What is the difference between the troposphere and the stratosphere

Troposphere: It is the first layer of atmosphere. The region from the earth surface to 10 kilometers. Many important gases come in this area. These gases are oxygen, nitrogen and carbondioxide.

Stratosphere: Stratosphere is the region which comes above troposphere and below mesosphere. It is the second layer of atmosphere. Its length is 11 to 50 kilometers.

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:

answer: 21

step-by-step explanation:

divide 630 by 30. 30 goes into 630 21 times