Wikipedia:Reference desk/Archives/Science/2015 April 24
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April 24 edit
What came first, the chicks or the chicken? edit
What came first, the chicks or the chicken?
Do women lay an evolved egg (which is internal and better protected), or, do chicken lay an evolved ovum (which has its own nutrients, and can be laid anywhere and forgotten about)? What evolved from what? --Llaanngg (talk) 01:38, 24 April 2015 (UTC)
- Explained here. Count Iblis (talk) 01:58, 24 April 2015 (UTC)
- Mammals (including humans) evolved from egg-laying animals, although not specifically from chickens. StuRat (talk) 04:24, 24 April 2015 (UTC)
- Indeed monotremes still lay eggs; only the other mammals evolved vivipary. Note that vivipary has evolved many times in many different groups of organisms, even full-fledged hemotrophic vivipary (i.e. sustenance from the maternal blood supply) in sharks with yolk sac placentas. A cruder example is Limnonectes larvaepartus, a frog that bears tadpoles that apparently eat feces and one another while inside the mother's body. Wnt (talk) 13:06, 24 April 2015 (UTC)
- Minor correction: from vivipary - "When considering squamate reptiles in particular, there is a correlation between high altitudes or latitudes, colder climates and the frequency of viviparity. " - Viviparous reptiles are a little different than viviparous mammals in terms of the means and mechanisms of reproduction, but they are still considered viviparous. SemanticMantis (talk) 15:15, 24 April 2015 (UTC)
- Indeed monotremes still lay eggs; only the other mammals evolved vivipary. Note that vivipary has evolved many times in many different groups of organisms, even full-fledged hemotrophic vivipary (i.e. sustenance from the maternal blood supply) in sharks with yolk sac placentas. A cruder example is Limnonectes larvaepartus, a frog that bears tadpoles that apparently eat feces and one another while inside the mother's body. Wnt (talk) 13:06, 24 April 2015 (UTC)
- Modern amniotic vertebrate eggs arose with the amniota 330 million years ago, flying dinosaurs have been around since the Jurrasic, and the land and waterfowl (Galloanseres) have been around since before the K/T event. The genus Gallus has been around since the mid-Pleistocene at least. Since we use the term chick nowadays to refer to all baby birds, they have been around since before the dinosaurs went extinct, the modern domesticated chicken only since the end of the last ice-age, and the hard-shelled egg since the late Carboniferous.
What are the signs that there's a sinkhole beneath the ground you're on? edit
Are there telltale signs that there's a sinkhole below the ground you're on or the building you're in? --108.52.38.146 (talk) 02:48, 24 April 2015 (UTC)
- watch here. Count Iblis (talk) 03:05, 24 April 2015 (UTC)
- Not until it's rather too late, when the ground starts to sink. Sometimes there's enough warning to evacuate before total collapse, sometimes not. To avoid this risk, you'd want to use ground-penetrating radar (dragging a device that looks like a lawn mower back and forth across the surface in a grid pattern), especially if you are in an area with karst topography. StuRat (talk) 04:21, 24 April 2015 (UTC)
- Here's what happens when you don't realize you are walking on a sinkhole. μηδείς (talk) 20:20, 24 April 2015 (UTC)
- Have a look at Detection & Warning Signs of Imminent Sinkhole Collapse --Aspro (talk) 21:54, 24 April 2015 (UTC)
- We had a sinkhole forming around a manhole above a sewer. The manhole kept getting lower, and there were holes along the sides going all the way down to the sewer. When we first sounded the alarm, they just patched over the holes with asphalt, but I knew that was no good. Soon enough the holes were even larger. Fortunately, they then repaired it correctly. StuRat (talk) 23:37, 24 April 2015 (UTC)
What is the difference between meteorology and aerology? --IEditEncyclopedia (talk) 13:13, 24 April 2015 (UTC)
- Meteorology is a part of aerology—atmospheric sciences. Ruslik_Zero 13:43, 24 April 2015 (UTC)
- "Aerology" is an old term that is rarely used any more. It had two main usages. First, it was the U.S. Navy's term for meteorology in general. (The Navy tends to have their own way of doing things.) Second, it was the study of the free atmosphere, above the boundary layer. In the second sense aerology is part of meteorology, not the other way around. Short Brigade Harvester Boris (talk) 19:49, 25 April 2015 (UTC)