A single-celled marine plankton has evolved a miniature version of an eye to help see its prey better. It’s an amazingly complex structure for a single-celled organism to have evolved. It contains a collection of sub-cellular organelles that look very much like the lens, cornea, iris and retina of multicellular eyes found in humans and other larger animals.
Tag: biology
Has life evolved multiple times?
Desert varnish – into which people have scraped petroglyphs for 1000s of years – appears layer by layer, growing only the width of a human hair each millennium. The varnish is replete with arsenic, iron and manganese, although the rocks it coats are not. No known geochemical or biological process can account for its ingredients. And yet there it is.
Self-fertilization
hermaphroditic flatworms with needle-tipped male organs inject themselves with sperm in whatever body region is easy to stab.
Hydrothermal Vents
the hydrothermal vents were a relic environment, one we believe resembles what the early conditions on Earth might have been. What we’re doing ultimately is trying to understand how life evolved on the planet. For all of their extremes of temperature, pressure, and other properties, deep-sea vents may have offered a relatively cozy refuge on the violent world of the early Earth. Our young planet was bathed in much stronger ultraviolet radiation from the sun because it hadn’t yet developed a protective ozone layer. That didn’t come along until after the evolutionary invention of photosynthesis pumped a steady supply of oxygen into our atmosphere. One big attraction is the presence of an ion gradient—a key ingredient in just about every known form of life—between the vent fluids and the seawater. The alkaline fluids are basic, with a pH (a measurement of acidity and alkalinity levels) of around 10 or 11, meaning they have a low concentration of protons. Seawater, with a pH of around 8, is less alkaline—that is, slightly more acidic—so it has more protons than the vent fluids. The vent would have acted as a natural hydrothermal reactor. Reactions between carbon dioxide and hydrogen, catalyzed by minerals found in the vents, can form a molecule known as pyruvate. Pyruvate is a precursor of many amino acids, which in turn can link together to create proteins.
Life at the limits
this seems worthwhile to check out, though a bit steep at 27$.
Why males?
why males? why do so many complex organisms have a whole sex which does not bear offspring? One hypothesis is that males are good for purging genetic load via sexual selection. On a genetic level all individuals carry deleterious mutations, which they pass on to their offspring. But, because of sample variance in transmission, there will be a distribution of outcomes in any given set of offspring. By chance some individuals will exhibit a higher load of deleterious alleles, while others will carry fewer alleles. If this load is correlated to traits which are visible to the opposite sex, then excess load every generation can be purged through reproductive skew
Most Ocean Virus Genes
This flattened curve suggested something profound: that they have probably found almost all the virus genes in the upper oceans of the entire planet
12 ga planets
PSR B1620-26 b is an extrasolar planet located 12k light-years away from Earth in the constellation of Scorpius. it is one of the oldest planets in the universe, at 12.7 ga
Can life survive for billions of years longer than the expected timeline on Earth? As scientists discover older and older solar systems, it’s likely that before long we’ll find an ancient planet in a habitable zone. Knowing if life is possible on this exoplanet would have immense implications for habitability and the development of ancient life
Living computers
Our ultimate goal is to make living computers. Biological systems can do signal processing like human brains at very low power. We want to see if we can build a CMOS hybrid life form, eventually
DNA rewriting for memory
We used to think that once a cell reaches full maturation, its DNA is totally stable, including the molecular tags attached to it to control its genes and maintain the cell’s identity. Some cells actually alter their DNA all the time, just to perform everyday functions
2021-08-30: DNA breaks for memory consolidation
When the team mapped genes undergoing double-strand breaks in the prefrontal cortex and hippocampus of mice that had been shocked, they found breaks occurring near 100s of genes, many of which were involved in synaptic processes related to memory. DNA breakage might be a regulatory mechanism in many other cell types. But even if breaking DNA is a particularly fast way to induce crucial gene expression, whether for memory consolidation or for other cellular functions, it’s also risky. If the double-strand breaks occur at the same locations over and over again and aren’t properly repaired, genetic information could be lost. Moreover, “this type of gene regulation could render neurons vulnerable to genomic lesions, especially during aging and under neurotoxic conditions. It is interesting that it’s used so intensively in the brain, and that the cells can get away with it without incurring damage that’s devastating.”
Gregor J. Rothfuss 