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Chapter 13 – How Populations Evolve I. The Blue-Footed Booby A. Found on Galapagos islands B. “booby” – slang for stupid 1. Easily approachable by humans (easily killed) C. Why do they have the physical features they do? blue feet, etc… 1. Helps them succeed in environment of course a) large webbed feet – (1) great for swimming (they hunt in water) (2) terrible on land for walking or taking off (flight) b) body and bill streamlined like torpedo (1) minimize friction on 80 foot high dives into shallow water c) Large tail (1) to steer them out of dive before hitting ocean floor d) nostrils that close (1) prevent water intake e) many glands (specialized groups of cells that secrete substance into blood (endocrine), body cavity or surface of body (exocrine)) (1) preen gland - base of tail secretes oil (fatty acid) for waterproofing (2) supraorbital gland – found in bird eye socket – converts salt water to fresh water (a) removes excess salt from blood, concentrates it, and puts it into nasal cavity and expelled when bird shakes head from side to side. D. Are all adaptations positive all the time? 1. Adaptations usually represent a trade-off a) webbed feet – water vs. dry land (1) net advantage - improves chance of surviving long enough to reproduce. E. Evolutionary adaptations – inherited traits that enhance an organism’s ability to survive and reproduce in a particular environment 1. We will examine some of the processes by which species develop evolutionary adaptations – EVOLUTION (inherited change in organisms over time). F. How do organisms change? EVIDENCE OF EVOLUTION II. A sea voyage helped Darwin frame his theory of evolution A. The main idea advanced by Darwin 1. Species change over time and that living species have arisen from earlier life-forms B. This idea can be traced back to the ancient Greeks 1. 2500 years ago Anaximander (greek philosopher) a) life arose in water and simpler forms preceeded more complicated forms C. The road from Anaximander to Darwin – long, torturous 1. Aristotle – very influential – species are fixed and do not evolve 2. Judeo-Christian culture – literal interpretation of the Book of Genesis – all species individually designed by a divine creator 3. Static species on a 6,000 year old Earth dominated Western world for centuries 4. In the century before Darwin, only a few scientists questioned the biblical story of creation and fixed species. a) mid 1700’s – study of Fossils by French Naturalist Georges Buffon suggested that the Earth might be older than 6,000 yrs. (1) Fossils – imprints or remnants of organisms that once lived b) Similarities observed between living organisms and fossils c) 1766 – Buffon proposed that certain fossil forms might be ancient versions of similar living species d) Early 1800’s – French Naturalist Jean Baptiste Lamarck suggested that this is best explained by organisms evolving. (1) Lamarck is today remembered most for his erroneous view of how species evolve. (a) INHERITANCE OF ACQUIRED CHARACTERISTICS - Proposed that by using or not using its body parts and individual may develop certain traits which it passes on to offspring (i) Ex – Giraffes inherited long neck from ancestors who stretched their necks higher and higher to reach leaves in trees (2) Lamarck set the stage for Darwin!! D. Darwin – Dec. 1831, age of 22, embarked on a round-the world sea voyage as a crewmember of the HMS Beagle. 1. HMS Beagle – Surveying ship to chart the poorly known stretches of South American coastline. 2. He collected thousands of living and fossilized specimens along the south American shoreline 3. He noted that the fossils resembled the living species in the region which the fossils were found! 4. Organism distribution on the Galapagos islands also made strong impressions on Darwin. 5. He was influenced by geologist Charles Lyell’s Principles of Geology – Earth undergoes continual, gradual, persistent change – explaining why he found fossils of marine snails in the Andes. 6. The beagle returned to England in 1836 and Darwin began work on an essay to document his observations, which was completed in the early 1840’s, but did not publish it fearing rightfully that it would cause a social furor. 7. In the mid-1850’s, Alfred Wallace, a British Naturalist, conceived a theory similar to Darwins – Darwin was sent the manuscript (unpublished) 8. In 1858, Wallace’s manuscript along with excerpts of Darwin’s essay were presented together. 9. 