Answer: More than 99 percent of all organisms that have ever lived on Earth are extinct. As new species evolve to fit ever changing ecological niches, older species fade away. But the rate of extinction is far from constant. At least a handful of times in the last 500 million years, 75 to more than 90 percent of all species on Earth have disappeared in a geological blink of an eye in catastrophes we call mass extinctions.
Though mass extinctions are deadly events, they open up the planet for new forms of life to emerge. The most studied mass extinction, which marked the boundary between the Cretaceous and Paleogene periods about 66 million years ago, killed off the nonavian dinosaurs and made room for mammals and birds to rapidly diversify
Answer:
Lay the leaves to be measured on a 1-cm grid and trace their outlines. Count the number of square centimeters. Estimate the area of the partial squares. ... Do not include the area of the stem (petiole) in your calculations.
Molecules produced in the nucleus are transported to the cytoplasm via ribosomes.
Answer:
Whereas both bacteria and archaea lack a nuclear envelope and membrane-bound organelles, archaea and eukaryotes have similarities beyond those seen between bacteria and eukaryotic cells. Bacteria have the macromolecule peptidoglycan in their cell walls; archaea and eukarya lack this polymer.
Explanation:
-3x + 3(2x - 6) = 6
-3x +6x - 18 = 6
3x - 18 = 6
3x = 6 + 18
3x = 24
x = 8
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