One reason that bacteria can be harmful is that they:

A. can remove nitrogen gas from the air.

B. have cell walls with peptidoglycan.

C. can produce toxins that kill other cells.

D. live in the digestive tracts of animals.

Describe how the temperature and chemical composition of the troposphere vary

What structure is responsible for gas exchange in most spiders?

Which of the following is a metamorphic rock formed from shale? A. limestone B. gneiss C. slate D. sandstone

Are earth like planets common

If a cell has 16 chromosomes, how many chromosomes will each of its daughter cells have after mitosis and cytokinesis?

Why might a water table drop

How did the 1898 discovery of blood types affect society?

Which of the following is a feeding source for fens? aquifers dexfoliants exfoliants nitrates

What system includes oceans, lakes, rivers, and groundwater? a. geosphere b. hydrosphere c. atmosphere d. biosphere

Fungal spores a. are only asexually produced. b. cannot be seen in a light microscope. c. are used to identify fungi. d. are produced by molds but not by yeasts. e. are only produced under harmful environmental conditions