According to the phylogenetic species concept, what is a species?

Ais a group of individuals of the same that exist together in the same place at the same time

Crossing over is a method of (blank)?

Which one is an advantage of external fertilization a. the offspring are genetically identical to the parents b. more eggs can be fertilzed at one time c. more sperm can be released at one time d. more protection is available for developing plz