The common grackle is a species of robin-sized blackbirds that are fairly common over most of the United States. Suppose that long tails (L) were dominant to short tails (1) in these birds. A female short-
tailed grackle mates with a male long-tailed grackle that had one parent with a long tail and one parent
with a short tail. What is the tail length probability of their offspring?

Long tail (Ll) = 1/2 or 50%

Short tail (ll) = 1/2 or 50%

Explanation:

This question involves a single gene coding for tail length in grackle birds. The allele for long tails (L) were dominant to short tails (l) in these birds. This means that a bird that is heterozygous (Ll) for the gene will be phenotypically long tailed.

According to the question, a female short-tailed grackle (ll) mates with a male long-tailed grackle that had one parent with a long tail and one parent with a short tail. This male grackle will have a genotype: Ll because of his parental genotype. Hence, crossing ll × Ll, the following gametes will be produced by each parent:

Ll (male) = L and l

ll (female) = l and l

Using these gametes in a punnet square (see attached image), the following proportion of offsprings will be produced:

Ll, Ll, ll and ll

2 Ll out of 4 are long-tailed i.e 1/2 or 50% probability

2 ll out of 4 are short-tailed i.e 1/2 or 50% probability

the answer is true when observing or determining population size, a direct observation is use, in which each organism is counted in a population or in an area. one benefit of this measure is that you get the exact population count but it will take a long time to  determine  the  size  of a  population.