List two ways in which the conditions on an early earth differed from conditions today

The early Earth and the Earth today differ a lot in what the conditions on the planet were and are in the present.

1. The days and nights were much shorter;

Because the Moon was much closer to the Earth than what is now, the days and the nights lasted much less. The reason for that is that the Moon was orbiting faster around the Earth than in the present.

2. The atmosphere had much different composition;

The atmosphere of the early Earth was nothing like today's atmosphere, as for starters, that atmosphere would not be enabling breathing, especially not for the bigger species. The thing is that the oxygen levels were very low, and they only started to increase after the marine organisms started to use the process of photosynthesis when they released very large amounts of oxygen in the atmosphere.

relative dating involves things like higher layers are most recent than rocks lower in the sequence. this can be extended to the known sequence of fossils. rocks containing rabbit fossils are later than those containing dinosaur fossils.  

absolute dating methods mainly use radioactive elements that have known rates of decay and produce recognizable products. for example potassium 40 decays to produce argon. once a rock has solidified the argon is trapped. by measuring the argon and potassium0 you can get an accurate number for the age.  

some other methods are good for archaeological ages. dendrochronology involves recognizing the sequence of tree rings. the orientation of magnetized particles in baked clay can be used to date a fire.

hope this .. .

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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