LUCA and the evidence for a last universal common ancestor
Practice Flashcards
Flip to reveal answersWhat does LUCA stand for, and what is it?
Track your progress — Sign up free to save your progress and get smart review reminders based on spaced repetition.
All 7 Flashcards — LUCA and the evidence for a last universal common ancestor
Sign up free to track progress and get spaced-repetition review schedules.
Question
What does LUCA stand for, and what is it?
Answer
The **Last Universal Common Ancestor** — the single ancestral population from which **all life alive today** descends.
Question
Is LUCA the first cell ever?
Answer
No — it is the **LAST** (most recent) common ancestor of all surviving life. Earlier cells almost certainly existed.
Question
Name the shared features that are evidence for LUCA.
Answer
A near-universal **genetic code**, **DNA/RNA**, **ATP** as energy currency, **ribosomes**, and **common metabolic pathways** — all best explained by **common ancestry**.
Question
How is the age of LUCA estimated?
Answer
By comparing DNA/protein **sequences** and using the **molecular clock**, giving roughly **4 billion years ago** (likely at hydrothermal vents).
Question
State the endosymbiotic theory for mitochondria.
Answer
A host cell **engulfed a free-living aerobic bacterium** that **survived inside** as an endosymbiont and became the **mitochondrion**.
Question
What are the four pieces of evidence for endosymbiosis?
Answer
Mitochondria/chloroplasts have their own **circular DNA**, **70S ribosomes**, a **double membrane**, and divide by **binary fission** — all bacterial features.
Question
Which bacterium gave rise to chloroplasts?
Answer
A photosynthetic **cyanobacterium** — engulfed and kept as an endosymbiont. (An aerobic bacterium gave the mitochondrion.)
Read the notes
Full study notes for LUCA and the evidence for a last universal common ancestor
Topic 1.3 hub
Origins of cells
More from Topic 1.3
All flashcards in this topic
Biology exam skills
Paper structures & tips
Track your progress with spaced repetition
Sign up free — Aimnova tells you exactly which cards to review and when, so you remember everything before your IB exam.
Start Free