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Bacteria are prokaryotic microorganisms that can either have a bacilli, spirilli, or cocci shape and measure between 0.5-20 micrometers. They were one of the first living cells to evolve [9] and have spread to inhabit a variety of different habitats including hydrothermal vents, glacial rocks, and other organisms.
Parasite virulence and host resistance are variables that strongly impact a pathogen's ability to replicate and be distributed to many hosts. Parasite virulence is the level of harm a host endures due to a virus, bacteria, or parasite. [1] The way a host lives contributes heavily to how their body will react to pathogens.
Evolutionary processes give rise to diversity at every level of biological organization, from kingdoms to species, and individual organisms and molecules, such as DNA and proteins. The similarities between all present day organisms imply a common ancestor from which all known species, living and extinct, have diverged.
The history of life on Earth traces the processes by which living and extinct organisms evolved, from the earliest emergence of life to the present day. Earth formed about 4.5 billion years ago (abbreviated as Ga, for gigaannum) and evidence suggests that life emerged prior to 3.7 Ga. [1] [2] [3] The similarities among all known present-day species indicate that they have diverged through the ...
An early basic, functional division of parasites distinguished microparasites and macroparasites. These each had a mathematical model assigned in order to analyse the population movements of the host–parasite groupings. [16] The microorganisms and viruses that can reproduce and complete their life cycle within the host are known as ...
Host–parasite coevolution is a special case of coevolution, where a host and a parasite continually adapt to each other. This can create an evolutionary arms race between them. A more benign possibility is of an evolutionary trade-off between transmission and virulence in the parasite, as if it kills its host too quickly, the parasite will ...
Many modern Jains assert that Mahavira's teachings presage the existence of microorganisms as discovered by modern science. [5] The earliest known idea to indicate the possibility of diseases spreading by yet unseen organisms was that of the Roman scholar Marcus Terentius Varro in a 1st century BC book entitled On Agriculture in which he called ...
The history of biology traces the study of the living world from ancient to modern times. Although the concept of biology as a single coherent field arose in the 19th century, the biological sciences emerged from traditions of medicine and natural history reaching back to Ayurveda, ancient Egyptian medicine and the works of Aristotle, Theophrastus and Galen in the ancient Greco-Roman world.