One source of fossils from early cells is stromatolites. What are stromatolites and how are they formed?
What will be an ideal response?
A stromatolite is a rocky conical or dome-shaped structure composed of layers of cells, cell remains, and sediment. It forms when photosynthetic bacteria living in shallow sunlit water form a mat that traps sediments. Once a layer of sediment covers the bacteria, they grow up through it and trap more sediment. Fossils that are undisputed stromatolites first appear about 2.8 billion years ago.
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Reproductive isolating mechanisms are
a. specific behaviors that allow males to compete against other males for females. b. the processes by which sexual selection evolves within a population. c. the ways that gene flow is blocked between populations. d. the ways in which individuals within a species are unable to produce fertile offspring. e. the various geographic barriers to immigration and emigration of individuals between populations.
Which of the following statements is not true concerning root hairs?
a. They are tubular extensions of epidermal cells. b. They are continually formed in the area of cell maturation. c. They are quite numerous. d. They greatly increase the absorptive capacity of roots. e. They are long lived .
In bacterial cell division, the cell divides into two nearly equal halves. This process is referred to as
A. binary fission B. meiosis C. cytokinesis D. fusion E. mitosis
How does glucose enter a cell if levels of blood glucose are high?
A) The glucose molecules diffuse through the membrane. B) An electrical signal is passed through the blood, opening glucose channels within the membranes of cells. C) Glucose pokes a hole in the cell's membrane, creating a channel through which it can move. D) Insulin molecules bind to glucose receptors, causing cellular responses to take up glucose.