Biology, 07.11.2019 19:31 blondie02

Why is small surface area important in a cell

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The important point is that the surface area to the volume ratio gets smaller as the cell gets larger. Thus, if the cell grows beyond a certain limit, not enough material will be able to cross the membrane fast enough to accommodate the increased cellular volume.

Answer from: Quest

from almost the creation of the first true maps of the earth, people started seeing how continents would be able to fit together. in particular, people noticed that south america fits almost exactly into africa.

you should be aware that while world maps were around early in the 1600’s and better defined by the end of the 1700’s, those maps were not ‘public’ but were treated as state secrets. and so it was not till much later that the broader ‘science’ community had access to good quality and accurate world maps.

get the whole story here…

it is now known that most of the major continental masses can be fit together in a jigsaw process. in fact we now know that the continents were indeed once all joined together as one land mass – the supercontinent of pangaea.

if you look at most world maps you will ponder how this is evidence, as the continents really don’t appear to ‘fit’ together very well. what you need to understand is that the vast majority of maps are drawn using a map projection that has the north and south poles (which are points) are a line the width of the map at the top and bottom. this means that the map distorts the true shape of the earth’s land and oceans as you love closer to the poles. some other map projections distort less, but have the map shape looking like segments of an orange. see here for a range of map projections. check out the way greenland changes size in each!

what is more remarkable, is the next piece of evidence when added to the shape of continents.

location of mountains and fossils

what is remarkable, when you reassemble all the continents together, the ancient mountain ranges (many now eroded to their cores) and the location of rock types and fossils all match up.

Answer from: Quest

Mantle convection is the slow creepingmotion of earth's solid silicate mantle caused by convection currents carrying heat from the interior to the planet's surface.[1][2] the earth's surface lithosphere, which rides atop the asthenosphere (the two components of the upper mantle), is divided into a number of plates that are continuously being created and consumed at their opposite plate boundaries. accretion occurs as mantle is added to the growing edges of a plate, associated with seafloor spreading. this hot added material cools down by conduction and convection of heat. at the consumption edges of the plate, the material has thermally contracted to become dense, and it sinks under its own weight in the process of subduction usually at an ocean trench.[3]this subducted material sinks through the earth's interior. some subducted material appears to reach the lower mantle,[4] while in other regions, this material is impeded from sinking further, possibly due to a phase transition from spinel to silicate perovskiteand magnesiowustite, an endothermic reaction.[5]the subducted oceanic crust triggers volcanism, although the basic mechanisms are varied. volcanism may occur due to processes that add buoyancy to partially melted mantle causing an upward flow due to a decrease in density of the partial melt.secondary forms of convection that may result in surface volcanism are postulated to occur as a consequence of intraplate extension[6] and mantle plumes.[7]it is because the mantle can convect that the tectonic plates are able to move around the earth's surface.[8]mantle convection seems to have been much more active during the hadean period, resulting in gravitational sorting of heavier molten iron, and nickel elements and sulphides in the core, and lighter silicate minerals in the mantle.