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Vaccines cause herd immunity. If the majority of people in a community have been vaccinated against a disease, an unvaccinated person is less likely to get the disease since others are less likely to become sick from it and spread the disease.
The longest a person has survived after a heart transplant is 24 years.
When blood is deoxygenated and flowing back to the heart through the veins, it is dark reddish-blue in color. Blood in the arteries that is oxygenated and flowing out to the body is bright red. Whereas arterial blood comes out in spurts, venous blood flows.
Most fungi that pathogenically affect humans live in soil. If a person is not healthy, has an open wound, or is immunocompromised, a fungal infection can be very aggressive.
It is believed that humans initially contracted crabs from gorillas about 3 million years ago from either sleeping in gorilla nests or eating the apes.
![Triangle plot showing gene expression related to xylem, phloem, and nonvascular tissue in Arabidopsi](https://biology-forums.com/gallery/47/medium_33_25_07_11_12_59_28.jpeg)
![(A) Lymphatic vessel with valves within tissue cells; (B) photomicrograph of lymphatic vessel with v](https://biology-forums.com/gallery/47/medium_14755_10_09_12_7_17_45_85041332.jpeg)