Environments are covered with manmade structures like roads, buildings, and sewers. green spaces such as parks, backyards, and undeveloped lots are scattered in among the developed areas instead of all connected together. plants and animals have to deal with exposure to toxins from vehicles and loss of habitat and food sources. these are all ways that a. humans have intervened to both manage and manipulate the environment to ensure species survival b. nonhuman life in an urban ecosystem differs from that in an undeveloped forest ecosystem c. cities have been developed to keep wildlife out of public areas d. humans have impacted the environment and caused wildlife species to become domesticated

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: