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Biological rules. The pygmy mammoth is an example of insular dwarfism, a case of Foster's rule, its unusually small body size an adaptation to the limited resources of its island home. A biological rule or biological law is a generalized law, principle, or rule of thumb formulated to describe patterns observed in living organisms.
Chargaff's rules. Chargaff's rules (given by Erwin Chargaff) state that in the DNA of any species and any organism, the amount of guanine should be equal to the amount of cytosine and the amount of adenine should be equal to the amount of thymine. Further, a 1:1 stoichiometric ratio of purine and pyrimidine bases (i.e., A+G=T+C) should exist.
Ecological efficiency is a combination of several related efficiencies that describe resource utilization and the extent to which resources are converted into biomass. [ 1] Exploitation efficiency is the amount of food ingested divided by the amount of prey production ( ) Assimilation efficiency is the amount of assimilation divided by the ...
The trophic level of an organism is the position it occupies in a food web. Within a food web, a food chain is a succession of organisms that eat other organisms and may, in turn, be eaten themselves. The trophic level of an organism is the number of steps it is from the start of the chain. A food web starts at trophic level 1 with primary ...
In medical diagnosis, test sensitivity is the ability of a test to correctly identify those with the disease (true positive rate), whereas test specificity is the ability of the test to correctly identify those without the disease (true negative rate). If 100 patients known to have a disease were tested, and 43 test positive, then the test has ...
An ecological pyramid (also trophic pyramid, Eltonian pyramid, energy pyramid, or sometimes food pyramid) is a graphical representation designed to show the biomass or bioproductivity at each trophic level in an ecosystem . A pyramid of energy shows how much energy is retained in the form of new biomass from each trophic level, while a pyramid ...
The 4% rule is designed to make your retirement savings last for 30 years. For example, if you retire at age 65 with $1 million in savings, the rule suggests you can withdraw $40,000 per year ...
Organism. An organism is defined in a medical dictionary as any living thing that functions as an individual. [ 1] Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have been proposed to define what is an organism.