Answer:
olecules can diffuse across membranes via transport proteins, or they can be aided in active transport by other proteins. Organelles such as the endoplasmic reticulum, Golgi apparatus, mitochondria and peroxisomes all play a role in membrane transport.
Species evolve independently possibly due to geographical isolations or behavioural isolations.
Geographical isolation includes the isolation of 2 groups of the same species. Since these 2 groups live in different locations, (e.g. a volcanic eruption resulting in a barrier between one side of an ocean and another side of the ocean), they will have different selection pressures in their different environments as well (e.g. one side of the ocean may have more sunlight and thus more underwater plantations than the other side of the ocean). Natural selection will eliminate those with disadvantageous characteristics (e.g. Fishes that only eat plants and nothing else on the side of the ocean with little plantations) with unfavourable alleles, and select for those with advantageous characteristics (e.g. Fishes are able to eat plants and other organic substances as well on the side of the ocean with little plantations) with favourable alleles.
Since the 2 groups have different selection pressures, natural selection will occur in different ways, selecting for and against different types of fishes with different types of alleles. Also, because of the barrier, they are not able to mate with each other, and there are no mixing of genes from one side of the ocean and the other side. They are genetically isolated. As genetic drift occurs over time, their gene pools become different from each other. Thus, they evolve independently.
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Cellular respiration and photosynthesis are essentially opposite processes. Photosynthesis is the process by which organisms make high-energy compounds -- the sugar glucose in particular -- through the chemical "reduction" of carbon dioxide (CO2). Cellular respiration, on the other hand, involves the breakdown of glucose and other compounds through chemical "oxidation." Photosynthesis consumes CO2 and produces oxygen. Cellular respiration consumes oxygen and produces CO2.
