Annual rings in a tree trunk result from
A. deposition of colored materials in the oldest cells.
B. the variation in cell size due to different growth conditions throughout a year.
C. the alternation of xylem and phloem produced in one year.
D. the kinds of cells, parenchyma or sclerenchyma, produced by the cambium.
E. the proportion of wood cells and cork cells in the xylem.
B. the variation in cell size due to different growth conditions throughout a year.
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Researchers generally insert engineered Ti plasmids into plant cells by ________
a. electric shock b. inserting the plasmid into A. tumefaciens and allowing the bacteria to infect a plant c. chemical shock d. coating microscopic bullets with the plasmid and shooting them into a plant cell
Which of the following is NOT an example of a CURRENT use of bioinformatics?
a. locating individual genes in a genomic sequence b. aligning sequences in databases to determine similarities between organisms c. predicting the structure and function of gene products d. identifying possible evolutionary relationships between organisms e. determining the final protein structure of novel proteins based on just the nucleotide sequence
Which of the following is not associated with leaf abscission?
a. Chlorophyll breaks down. b. Anthocyanins accumulate. c. A layer of cork develops. d. The middle lamella is strengthened. e. Carotenoids become visible.
Destruction of which biome would result in the greatest loss of biodiversity?
A. Grassland B. Desert C. Tropical rain forest D. Taiga forest E. Savanna