You are observing a developing embryo under a microscope and see that it has a space in the middle of the endoderm, but no features of a notochord are present. In which stage of development is this embryo?
A) zygote
B) blastula
C) gastrula
D) fetus
Answer: C
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Lyell’s theory of uniformity proposed that ____
a. Earth was shaped by gradual, repetitive change b. catastrophic geological events caused extinctions c. geologic events that occurred to shape Earth no longer occur d. all populations produce more offspring than their environment can support e. natural selection drives evolutionary change
Methanogens can live only in ________ environments.
A. anaerobic B. microaerophilic C. aerobic D. All of the choices are correct.
DNA contains two identical polynucleotide chains
a. True b. False
You modify one species of rhizobia (Species A) to express flavonoid receptors and Nod factors from another species of rhizobia (Species B). This modified rhizobia is likely to
A. form a symbiosis with the plant with which species A normally forms a symbiosis. B. be unable to bind flavonoids. C. form a symbiosis with the plant with which species B normally forms a symbiosis. D. be unable to fix nitrogen.