The oldest definitive trace of flowering plants in the fossil record consists of:
a. pollen grains in an anther.
b. pistils on vegetative stems.
c. petals and sepals.
d. ovules enclosed in podlike fruits.
e. primitive embryo sacs.
D
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A mutation is more likely to affect a differentiated cell than a stem cell due to
A) skewed distribution of parental versus newly replicated DNA. B) a conscious effort on the part of the individual. C) lack of DNA replication in stem cells. D) skewed distribution of stem and progenitor cells.
Although organisms result from a combination of genetic and environmental factors, only _______ factors are passed on to the next generation.
Fill in the blank(s) with the appropriate word(s).
Why is it more difficult to obtain sufficient oxygen at higher altitudes? What will be an ideal response?
The diffusion of water across a selectively permeable membrane is
What will be an ideal response?