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 endangeredspecies 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