1859 – Darwin published his complete text, On the Origin of Species by Means of Natural Selection – contained a ton of evidence and presented a strong, logical argument for evolution and how he thought it worked – Natural Selection 10. Descent with modification – the term used by Darwin in the first edition of his book until the last paragraph where it switched to evolution. a) All organisms related through descent from an unknown species in the distant past b) As descendents spread into various habitats over millions of yrs, they accumulated diverse modifications (adaptations), that acommidated them to diverse ways of life c) Resembled a tree with the common ancestor at the trunk E. Darwins idea of Evolution has been greatly extended since the 1800’s, but his idea remains the core of evolution to this date. It has stood the test of time. There has not been one shred of evidence to disprove what Darwin suggested! There have been few contributions in science that have explained as much and stimulated as much research as those of Charles Darwin. III. Evidence for Evolution A. Fossils – evidence of past life – preserved remains or traces of organisms 1. critical in the understanding of evolution (Darwin) a) they document change over time 2. Mostly hard parts of organisms found – soft, organic parts decay quickly 3. Only a tiny fraction of organisms have been fossilized. 4. 2 main forms of fossils a) true form fossils – fossils of animal or remnant b) trace fossils (ichnofossils) – fossilized nest, burrows, footprints… 5. Types of fossils a) petrified fossils – hard or soft parts (usually hard) are replaced with minerals b) unaltered fossils (rare) – insect stuck in amber -protected from bacteria and fungi c) mold fossils – a fossilized impression made by substrate (negative image) d) cast fossils – formed when a mold is filled 6. Paleontologists – the scientists who study fossils 7. Fossil Record – ordered array in which fossils appear within layers of sedimentary rock a) Sedimentary rock – forms from layers of minerals that settle out of water – younger strata on type and older on bottom 8. Oldest known fossil – 3.5 billion years – prokaryotes (surprised?) 9. Vertebrate fossil record – fishlike fossils are first observed, then amphibians, then reptiles, then mammals and birds 10. If evolution is correct, what should we find? a) transitional fossils (missing links) – fossils that link two modern day species to each other -Whales – hind leg bones, fossils of extince whales with hind limbs -Feathered dinosaurs -Change in skull size in humans B. Biogeography – geographic distribution of species 1. Darwin noticed that the animals on the Galapagos were more similar to animals on the near mainland of South America as compared to animals on similar islands elsewhere in the world – Galapagos species evolved from South American immigrants. C. Comparative Anatomy – comparison of body structures in different species 1. anatomical similarity gives sign of common descent 2. Also sited by Darwin 3. Homologous structures – structurally similar, different function a) If the structures (a bats wing and whales forelimb) had been uniquely engineered, we would expect different designs b) Evolution builds on what is already present. It remodels organisms, it doesn’t create anew – what served as a flipper can be tweaked to serve a new function c) Human spine and knee – modified from ancestral structures that supported four-legged animals – knee and back problems. D. Comparative Embryology – study of structures appearing during development of different organisms 1. Closely related organisms have similar stages in embryonic development a) Pharyngeal slits on sides of throat present in all vertebrates (fishes, frogs, snakes, birds, apes, humans!) - Most become gills in fish -Become bones of skull, bones supporting tongue and voice box of mammals E. Molecular Biology – the study of the molecular basis of genes and gene expression 1. Universal genetic code 2. Within species - Related individuals of the same species have greater similarity in DNA and proteins compared to unrelated individuals 3. Between species - Closely related species have a greater similarity in DNA and proteins compared to more distantly related species 4. Hemoglobin polypeptide comparison (146 amino acids) 5. Master Control Genes – homeotic genes (code for transcription factors) – regular groups of other genes during embryonic development. Similar nucleotide sequences in these genes especially of related organisms F. So how does evolution operate? DARWIN’S THEORY and the MODERN SYNTHESIS HOW DOES NATURAL SELECTION OPERATE? IV. Darwin proposed natural selection as the mechanism of evolution A. Darwin - Influenced by British economist Thomas Malthus – much of human suffering (disease, famine, homelessness, war) was the consequence of our ability to grow in population faster than we could produce what we need to live. B. Darwin recognized that: 1. All species tend to produce excessive numbers of offspring (Will all humans born today get to survive and reproduce?) 2. Only a percentage of offspring will survive in each generation – limited by natural resources (Who is most likely to survive and reproduce?) 3. Individuals of a population vary extensively and their survival depends on their traits. 4. If an organism gets the chance to reproduce, these traits will be passed on (inherited). a) Natural Selection - Individuals whose characteristics adapt them best to their environment are more likely to survive and reproduce, leaving more offspring b) Essence of natural selection = differential (unequal) reproduction c) environment filters variations, favoring some characteristics over others. d) Favorable characteristics will be present more and more and unfavorable ones less and less over generations leading to a gradual change in the population over time. Darwin saw evidence in: C. Artificial Selection – if nature can do it, we should be able to do it too – selective breeding of domesticated plants and animals. 