How does the genus Pfiesteria cause problems in both humans and fish?
What will be an ideal response?
Answer: The toxic dinoflagellate P. piscicida produces spores containing neurotoxins that can kill the skin of fish. The lesion is then subject to opportunistic pathogens that cause more diseases, often resulting in death. The neurotoxins also affect humans by giving rashes to swimmers as well as respiratory problems.
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The life cycle of a zygomycete differs markedly from that of animals because in this fungus, ____
a. a sexual stage is absent b. mitosis occurs in the haploid growth stage c. there is no fusion of nuclei d. mitosis occurs to produce the haploid reproductive cells e. a diploid stage is absent
Tetrazolium chloride is used by the seed industry to indicate
a. if a seed is undergoing photosynthesis. b. if seeds are undergoing aerobic respiration. c. if seeds are alive. d. both b and c.
Two groups of tomatoes were grown under laboratory conditions, one with humus added to the soil and one a control without humus
The leaves of the plants grown without humus were yellowish (less green) compared with those of the plants grown in the humus-enriched soil. The best explanation for this difference is that _____. A) the healthy plants used the food in the decomposing leaves of the humus for energy to make chlorophyll B) the humus made the soil more loosely packed, so water penetrated more easily to the roots C) the humus contained minerals such as magnesium and iron, needed for the synthesis of chlorophyll D) the heat released by the decomposing leaves of the humus caused more rapid growth and chlorophyll synthesis
Which extant chordates are postulated to be most like the earliest chordates in appearance?
A) lancelets B) adult tunicates C) amphibians D) chondrichthyans