Not every cell is like yours
- The idea
- Predict
- See it
- Why
- Check
The idea
“Every living thing has a nucleus and mitochondria and needs oxygen, like my cells do.”
Nearly every cell you've drawn was a plant or animal cell, so a nucleus and mitochondria seem standard. Those cells come from one branch of life.
The short version
The mistake: Every living thing has a nucleus and mitochondria and needs oxygen, like my cells do.
What's actually true: All life shares a membrane, DNA, ribosomes and ATP. A nucleus, mitochondria, oxygen use and photosynthesis belong to some groups.
- Most cells you study are eukaryotes. Bacteria and archaea, the other two domains, are prokaryotes. They have no nucleus or membrane-bound organelles.
- Every organism has a membrane, DNA, ribosomes and ATP, and nearly all use the same genetic code. That's evidence of common ancestry.
- A feature only some groups have, like a nucleus, shows those groups share a more recent ancestor. It says nothing about life's common ancestor.
On the exam: Before you call a feature universal, picture a bacterium. If a bacterium lacks it, not all life has it.