At the time life arose on Earth, Earth's atmosphere contained all but which of the following?
a. H2
b. N2
c. O2
d. H2S
Ans: c. O2
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A cell biologist examines a leaf cell from an alfalfa plant during metaphase of mitosis and determines that 32 chromatids are present. The role of fertilization in this species is to (Check all that apply)
_____ Produce a new cell that has a combination of chromosomes from 2 different parents. _____ Increase the number of chromosomes per cell from 16 to 32. _____ Increase the number of chromosomes per cell from 8 to 16. _____ Combine the chromosomes from 2 haploid cells into a single diploid cell. Clarify Question · What is the key concept addressed by the question? · What type of thinking is required? · What key words does the question contain and what do they mean? Gather Content · What do you know about fertilization? How does it relate to the question? Consider Possibilities · What other information is related to the question? Which information is most useful? Choose Answer · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer? Reflect on Process · Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
What is the function of the contractile vacuole?
A. to help single-celled organisms maintain homeostasis in a hypotonic environment B. to help single-celled organisms change shape in response to environmental changes C. to help maintain water balance for singlecelled organisms living in a hypertonic environment D. to maintain cell shape through turgor pressure
Which phrase best describes "honeydew"?
a. phloem sap leaving the anus of an aphid b. phloem sap harvested as syrup c. xylem sap separated from syrup d. xylem sap forced out of the margins of leaves
At some stage of the life cycle, all chordates have
A) a pre-anal tail. B) an external skeleton. C) a ventral nerve cord. D) a backbone. E) pharyngeal gill slits.