The greatest cause of extinction of species is
(a) runoff.
(b) habitat loss.
(c) invasive species.
(d) evapotranspiration
(c) invasive species.
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You add an unknown phage to a mixture of F+ and F- cells of E. coli and plate out the bacteria. The bacterial colonies that grow are all F-. How can you explain this phenomenon?
A. The phage bound to a receptor on the sex pilus, and therefore only infected the F+ cells (leaving the F- cells alone). B. The phage bound to a receptor on the F- cells, leaving only them alive and allowing the F+ cells to die off. C. The phage integrated (lysogenized) the F- cells, giving them a selective advantage over the F+ cells. D. F+ cells are uniquely susceptible to phage attack for unknown reasons.
Which of the following statements is true?
a. Chromosomes are classified into two categories, the sex chromosomes that determine gender and autosomes that determine non-gender related traits. b. Homologous chromosomes differ in banding patterns, the traits they code for and size. c. While sex chromosomes determine different genders they look the same until they are stained. d. In humans all 46 chromosomes have an identical match called the homologue.
Which statement about the beak size of finches on the island of Daphne Major during prolonged drought is true?
A) Each bird evolved a deeper, stronger beak as the drought persisted. B) Each bird's survival was strongly influenced by the depth and strength of its beak as the drought persisted. C) Each bird that survived the drought produced only offspring with deeper, stronger beaks than seen in the previous generation. D) The frequency of the strong-beak alleles increased in each bird as the drought persisted.
When does replication of DNA occur?
a. during the S phase b. during the G1 phase c. during the prophase d. during the G0 phase