment Modern medicine Prenatal genetic testing 38 Small Group Discussion Have humans disrupted natural selection for our species? What do you think are the most detrimental innovations or choices we make that work against natural selection? 39 17  Artificial Selection Intentional reproduction (selective breeding) of individuals in a population that have desirable traits. 40 The power of selective breeding Brassica oleracea 41 18  Are you opposed to “GMOs”? 42 What is a “GMO” A genetically modified organism (GMO) is an organism in which the genetic material has been altered in a way that does not occur naturally through fertilization and/or natural recombination. --European Food Safety Authority Historic Selective Breeding Techniques Biotechnology 43 19  GMOs Major goals of GMOs: pest protection, herbicide resistance, and drought tolerance GMOs are regulated with the same “Frankenfoods” vigor as non-GMO foods and by the same agencies In the US, companies are not required to label GMO foods No reports of ill effects have been proven in the human population from ingesting GMO food 44 GMOs Herbicide-tolerant and Bt-transgenic crops now dominant U.S. agriculture, accounting for around 95% of soybean and cotton acres, and over 85% of corn acres. Over the first six years of commercial use (1996-2001), HT and Bt crops reduced pesticide use by 31 million pounds, or by about 2%, compared to what it likely would have been in the absence of GE crops. However, shifts in weed communities and the emergence of resistant weeds has increased herbicide use. Overall pesticide use in 2011 was about 20% higher on each acre planted to a GE crop, compared to pesticide use on acres not planted to GE crops. 45 20  Mechanisms of Evolution: Genetic Drift Genetic drift occurs when chance events determine which alleles are passed to the next generation. AA = red, Aa = pink, aa=white Population 1 Population 2 46 Mechanisms of Evolution: Genetic Drift Genetic drift is typically only a significant force in small populations. Because it is based on chance alone:  allele frequencies can fluctuate randomly and possibly disappear (resulting in decreased genetic variation)  Harmful alleles may increase in frequency 47 21 Mechanisms of Evolution: Gene Flow Gene flow occurs when alleles are transferred from one population to another via movement of individuals or gametes (i.e., pollen). Two effects: 1) Populations become more similar  Gene flow always acts to slow down or prevent speciation 2) New alleles are introduced into a population 48 Mechanisms of Evolution: Gene Flow Gene flow can limit the match between an organisms and it’s environment Ex) Bentgrass has a highly tolerant genotype that can grow in acid mine drainage, but grows poorly in normal soils. Wind-driven pollination continuous introduces the tolerant genotype into normal soils. 49 22  Adaptation connects Ecology and Evolution Adaptations are features of organisms that improve their ability to survive and reproduce in their environments. Ecology is the basis for understanding evolution 51 Adaptive Evolution can be rapid The growing season of many plant species have evolved in response to climate change. Bacteria (days to months) Insects (months to years) Mammals (several years) 52 23  Adaptations are not perfect The environment changes continuously Constraints on adaptive evolution:  Lack of genetic variation  Mutations arise by chance, not on demand  Natural selection works on modifying the traits already present  Constrained by natural history of organisms  Trade-offs always exist, so adaptation represents a compromise 53 Lack of Genetic Variation Organophosphate pesticides were effective in killing mosquitos for decades Until gene flow from Asia introduce a resistant gene into the US population 54 24  Evolutionary History 55 Ecological Trade-offs Reproducing at a young age increases mortality in red deer. Reproducing females Non-reproducing females 56 25  Long-term consequences of evolution Long-term patterns of evolution are shaped by large-scale processes such as speciation, mass extinction, and adaptive radiation. All 1.5+ million species of today originated from mutations and subsequent speciation- one species splits into 2 or more 57 Speciation on Earth If you wanted to squeeze the 3.5 billion years of the history of life on Earth into 1 minute, you would have to wait about 50 seconds for multicellular life to evolve, another 4 seconds for vertebrates to invade land, another 4 seconds for flowers to evolve — and only in the last 0.002 seconds would "modern" humans arise. 58 26 Speciation Speciation—the process by which one species splits into two or more species. Often results from a barrier to gene flow (geographic or ecological) *Must result in a reproductive barrier between new species 59 Speciation 60 27 mass extinction = events in which a large proportions of Earth’s species were driven to extinction worldwide in a relatively short time. 265 mybp: amphibians were replaced by reptiles as the dominate terrestrial vertebrate 65 mybp: reptiles were replaced by mammals as the dominate terrestrial vertebrate 62 6th Mass extinction underway? About 477 vertebrates have gone extinct since 1900; based on “baseline” extinction rates, we would expect only ~9 species in that time frame Amphibian have the highest rate of endangerment This would be the first mass extinction caused by a single species- humans 63 28  The Evolutionary History of Life Repeated speciation events increases the number of species in a group, but some species are also lost to extinction. An evolutionary tree is a branching diagram that represents the evolutionary history of a group. 64 Extinction often provides the “missing link” 65 29  Mass extinctions are devastating on biodiversity, but are followed by great increases in diversity of surviving groups adaptive radiations are events in which a group of organisms gives rise to many new species that expand into new habitats or new ecological roles in a relatively short time 66 Speciation and adaptation of one group, can lead to increased diversity in another  Introduced Caused sympatric speciation of maggot fly species and its’ predator  Predator-prey arms race  Range New food source expansions 67 30  Joint Ecology and Evolution Ecological interactions and evolution exert a profound influence on one another. Evolution can result from a range of ecological interactions, including predation, competition, herbivory, parasitism, and mutualism. 68 Summary Ecology is the study of the interactions between organisms and each other, and organisms and their environment; evolution (especially natural selection) directly influences these interactions Mutations, natural selection, genetic drift, gene flow, and artificial selection are all mechanisms for evolution Speciation, mass extinction, and adaptive radiation shape long-term patterns in evolution 69 31