Answer:
A <u><em>polar covalent bond</em></u> is a covalent bond in which the atoms have an unequal attraction for electrons and so the sharing is unequal. In a polar covalent bond, sometimes simply called a polar bond, the distribution of electrons around the molecule is no longer symmetrical.
Explanation:
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Climate change
Greenhouse effect
Some heat energy from the Earth’s surface escapes into space. If too much heat energy escaped, the planet would be very cold. However some gases in the atmosphere can trap escaping heat energy, causing some of it to pass back to the surface.
These are called greenhouse gases, and they keep our planet warm, which is a good thing. Carbon dioxide is an important greenhouse gas.
Increasing carbon dioxide levels
Humans burn fossil fuels such as oil, coal and natural gas. The energy released is used to power cars and other machines, to generate electricity, and to keep buildings warm. The burning fuel releases waste gases, including carbon dioxide. As the human population increases, more fuel is used, and more carbon dioxide is released.
Global warming
The extra carbon dioxide increases the greenhouse effect. More heat is trapped by the atmosphere, causing the planet to become warmer than it would be naturally. The increase in global temperature this causes is called global warming.
Answer:
sympatric speciation
Explanation:
Species of fruit fly larvae in the genus Rhagoletis each feed on a particular kind of fruit. Rhagoletis pomonella feeds on the small red fruit of the hawthorn tree. In 1865, farmers in the Hudson River valley found that R. pomonella flies had begun attacking their apples and then spread to apple orchards in adjacent areas of Massachusetts and Connecticut. These now separate varieties of flies, the apple and haw flies, usually don't interbreed with each other because their periods of mating coincide with the different ripening times of apples and hawthorn fruit. Each variety is becoming specialized to feed and reproduce in its own particular microhabitat and may be transitioning to separate species.If the apple and haw flies become distinct enough to be separate species, their evolution is an example of sympatric speciation