1. Darwin found convincing evidence in artificial selection 2. Humans play role of environment a) Dogs b) Vegetables 3. Achieved over relatively short span of time – compare to evolutionary time scale V. Scientists can observe natural selection in action 1. Over 100 cases have been identified a) Changes in population of ground finch beak size in 20 years on Galapagos observed (1) Depends on wet or dry season (2) Wet years = many small seeds = birds with smaller beaks have advantage (vice versa for dry years) b) Insecticide resistance (1) Poisons might kill 99% of the insects, but 1% remains – resistant (2) Could be considered artificial selection for resistant insects B. Natural selection is an EDITING PROCESS – it does not create – C. Natural selection depends on time and place – favors characteristics that fit current, local environment. D. Significant changes can occur in a short time. VI. THE MODERN SYNTHESIS: A. Darwin (published 1859) did not understand the genetic basis of evolution - Mendel’s work did not come to light until 20 years after Darwin’s death (1902) – published 1866. 1. He could not explain the cause of variation among individuals (law of segregation and independent assortment, crossing over, mutation, etc…) within a population or the perpetuation of parents traits in their offspring. 2. He knew nothing of genes B. Modern Synthesis (1940’s) – theory of evolution that includes genetics in combination with Darwin’s ideas (natural selection). 1. What kind of genetics? The genetics of an individual? What evolves? An individual? 2. A Population is the smallest unit that can evolve a) Population – group of individuals of the same species, living in the same place at the same time. b) Populations can be isolated from each other -Galapagos finches c) Partially isolated -New York City and Mexico City population (partially isolated) d) Population centers – not isolated, but more likely to mate locally. e) Result – individuals in one population are more closely related on average to one another than to members of other populations 3. Population genetics – focuses on two ideas a) gene pool – total collection of alleles at any given time (Evolution can’t make new alleles, it can only edit alleles already present. How do new alleles arise?) -Reservoir for the next generation, most loci have two or more alleles b) allele frequency – how often a particular allele appears in a population 4. Examples of shifts in allele frequency a) Example : Insecticide Resistance b) Two alleles for an enzyme – one gives insecticide resistance (breaks down insecticide), the other does not. c) Initially the one that does not give resistance has higher frequency in population. d) Spray fields with insecticides. e) Allele that confers resistance increases in frequency while the other decreases. f) Example: House Sparrows 5. Microevolution – change in relative frequencies of alleles over time – evolution on its smallest scale VII. Let’s Consider a hypothetical, non-evolving population of blue footed boobies. A. Two varieties - differ in foot webbing controlled by a single gene 1. Allele for non-webbed feet - dominant (W) 2. Allele for webbed feet - recessive (w) 3. After many generations, which allele will win? 4. Neither, sexual reproduction simply shuffles the genes, it does not make one appear more or less than the other – shuffle a deck of cards, do you end up with more of one card than another?? 5. Hardy-Weinberg Equilibrium - Gene frequency will remain the same (equilibrium) in a hypothetical nonevolving population unless acted on by OTHER agents. B. Calculating allele frequencies 1. p + q = 1 p = frequency of dominant allele q = frequency of recessive allele 2. Hardy-Weinberg Equation: a) p2 + 2pq + q2 = 1 heterozygotes frequencies homozygotes and VIII. Five conditions are required for Hardy-Weinberg equilibrium A. The Five: 1. The population is very large 2. The population is isolated; that is, there is no migration of individuals or gametes into or out of the population 3. Mutations (changes in genes) do not alter the gene pool 4. Mating is random 5. All individuals are equal in reproductive success; that is natural selection does not occur B. Can you think of a population where all 5 are met??? IX. The causes of microevolution A. Deviations in Hardy-Weinberg equilibrium causes changes in gene pools = microevolution B. 4 causes of microevolution 1. Genetic drift (major) 2. Natural selection (major) 3. gene flow 4. mutation C. Genetic Drift – change in gene pool of a small population due to chance 1. The smaller the sample the greater the chance of deviation from an ideal result a) Ex – compare flipping coin 10 times getting 3 heads and 7 tails vs. 1000 times getting 300 heads and 700 tails! 2. If population is large, then its more likely that the new generation will be representative of the gene pool of the previous. 