<span>Antibiotics need to be used with caution because of evolution. If you treat bacteria with an antibiotic, some will be resistant by sheer chance. Those ones will survive and go on to divide - producing more antibiotic resistant bacteria. With medical antibiotics, they must be taken for the entire course. Even after symptoms have passed, bacteria remain in the body. If a patient stops taking antibiotics too early, the survivors can keep dividing and cause a new antibiotic resistant infection. With the normal course of medication, antibiotics kill off enough bacteria and keep them at bay long enough for the immune system to finish the job and take care of any resistant stragglers.
The real danger, though, comes from antibiotic use in livestock. It's more cost effective to feed cattle with a constant supply of antibiotics, whether they're sick or not (as opposed to just treating them when they're sick). These antibiotics keep them from getting sick, but it means that eventually bacteria adapt to them and gain resistant. To make matters worse, the antibiotics are often passed from their bodies in their waste, which can go on to contaminate waterways. This can disrupt ecosystems and produce antibiotic-resistant bacteria in the wild. This type of usage is of much more concern because of its scale - there are far more cows on antibiotics than people</span>
Answer:
a. 500
Explanation:
The effective size of a given population is calculated by simply counting the total amount of organisms that actually are in conditions of reproduce and produce certain offspring in the next generation. In this particular case, althugh the population is formed by a total of 1000 individuals, only 500 organisms are capable of reproduce at that particular instant, and therefore contribute with offspring to the next generation.
What we know about shark and ray fossils comes from bones in rocks from the Cretaceous period in Mexico that left behind, their only hard parts.
<h3>Shark fossils</h3>
The idea of a stingray-like shark may seem like something out of a B-movie. But paleontologists have just reported the discovery of such a creature in Cretaceous rocks in Mexico. This strange shark combines a streamlined body with large, wing-shaped fins, an ancient animal unlike any seen in the fossil record.
<h3>Whose are the fossils?</h3>
Fossils are the remains or traces of living beings that inhabited the Earth in previous geological periods. Fossil remains are parts of animals or plants, such as a bone or some limb or organic remains that have been preserved in some way.
With this information, we can conclude that Fossils are remains or traces of animals and plants preserved in rocks.
Learn more about Fossils in brainly.com/question/22502144
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