Answer:
The original water sample contains 830,000 cells per milliliter.
Explanation:
A sample of well water is tested for its bacterial content in a plate count assay. A one-milliliter sample of the water is diluted in a 1:10 dilution series. One milliliter of the fourth dilution tube is plated in a pour plate. After incubation, the plate has 83 colonies, indicating that the original water sample contained 830,000 cells per milliliter.
Answer: B
Explanation: Most mammals have only one pair of sex chromosomes in each cell. Males have only one Y chromosome and one X chromosome, while females have two X chromosomes. In Mammals, the Y chromosome contains a gene, SRY, which triggers embryonic development in a male.
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Answer:
Option 1.
Explanation:
r-selected species may be defined as the species that has higher growth rate, shows less parental care and the rate of survival of the off spring is low as compared with k selected species.
Black widow spiders have the ability to produce 1000 offspring. Their chances of survival are extremely low and only few species of black widow spiders survive. Hence, black widow spider is r-selected species.
Thus, the correct answer is option (1).
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