3. If its small, it may not be 4. Example a) 10 Ww x Ww crosses in a population. Each cross produces a single offspring. b) 1000 Ww x Ww crosses in a population – more likely to be closer to a 1:2:1 ratio 5. This is genetic drift, an allele becomes more frequent by chance alone having nothing to do with other agents like the environment. a) It’s most likely to play a major role in evolution when populations have 100 or fewer individuals. b) What can shrink populations down to a small size?: (1) Bottle neck effect – events that drastically reduce population like earthquakes, floods, or fires that do so unselectively (randomly) – shaking marbles out of a bottle. (a) Ex. Human hunters (1890’s) – reduced population of northern elephant seals to ~20! (b) Protected now and back to 30,000, but upon examination of 24 gene loci, scientists found only 1 allele! (c) Southern elephant seal has great variation (not bottlenecked) (2) Founder effect – colonization of a new location by a small number of individuals (a) Extreme case – single seed or single pregnant animal populates a new place. (b) Contributed to evolutionary divergence of finches that initially arrived on the Galapagos. (c) Explains relatively high frequencies of certain inherited human disorders in human populations established by small numbers of colonists. (i) 1814 – 15 people founded a British colony on Tristan da Cunha- small group of islands in middle of Atlantic. (ii) One colonist carried recessive allele for retinitis pigmentosa (RP - progressive form of blindness) 1 in 30 genes (iii)Result – of 240 descendants still living on the island in the 1960’s, 4 had RP, 9 others were carriers – frequency is much higher than frequency from which the allele came! 1 in 14 D. Gene Flow – fertile individuals move into or out of a population or when gametes are transferred between populations (ex. Sperm of plant pollen). 1. Tends to reduce genetic differences b/w populations a) The isolation of human populations has reduced gene flow over history resulting in phenotypic variations such as skin color and facial characteristics. b) Things like migration and war work against reproductive isolation – tend to increase interbreeding (gene flow) c) Today there is more gene flow between geographically different populations than ever before. E. Mutation – Random change in an organism’s DNA that may create a new allele 1. Rare event – once per gene locus per 105 or 106 gametes. a) Does not have much of an effect in a single generation of a large population b) Over the long term, it is the only force that generates new alleles!!! – creates – ultimate source of genetic variation!! F. Natural Selection 1. Only cause of microevolution that is likely to result in adaptive change in a gene pool. 2. Blue-footed booby example – webbed feet variation (ww) might product more offspring because they find food more efficiently than birds with non-webbed feet (Ww or WW). 3. The frequency of the w allele would increase as the frequency of the W allele decreases. 4. If environment changes, so might the favored traits for that new environement (the W gene may make a comeback) 5. What limits the degree of adaptation? Amount and kind of genetic variation. VARIATION AND NATURAL SELECTION X. Variation A. extensive in most populations B. Individual vary in sexually reproducing populations C. Obvious differences at the anatomical level D. Some ONLY observed at the molecular level E. Not all variation is heritable 1. Can’t pass on muscle mass from working out 2. Only the genetic component is subject to natural selection F. POLYMORPHISM - two or more morphs (different forms of a phenotypic trait) for a characteristic are present in noticeable numbers 1. Humans - Presence or absence of freckles, ABO blood types 2. California King Snakes G. Most species exhibit geographic variation between populations 1. Cline – a graded change in an inherited characteristic along a geographic continuum. a) Ex. Body size of birds and mammals tends to increase with increasing latitude in North America – large size in colder regions to conserve body heat H. How do we measure genetic variation 1. Look at gene diversity and nucleotide diversity a) Gene diversity – average percent of gene loci that are heterozygous in a population b) Nucleotide diversity – compare nucleotide sequences of DNA samples 2. Humans have LESS genetic diversity than most other species!! a) Gene diversity = 14% and nucleotide diversity is ~0.1% b) Why do you think this is? XI. Mutation and sexual recombination generate variation A. Most mutations in DNA will be harmless or harmful B. On rare occasions, a mutant allele might actually improve the adaptation of its bearer to the environment and enhance reproductive success. 