Biology • Year 11 • Module 3 • Lesson 4
Darwin's Observations and the Galapagos
Lock in the key vocabulary, Darwin's Beagle observations, the Galapagos finches, and Australian fauna before moving to application tasks.
1. Complete the paragraph
Fill each blank with the correct term from the word bank. Use each term once only. 8 marks
From 1831 to 1836, Darwin served as a naturalist aboard HMS _______________, collecting specimens and recording observations. On the Galapagos he documented finch species that all descended from a single South American _______________; the diversification of one species into many, each suited to a different food source, is called _______________. In Australia he noticed marsupials filling the same _______________ as unrelated placental mammals elsewhere, an example of _______________. Darwin reasoned that _______________ exists within populations, and that individuals with advantageous traits survive and reproduce more, a process called _______________. The overall mechanism that shapes populations over generations is _______________.
2. Term–definition match
Write the matching term from this list in the right-hand column: adaptive radiation • convergent evolution • natural selection • heritable variation • ecological niche • differential survival • secondary source • selection pressure. 8 marks
| # | Definition | Matching term |
|---|---|---|
| 2.1 | The diversification of one ancestral species into many, each adapted to a different niche. | |
| 2.2 | Unrelated species independently evolving similar traits due to similar selection pressures. | |
| 2.3 | The process by which heritable variations that increase survival become more common over generations. | |
| 2.4 | Differences between individuals that can be passed from parents to offspring. | |
| 2.5 | The role and position a species occupies in its environment, including what it eats. | |
| 2.6 | When individuals with certain traits are more likely to survive and reproduce than others. | |
| 2.7 | Information collected and reported by someone other than the original observer. | |
| 2.8 | An environmental factor that affects an organism's chance of surviving and reproducing. |
3. Classify the evolutionary process
For each example below, write R (adaptive radiation / divergent) or C (convergent evolution) in the Type column. 8 marks
| Type (R/C) | Example |
|---|---|
| The large ground finch and the warbler finch, both from one Galapagos ancestor | |
| The thylacine (marsupial) and the wolf (placental) have similar body forms | |
| The sugar glider (marsupial) and the flying squirrel (placental) both glide | |
| Darwin's 13 Galapagos finch species, all from one South American ancestor | |
| The numbat (marsupial) and the anteater (placental) both eat ants and termites | |
| The cactus finch and the vegetarian finch arose from the same ancestor | |
| The wombat (marsupial) digs like the unrelated badger (placental) | |
| One finch ancestor gave rise to species with crushing, probing and parrot-like beaks |
4. True or false, with correction
Circle T or F. If the statement is false, write the corrected version on the line below. 8 marks, 1 for T/F, 1 for correction where needed
4.1 Darwin formulated his theory of natural selection immediately upon arriving at the Galapagos in 1835. T / F
4.2 The Galapagos finch beak shapes are related to the different food sources available on each island. T / F
4.3 The thylacine and the wolf are similar because they share a recent common ancestor. T / F
4.4 Lamarck proposed that traits acquired during an organism's lifetime could be inherited, whereas Darwin argued that selection acts on variation that already exists. T / F
5. Build a concept map
Draw labelled arrows between the five terms below to show how they connect. Each arrow must carry a linking phrase (e.g. “requires”, “produces”, “is shown by”). Aim for at least 5 labelled arrows. 5 marks
Supplied terms: natural selection • heritable variation • selection pressure • adaptive radiation • Galapagos finches.
Q1, Cloze paragraph
In order: Beagle • ancestor • adaptive radiation • ecological niche • convergent evolution • heritable variation • differential survival • natural selection.
Q2, Term–definition matches
2.1 adaptive radiation • 2.2 convergent evolution • 2.3 natural selection • 2.4 heritable variation • 2.5 ecological niche • 2.6 differential survival • 2.7 secondary source • 2.8 selection pressure.
Q3, Classification answers
R Large ground finch and warbler finch • C Thylacine and wolf • C Sugar glider and flying squirrel • R 13 finch species from one ancestor • C Numbat and anteater • R Cactus finch and vegetarian finch • C Wombat and badger • R One ancestor giving many beak types.
Q4, True/False with correction
4.1 False. Correction: Darwin collected evidence for nearly 28 years before publishing in 1859. He did not even realise the Galapagos birds were all finches at the time; the ornithologist John Gould identified them when Darwin returned to England.
4.2 True.
4.3 False. Correction: The thylacine (marsupial) and the wolf (placental) are unrelated lineages; their similar body forms are the result of convergent evolution under similar selection pressures, not a recent common ancestor.
4.4 True.
Q5, Sample concept map
Accept any biologically valid linking phrases. A correct map should include arrows such as:
- natural selection requires → heritable variation
- natural selection is driven by a → selection pressure
- selection pressure differs per island, producing → adaptive radiation
- adaptive radiation is shown by the → Galapagos finches
- Galapagos finches are evidence for → natural selection
Award 1 mark per correctly labelled arrow with a valid linking phrase. Maximum 5 marks.