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CHAPTER 12 EVOLUTION AND EXTINCTION A TROPICAL MURDER MYSTERY Finding the missing birds of Guam. 12. A TROPIAL MURDER MYSTERY Finding the missing birds of Guam. At the end of this chapter you will know: A variety of factors influence natural selection and contribute to evolution.
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CHAPTER 12 EVOLUTION AND EXTINCTION A TROPICAL MURDER MYSTERYFinding the missing birds of Guam
12 A TROPIAL MURDER MYSTERYFinding the missing birds of Guam • At the end of this chapter you will know: • A variety of factors influence natural selection and contribute to evolution. • Factors that contribute to endangerment of species. Learning Outcomes
12 A TROPIAL MURDER MYSTERYFinding the missing birds of Guam Main Concept Extinction is part of natural selection but the background rate at present is several times what we would expect of nature. Human action has contributed to extinction around the world in what is being called the “sixth great extinction.” The fifth extinction was 65 million years ago and included dinosaurs. TERMS TO KNOW: Invasive species Extinct/extinction
12 A TROPIAL MURDER MYSTERYFinding the missing birds of Guam Case study: Beginning in the late 1960s, indigenous bird species began disappearing from Guam. Within twenty years, four species had become extinct. TERMS TO KNOW: Invasive species Extinct/extinction Scientists’ hypotheses about the birds’ demise included blood parasites and pesticides. By asking local people about the problem, the answer came back—non-native snakes. Brown tree snake Boigairregularis
12 Natural selection is the main mechanism by which populations adapt and evolve Within any population, some individuals are better suited to their environment than others. Those with the “right stuff” will be successful and reproduce. This pressure from the environment is non-random and results in genes for specific adaptations like coloration or size becoming more common within a population. It is through this process of natural selection of individuals that populations evolve.
12 Natural selection is the main mechanism by which populations adapt and evolve Within any population, some individuals are better suited to their environment than others. Those with the “right stuff” will be successful and reproduce. This pressure from the environment is non-random and results in genes for specific adaptations like coloration or size becoming more common within a population. It is through this process of natural selection of individuals that populations evolve.
12 Natural selection is the main mechanism by which populations adapt and evolve Within any population, some individuals are better suited to their environment than others. Those with the “right stuff” will be successful and reproduce. This pressure from the environment is non-random and results in genes for specific adaptations like coloration or size becoming more common within a population. It is through this process of natural selection of individuals that populations evolve.
12 Natural selection is the main mechanism by which populations adapt and evolve Within any population, some individuals are better suited to their environment than others. Those with the “right stuff” will be successful and reproduce. This pressure from the environment is non-random and results in genes for specific adaptations like coloration or size becoming more common within a population. It is through this process of natural selection of individuals that populations evolve.
12 Natural selection is the main mechanism by which populations adapt and evolve Within any population, some individuals are better suited to their environment than others. Those with the “right stuff” will be successful and reproduce. This pressure from the environment is non-random and results in genes for specific adaptations like coloration or size becoming more common within a population. It is through this process of natural selection of individuals that populations evolve. Potential outcomes of natural selection
12 Natural selection is the main mechanism by which populations adapt and evolve Within any population, some individuals are better suited to their environment than others. Those with the “right stuff” will be successful and reproduce. This pressure from the environment is non-random and results in genes for specific adaptations like coloration or size becoming more common within a population. It is through this process of natural selection of individuals that populations evolve. Potential outcomes of natural selection
12 Natural selection is the main mechanism by which populations adapt and evolve Within any population, some individuals are better suited to their environment than others. Those with the “right stuff” will be successful and reproduce. This pressure from the environment is non-random and results in genes for specific adaptations like coloration or size becoming more common within a population. It is through this process of natural selection of individuals that populations evolve. Potential outcomes of natural selection
12 Natural selection is the main mechanism by which populations adapt and evolve Within any population, some individuals are better suited to their environment than others. Those with the “right stuff” will be successful and reproduce. This pressure from the environment is non-random and results in genes for specific adaptations like coloration or size becoming more common within a population. It is through this process of natural selection of individuals that populations evolve. Potential outcomes of natural selection: Stabilizing selection, directional stability, disruptive selection
12 Populations need genetic diversity to evolve TERMS TO KNOW: Selective pressure Adaptation Natural selection Genes Evolution Gene frequencies Genetic diversity Two or more species can put pressure on one another like a ratchet. As one characteristic rises to dominance in a species, other species affected by the characteristic will also experience selective pressure. Coevolution is the outcome when two species provide the selective pressure that determines the traits favored by natural selection.
12 Populations need genetic diversity to evolve TERMS TO KNOW: Selective pressure Adaptation Natural selection Genes Evolution Gene frequencies Genetic diversity Two or more species can put pressure on one another like a ratchet. As one characteristic rises to dominance in a species, other species affected by the characteristic will also experience selective pressure. Coevolution is the outcome when two species provide the selective pressure that determines the traits favored by natural selection.
12 Populations need genetic diversity to evolve The invasive brown tree snake was well adapted to successfully prey on Guam’s birds, but the birds had never faced a predator like this. Without any natural defenses, the birds disappeared so quickly that it was difficult to determine the cause of their extinction. By matching the pattern of declining bird populations with the reported appearance of snakes, researchers were able to establish correlation. Coevolution is the outcome when two species provide the selective pressure that determines the traits favored by natural selection.
