Biology by Bradford
7.7.AThe three domains
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7.7 Common Ancestry: revision map
The subtopic in the middle and four tasks round it: label a diagram, complete a table and fill 8 gaps. Every box rests on a learning objective of the topic in the AP Biology course and exam description. Type into the blanks and check them, or print it on A4, Letter or A3 with an answer key.
Common Ancestry
AP Biology ยท Unit 7 Natural SelectionHover over a box to see it. Untick it to leave it off this sheet and its printout.
Name7.7.AWhy shared features matter
Features that are shared by all living things and that could work another way, such as the genetic code, are evidence that all life descends from a . If life had arisen several times, we should expect different codes and different ways of storing information. Features shared by a smaller group, such as the nucleus, mark groups that share a more recent ancestor.
Topic 7.7Common Ancestry
7.7.AWhat all life shares
| Feature | Found in |
|---|---|
| as the genetic material | every cellular organism |
| Nearly the same genetic code | all living things |
| Ribosomes and a plasma membrane | all cells |
| Glycolysis and ATP | almost every cell |
| A membrane-bound nucleus and linear chromosomes | eukaryotes only |
7.7.AReading the tree
A tree of life shows how lineages split. Two groups that share a recent node are more closely related than groups that join only further back. Archaea and eukaryotes share a more recent ancestor with each other than either does with , even though archaea look like them, which shows that appearance is not a reliable guide to relatedness.
Word bank ArchaeaBacteriabacteriacommon ancestorDNAEukaryalast universal common ancestornode
Answer key
Every box on the sheet with its gaps filled in, as the subtopic reads in full.
LabelThe three domains
- last universal common ancestor
- Bacteria
- Archaea
- Eukarya
- node
TableWhat all life shares
Feature Found in DNA as the genetic material every cellular organism Nearly the same genetic code all living things Ribosomes and a plasma membrane all cells Glycolysis and ATP almost every cell A membrane-bound nucleus and linear chromosomes eukaryotes only GapsWhy shared features matter
Features that are shared by all living things and that could work another way, such as the genetic code, are evidence that all life descends from a common ancestor. If life had arisen several times, we should expect different codes and different ways of storing information. Features shared by a smaller group, such as the nucleus, mark groups that share a more recent ancestor.
GapsReading the tree
A tree of life shows how lineages split. Two groups that share a recent node are more closely related than groups that join only further back. Archaea and eukaryotes share a more recent ancestor with each other than either does with bacteria, even though archaea look like them, which shows that appearance is not a reliable guide to relatedness.