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:
Explanation:
1- closely packed osteons or haversian systems, used to provide strength and protection to bones.
2- Spongy bone consists of plates (trabeculae) and bars of bone adjacent to small, irregular cavities that contain red bone marrow. provides balance to the dense and heavy compact bone by making bones lighter so that muscles can move them more easily.
Answer:
The average adult, when resting, inhales and exhales about 7 or 8 liters of air per minute. That totals about 11,000 liters of air per day. Inhaled air is about 20-percent oxygen. Exhaled air is about 15-percent oxygen.
Explanation:
The lung is not considered a living organism since it can not reproduce and it does not have cells
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-SmartCookies
It would probably be global warming such as burning fossil fuels,and nuclear energy that can cause the dearth to because hotter any causes global warming. That’s why temperatures are going up.
