Wikipedia:Reference desk/Archives/Science/2013 October 12

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October 12

Eat stuff or convert light into energy

Is there a living being that can or could do both? Did some species lose the ability to do photosynthesis and started eating things? OsmanRF34 (talk) 02:42, 12 October 2013 (UTC)

Euglenozoa ancestrally have the ability to do both (autotrophic and heterotrophic) but kinetoplastids have lost the ability, including some very serious human etiologic agents. Wnt (talk) 03:08, 12 October 2013 (UTC)

Carnivorous plants do both. --Jayron32 03:16, 12 October 2013 (UTC)

There's also a certain Mediterranean wasp that can both eat stuff and do photosynthesis -- I forgot its name, though. 24.23.196.85 (talk) 20:16, 12 October 2013 (UTC)

The Oriental hornet has been featured in some articles for this. — Quondum 01:07, 13 October 2013 (UTC)

(edit conflict) There are many examples of living things that do both. Photosynthesis#Evolution might be a good place to start. Giant clams and upside-down jellyfish are a few examples. Saprophytic plants (no article?) such as some species of Triuridaceae are examples of species that have lost the ability to photosynthesize.--Wikimedes (talk) 20:19, 12 October 2013 (UTC)

File:Elysia chlorotica (1).jpg

Elysia chlorotica larva

There is Elysia chlorotica, a sea slug (gastropod) and other members of its genus. And I believe there are symbiotic flatworms as well, but I couldn't find a name or get an article. μηδείς (talk) 00:24, 13 October 2013 (UTC)

Here's a bit on photosynthetic flatworms [1]. Apparently they are considered to be salt water aquarium pests.--Wikimedes (talk) 02:08, 13 October 2013 (UTC)

Yeah, I saw that link. They don't give or link to a scientific name, and the pictures in the gallery look like different species. μηδείς (talk) 16:34, 13 October 2013 (UTC)

But, species that eat stuff and transform light into energy, just use the eaten stuff as nutrient, or as a source of energy too? And why would any species lose the ability to use light? Where is the advantage of having to hunt other living beings? OsmanRF34 (talk) 22:31, 13 October 2013 (UTC)

There will be no general rule about whether nutrients or energy are the primary benefit derived. Some species will use energy obtained from eaten stuff (e.g. the Oriental hornet), some probably not (such as the Venus flytrap, which probably primarily derives nitrogen-containing nutrients from the digested insects, which tend to be insufficiently supplied by the soils that it grows in). As a general rule, though, when a species occupies an ecological niche in which it gains no benefit from an adaptation, this adaptation will eventually disappear. A fish species that lives in lightless caves eventually loses its eyes after many generations; species that live where light or other necessary factors for using the energy in light is lacking will lose the ability to use the light in time. Even if a reliable alternative is present which makes an adaptation valueless, the adaptation will be lost. — Quondum 23:56, 13 October 2013 (UTC)

Einstein disproof of Friedmann's expanding universe calculations?

When Friedmann showed that the equation of General Relativity meant that the universe must be either expanding or contracting, did Einstein at first propose a proof that Friedmann was wrong (and later retract the proof)? Bubba73 ^{You talkin' to me?} 05:09, 12 October 2013 (UTC)

That would be Einstein's non-zero Cosmological constant which he later described as his "greatest blunder". SpinningSpark 21:31, 12 October 2013 (UTC)

That is what the statement sounds like to me, but it said that he had a proof "later retracted" that Friedmann was wrong about asserting that the original GR says that the universe must be either expanding or contracting - and that part I don't know about. Bubba73 ^{You talkin' to me?} 21:39, 12 October 2013 (UTC)

Searching Google Books, I found a reference to this in "The Inflationary Universe" by Alan Guth, p.45: [2]. -- BenRG (talk) 05:28, 13 October 2013 (UTC)

Google won't allow access to that page of the book for me, but here is part of Einstein's retraction I got with a differnt search for anyone else having the same problem;

My objection rested however — as Mr. Krutkoff in person and a letter from Mr. Friedmann convinced me — on a calculational error. I am convinced that Mr. Friedmann's results are both correct and clarifying. They show that in addition to the static solutions to the field equations there are time varying solutions with a spatially symmetric structure.

Guth also says "In spite of this comment, Einstein still believed that the Friedmann solutions were of no relevance, as he remained confident that the universe is static". A belief he held until Hubble's momentous discovery. SpinningSpark 09:44, 13 October 2013 (UTC)

What roads (non-mwy) in the UK have jct numbers?

I know the A55, the A14, and the A12.Is that all?Or is there more?I don't know. Pls if someone would give those in Ireland then help welcome. — Preceding unsigned comment added by Puntaalpo (talk • contribs) 09:29, 12 October 2013 (UTC)

This is more of a Misc Desk Q than Science. StuRat (talk) 10:54, 12 October 2013 (UTC)

It doesn't belong here, but I will note the A1 in England does (there is also an A1 in Northern Ireland and I can't speak for that one). --TammyMoet (talk) 12:59, 12 October 2013 (UTC)

You can download a pdf map from this Highways Agency page which seems to have the answers to your question. It is very detailed and takes a while to download and load. SpinningSpark 22:38, 12 October 2013 (UTC)

mwy = motorway and jct = junction? --NorwegianBlue ^talk 17:28, 13 October 2013 (UTC)

That was my understanding when I answered. Fairly unambiguous I think. SpinningSpark 19:35, 13 October 2013 (UTC)

Peterborough is a hotbed of junction numbers[3][4] and, as you would expect, WP regards the matter as encyclopedic – Road transport in Peterborough#Numbered Junctions. Thincat (talk) 20:14, 13 October 2013 (UTC)