1. Likely to come to light when the environment changes in such a way that mutations that were once disadvantageous are now favorable. a) Example (1) Mutations occur that make HIV resistant to antiviral drugs. (2) These same mutations also slow viral reproduction (3) The mutant alleles can be positive or negative for the success of the organisms depending on the presence or absence of antivirals. C. Chromosomal mutations – larger scale (8.23A and 8.23B) 1. A single chromosomal mutation affects many genes and likely will be harmful 2. Very rarely, a duplication of a chromosomal segment might bring benefits a) May provide a larger genome with extra genes that take on new functions – show protein examples. D. Microorganisms with very short generation spans – mutation generates genetic variation rapidly! 1. HIV – generation span of 2 days a) Produces >1010 new viruses a day in an AIDS patient b) Each replication is a chance for mutation! c) HIV also uses RNA = greater mutation rate (no proofreading) d) Result – single drug treatments will not be very effective against HIV – double drug treatments don’t work well either – need drug “cocktails”, greater than 2 drugs at once. 2. Bacteria – also multiply rapidly a) Like viruses, they are generally haploid (one gene per trait) – newly created allele can have an instant effect 3. Plants and Animals – typically long generation time and diploid architecture a) Most mutations prevented from significantly affecting genetic variation from one generation to the next b) So how do get our genetic diversity?...by shuffling up existing alleles - sexual recombination (Fig. 13.14): (1) Crossing over (2) Independent assortment of homologous chromosomes (3) Random fertilization XII. Overview: How natural selection affects variation A. Why aren’t the less adaptive alleles eliminated completely by natural selection as the best are passed on??? B. Natural selection typically strives to reduce genetic variation in a population – what counters natural selection? 1. Two sets of chromosomes (diploid) – recessive alleles can hide behind dominant ones (heterozygotes) – if they do not influence phenotype and thus are not subject to natural selection. a) When are recessive alleles subject to natural selection? b) Individuals who are homozygous recessive may be selected against in one environment, but selected for in another. 2. Balanced polymorphism – ability of natural selection to maintain stable frequencies of two or more phenontypic forms in a population. a) Sometime there is a heterozygote advantage – heterzygotes have a greater reproductive success compared to homozygotes – (1) Two or more traits are thus maintained by natural selection (2) Ex. Resistance to malaria conferred by the recessive sickle-cell allele (heterozygotes resistant to malaria) b) Frequency-dependent selection – survival and reproduction of any one morph declines if that phenotype form becomes too common. (1) Ex. A butterfly population has many different morphs. Birds may more easily locate one morph over others if it becomes too common allowing other morphs to catch up. XIII. Not all genetic variation may be subject to natural selection A. Neutral variation – variation in a heritable characteristic that provides no apparent selective advantage 1. Ex. Fingerprints 2. Some neutral alleles will increase frequency in gene pools and others decrease due to genetic drift, but are not touched by natural selection. 3. It is impossible to determine what degree a genetic variation is neutral – what appears neutral may confer some advantage or disadvantage that we don’t yet understand. XIV. Endangered species often have reduced variation A. Many species are in danger of becoming extinct thank to our species. B. Population declines = gene pool declines 1. Ex. Cheetah – fastest land animal (70mph top speed) 2. Thought to have suffered a severe bottleneck from drought, human hunting, disease – 10,000 yrs ago 3. Only three small cheetah populations exist – East Africa, South Africa, Northern Iran (number less than 50) 4. African cheetah – 0.04% of gene loci heterozygous 5. Second bottleneck during 19th century – South African farmers hunted them to near extinction 6. Little genetic variation = reduced capacity to adapt to ever increasing environmental challenges – read pg 275 – 13.17 last paragraph. XV. The perpetuation of genes defines evolutionary fitness A. “survival of the fittest” is highly misleading implying direct competitive contests b/w individuals in a population. B. Reproductive success is more subtle and passive 1. Ex. Wing color in moths to hide from predators, plants and their ability to attract pollinators due to flower color, shape, fragrance, etc… C. Darwinian Fitness – the contribution and individual makes to the gene pool of the next generation relative to the contributions of other individuals. 1. Thus, fittest individuals are those that pass on the greatest number of genes to the next generation. 