Trace evidence occurs when objects make contact, and material is transferred. This type of evidence may not even be visible to the naked eye and requires specific tools and techniques to be located and obtained. Microscopic hair and dead skin cells can be collected, as well as droplets of blood, saliva, or semen for DNA evidence. Fingerprints can be identified but may also leave secretions, skin oils and dead cells which show chemicals and metabolites present in the body at the time. Forensic identification is the application of forensic science and technology to identify specific objects from the trace evidence they leave.

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In biology, homeostasis is the state of steady internal physical and chemical conditions maintained by living organisms. The body’s ability to maintain homeostasis is a critical function. The body has many aspects that it maintains using homeostatic control mechanisms including: optimal temperature, fluid balance, cerebrospinal fluid, pH of extracellular fluid, concentrations of oxygen, carbon dioxide, sodium, potassium, calcium ions, copper, iron levels, blood sugar levels, plasma pH, blood oxygen content as well as blood pressure. These levels are kept within certain pre-set limits (homeostatic range) even during changes in the environment, diet, or level of activity.

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The Great Oxygenation Event (GOE) was a time interval during the Earth’s Paleoproterozoic era (2,500 to 1,600 million years ago) when the Earth experienced a rise in the concentration of free oxygen from practically none. The GOE is inferred to have been caused by cyanobacteria, which evolved chlorophyll-based photosynthesis that releases dioxygen as a waste byproduct of water photolysis. Scientists believe the GOE may have caused an extinction of many early Earth organisms, including the retinal using (Purple Earth hypothesis) organisms that lived during that time. The adaptation of surviving archaea (leading to mitochondria) may have led to the rise of eukaryotic organisms and eventually multicellular life-forms. So Earth may have been purple before, and we’re only here thanks to cyanobacteria!

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A placebo is a medicine or treatment intended to appear genuine, but actually have no pharmaceutical effect, such as inert sugar pills. The placebo effect is a genuine psychobiological phenomenon in which the mere expectation of improvement from a placebo can lead to some actual physiological changes. Modern studies find that placebos can affect some outcomes such as pain and nausea, but otherwise do not generally have important clinical effects. There is also the effect called a nocebo effect. The nocebo effect is falling ill simply by consciously or subconsciously anticipating a harmful event. Both placebo and nocebo effects are presumably psychogenic but can induce measurable changes in the body.

Source 1 – Placebo – Source 2 – Placebo Paper – Source 3 – Nocebo

Energy can neither be created nor destroyed; rather, it can only be transformed or transferred from one form to another. The law of conservation of energy states that the total energy of an isolated system remains constant; it is said to be conserved over time. In the case of a closed system, the principle says that the total amount of energy within the system can only be changed through energy entering or leaving the system. Special relativity shows that mass is related to energy and vice versa by E = mc², the equation representing mass–energy equivalence, and science now takes the view that mass-energy as a whole is conserved. This implies that mass can be converted to energy, and vice versa.

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