SCIENCE: NATURAL SELECTION UNIT TEST.

Question

CONSIDER THE FOLLOWING SCENARIO:

A DROUGHT HITS THE HABITATF OF A SEMI-AQUATIC BIRD POPULATION. ALL PONDS DRY UP, AND FISH POPULATIONS DECLINE. THERE ARE TWO GROUPS OF BIRDS IN THE POPULATION THAT DIFFER IN LEG LENGH AND DIET. LONG-LEGGED BIRDS EAT FISH, WHILE SHORT-LEGGED BIRDS EAT INSECTS. THE DROUGHT HAS LITTLE EFFECT ON INSECT POPULATIONS.

WHAT IS THE MAIN SELECTIVE PRESSURE IN THIS SCENARIO?
1. DROUGHT
2. INSECT POPULATION
3. LEG LENGH
4. FISH POPULATION

Answer 1

The main selective pressure in this scenario is the drought. The drought is causing ponds to dry up, leading to a decline in fish populations. Since long-legged birds eat fish and short-legged birds eat insects, the decline in fish populations will affect the survival and reproductive success of the long-legged birds, as their food source becomes scarce. This will put selective pressure on the bird population to adapt to the changing conditions caused by the drought.