2. Survival alone is not enough. Biggest, fastest, strongest of any organism has a fitness of ZERO if it is sterile 3. Production of fertile offspring is the only score that counts in natural selection! D. Evolutionary fitness has to do with genes, but it is the phenotype that is exposed to the environment 1. The fitness of any one allele depends on the entire genetic content – a) Ex. A gene that enhance tree trunk growth would be useless in the absence of alleles to enhance root growth as well – Homerun slugger on a last place team. b) Ex. Alleles that are neutral of maladaptive might get to hang around if they are perpetuated in individuals with high fitness – whole baseball team wins world series! XVI. There are three general outcomes of natural selection A. Starting with a hypothetical, bell-shaped, polygenic population – 1. Stabilizing selection – a) Favors intermediate variants – reduce phenotypic variation b) Typically occurs in a relatively stable environment c) Likely prevails in most populations most of the time (1) Ex. Human birth weight 6.5 to 9lbs – larger or smaller increases infant mortality. 2. Directional Selection a) Shifts overall makeup of population by acting against individuals at ONE of the phenotypic extremes. b) Common during periods of environmental change or when members of a species migrate to a new environment. (1) Ex. Insects exposed to insecticide or HIV exposed to antivirals. 3. Diversifying selection a) Occurs when the environment favors individuals at BOTH extremes b) Can lead to balanced polymorphism with two or more contrasting morphs (1) Ex. California King Snakes XVII. Sexual selection may produce sexual dimorphism A. Males and females obviously have different reproductive organs. B. Secondary Sexual Characteristics - they may also differ in other aspects not directly related to reproduction C. Sexual Dimorphism – the resulting distinction in appearance 1. Often results in a size difference 2. Also evident in the form of male adornment (males are usually the showier sex in vertebrates) a) Colorful plumage in birds b) Manes on lions c) Antlers on deer D. Sexual Selection – determining of who mates with whom 1. Intrasexual selection – common in species where the winning male garners a harem of females a) Secondary sex structures might be used to compete with members of same sex for mates (1) Usually ritualized displays (2) Can by physical combat 2. Intersexual selection – mate choice, more common type a) Individuals of one sex (usually female) select a mate (1) Males with the most impressive feathers are most attractive apparently – ex. Peacock/peahen (2) Darwin was intrigued because some of the mateattracting features do not seem adaptive otherwise and in some cases pose risks – make male birds more visible to predators or less maneuverable. (3) Regardless, they enhance reproductive success (Darwinian Fitness) (4) When a female chooses a mate based on appearance or behavior, the alleles that caused her to make those decisions as well as the alleles she found attractive in the male are perpetuated, and it goes on and on and on…. XVIII. Natural selection cannot fashion perfect organisms A. Why?? 1. Organisms are locked into historical constraints – evolution does not scrap ancestral anatomy and build new structures from scratch. It modifies existing structures for new situations. 2. Adaptations are often compromises – organisms must do many different things. A foot good in water will not be great on land and vice versa – blue footed booby. 3. Not all evolution is adaptive – chance likely affects evolution more than we realize. Sometimes good genes are lost and poor genes are kept. 4. Selection can only edit existing variations – Natural selection can only work with the variations that it has. New alleles arise by chance. You can’t just order up some new alleles for the occasion. B. Natural selection operates on a “better than” basis… C. We can see evidence of evolution in an organism’s subtle imperfections? What are ours? XIX. The evolution of antibiotic resistance in bacteria is a serious public health concern A. Most antibiotics are naturally occurring chemicals found derived from other microorganisms than the ones they affect. 1. Ex. Penicillin is from a mold (prescribed since the 1940’s) – cured many once fatal infections – strep throat B. 1950’s some doctors predicted the end of human infectious diseases!! Why has this not happened? C. Antibiotics select for resistant bacteria 1. Genes conferring resistance are carried on R plasmids, which are transferred to offspring and to OTHER bacteria. D. For almost every antibiotic ever developed, a resist strain of bacteria has arisen within a few decades. 1. Ex. Multi-drug resistant tuberculosis – resistant to all three commonly used antibiotics. E. How do we contribute to this problem?? 1. Livestock producers add antibiotics to animal feed as a growth promoter! – much of the packaged meat in supermarkets contain antibiotic resistant bacteria. 2. Doctors overprescribe antibiotics a) To patients with viral infections!! 3. Patients misuse antibiotics a) Stop taking them early because they feel better – mutant bacteria that are slower to die by the drug now multiply and subsequent mutations may lead to antibiotic resistance. F. Penicillin was effective against nearly all bacterial infections in the 1940’s and today is essentially useless in its original form!!! G. New drugs have been developed, but they continue to be rendered ineffective H. There is a silent war between man and bacterial evolution with the medical community and pharmaceutical companies on the front line…