What are the two phases of speciation?
a. geographic isolation and variation
b. adaptation and reproductive isolation
c. adaptation and variation
d. geographic isolation and reproductive isolation

D is the right answer for this question on e2020

D. geographic isolation and reproductive isolation

Speciation can be defined as a evolutionary process by which a new species develop from a parent species. It occurs when the members of the species becomes reproductively isolated and physically get separated due to geographical barriers. In allopatric speciation, the ancestral population evolve into a new species due to geographical barriers like river which separate the two populations of the same species apart. In sympatric speciation, the ancestral population evolve into a new species due to the reproductive and behavioral isolation. This is due to the fact that the members of the two species becomes incapable of inbreeding.

it is called an accent mark

fertilization, pictured in figure 24.23a is the process in which gametes (an egg and sperm) fuse to form a zygote. the egg and sperm each contain one set of chromosomes. to ensure that the offspring has only one complete diploid set of chromosomes, only one sperm must fuse with one egg. in mammals, the egg is protected by a layer of extracellular matrix consisting mainly of glycoproteins called the zona pellucida. when a sperm binds to the zona pellucida, a series of biochemical events, called the acrosomal reactions, take place. in placental mammals, the acrosome contains digestive enzymes that initiate the degradation of the glycoprotein matrix protecting the egg and allowing the sperm plasma membrane to fuse with the egg plasma membrane, as illustrated in figure 24.23b. the fusion of these two membranes creates an opening through which the sperm nucleus is transferred into the ovum. the nuclear membranes of the egg and sperm break down and the two haploid genomes condense to form a diploid genome.

explanation: