Learning Objectives By the end of this section, you will be able to: The process by which an organism develops from a single-celled zygote to a multi-cellular organism is complex and well regulated. The regulation occurs through signaling between cells…
Learning Objectives By the end of this section, you will be able to: Some animals produce offspring through asexual reproduction while other animals produce offspring through sexual reproduction. Both methods have advantages and disadvantages. Asexual reproduction produces offspring that are genetically identical…
Figure 18.1 Female seahorses produce eggs that are then fertilized by the male. Unlike with almost all other animals, the young then develop in a pouch of the male seahorse until birth. (credit: “cliff1066″/Flickr) Chapter Outline 18.1 How Animals Reproduce 18.2 Development and Organogenesis…
Viruses Viruses are acellular entities that can usually only be seen with an electron microscope. Their genomes contain either DNA or RNA, and they replicate using the replication proteins of a host cell. Viruses are diverse, infecting archaea, bacteria, fungi,…
Learning Objectives By the end of this section, you will be able to: A functioning immune system is essential for survival, but even the sophisticated cellular and molecular defenses of the mammalian immune response can be defeated by pathogens at…
Learning Objectives By the end of this section, you will be able to: The adaptive, or acquired, immune response takes days or even weeks to become established—much longer than the innate response; however, adaptive immunity is more specific to an…
Learning Objectives By the end of this section, you will be able to: The vertebrate, including human, immune system is a complex multilayered system for defending against external and internal threats to the integrity of the body. The system can…
Learning Objectives By the end of this section, you will be able to: Figure 17.2 (a) The tobacco mosaic virus, seen by transmission electron microscopy, was the first virus to be discovered. (b) The leaves of an infected plant are shown. (credit…
Figure 17.1 (a) This smallpox (variola) vaccine is derived from calves exposed to cowpox virus. Vaccines provoke a reaction in the immune system that prepares it for a subsequent infection by smallpox. (b) Viewed under a transmission electron microscope, you can see…
Homeostasis and Osmoregulation Homeostasis is a dynamic equilibrium that is maintained in body tissues and organs. It is dynamic because it is constantly adjusting to the changes that the systems encounter. It is an equilibrium because body functions are kept…