Evidence unearthed by scientists supports the conclusion that about 65 million years ago a large object from space crashed into an area north of what is now the Yucatan Peninsula of Mexico. The impact threw huge amounts of dust into the atmosphere which spread across Earth's
sky, blocking the sunlight. At about the same time
dinosaurs, and many other forms of life in all regions of Earth, became extinct.
Describe how this event could have caused herbivorous and carnivorous organisms to become extinct.

Match the types of competition to their descriptions.

Which organelle releases chemicals that break down large food particles into smaller ones?

Neelaredoxin is a 15-kda protein that is a gene product common in anaerobic prokaryotes. it has superoxide-scavenging activity, and it is constitutively expressed. in addition, its expression is not further induced during its exposure to o2 or h2o2 (silva, g., et al. 2001. j. bacteriol. 183: 4413–4420). which of the following statements best describes neelaredoxin synthesis? a-neelaredoxin is produced at all times; levels are constant even when exposed to o2 or h2o2.b-neelaredoxin is produced at all times; exposure to o2 or h2o2 increases expression.c-neelaredoxin is produced at all times; exposure to o2 or h2o2 decreases or prevents expression.d-neelaredoxin is only produced when there is exposure to o2 or h2o2.