Chromium: Water Quality and Biogeochemical Engine

This lecture covers the properties of chromium, a metal widely used in various industries, its two oxidation states, and the impact of each on human health and the environment. It discusses the presence of chromium in tap water, its cycling in different environments, contamination issues, redox transformations, pathways of transformation, uptake and efflux mechanisms, reduction processes, detoxification strategies, and the resistance of some organisms to chromium. The lecture also explores the importance of harnessing natural processes for remediating chromium-contaminated sites, focusing on in situ microbial reduction as a potential solution.

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Water quality and the biogeochemical engine

Learn about how the quality of water is a direct result of complex bio-geo-chemical interactions, and about how to use these processes to mitigate water quality issues.

Speciation

Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within lineages. Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book On the Origin of Species. He also identified sexual selection as a likely mechanism, but found it problematic.

Peripatric speciation

Peripatric speciation is a mode of speciation in which a new species is formed from an isolated peripheral population. Since peripatric speciation resembles allopatric speciation, in that populations are isolated and prevented from exchanging genes, it can often be difficult to distinguish between them. Nevertheless, the primary characteristic of peripatric speciation proposes that one of the populations is much smaller than the other.

Sympatric speciation

Sympatric speciation is the evolution of a new species from a surviving ancestral species while both continue to inhabit the same geographic region. In evolutionary biology and biogeography, sympatric and sympatry are terms referring to organisms whose ranges overlap so that they occur together at least in some places. If these organisms are closely related (e.g. sister species), such a distribution may be the result of sympatric speciation. Etymologically, sympatry is derived from the Greek roots συν ("together") and πατρίς ("homeland").

Parapatric speciation

In parapatric speciation, two subpopulations of a species evolve reproductive isolation from one another while continuing to exchange genes. This mode of speciation has three distinguishing characteristics: 1) mating occurs non-randomly, 2) gene flow occurs unequally, and 3) populations exist in either continuous or discontinuous geographic ranges. This distribution pattern may be the result of unequal dispersal, incomplete geographical barriers, or divergent expressions of behavior, among other things.

History of speciation

The scientific study of speciation — how species evolve to become new species — began around the time of Charles Darwin in the middle of the 19th century. Many naturalists at the time recognized the relationship between biogeography (the way species are distributed) and the evolution of species. The 20th century saw the growth of the field of speciation, with major contributors such as Ernst Mayr researching and documenting species' geographic patterns and relationships.

Arsenic in SE Asia Delta ENV-202: Microbiology for engineers

Delves into the biogeochemistry of arsenic in the SE Asia delta, covering speciation, human exposure, microbial transformations, and groundwater contamination.

Sulfur and Nitrogen Cycles ENV-202: Microbiology for engineers

Explores the environmental significance of sulfur and nitrogen cycles, including key microbial processes and organisms involved.

Sulfur Cycle: Microbial Processes and Energy Conservation ENV-202: Microbiology for engineers

Explores microbial processes in the sulfur cycle and energy conservation mechanisms.

Redox Reactions: Part 2 ENG-400: Water quality modeling

Explores pe-pH diagrams for redox reactions, nitrogen species stability, iron-nitrate co-occurrence, and abiotic nitrogen kinetics.

Toxicity vs. deficiency MOOC: Water quality and the biogeochemical engine

Discusses bioavailability, toxicity, and the role of softness in toxicity.