They train our immune system so it's ready when our bodies are attacked, and they aid in digestion and supply us with vitamins. ... Scientists and doctors can even utilize prokaryotes to help the human body.
Answer:
It occurs in organisms because an organism with a beneficial trait/mutation have a higher chnace of surviving compared to organisms that do not. So the organsims that do survive pass on their genes to the next generation, and the bext generation will pass on those genes to the generation after and so on. But all the organisms that do not possess a beneficial trait/mutations will not survive, therefore they cannot reproduce and pass on those genes to their offspring. This means that most of the population will posses that trait/mutation.
Example: Spotted moths camouflage with bark so they are seen by predators and eaten. Black moths are easily seen by predators and are eaten. Spotted moths then pass on their genes to the next generation of moths.
Because they are genetically diverse cells that are used in sexual reproduction
The carry the deoxygenated blood from the heart to the lungs and Pulmonary veins do the opposite!
Autotrophs are organisms that can produce their own food from the substances available in their surroundings using light (photosynthesis) or chemical energy (chemosynthesis). Heterotrophs cannot synthesize their own food and rely on other organisms — both plants and animals — for nutrition.
Explanation: autotroph eg plant
hetrotroph eg animals
