You are studying a population of American robins, Turdus migratorius, in which approximately 2% of all individuals carry a recessive allele for leucistic (unusually white) coloration. The population suddenly expands when an influx of robins arrives during spring migration, and the frequency of the leucistic allele drops to only 1.5%. Next season the frequency is still 1.5%. Does it appear that evolution occurred in the robin population in your study area?

Yes, It seems that evolution has occurred in this area.

Explanation:

Evolution refers to a phenomena in which new traits or alleles that favor a better survival of organisms in a given environment, become fixed in the population.

Evolution is characterized by appearance of new characters and change in allele frequencies.

In the given situation we find that the frequency of the recessive allele in the population has changed over time and the percentage has become fixed.

So, we can say that evolution has occurred in the robin population

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.

one characteristic that is shared by all is a soft body. many

of these invertebrate animals also have an outer shell to protect their

body. oysters, clams, snails, and mussels are all mollusks. so are octopuses, squids, and slugs. mollusks live on land and in freshwater.