During erythroblastosis fetalis, a rh- mother's anti-rh antibodies that have crossed the placenta will cause agglutination of the fetus's rh+ rbcs. however, the reverse problem never happens when a rh+ mother is pregnant with a rh- fetus, that is, antibodies produced by the fetus cannot cause agglutination of the mother's rh+ rbcs. this is true because during erythroblastosis fetalis, a rh- mother's anti-rh antibodies that have crossed the placenta will cause agglutination of the fetus's rh+ rbcs. however, the reverse problem never happens when a rh+ mother is pregnant with a rh- fetus, that is, antibodies produced by the fetus cannot cause agglutination of the mother's rh+ rbcs. this is true because agglutinins are physically too large to pass across the placenta fetal antibodies are immature and non-functional antibodies that can cause this agglutination are not produced by a fetus the placenta is a barrier that prevents the passage of all antigens

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:

and after water is usually warmed by the sun the water temperature raises and then evaporates .