Human Biology quiz

More questions about Human Biology

These visible examples show the question style. LearnClash turns the full topic into ranked duels and spaced repetition.

1. 1 Easy

   How many bones do humans typically have at birth before fusion occurs?

   Answer: Around 270

   Why: The skull's soft spots close by about age two, but the sacrum's five vertebrae only fuse into one bone in the twenties.

2. 2 Medium

   What color is deoxygenated blood traveling through human veins?

   Answer: Dark red

   Why: Veins only appear blue through the skin because subcutaneous tissue and skin selectively scatter blue wavelengths.

3. 3 Hard

   Which gene on the Y chromosome makes an embryo develop testes?

   Answer: SRY gene

   Why: SRY activates transcription factor SOX9, which halts ovarian development pathways and drives Sertoli cell differentiation.

4. 4 Easy

   How does the human stomach avoid being destroyed by its own digestive acid?

   Answer: A rapidly regenerating mucus layer

   Why: Epithelial cells in the stomach lining fully replace themselves roughly every three to five days.

5. 5 Medium

   Which blood type lacks A, B, and Rh surface antigens?

   Answer: O negative

   Why: While O negative is the universal red blood cell donor, AB positive is the universal plasma donor.

6. 6 Hard

   What is the approximate ratio of glial cells to neurons in the human brain?

   Answer: 1:1

   Why: Neuroscience textbooks long claimed a ten-to-one ratio until isotropic fractionator counts established roughly 85 billion of each.