A change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a stimulus indicating lowered oxygen tension. Hypoxia, defined as a decline in O2 levels below normoxic levels of 20.8 - 20.95%, results in metabolic adaptation at both the cellular and organismal level [goid 1666] [evidence ISS]; The cleavage of DNA during apoptosis, which usually occurs in two stages: cleavage into fragments of about 50 kbp followed by cleavage between nucleosomes to yield 200 bp fragments [goid 6309] [pmid 10891486] [evidence IDA]; Dynamic structural changes to eukaryotic chromatin occurring throughout the cell division cycle. These changes range from the local changes necessary for transcriptional regulation to global changes necessary for chromosome segregation [goid 6338] [pmid 10891486] [evidence IDA]; The chemical reactions and pathways involving dioxygen (O2), or any of the reactive oxygen species, e.g. superoxide anions (O2-), hydrogen peroxide (H2O2), and hydroxyl radicals (-OH) [goid 6800] [pmid 10891486] [evidence IDA]; A process which directly inhibits any of the steps required for cell death by apoptosis [goid 6916] [pmid 7954800] [evidence TAS]; A process that directly activates any of the steps required for cell death by apoptosis [goid 6917] [pmid 9396766] [evidence IDA]; A process that directly activates any of the steps required for cell death by apoptosis [goid 6917] [pmid 10381623] [evidence IDA]; A process that directly activates any of the steps required for cell death by apoptosis [goid 6917] [pmid 9973195] [evidence IDA]; The specific activation or halting of processes within a cell so that its vital functions markedly cease, rather than simply deteriorating gradually over time, which culminates in cell death [goid 8219] [pmid 10891486] [evidence IDA]; The specific activation or halting of processes within a cell so that its vital functions markedly cease, rather than simply deteriorating gradually over time, which culminates in cell death [goid 8219] [evidence ISS]; Any process that stops, prevents or reduces the frequency, rate or extent of survival gene product expression; survival gene products are those that antagonize the apoptotic program. Regulation can be at the transcriptional, translational, or posttranslational level [goid 8634] [pmid 9973195] [evidence IDA]; Any process by which an organism has an effect on an organism of a different species [goid 44419] [evidence IEA]; Any process that stops, prevents or reduces the frequency, rate or extent of establishment or extent of a membrane potential, the electric potential existing across any membrane arising from charges in the membrane itself and from the charges present in the media on either side of the membrane [goid 45837] [pmid 10891486] [evidence IDA]; Any process that modulates the frequency, rate or extent of the passage or uptake of molecules by the mitochondrial membrane [goid 46902] [pmid 10891486] [evidence IDA]; The process of apoptosis in neurons, the basic cellular unit of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the nervous system [goid 51402] [evidence ISS]; Reactions triggered in response to the presence of a virus that act to protect the cell or organism [goid 51607] [pmid 9973195] [evidence IDA]