Chapter 9 An Evolving Enemy Natural Selection Fourth

1 Return of an Ancient Killer § Tuberculosis has infected humans for 1000 s

1 Return of an Ancient Killer - What is Tuberculosis? § Symptoms of TB

1 Return of an Ancient Killer - What is Tuberculosis? § Consumptive symptoms occur

1 Return of an Ancient Killer - What is Tuberculosis? § Transmission of TB

1 Return of an Ancient Killer - Treatment – and Treatment Failure § In

1 Return of an Ancient Killer - Treatment – and Treatment Failure § Since

2 Natural Selection Causes Evolution § Darwin discussed two ideas in Origin: common descent

2 Natural Selection Causes Evolution - Four Observations and an Inference § Natural selection

2 Natural Selection Causes Evolution - Four Observations and an Inference 1. Individuals within

2 Natural Selection Causes Evolution - Four Observations and an Inference 2. Some of

2 Natural Selection Causes Evolution - Four Observations and an Inference 3. Populations of

2 Natural Selection Causes Evolution - Four Observations and an Inference 4. Survival and

2 Natural Selection Causes Evolution - Four Observations and an Inference § Survival and

2 Natural Selection Causes Evolution - Four Observations and an Inference § Adaptations do

2 Natural Selection Causes Evolution - Darwin’s Inference: Natural Selection Causes Evolution § Result

2 Natural Selection Causes Evolution Testing Natural Selection § Artificial selection: Selection imposed by

2 Natural Selection Causes Evolution Testing Natural Selection § In laboratory, environmental conditions can

2 Natural Selection Causes Evolution - Testing Natural Selection § Natural selection in wild

Animation: Natural Selection Click “Go to Animation” / Click “Play” © 2013 Pearson Education,

3 Natural Selection Since Darwin - The Modern Synthesis § The union of genetics

3 Natural Selection Since Darwin - The Modern Synthesis § Mutation and natural selection

3 Natural Selection Since Darwin - Overview: The Subtleties of Natural Selection § Common

Animation: Drug Resistance and Natural Selection Click “Go to Animation” / Click “Play” ©

3 Natural Selection Since Darwin - A Closer Look: Subtleties of Natural Selection §

3 Natural Selection Since Darwin - Patterns of Selection § Different environmental conditions can

4 Natural Selection and Human Health Tuberculosis Fits Darwin’s Observations § Mycobacterium tuberculosis has

4 Natural Selection and Human Health - Selecting for Drug Resistance § Simple antibiotic

4 Natural Selection and Human Health - Stopping Drug Resistance § Combination therapy is

4 Natural Selection and Human Health - Can Natural Selection Save Us From Superbugs?

What causes tuberculosis? § virus § bacteria § spores § pollution © 2013 Pearson

From 2000 to 2004, what percentage of TB cases did not respond to standard

Which of the following is an example of artificial selection? § a beetle’s acquired

Which of the following statements does not cause natural selection? § individuals within populations

What type of selection results when the average variant in the population has the

True or False: Natural selection cause new traits to arise. § True § False

What is often the result when people stop taking their antibiotics when they feel

Which of the following statements is not an efficient way to combat drug-resistant pathogens?

What type of selection is shown in this figure? § directional selection § artificial

What will the fly population look like after several generations? § The frequency of

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Chapter 9 An Evolving Enemy Natural Selection Fourth Edition BIOLOGY Science for Life | with Physiology Colleen Belk • Virginia Borden Maier © 2013 Pearson Education, Inc. Copyright © 2009 Pearson Education, Inc. Power. Point Lecture prepared by Jill Feinstein Richland Community College

1 Return of an Ancient Killer § Tuberculosis has infected humans for 1000 s of years. § Evidence of TB has been found in Egyptian mummies. § Hippocrates described a TB-like condition. § In 1906, TB accounted for 2 out of every 1000 deaths in the U. S. § TB is caused by bacterium, Mycobacterium tuberculosis. § 2 billion people carry TB. § New infections occur at rate of 1 per second. § TB causes roughly 2 million deaths per year. © 2013 Pearson Education, Inc.

1 Return of an Ancient Killer - What is Tuberculosis? § Symptoms of TB include: § Cough that produces blood § Fever § Fatigue § Period of wasting – patient becomes weaker and thinner § Led to calling the disease “consumption” © 2013 Pearson Education, Inc.

