CHAPTER 4

• Amphibians

  • Sensitive biological indicators
  • Play important ecological roles in their communities
  • Skin secretions source of many valuable pharmaceutical products
• Since the 1980s, populations of hundreds of amphibian species have declined or gone extinct
• Prokaryotic

  Bacterial cells with no distinct nucleus or internal parts enclosed by membranes
• Eukaryotic

  All nonbacterial organisms
• Taxonomic classification

  • Kingdom
  • Phylum
  • Class
  • Family
  • Genus
  • Species
• Six kingdoms

  • Eubacteria
  • Archaebacteria
  • Protists (algae and protozoans)
  • Plants (mosses, ferns, and flowering plants)
  • Fungi (mushrooms, molds, mildew, and yeasts)
  • Animals (invertebrates and vertebrates)
• Estimated 7–10 million species exist, about 2 million species have been identified, about half of those are insects, many of which provide pollination as a vital ecosystem service
• Some insect species reproduce rapidly and can produce new genetic traits, for example pesticide resistance
• Biological diversity

  The diversity of life on earth
• Types of diversity

  • Species diversity
  • Genetic diversity
  • Ecosystem diversity
  • Functional diversity
• Species diversity

  Includes species richness and evenness
• Genetic diversity

  Variety of genes in a population or species
• Ecosystem diversity

  • Biomes: regions with distinct climates and species
  • Large forests have edge effects
  • Transition areas between ecosystems are ecotones
• Functional diversity

  Variety of processes within ecosystems, such as energy flow and matter cycling
• Biologically diverse ecosystems produce more plant biomass to support a greater number of consumer species, and contain species traits that enable them to adapt to changing environmental conditions
• Each species plays a specific ecological role called its ecological niche, which includes everything that affects its survival and reproduction
• Generalist species

  Broad niche - wide range of tolerance
• Specialist species

  Narrow niche - narrow range of tolerance
• Four major ecosystem roles

  • Native species
  • Nonnative species
  • Invasive species
  • Indicator species
  • Keystone species
• Native species

  Normally live and thrive in a particular ecosystem
• Nonnative species

  Migrate or are accidentally introduced into an ecosystem
• Invasive species

  Harmful nonnative species
• Indicator species

  Provide early warnings of environmental changes
• Keystone species

  Have a large effect on the types and abundance of other species
• The American alligator is a keystone species in its subtropical wetland ecosystem, digging gator holes that hold freshwater and serve as a refuge for aquatic life

  
• In the 1930s, the American alligator was hunted for sport, meat, and skin, and was added to the endangered species list in 1967, but made an impressive comeback by 1987 with more than a million alligators today in Florida

  
• Factors causing decline and disappearance of reptiles and amphibians include parasites, viral and fungal diseases, habitat loss and fragmentation, higher levels of UV radiation, pollution, climate change, and overhunting
• Biological evolution is the process by which Earth's life forms change genetically over time, and is a widely accepted scientific theory
• Natural selection

  The process by which species have evolved from earlier species
• Fossils are physical evidence of past organisms preserved in rocks or ice, and the fossil record represents the entire body of fossil evidence, which is uneven and incomplete, estimated to represent only 1% of all species that have ever lived
• Genetic variability occurs through mutations, which are random changes in DNA that can result in heritable traits, and the gene pool represents all of the genetic differences within a population
• Natural selection

  Environmental conditions favor increased survival and reproduction of certain individuals in a population
• Adaptive trait

  Improves the ability of an individual organism to survive and reproduce at a higher rate than other individuals in a population, given prevailing environmental conditions
• Genetic resistance is an example of natural selection at work
• Genetic resistance

  Occurs when organisms have genes that can tolerate a chemical designed to kill them, allowing resistant individuals to survive and reproduce
• Some disease-causing bacteria have developed resistance to antibacterial drugs (antibiotics)
• Human species adaptations

  • Strong opposable thumbs
  • Ability to walk upright
  • A complex brain
• Phylogenetic tree diagrams

  Depict the evolution of species from common ancestors, based on fossil and DNA evidence
• Adaptive genetic traits

  Must precede change in the environmental conditions
• A population's reproductive capacity

  Species that reproduce rapidly and in large numbers are better able to adapt