Crossing over shuffles alleles on:.a. sister chromatids. b. different non-homologous chromosomes. c. chromosomes within different cells. d. different homologous chromosomes. d. none of the answers are correct.

Ablastocyst is a group of cells that forms after a human egg is fertilized. the blastocyst consists of two types of cells. some of these cells will become the placenta. what do the other cells develop into?

The phylogenetic tree illustrates the relationship between humans and our closest living relatives. the tree was based on biochemical comparisons, including dna and amino acid sequences. according to the biomolecular data, we could infer that a) the four organisms do not have a common ancestor. b) humans are more closely related to chimps than any other apes. c) chimps are more closely related to gorillas than they are to humans. eliminate d) there is no evidence if any relationship between the four branches on the tree.

The eruption of a nearby volcano causes a prairie ecosystem to receive a lot less sunlight. which of these is most likely effect on the ecosystem?