1 Return of an Ancient Killer - What is Tuberculosis? § Transmission of TB occurs through the air, from infected individuals. § A single sneeze can contain 40, 000 droplets, all containing infectious bacteria. § Most individuals can fight off the infections, except young children, elderly and immune compromised individuals. © 2013 Pearson Education, Inc.

1 Return of an Ancient Killer - Treatment – and Treatment Failure § In the 19 th and early 20 th century, TB treatment consisted of “sanitariums. ” § The discovery of antibiotics revolutionized TB treatment. § After 2 weeks of antibiotic treatment the individual is no longer contagious. § However, treatment with antibiotics needs to continue for 6 to 12 months to completely eliminate the organism. § Since the 1980 s, scientists have noticed an increase in TB that is resistant to antibiotics. § Because of resistance to antibiotics, the number of TB cases worldwide is increasing. © 2013 Pearson Education, Inc.

1 Return of an Ancient Killer - Treatment – and Treatment Failure § Since the 1980 s, scientists have noticed an increase in TB that is resistant to antibiotics. § Because of resistance to antibiotics, the number of TB cases worldwide is increasing. § There is a strain of TB that is now resistant to both the original treatment but also resistant to secondline drugs. § 1/3 of individuals with this extreme strain die of the disease © 2013 Pearson Education, Inc.

2 Natural Selection Causes Evolution § Darwin discussed two ideas in Origin: common descent and natural selection § Natural selection is considered to be the primary cause of evolution § Other factors of evolution include genetic drift and sexual selection © 2013 Pearson Education, Inc.

2 Natural Selection Causes Evolution - Four Observations and an Inference § Natural selection is an inference based on four observations: 1. Individuals within populations vary 2. Some of the variation within individuals can be passed on to their offspring 3. Populations of organisms produce more offspring than will survive 4. Survival and reproduction are not random © 2013 Pearson Education, Inc.

2 Natural Selection Causes Evolution - Four Observations and an Inference 1. Individuals within populations vary. § This is true of human and non-human populations. § Variation can include traits other than appearance, such as blooming time in flowers. © 2013 Pearson Education, Inc.

2 Natural Selection Causes Evolution - Four Observations and an Inference 2. Some of the variation within individuals can be passed on to their offspring. § Darwin noticed that animal breeders could get exaggerated traits through selective breeding. © 2013 Pearson Education, Inc.

2 Natural Selection Causes Evolution - Four Observations and an Inference 3. Populations of organisms produce more offspring than will survive. § Even slow-breeding animals can produce large populations quickly. © 2013 Pearson Education, Inc.

2 Natural Selection Causes Evolution - Four Observations and an Inference 4. Survival and reproduction are not random § Fitness: Relative survival and reproduction of one variant § Adaptation: Traits that increase individual fitness in an environment § Individuals with adaptations for a particular environment are more likely to survive and reproduce. © 2013 Pearson Education, Inc.

2 Natural Selection Causes Evolution - Four Observations and an Inference § Adaptations do not only affect survival. § A flower’s reproduction is impacted by traits that affect the number of pollinators it receives. § Therefore, color or nectar production might be adaptations. © 2013 Pearson Education, Inc.

2 Natural Selection Causes Evolution - Darwin’s Inference: Natural Selection Causes Evolution § Result of natural selection § Favorable inherited variations tend to increase in frequency § Unfavorable variations tend to be lost § End result is a change in the traits of individuals in a population over generations © 2013 Pearson Education, Inc.

2 Natural Selection Causes Evolution Testing Natural Selection § Artificial selection: Selection imposed by human choice § Breeds of pigeons studied by Darwin arose through artificial selection § Breeds of dog have been artificially selected by humans © 2013 Pearson Education, Inc.

2 Natural Selection Causes Evolution Testing Natural Selection § In laboratory, environmental conditions can be manipulated and effects on population examined § Scientists examined alcohol metabolism in fruit flies § Variations in ability to metabolize alcohol exist in populations © 2013 Pearson Education, Inc.

2 Natural Selection Causes Evolution - Testing Natural Selection § Natural selection in wild populations § Many examples exist: § Evolution of resistance of M. tuberculosis to antibiotics § Many other disease-causing pathogens have also evolved resistance § Galapagos finches provide another classic example § Blue mussel has evolved the ability to thicken its shell to protect against the invasive Asian crab species. © 2013 Pearson Education, Inc.

