Biology Words That Start With J: Essential Terms

Welcome to our biology word list starting with the letter J, where you’ll discover jargon like “juvenile” and “Jacobson’s organ.

  1. Jellyfish- A free-swimming marine coelenterate with a jelly-like, bell- or saucer-shaped body.
  2. Jugular- Relating to the throat or neck, especially one of the large veins in that area.
  3. Joint- The location at which two or more bones make contact.
  4. Juvenile- Pertaining to a young organism, especially one that has not yet reached maturity.
  5. Jaundice- A medical condition with yellowing of the skin or eyes due to bile pigment.
  6. Jejunum- The part of the small intestine between the duodenum and ileum.
  7. Jowl- The lower part of a person’s or animal’s cheek.
  8. Jacal- Pre-Columbian habitat structures built by indigenous peoples in Mesoamerica.
  9. Jacob’s Ladder- Various climbing plants with ladder-like leaves; also used to refer to a biochemical cycle.
  10. Juglone- A chemical compound found in the black walnut tree, toxic to many other plants.
  11. Jackrabbit- A species of hare that is large, leporids found in North America.
  12. Jumping Gene- A segment of DNA that can move around to different positions within the genome.
  13. Jacobson’s Organ- Also called vomeronasal organ, used by animals to detect pheromones.
  14. Jaw- The upper and lower bony structures in vertebrates forming the framework of the mouth.
  15. Jukebox Gene- Genes that can turn on or off in response to environmental factors.
  16. Jerboa- Small desert rodents with long hind legs enabling them to leap great distances.
  17. Jowl- Facial structure constituting the jaw or the area below the cheeks.
  18. Jugal- A bone on the side of the skull in animals, often part of the cheek.
  19. Jelly Layer- The gelatinous coating surrounding some eggs, especially those of amphibians and marine organisms.
  20. Jacobin Cuckoo- A member of the cuckoo family known to lay its eggs in the nests of other birds (brood parasitism).

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