Temporary changes would be weather, since it can change at any givin time another example would be tides coming in because they vary by day, or wet sand becoming dry sand!
Answer:
The correct answers are:
1. Greenhouse gases: Earth's heat is kept from going away.
Greenhouse gases, particularly CO2 and methane, have properties that allow them to trap heat in the atmosphere. This means that the more of these gases there are in the air, it will be hotter on Earth.
2. Chemicals released into the river—unfit for human consumption.
The chemicals released into rivers pollute the water, making it unfit for human consumption. There are only a few places in the world where there is enough freshwater to go around, so the fact that so many rivers have been poisoned is very worrying.
3. Excessive agricultural land use—forest fragmentation.
People cut down the trees so that there is more land that can be used for farming, As a result of this process, forests are being destroyed to the point of total devastation, and it is likely that this percentage will rise in the coming years as things continue.
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<em>I hope this helps you</em>
<em>:)</em>
I believe you meant to say is this mistake called a base pair and if that is your question then no. it would be called Mutation. But you can double check that answer.
Well, when chromosomes cross over during prophase 1 of meiosis, the homologous pair of chromosomes exchange segments of DNA which happen to be the genes. So the significance of crossing-over during prophase 1 is that it adds genetic variation to sexually reproducing organisms.
The outer skeleton provides protection due to the fact that invertebrates do not have backbones