3 Natural Selection Since Darwin - The Modern Synthesis § The union of genetics and evolution is called “the modern synthesis. ” § Knowledge of genetics facilitates understanding of the mechanisms of evolution. § Alleles are the basis of variation of traits. § Half of the alleles carried by a parent are passed to their offspring through their egg or sperm. § Mutations can create new alleles and provide the basis for new traits. § Natural selection provides a filter that selects for or against new traits. © 2013 Pearson Education, Inc.

3 Natural Selection Since Darwin - A Closer Look: Subtleties of Natural Selection § Natural selection cannot cause new traits to arise § Not an issue of choice or “will” of organisms § Selection can only act on variations that already exist § For example, alcohol-rich environment in flies did not cause a gene to arise, instead differential survival caused allele to become more common © 2013 Pearson Education, Inc.

3 Natural Selection Since Darwin - A Closer Look: Subtleties of Natural Selection § Natural selection does not result in perfection § Natural selection does cause organisms to become a better fit to their environment § Organisms are not necessarily “better, ” just better fit to a particular situation § Adaptation that is beneficial in one situation might be a liability in another § Adaptations are trade-offs between better fit in one situation versus another § Adaptations are constrained by underlying biology © 2013 Pearson Education, Inc.

3 Natural Selection Since Darwin - A Closer Look: Subtleties of Natural Selection § Natural selection does not cause progression towards a goal § Natural selection favors variants with the most appropriate adaptations for current environment § Organisms do not choose to change or adapt § Natural selection depends on the situation of the population © 2013 Pearson Education, Inc.

3 Natural Selection Since Darwin - Patterns of Selection § Different environmental conditions can lead to different changes in populations § Directional selection – change in population traits © 2013 Pearson Education, Inc.

3 Natural Selection Since Darwin - Patterns of Selection § Different environmental conditions can lead to different changes in populations § Stabilizing selection – selection for the average traits © 2013 Pearson Education, Inc.

3 Natural Selection Since Darwin - Patterns of Selection § Different environmental conditions can lead to different changes in populations § Diversifying selection – selection for extremes © 2013 Pearson Education, Inc.

4 Natural Selection and Human Health Tuberculosis Fits Darwin’s Observations § Mycobacterium tuberculosis has evolved resistance to antibiotics because it fulfills the same observations Darwin made 1. Organisms in the population vary 2. The variation among organisms can be passed on to offspring 3. More organisms are produced than survive 4. An organism’s survival is not random © 2013 Pearson Education, Inc.

4 Natural Selection and Human Health - Can Natural Selection Save Us From Superbugs? § If bacteria can evolve resistance to antibiotics, can humans evolve resistance to bacteria? § Humans do vary in their immune capacity § To evolve resistance to superbugs would require many humans to die § Evolution of resistance requires exposure to pathogens, most humans are never exposed § Natural selection has also resulted in our brains, giving us another tool to fight disease © 2013 Pearson Education, Inc.

Which of the following is an example of artificial selection? § a beetle’s acquired immunity to pesticide § horse breeding § the average bill size increasing for finches due to drought § none of the above © 2013 Pearson Education, Inc.

Which of the following statements does not cause natural selection? § individuals within populations vary § some of the variation within individuals can be passed on to their offspring § populations of organisms produce more offspring than will survive § survival and reproduction are random © 2013 Pearson Education, Inc.

What type of selection results when the average variant in the population has the highest fitness? § directional selection § stabilizing selection § diversifying selection § artificial selection © 2013 Pearson Education, Inc.

What is often the result when people stop taking their antibiotics when they feel better? § A drug-resistant strain is born. § The person will have to restart the antibiotic course. § The person will continue to feel fine. § The person will be immune to that type of infection. © 2013 Pearson Education, Inc.

Which of the following statements is not an efficient way to combat drug-resistant pathogens? § People can use drug cocktails. § People can evolve resistance to the pathogens. § People can continue to take their antibiotics for many months. § There is no way to combat drug-resistant pathogens. © 2013 Pearson Education, Inc.

What will the fly population look like after several generations? § The frequency of the mutant allele will increase § The frequency of the normal allele will increase § There will be an equal frequency of the normal and mutant alleles § There is no way to tell what the population will look like © 2013 Pearson Education, Inc.