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Class Notes S6 - Coggle Diagram
Class Notes S6
Chapter 12. Effects of pollutants on populations
o Population growth rate can be: Positive, Null, Negative
Density dependence
• Their net result is that population growth rate is affected by population density
• In the simplest case, population growth rate is a negative linear function of population density
• This population density is called the carrying capacity of the environment in which the population lives
• Ecologists give it the symbol “k” (la capacidad de carga del ecosistema, asociada a los factores, como quimicos, biologicos, nutrientes)
Biomarkers in populations
• Specific biomarkers,
o The end-points used to assess the damage caused to DNA by environmental pollutants are specific genotoxic effects, especially the increase of carcinogenesis, rather than effects on the reproductive process
o There is a sequence of events between the first interaction of a xenobiotic with DNA and consequent mutation, which may be divided into four broad categories
The first stage is the formation of adducts (covalent binding of reactive metabolites of environmental pollutants to DNA)
At the next stage, there may be secondary modifications of DNA, such as strand breakage or an increase in the rate of DNA repair
The third stage is reached when the structural perturbations to the DNA become fixed
Finally, when cells divide, damage caused by toxic chemicals can lead to the creation of mutant DNA and consequent alterations in gene function
o Porphyrins and haem synthesis
Two major disruptions of haem biosynthesis by environmentally important agents have been studied. These are the formation of excess amounts of porphyrins after exposure to some organochlorines (OCs) and the inhibition by lead on the enzyme aminolaevulinic acid dehydratase (ALAD)
o Induction of vitellogenin
The discovery of hermaphrodite roach in stretches of rivers close to sewage outlets was the trigger for research into the effect of estrogenic disruptors in fish because natural hermaphroditism is assumed to be low.
o Behavioral biomarkers
One of the early proponents of the value of behavioral toxicology stated that “the behavior of an organism represents the final integrated result of a diversity of biochemical and physiological processes