[Answer] Which is the most abundant vertebrate on the planet?

Step 1 : Introduction to the question "Which is the most abundant vertebrate on the planet?"

...Surprisingly, the most common vertebrate on the planet lives in the darkest depths of the Earth's oceans. The Bristlemouth fish has a population in the trillions or more. This small fish has a slender body only a few inches in length. Like most deep-ocean species, the Bristlemouth fish glows. It has rows of bioluminescent dots that line its abdomen. It uses this as a type of camouflage called counter-illumination. Since little daylight reaches the depths of the oceans, fish appear as silhouettes to predators below them. The bioluminescent dots on the Britlemouth's belly mask its silhouette.Source: Aqua.org.

[Answer] 4. This metal is the fifth most abundant element in the earth's crust, and is an essential constituent of leaves, shells, bone, and teeth.

Step 1 : Introduction to the question "4. This metal is the fifth most abundant element in the earth's crust, and is an essential constituent of leaves, shells, bone, and teeth."

...1. iodine 2. calcium 3. phosphorous 4. zinc Calcium is perhaps best known for its numerous compounds. Common chalk is a compound containing calcium.

[Answer] What is the most abundant gas in the Earth's atmosphere?

Step 1 : Introduction to the question "What is the most abundant gas in the Earth's atmosphere?"

...There's oxygen in Earth's air, which is a good thing for human life. But oxygen makes up only 21 percent of the atmosphere. The most abundant gas found in Earth's atmosphere is nitrogen. It makes up 78 percent of the atmosphere. It's a permanent gas, meaning the percentage found in the atmosphere doesn't change on a daily basis. There are trace gasses making up the remainder of the atmosphere, gases such as ozone, helium, nitrous oxide, methane, neo and carbon dioxide. The concentrations of these gasses are always changing. Source: Reference.com

[Answer] 5. We have a tragic tale of a tree which once was abundant across the eastern half of America but was virtually wiped out at the beginning of the 20th century by disease. Which nut has been sung about in a Christmas carol "roasting on an open fire"?

Step 1 : Introduction to the question "5. We have a tragic tale of a tree which once was abundant across the eastern half of America but was virtually wiped out at the beginning of the 20th century by disease. Which nut has been sung about in a Christmas carol "roasting on an open fire"?"

...1. Chestnut 2. Almond 3. Peanut 4. Pecan Unfortunately, the Asian fungus "diaporthe parasitica" was introduced to the area and caused the "Chestnut blight" from 1900 to 1908, virtually killing all but a few of the 4 billion American Chestnut trees. Only very few remain and many of those live just long enough to drop a seed before succumbing to the fungus. For over 100 years, efforts have been made to protect and help bring the species back but with little success. Before 1900, Chestnut trees were the staple lumber supply for building houses in eastern America.

[Answer] 4. We have a tragic tale of a tree which once was abundant across the eastern half of America but was virtually wiped out at the beginning of the 20th century by disease. Which nut has been sung about in a Christmas carol "roasting on an open fire"?

Step 1 : Introduction to the question "4. We have a tragic tale of a tree which once was abundant across the eastern half of America but was virtually wiped out at the beginning of the 20th century by disease. Which nut has been sung about in a Christmas carol "roasting on an open fire"?"

...1. Peanut 2. Pecan 3. Almond 4. Chestnut Unfortunately, the Asian fungus "diaporthe parasitica" was introduced to the area and caused the "Chestnut blight" from 1900 to 1908, virtually killing all but a few of the 4 billion American Chestnut trees. Only very few remain and many of those live just long enough to drop a seed before succumbing to the fungus. For over 100 years, efforts have been made to protect and help bring the species back but with little success. Before 1900, Chestnut trees were the staple lumber supply for building houses in eastern America.

[Answer] We have a tragic tale of a tree which once was abundant across the eastern half of America but was virtually wiped out at the beginning of the 20th century by disease. Which nut has been sung about in a Christmas carol "roasting on an open fire"?

Step 1 : Introduction to the question "We have a tragic tale of a tree which once was abundant across the eastern half of America but was virtually wiped out at the beginning of the 20th century by disease. Which nut has been sung about in a Christmas carol "roasting on an open fire"?"

...Unfortunately, the Asian fungus "diaporthe parasitica" was introduced to the area and caused the "Chestnut blight" from 1900 to 1908, virtually killing all but a few of the 4 billion American Chestnut trees. Only very few remain and many of those live just long enough to drop a seed before succumbing to the fungus. For over 100 years, efforts have been made to protect and help bring the species back but with little success. Before 1900, Chestnut trees were the staple lumber supply for building houses in eastern America.