Which nucleotide is only found in RNA?
a. adenine
b. thymine
c. adenine
d. guanine
e. uracil
e
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The persistence of the sickle-cell anemia allele in some African populations is the result of ____
a. a high rate of mutation of the normal allele to the sickle-cell anemia allele b. the advantage of the heterozygous form over the homozygous forms c. nonrandom mating d. a decline in the occurrence of malaria in Africa e. genetic drift
Matching. Choose the one most appropriate answer
for each. 1. ___ aggregate fruit 2. ___ anther 3. ___ carpel 4. ___ embryo sac 5. ___ endosperm mother cell 6. ___ megaspores 7. ___ micropyle 8. ___ microspores 9. ___ multiple fruit 10. ___ ovary 11. ___ ovule 12. ___ petal 13. ___ pollen grain 14. ___ sepal 15. ___ stigma A. male spores of anthers B. site where pollen tube usually penetrates the ovule C. develops into a fruit at maturity D. a 2n cell that will help form nutrients for the developing plant embryo E. cluster of matured ovaries attached to a common receptacle F. modified leaf with pigments and fragrance-producing cells G. immature male gametophyte H. female reproductive organ I. landing platform for pollen J. pollen-bearing structure K. female spores of ovule L. outermost whorl of leaf parts on a receptacle; generally green, but sometimes pigmented M. female gametophyte N. matured ovaries of several flowers fused together into a single mass (for example, pineapple, fig) O. forms a seed at maturity
For speciation to occur there must be
A) sexual reproduction. B) genetic variation. C) isolation. D) natural selection.
Why are most autotrophs referred to as the producers of the biosphere?
What will be an ideal response?