Chapter 4: Evolution, Biological Communities, and Species Interactions Advanced Environmental Science

EVOLUTION PRODUCES SPECIES DIVERSITY Section 4.1

Summary: artificial selection natural selection adaptation in ecosystems speciation evolution still at work

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