Help plz asap! What are the organisms still alive that display some of the earliest vertebrate evolutionary characteristics?

When lactate builds up in a runners muscles it causes a burning sensation what causes this to occur

In many humans, exposing the skin to sunlight over prolonged periods of time results in the production of more pigment by the skin cells (tanning). this change in skin color provides evidence that -

This problem has been solved! see the answeryou are investigating two traits in fruit flies controlled by one gene each. the b gene controls for body color (black or brown), while the r gene controls for body sculpture (rugose or smooth). after crossing rugose black flies with smooth brown flies, you obtain an f1 generation of 100% smooth black flies. what are the dominant alleles? (1 pt)what are the genotypes of the two parent flies to perform a dihybrid test cross? (1 pt)after running a dihybrid test cross, you find 1000 offspring with the following phenotypes: , rugose406black, smooth86brown, rugose94brown, smooth4141000fill in the expected column with the expected number of offspring in each class of phenotypes. (1 pt)what phenotype classes represent the recombinant offspring? (1 pt each)calculate the relative genetic distance between the body color gene and the body sculpting gene (show your work). (1 pt).