Question

peppered moths are active at night. during the day peppered moths rest on tree trunks and branches. some of these resting moths are eaten by birds. researchers have found that mortality is higher for the speckled form of the peppered moth in one type of environment, and mortality is higher for the block form of the peppered moth in a different type of environment.
1a. which form of the peppered moth do you think had higher mortality in forests in unpolluted areas where tree trunks and branches are lighter? black speckled
which form of the peppered moth do you think had higher mortality in forests in areas where air pollution had resulted in dark tree trunks and branches? black speckled
1b. explain your reasoning.

1. the difference between the black and speckled forms of the peppered moth is a heritable trait; specifically, this difference results from different alleles of a single gene. the allele for the black form (b) is dominant over the allele for the speckled form (b). in the punnett squares circle the genotypes of all parents and offspring that would have a speckled phenotype. based on these punnett squares, explain why peppered moths generally have offspring that look like their parents.

evolution by natural selection

1. in the first column of this table, there are three necessary conditions for evolution by natural selection to occur. in the second column, explain the evidence that each of these necessary conditions is satisfied by the black vs. speckled forms of the peppered moth.

Explanation:

1a. In unpolluted areas with lighter tree trunks and branches, the black - colored moths would stand out more, making them easier for birds to spot and eat. So, the black form has higher mortality. In polluted areas with dark tree trunks and branches, the speckled moths would be more visible, so the speckled form has higher mortality.
1b. The principle of camouflage and predation. Moths that are better camouflaged (matching the background of tree trunks and branches) are less likely to be eaten by birds.

1. The speckled phenotype is determined by the genotype \(bb\). In the Punnett squares:

• For the first Punnett square (parents \(bb\times bb\)), all offspring are \(bb\) (speckled).
• For the second Punnett square (parents \(BB\times BB\)), all offspring are \(BB\) (black, as \(B\) is dominant).
• For the third Punnett square (parents \(BB\times bb\)), the offspring are \(Bb\) (black, because \(B\) is dominant over \(b\)). When parents have genotypes that are either homozygous dominant (\(BB\)) or homozygous recessive (\(bb\)), their offspring will have genotypes that result in phenotypes similar to the parents. If a parent is \(BB\) (black), and assuming mating with another \(BB\) (or in some cases \(Bb\) where the dominant trait is expressed), the offspring will show the dominant (black) trait. If parents are \(bb\) (speckled), all offspring will be \(bb\) (speckled).

1. The three necessary conditions for evolution by natural selection are:

• Variation: There are two forms (black and speckled) of the peppered moth. This is a phenotypic variation.
• Heritability: The difference between black and speckled forms is due to different alleles (\(B\) and \(b\)) of a single gene. As shown in the Punnett squares, the traits are passed from parents to offspring.
• Differential survival and reproduction: In different environments (polluted vs. unpolluted), one form has higher mortality (lower survival). For example, in unpolluted areas, black moths are more likely to be eaten (lower survival), and in polluted areas, speckled moths are more likely to be eaten (lower survival). This differential survival affects their ability to reproduce and pass on their genes.

Answer:

1a. black; speckled
1b. Moths that match the background (tree trunks and branches) are less likely to be eaten by birds. In unpolluted areas, black moths are more visible (higher mortality), and in polluted areas, speckled moths are more visible (higher mortality).

1. Speckled phenotype is \(bb\). When parents are \(bb\) (speckled), all offspring are \(bb\) (speckled). When parents are \(BB\) (black), offspring get \(B\) alleles (and show black phenotype as \(B\) is dominant). So, generally, offspring look like parents because of the inheritance of alleles (\(B\) or \(b\)) that determine the phenotype.

3.

• Variation: Two forms (black and speckled) exist.
• Heritability: Traits are determined by alleles (\(B\) and \(b\)) of a single gene and passed via Punnett - square - like inheritance.
• Differential survival and reproduction: In different environments (polluted vs. unpolluted), one form has higher mortality (affecting reproduction and gene - passing).