12 Populations need genetic diversity to evolve The invasive brown tree snake was well adapted to successfully prey on Guam’s birds, but the birds had never faced a predator like this. Without any natural defenses, the birds disappeared so quickly that it was difficult to determine the cause of their extinction. By matching the pattern of declining bird populations with the reported appearance of snakes, researchers were able to establish correlation. Coevolution is the outcome when two species provide the selective pressure that determines the traits favored by natural selection.
12 Populations need genetic diversity to evolve The invasive brown tree snake was well adapted to successfully prey on Guam’s birds, but the birds had never faced a predator like this. Without any natural defenses, the birds disappeared so quickly that it was difficult to determine the cause of their extinction. By matching the pattern of declining bird populations with the reported appearance of snakes, researchers were able to establish correlation. Coevolution is the outcome when two species provide the selective pressure that determines the traits favored by natural selection.
12 Populations need genetic diversity to evolve Coevolution is the outcome when two species provide the selective pressure that determines the traits favored by natural selection.
12 Populations can diverge into subpopulations or new species TERMS TO KNOW: Extirpation Genetic drift Bottleneck effect Founder effect If some of the birds on Guam had characteristics that allowed them to evade the snakes or if they had not been restricted to an island, a few might have survived to reproduce. This new population may have been able to co-exsist with brown tree snakes.
12 Populations can diverge into subpopulations or new species TERMS TO KNOW: Extirpation Genetic drift Bottleneck effect Founder effect Genetic drift – Pure chance and random mating can increase or decrease the frequency of a trait.
12 Populations can diverge into subpopulations or new species TERMS TO KNOW: Extirpation Genetic drift Bottleneck effect Founder effect Bottleneck effect – Part of the population dies suddenly, leaving the survivors to produce a new generation .
12 Populations can diverge into subpopulations or new species TERMS TO KNOW: Extirpation Genetic drift Bottleneck effect Founder effect Founder effect – Small group contains only some of the original variants and becomes isolated.
12 The pace of evolution is generally slow but is responsive to selective pressures TERMS TO KNOW: Extirpation Genetic drift Bottleneck effect Founder effect In addition to genetic diversity, the size of the population makes a difference in how quickly natural selection can produce a change in population. Beneficial traits can spread more quickly in smaller populations because the likelihood of mates having similar traits is greater. A Guam rail, a critically endangered species. The species’ decline and status of “extinct in the wild” was caused by the introduction of the brown tree snake.
12 Extinction is normal, but the rate at which it is currently occurring appears to be increasing Extinction is a natural part of evolution. Estimates are that 99% of all species that ever lived on Earth have gone extinct. There have been five major extinction events, each leading to the extinction of 50% or more of the species present on Earth. TERMS TO KNOW: Background rate of extinction Fossil record The current global population of humans has triggered a sixth major extinction event—the one of which we are in the midst.
12 Extinction is normal, but the rate at which it is currently occurring appears to be increasing Extinction is a natural part of evolution. Estimates are that 99% of all species that ever lived on Earth have gone extinct. There have been five major extinction events, each leading to the extinction of 50% or more of the species present on Earth. Terms to know: Background rate of extinction Fossil record The current global population of humans has triggered a sixth major extinction event—the one of which we are in the midst.
12 Extinction is normal, but the rate at which it is currently occurring appears to be increasing Extinction is a natural part of evolution. Estimates are that 99% of all species that ever lived on Earth have gone extinct. There have been five major extinction events, each leading to the extinction of 50% or more of the species present on Earth. Terms to know: Background rate of extinction Fossil record The current global population of humans has triggered a sixth major extinction event—the one of which we are in the midst.
12 Extinction is normal, but the rate at which it is currently occurring appears to be increasing Extinction is a natural part of evolution. Estimates are that 99% of all species that ever lived on Earth have gone extinct. There have been five major extinction events, each leading to the extinction of 50% or more of the species present on Earth. Terms to know: Background rate of extinction Fossil record The current global population of humans has triggered a sixth major extinction event—the one of which we are in the midst.
12 Extinction is normal, but the rate at which it is currently occurring appears to be increasing Extinction is a natural part of evolution. Estimates are that 99% of all species that ever lived on Earth have gone extinct. There have been five major extinction events, each leading to the extinction of 50% or more of the species present on Earth. Terms to know: Background rate of extinction Fossil record The current global population of humans has triggered a sixth major extinction event—the one of which we are in the midst.
12 Humans affect evolution in a number of ways Artificial selection works the same way as natural selection, but humans are the source of selective pressure. All dogs are descendants of the wolf. By only breeding those males and females with the desired traits, humans have created more than 170 breeds
12 Humans affect evolution in a number of ways Misconceptions about Evolution
12 Humans affect evolution in a number of ways Misconceptions about Evolution
12 Humans affect evolution in a number of ways Misconceptions about Evolution
12 Humans affect evolution in a number of ways Misconceptions about Evolution
12 PERSONAL CHOICES THAT HELP
12 UNDERSTANDING THE ISSUE
12 UNDERSTANDING THE ISSUE
12 ANALYZING THE SCIENCE Species extinction and human population
12 EVALUATING NEW INFORMATION The effects of the sixth mass extinction on evolution: www.actionbioscience.org/evolution/myers_knoll.html www.iucnredlist.org/species-of-the-day/archives IUCN species of the day:
12 MAKING CONNECTIONS www.iucnredlist.org International Union for Conservation of Nature (IUCN)
