GEE001

• Amphibians (frogs, toads, and salamanders) show great biodiversity with more than 6,700 species
• Many amphibian populations have declined or vanished
• The loss of amphibian populations is significant because sustaining life on Earth depends on the biodiversity found in genes, species, ecosystems, and ecosystem processes
• Pharmaceutical companies are interested in the preservation of amphibian species
• Biodiversity is the variety in:

  • Species (species diversity)
  • The genes they contain (genetic diversity)
  • Ecosystems (ecological diversity)
  • Ecosystem processes, such as energy flow and nutrient cycling (functional diversity)
• Species diversity is the number and variety of species in a biological community
• Genetic diversity is the variety of genes in a population or species
• Each species has a specific ecological role called its niche
• There are four important roles that a species can play in a particular ecosystem: Native, Nonnative, Indicator, Keystone
• Generalist species (broad niches) can live in a wide range of environments and are less prone to extinction
• Specialist species (narrow niches) live in only a few types of habitats and are more prone to extinction
• Native species live and thrive in a specific ecosystem
• Nonnative species immigrate into, or are deliberately or accidentally introduced into an ecosystem, threatening native species through competition for resources
• Indicator species are sensitive to changes in an ecosystem and provide early warnings of community and ecosystem change
• Keystone species affect the type and abundance of other species in an ecosystem and can cause population crashes and extinction of dependent species if drawn to extinction itself
• Mutations are changes in genetic composition (DNA)
• Genetic resistance is the ability of one or more organisms in a population to tolerate chemicals designed to kill the population
• Organisms can only adapt to a change in environmental conditions if the necessary genetic traits are already present in a population’s gene pool
• Even if a beneficial heritable trait is present in a population, the population’s ability to adapt may be limited by its reproductive capacity
• Evolution by natural selection explains how life changes over time due to changes in the genes of populations
• Individuals with traits that increase their survivability are more likely to produce offspring and pass on these traits
• As environmental conditions change, biodiversity is determined by the balance between the formation of new species and the extinction of existing species
• Human activity has caused loss of biodiversity by causing extinction of species and through degradation of habitats needed for development of new species
• Speciation occurs when one species splits into two or more different species
• Geographic isolation occurs when groups of the same population become physically isolated from one another over time
• Reproductive isolation occurs when mutation and change by natural selection operate independently in the gene pool of geographically isolated populations
• Artificial selection contributes to the rise of new species by selectively breeding or crossbreeding between genetic variations of the same species
• Genetic engineering is used to quickly manipulate genes by altering segments of DNA for desired traits and transferring genes between different species
• Extinction occurs when a species ceases to exist (biological extinction)
• All species eventually become extinct
• Endemic species are very vulnerable to extinction because they are found in unique geographic areas, making it difficult for them to migrate or adapt during rapidly changing environmental conditions
• Background extinction occurs at a slower rate that existed before human population became significant
• Mass extinction is a significant rise in extinction over the background extinction rate, often tied to major widespread environmental change
• Fossil and geological evidence indicate that there have probably been five mass extinctions during the past 500 million years
• These mass extinctions have been followed by an increase in species diversity as new species arise to fill unoccupied niches or to exploit newly available ones
• Evidence suggests that speciation on average through time has kept ahead of extinction
• Scientists now think we may be experiencing the beginning of a new mass extinction that is the result of human activity
• The ivory-billed woodpecker, native to southeast U.S. wetlands and forests, was last sighted in the 1940s and was deemed extinct in the mid-1990s due to deforestation/habitat loss and overhunting
• In the early 2000s, a single male was sighted, confirming the research team and the director of the Cornell Ornithology Lab
• Endemic species are very vulnerable to extinction