CHAPTER 4 notes - CHAPTER 4 Striking gold in Costa Rica o...

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CHAPTER 4 Striking gold in Costa Rica o Golden toads were discovered in 1964, in Monteverde, Costa Rica. The mountainous cloud forest has a perfect climate for amphibians. 200 golden toads were found in one area, 5 m (16.4 ft) in diameter. The area was protected as the Monteverde Cloud Forest Preserve. o Unfortunately, the toads became extinct within 25 years. Due to global warming’s drying effect on the forest Evolution: the source of Earth’s biodiversity o Biological evolution: genetic change in populations of organisms across generations Has resulted in a lush world of millions of species o May be random or directed by natural selection Natural selection= the process by which traits that enhance survival and reproduction are passed on more frequently to future generations than those that do not Understanding evolution is vital o We need to understand how organisms adapt to their environment and change overtime o It is needed for ecology, a central component of environmental science Relevant for agricultural, medicine, pesticide resistance, environmental health Natural selection shapes organisms o In 1858, Darwin and Wallace both proposed natural selection as the mechanism of evolution Organisms face a constant struggle to survive and reproduce Organisms tend to produce more offspring than can survive Individuals of a species vary in their characteristics Some individuals are better suited to their environment and will survive and pass their genes on to their offspring Genetic variation o Genes of better adapted individuals will be more prevalent than those of less well-adapted individuals in future generations o Adaptive trait (adaptation)= a trait (characteristic) that promotes reproductive success o Mutations= accidental changes in DNA that may be passed on to next generation Non-lethal mutations provide the genetic variation on which natural selection acts o Sexual reproduction, which involves recombination (the mixing of parental genes), also leads to variation Evidence of natural selection is everywhere o The results of natural selection are evident in every adaptation of every organism o Evident in experiments with bacteria and fruit flies o Selective breeding of plants and animals exaggerates preferred traits Artificial selection o Artificial selection= the process of selection conducted under human direction For example, by allowing only like individuals to breed, breeders have created the great variety of dog breeds and crop plants Evolution generates biodiversity o Biological diversity (biodiversity)= an area’s sum total of all organisms The diversity of species Their genes Their populations Their communities o Population= a group of individuals of a species that live in the same area
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o Species= a population or group of populations whose members share characteristics and can freely breed with one another and produce fertile offspring
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This note was uploaded on 03/28/2011 for the course ISB 202 taught by Professor Johnson during the Spring '08 term at Michigan State University.

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CHAPTER 4 notes - CHAPTER 4 Striking gold in Costa Rica o...

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