An ionic bond can be formed after two or more atoms loss or gain electrons to form an ion. Ionic bonds occur between metals, losing electrons, and nonmetals, gaining electrons. Ions with opposite charges will attract one another creating an ionic bond.
<span>The correct answer is a. the overuse of fertilizer lead to reduced crop yields over time. This was unexpected because it is common for fertilizers to increase the yields and the quality of the product, but what happens over time is the opposite so it can be said that it's an unexpected consequence.</span>
Answer:
C. At least five mass-extinction events have occurred during the last 500 million years.
Explanation:
- The history of mass extinct is related to the five mass extinctions that are caused over by the 350 million years n which many species have disappeared in there short geologic time.
- A massive extinction is caused in the Permian Triassic extinction event i.e about 250 mn years ago which on an estimate has killed 90% of the species.
- The Cretaceous–Paleogene extinction event that occurred over 66 million years ago is known to have wiped out the dinosaurs and many other species.
Their bodies taper to points at both the snout and the tail, reducing water resistance. Also decreasing drag -- and therefore noise -- are dermal denticles, sharp scales that cover the skin of most shark species. Rather than bone, sharks have cartilage, which is much lighter and more flexible. In addition, their livers produce squalene, a fatty oil that helps them remain afloat. Their pectoral fins allow them to quickly change direction, dive and swim upward.
http://animals.mom.me/unique-adaptations-sharks-survive-7845.html
