A researcher is curious if Bt resistant bollworms are susceptible to an insecticide called DDT. Bollworms susceptible to Bt have genotype RR or Rr, whereas those resistant to Bt have genotype rr. Bollworms susceptible to DDT have genotype tt, whereas bollworms resistant to DDT have genotypes Tt or TT. In an effort to better understand how these two genes are inherited, the researcher crosses an RR tt bollworm with an rr TT bollworm to produce the F1 generation. Then, the researcher crosses the F1 generation to produce an F2 generation. What proportion of the F2 generation is resistant to both Bt and DDT

The correct answer is - 3/16 or 18.75% portion will be resistant to both Bt and DDT.

Explanation:

It is given that bollworms that are susceptible to Bt are represented by either RR or Rr and resistance one are shown by rr genotype and bollworms that are resistant to DDT are represent TT or Tt genotype and susceptible to DDT have tt genotype.

Cross: RR tt with rr TT

Gametes: Rt and rT

F1 cross:

    RT

rT  RrTt ( susceptible Bt and resistant DDT)

F1 Cross with F1

Gametes: RT, Rt, rT and rt

cross:

             RT      Rt        rT         rt

RT       RRTT   RRTt   RrTT    RrTt

Rt        RRTt    RRtt    RrTt      RrTt

rT       RrTT    RrTt     rrTt       rrTt

rt       RrTt      Rrtt     rrTt      rrtt

The bold genotypes are the three out of 16 that are resistant to both DDT and Bt.

answer: decrease

a limiting factor is the one which decrease the abundance, distribution and causes extinction of the population of species in a ecosystem. here, predators including hawks, owls and snakes are the limiting factor for the population of mexican free tailed bat.   although bats are nocturnal animals as they forge for food at night these predators also may remain active during night which can decrease the population of the mexican free-tailed bats. also, these bats eat only one type of insects that are moths. the food can also be a limiting factor as all 400 members are dependent upon same type of food needs that are moths. the decrease in the moth population can cause decrease in population size of the mexican free-tailed bats.

therefore, the scenarios will most likely to decrease the population size of the mexican free-tailed bats.