OCR GCSE Biology B (Twenty First Century)
OCR GCSE Biology B B6.3 How does our understanding of biology help us classify the diversity of organisms on earth? Exam Questions
Free OCR GCSE Biology B exam questions for B6.3 How does our understanding of biology help us classify the diversity of organisms on earth?, with a mark scheme for every pack. Covers classification, Linnaeus, kingdoms, binomial naming, the three domain system, DNA evidence, evolutionary trees and changing ideas about classification.
B6.3 How does our understanding of biology help us classify the diversity of organisms on earth? exam questions
2 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About OCR GCSE Biology B B6.3 How does our understanding of biology help us classify the diversity of organisms on earth?
B6.3 explains how organisms are classified and why classification systems have changed as biological understanding has improved. You need to describe Linnaeus's hierarchical system and binomial naming, explain how evidence from microscopes, biochemistry and DNA sequencing led to the three domain system proposed by Carl Woese, and interpret evolutionary trees. The topic links evolution in B6.1 with biodiversity in B6.4 and illustrates how scientific models change with new evidence. Examiners often ask you to use DNA or amino acid sequence data to decide which organisms are most closely related, or to name the levels of classification.
What you need to know
- Linnaean system Organisms are grouped by shared characteristics into a hierarchy: kingdom, phylum, class, order, family, genus, species.
- Binomial naming Each species has a two-part Latin name: genus then species, for example Homo sapiens. This gives a universal name used by scientists worldwide.
- Species A species is a group of organisms that can interbreed to produce fertile offspring.
- Three domains Woese used chemical analysis of genetic material to divide life into Archaea (primitive bacteria often in extreme environments), Bacteria (true bacteria) and Eukaryota (protists, fungi, plants and animals).
- DNA evidence Comparing DNA base sequences shows how closely related species are: the more similar the sequence, the more recently they shared a common ancestor. This has moved some species into different groups.
- Evolutionary trees Evolutionary trees use current classification data and fossil evidence to show relationships and common ancestors.
Common mistakes in B6.3 How does our understanding of biology help us classify the diversity of organisms on earth?
- Writing binomial names with two capitals. Only the genus has a capital, for example Panthera leo.
- Thinking classification never changes. Systems are updated as new evidence, such as DNA sequencing, becomes available.
- Saying similar looking organisms must be closely related. Similar features can evolve separately; DNA gives stronger evidence.
- Confusing domains and kingdoms. Domains are above kingdoms in the hierarchy.
- Mixing up the order of taxonomic groups. Remember kingdom, phylum, class, order, family, genus, species.
Try three B6.3 How does our understanding of biology help us classify the diversity of organisms on earth? exam-style questions
1. State the genus of the lion, Panthera leo. (1 mark)
Show the mark scheme answer
Panthera.
2. A 40 base DNA section of species A differs from species B at 6 bases. Calculate the percentage similarity. (2 marks)
Show the mark scheme answer
34 / 40 x 100; = 85%.
3. Explain why Woese introduced the three domain system. (3 marks)
Show the mark scheme answer
Improved microscopes and chemical analysis showed some organisms classed as bacteria were very different; analysis of genetic material showed Archaea differ fundamentally from true bacteria; so a new level above kingdoms was needed to reflect evolutionary relationships.
B6.3 How does our understanding of biology help us classify the diversity of organisms on earth? FAQs
What does OCR GCSE Biology B B6.3 cover?
It covers the Linnaean system, binomial naming, the three domain system, the use of DNA evidence and evolutionary trees in classification.
Which paper is B6.3 examined in?
J257 has two papers at each tier, Breadth in Biology and Depth in Biology, and content from any chapter, including B6, can be assessed on either one. Expect it to be linked to ideas about science and to other chapters.
How do I use sequence data to decide relationships?
Count the differences between each pair of sequences; the pair with the fewest differences is most closely related and shared a common ancestor most recently.
