Chapter 4:
Evolution, Biological Communities, and Species Interactions
Advanced Environmental Science
EVOLUTION PRODUCES SPECIES DIVERSITYSection 4.1
Summary:
• artificial selection• natural selection• adaptation in ecosystems• speciation• evolution still at work
Artificial Selection
Artificial Selection
Natural Selection
adaptation:the acquisition of traits that allow a species to survive in its environment
natural selection:the process of better-selected individuals passing their traits on to the next generations
selection pressures:factors in the environment that favor successful reproduction of individuals possessing heritable traits and that reduce viability/fertility of individuals not possessing those traits
(examples…)
critical factor:the single factor in shortest supply relative to demand
tolerance limits:minimum and maximum levels for each environmental factor
Adaptation in Ecosystems
habitat vs. niche
competitive exclusion principle:no two species can occupy the same niche for long (the more successful will exclude the other)
resource partitioning:allows several species to utilize the same resource and coexist (examples…)
Speciation
speciation:development of new species
allopatric speciation:geographic barriers cause reproductive isolation
sympatric speciation:biological or behavioral barriers cause reproductive isolation
(once isolation occurs species diverge genetically)
Evolution is still at work…
• Galapagos island finches
• pesticide resistant insects• drug-resistant pathogens
SPECIES INTERACTIONS SHAPE BIOLOGICAL COMMUNITIES
Section 4.2
Competition
intraspecific
interspecific
Predation
• Predator-prey relationships exert selection pressures that favor evolutionary adaptation.
• Predators become more efficient at searching and feeding, and prey become more effective at escape and avoidance.
coevolution:species exert selective pressures on each other and gradually change as a result
Predator Avoidance
Batesian mimicry:species that are harmless resemble poisonous or distasteful ones
Müllerian mimicry:two unpalatable or dangerous species look alike
Batesian mimicry
Symbiosis
mutualism
Symbiosis
commensalism
Symbiosis
parasitism
keystone species:a species that plays a critical role in a biological community that is out of proportion to its abundance
COMMUNITY PROPERTIES AFFECT SPECIES POPULATIONS
Section 4.3
primary productivity:rate of biomass production
abundance:total number of organisms in a community
diversity:number of different species, niches, or genetic variation present in a community
complexity:the number of species at each trophic level and the number of trophic levels in a community
Stability and Resiliency in Ecosystems
constancy:lack of fluctuations in composition or functions
inertia:resistance to perturbations
renewal:ability to repair damage after disturbance
edge effects:changes encountered at the boundary between two ecosystems
ecotone:a boundary between two types of biological community
*interior area is significant*
COMMUNITIES ARE DYNAMIC AND CHANGE OVER TIME
Section 4.4
Ecological Succession
primary succession:succession that occurs in an area where no community existed before
secondary succession:succession that occurs in an area where the existing community is disturbed
pioneer species:the first species to colonize a new area
climax community:the community that develops last and stays the longest
• represents the maximum complexity and stability possible
• depends on climate and soil
disturbance:any force that disrupts the established patterns of species diversity and abundance, community structure or community properties
disturbance-adapted species:species that depend on disturbances to succeed