Molecular evidence and the molecular clock
Practice Flashcards
Flip to reveal answersWhat is molecular evidence in classification?
Track your progress — Sign up free to save your progress and get smart review reminders based on spaced repetition.
All 6 Flashcards — Molecular evidence and the molecular clock
Sign up free to track progress and get spaced-repetition review schedules.
Question
What is molecular evidence in classification?
Answer
Data from **molecular sequences** — the **base sequence** of a gene or the **amino-acid sequence** of a protein — used to work out how closely species are related.
Question
Name two kinds of molecule compared to build cladograms.
Answer
A **gene's base sequence** (e.g. the **rRNA** gene) and a **protein's amino-acid sequence** (e.g. **haemoglobin**).
Question
What do MORE sequence differences between two species mean?
Answer
They **diverged longer ago** (more time for mutations to accumulate) and are **more distantly related**.
Question
What do FEWER sequence differences mean?
Answer
A **more recent** split — the species are **more closely related**.
Question
What is the molecular clock?
Answer
Because **neutral mutations** accumulate at a **roughly constant rate**, the **number of sequence differences** can **estimate the time** since two species shared a common ancestor.
Question
Give one strength and one caution of the molecular clock.
Answer
**Strength:** it is objective/quantitative and works even **without fossils**. **Caution:** rates **vary between genes and lineages**, so it must be **calibrated against fossils**.
Read the notes
Full study notes for Molecular evidence and the molecular clock
Topic 1.7 hub
Classification and cladistics
More from Topic 1.7
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