* Vertebrates: Vertebrates (including humans) have both specific and nonspecific immunity.
* Nonspecific immunity: This is the first line of defense, acting immediately against a wide range of pathogens. It includes things like skin, mucous membranes, phagocytic cells, and the inflammatory response.
* Specific immunity: This is a more targeted response, involving lymphocytes (T cells and B cells) and antibodies. It remembers specific pathogens and mounts a stronger, faster response upon re-exposure.
* Invertebrates: Invertebrates only have nonspecific immunity. They lack the specialized cells and complex mechanisms found in vertebrate specific immunity. However, their nonspecific defenses can be surprisingly effective.
Examples of Invertebrate Defenses:
* Exoskeletons: Provide a physical barrier against pathogens.
* Hemocytes: Circulating cells with phagocytic activity.
* Antimicrobial peptides: Proteins that directly kill bacteria and fungi.
* Encapsulation: Insects can surround and isolate parasites or pathogens with a layer of cells.
In short, while invertebrates lack the adaptive (specific) immune system found in vertebrates, their nonspecific defenses are still crucial in protecting them from disease.