Which of these is an example of gene flow?

a) german immigrants settle in a colony in eastern pennsylvania without mixing with the locals.
b) a few black sparrows join a population of brown sparrows and mate with them.
c) indiscriminate hunting reduces the blue whale population, which later revives.

When does a spring tide occur? question 9 options: they occur when the sun, moon, and earth are aligned. in spite of their name, these tides occur twice a year in the spring and fall. they occur on the date of the vernal equinox each year, no matter what stage the moon is in. this is why they are called spring tides. they occur when the sun, moon, and earth are at 45-degree angles from each other. this happens once every spring. they occur when the sun, moon, and earth are aligned. in spite of their name, these tides occur all year long.