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- https://bio.libretexts.org/Courses/Butte_College/BC%3A_BIOL_2_-_Introduction_to_Human_Biology_(Grewal)/Text/20%3A_Immune_System/20.2%3A_Introduction_to_the_Immune_SystemThe immune system is a host defense system. It comprises many biological structures —ranging from individual white blood cells to entire organs — as well as many complex biological processes. The func...The immune system is a host defense system. It comprises many biological structures —ranging from individual white blood cells to entire organs — as well as many complex biological processes. The function of the immune system is to protect the host from pathogens and other causes of disease such as tumor cells. To function properly, the immune system must be able to detect a wide variety of pathogens.
- https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/General_Biology_1e_(OpenStax)/5%3A_Biological_Diversity/21%3A_Viruses/21.4%3A_Other_Acellular_Entities_-_Prions_and_ViroidsPrions and viroids are pathogens (agents with the ability to cause disease) that have simpler structures than viruses but, in the case of prions, still can produce deadly diseases.
- https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/General_Biology_1e_(OpenStax)/7%3A_Animal_Structure_and_Function/42%3A_The_Immune_System/42.0%3A_Prelude_to_the_Immune_SystemComponents of the immune system constantly search the body for signs of pathogens. When pathogens are found, immune factors are mobilized to the site of an infection. The immune factors identify the n...Components of the immune system constantly search the body for signs of pathogens. When pathogens are found, immune factors are mobilized to the site of an infection. The immune factors identify the nature of the pathogen, strengthen the corresponding cells and molecules to combat it efficiently, and then halt the immune response after the infection is cleared to avoid unnecessary host cell damage.
- https://bio.libretexts.org/Courses/Thompson_Rivers_University/Principles_of_Biology_II_OL_ed/03%3A_Systematics_Phylogeny_and_Biological_Diversity/3.04%3A_Biological_Diversity/3.4.01%3A_Acellular_Entities_-_Viruses_Prions_and_ViroidsViruses are acellular, parasitic entities that are not classified within any kingdom. Viruses are not cells and cannot divide. They infect a host cell and use the host’s replication processes to produ...Viruses are acellular, parasitic entities that are not classified within any kingdom. Viruses are not cells and cannot divide. They infect a host cell and use the host’s replication processes to produce identical progeny virus particles. Viruses infect organisms as diverse as bacteria, plants, and animals and exist in a netherworld between a living organism and a nonliving entity. Living things grow, metabolize, and reproduce.
- https://bio.libretexts.org/Courses/North_Central_State_College/BIOL_1550%3A_Microbiology_(2025)/01%3A_Introduction_to_Microbiology/1.07%3A_Types_of_MicroorganismsMicroorganisms are very diverse and are found in all three domains of life: Archaea, Bacteria, and Eukarya. Archaea and bacteria are classified as prokaryotes because they lack a cellular nucleus. Arc...Microorganisms are very diverse and are found in all three domains of life: Archaea, Bacteria, and Eukarya. Archaea and bacteria are classified as prokaryotes because they lack a cellular nucleus. Archaea differ from bacteria in evolutionary history, genetics, metabolic pathways, and cell wall and membrane composition. Archaea inhabit nearly every environment on earth, but no archaea have been identified as human pathogens.
- https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_(OpenStax)/01%3A_An_Invisible_World/1.03%3A_Types_of_MicroorganismsMicroorganisms are very diverse and are found in all three domains of life: Archaea, Bacteria, and Eukarya. Archaea and bacteria are classified as prokaryotes because they lack a cellular nucleus. Arc...Microorganisms are very diverse and are found in all three domains of life: Archaea, Bacteria, and Eukarya. Archaea and bacteria are classified as prokaryotes because they lack a cellular nucleus. Archaea differ from bacteria in evolutionary history, genetics, metabolic pathways, and cell wall and membrane composition. Archaea inhabit nearly every environment on earth, but no archaea have been identified as human pathogens.
- https://bio.libretexts.org/Workbench/General_Ecology_Ecology/Chapter_12%3A_Sex_Strategies/12.4%3A_Mating_Systems_in_PlantsSI is one of the most important means of preventing inbreeding and promoting the generation of new genotypes in plants and it is considered one of the causes of the spread and success of angiosperms o...SI is one of the most important means of preventing inbreeding and promoting the generation of new genotypes in plants and it is considered one of the causes of the spread and success of angiosperms on the earth. Plants that use insects or other animals to move pollen from one flower to the next have developed greatly modified flower parts to attract pollinators and to facilitate the movement of pollen from one flower to the insect and from the insect back to the next flower.
- https://bio.libretexts.org/Workbench/General_Ecology_Ecology/Chapter_16%3A_Antagonistic_Interactions/16.4%3A_PathogensAn infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host tissues to the infectious agents and the toxins they produce. An ex...An infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host tissues to the infectious agents and the toxins they produce. An example of the former is the anaerobic bacteria species, which colonizes the mammalian colon, and an example of the latter are the various species of staphylococcus that exist on human skin.
- https://bio.libretexts.org/Courses/Mansfield_University_of_Pennsylvania/BSC_3271%3A_Microbiology_for_Health_Sciences_Sp21_(Kagle)/01%3A_Introduction/1.01%3A_An_Invisible_World/1.1.02%3A_Types_of_MicroorganismsMicroorganisms are very diverse and are found in all three domains of life: Archaea, Bacteria, and Eukarya. Archaea and bacteria are classified as prokaryotes because they lack a cellular nucleus. Arc...Microorganisms are very diverse and are found in all three domains of life: Archaea, Bacteria, and Eukarya. Archaea and bacteria are classified as prokaryotes because they lack a cellular nucleus. Archaea differ from bacteria in evolutionary history, genetics, metabolic pathways, and cell wall and membrane composition. Archaea inhabit nearly every environment on earth, but no archaea have been identified as human pathogens.
- https://bio.libretexts.org/Bookshelves/Human_Biology/Human_Biology_(Wakim_and_Grewal)/20%3A_Immune_System/20.2%3A_Introduction_to_the_Immune_SystemThe immune system is a host defense system. It comprises many biological structures - ranging from individual white blood cells to entire organs - as well as many complex biological processes. The fun...The immune system is a host defense system. It comprises many biological structures - ranging from individual white blood cells to entire organs - as well as many complex biological processes. The function of the immune system is to protect the host from pathogens and other causes of disease such as tumor cells. To function properly, the immune system must be able to detect a wide variety of pathogens.
- https://bio.libretexts.org/Workbench/Principles_of_the_Human_Body/18%3A_Immune_System/20.2%3A_Introduction_to_the_Immune_SystemThe immune system is a host defense system. It comprises many biological structures - ranging from individual white blood cells to entire organs - as well as many complex biological processes. The fun...The immune system is a host defense system. It comprises many biological structures - ranging from individual white blood cells to entire organs - as well as many complex biological processes. The function of the immune system is to protect the host from pathogens and other causes of disease such as tumor cells. To function properly, the immune system must be able to detect a wide variety of pathogens.
