In order for an ovule (egg cell) in a flower to be fertilized and form a viable seed, pollination must occur
In this process, a sperm cell is delivered to the ovule when the pollen grain lands on the stigma and grows a tube, which enters the ovary and discharges the sperm cell to form a diploid zygote when it fuses with the egg cell. Although it only takes one pollen grain to successfully deliver sperm to the egg, numerous pollen grains are generally transferred to the stigma during insect pollination of flowering plants. Which phenotypic traits of pollen would you predict to be selected upon to promote survival and fitness within an insect-pollinated flowering plant? A) High pollen tube growth rate and ability to detect chemicals from cells surrounding the egg.
B) Ability to produce the most cells during mitotic growth of the pollen tube.
C) Elaborate and striking UV "nectary guides" on the petals to guide an insect to the stigma.
D) Larger pollen in order to carry the tube that is necessary for delivery of the sperm cells.
A
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In Pasteur's experiment showing that living organisms arise from other living organisms, which one of the following statements most accurately describes Pasteur's hypothesis?
A. Straight-neck flasks allow for more contamination than swan-neck flasks. B. Sterilization of broth kills microbes. C. If microbes arise from non-living matter, they should appear spontaneously in sterile broth. D. Microbes should be capable of growing equally well in sterile broth contained in both straight-neck and swan-neck flasks. E. The first cells must have come from chemical reactions occurring in early Earth.
Which of the following pathways does not require DNA ligase?
A. gap repair B. fork regression and resolution of a stalled replication fork C. synthesis-dependent strand annealing D. double-strand break repair E. All of the pathways given require DNA ligase.
An increase in sympathetic nervous activity to arterioles will have little effect on vasoconstriction of the
A) brain and heart. B) heart and kidneys. C) kidneys. D) skeletal muscles. E) gastrointestinal tract
Both human pathogens and normal microbiota are typically classified as:
psycrophiles thermophiles mesophiles hyperthermophiles