Many songbirds breed in north america in the spring and summer, and then migrate to central and south america in the fall. they spend the winter in these warmer areas where they feed and prepare for the spring migration north and another breeding season. two hypothetical species of sparrow. a and b. overwinter together in mixed flocks in costa rica. in spring. species a goes to the east coast of north america, and species b goes to the west coast. what can you say about the isolating mechanisms of these two species? a) they must have strong postzygotic isolating mechanisms to spend winter in such close proximity b) they must have strong prezygotic isolating mechanisms to spend winter in such close proximity. c) these two species mate in different climates. d) reinforcement must be occurring when they winter together.

C. These two species mate in different climates.

Explanation:

Many songbirds breed in North America in the spring and summer, and then migrate to Central and South America in the fall. They spend the winter in these warmer areas where they feed and prepare for the spring migration north and another breeding season. Two hypothetical species of sparrow. A and B. overwinter together in mixed flocks in Costa Rica. In spring. species A goes to the east coast of North America, and species B goes to the west coast. What can you say about the isolating mechanisms of these two species?

It is visible that the species, their winter habitat has no bearing on their degree of reproductive isolation. One of the characteristics of living organism is ADAPTATION.  They are adapted to different region during mating period.

The answer is not A, neither do they have a strong prezygotic isolating mechanism,

they do not have reinforcement must be occurring when they winter together

C is the answer

stress fractures occur largely in the feet and legs and are common in sports that require repetitive impact, primarily running/jumping sports such as gymnastics or track and field.

answer: - b cells

explanation: -

so, the b cells mediate their action by identifying the antigens present on the surface of the pathogens and then producing antibodies in return to mediate its effect.