Population Ecology Practice Test

A rabbit population in a grassland was monitored monthly. It increased from 50 to 80 to 130 over the first three months. In month 4, a viral disease outbreak occurred; counts then were 70 in month 4 and 60 in month 5. No major changes in predators or food were observed. Which factor most directly explains the population decrease after month 3?

A biologist monitors a yeast population in a closed flask with abundant sugar and stable temperature. Cell counts (millions/mL) are: 2 at 0 h, 4 at 2 h, 8 at 4 h, 16 at 6 h, and 32 at 8 h. Waste products remain low during this interval, and no cells are removed from the flask. Which explanation best accounts for the growth pattern observed from 0 to 8 hours?