History of Marine Sciences
Four investigations. Re-enact the crudest sampling technique in the history of the subject and measure how badly it fails, work out what each later tool could and could not see, argue about a fish that came back from the dead, and interview a marine scientist.
Investigations column, block 3, in full: "Museums and the Dept. of Environmental Affairs warehouse for the SA Agulhas" and "Talk by scientists at the school to indicate a marine sciences career and show the different equipment to the students."
Both are Investigation 4, and both assume a school with a bus and a visiting speaker. You have neither, so both ship with the visit and the talk supplied in described form — and if you can get to a museum or an aquarium, the same worksheet works there. Investigations 1–3 come from the block's own key concepts, which name the sampling techniques and the four South Africans directly.
What you need
- 🟡 hardware About 5 m of string, and a heavy weight — a large nut, a fishing sinker, a stone in a bag
- 🟢 kitchen Press-stick, plasticine or a candle stub — anything soft that sediment will press into
- 🟢 kitchen A tape measure or metre stick, a marker, and a calculator
- 🌊 or A bucket, a bath, a swimming pool, or a harbour wall — anything with a measurable depth
- 🏛️ optional A museum, aquarium or science centre, for the real version of Investigation 4
That is the normal case, and it is why both of CAPS's investigations are supplied in described form. Investigation 4's data panel contains a described exhibit and a described interview with a marine scientist, both built to carry exactly what CAPS asks the visit and the talk to deliver — the equipment, the career path, and what the job is actually like. Every mark on this sheet is reachable from your kitchen table.
Aim
To measure a water depth and collect a bottom sediment sample using the historical "wax on a weight and line" technique, and to quantify the error it produces.
Method
- Tie the weight securely to one end of the string. Press a lump of press-stick onto the underside of the weight, so it will hit the bottom first.
- Mark the string at 10 cm intervals from the weight upward.
- Choose your water: a bucket, a bath, the deep end of a pool, or a harbour wall. Measure the true depth first with a tape measure or metre stick, and write it down. This is your control.
- Now do it the historical way. Lower the weight until you feel it touch bottom, then read off the depth from your marks. Do not look at your control measurement.
- Repeat five times, recording each reading.
- Haul up and examine the press-stick. Record what stuck to it.
- Now make it fail on purpose. Repeat twice more, but this time pull the line at an angle rather than straight down — simulating a current dragging it sideways. Record those readings separately.
Supplied results — a 2.40 m pool, five soundings
| Sounding | 1 | 2 | 3 | 4 | 5 | angled 1 | angled 2 |
|---|---|---|---|---|---|---|---|
| Reading (m) | 2.5 | 2.6 | 2.5 | 2.7 | 2.6 | 3.1 | 3.3 |
On the press-stick: a thin smear of fine grit, perhaps twenty or thirty grains, plus one small fragment of leaf. Total recovered material would not cover a fingernail.
Results
| Sounding | 1 | 2 | 3 | 4 | 5 | angled 1 | angled 2 |
|---|---|---|---|---|---|---|---|
| Reading (m) |
True depth measured with a rigid instrument: ______________ m
Analysis
- Calculate the mean of your five straight-down soundings, and the difference between that mean and the true depth. 4
- Were your readings too deep or too shallow? Explain why the rope produces an error in that direction. 4
- What happened to the angled readings? Explain what this tells you about sounding from a ship in a current. 4
- Describe what you recovered on the press-stick, and estimate how much sea floor it actually represents. 3
- Give two separate reasons this method gives a poor picture of the sea floor — one about the depth reading, one about the sample. 4
- Piano wire replaced rope for this job. State the single property that made it better, and explain which of your errors it fixes and which it does not. 5
- A century of this method produced only about 7 000 soundings, none deeper than 2 000 m. Using your own timing, explain why so few. 3
Aim
To work out what each sampling technology in CAPS's list can and cannot tell you about the same patch of sea floor.
Method
The scenario. You are 40 km off Gqeberha, over a patch of continental shelf at about 90 m depth. You want to know four things: (a) how deep it is, (b) what the bottom is made of, (c) how salty and how warm the water is at 50 m, and (d) whether anything is living down there.
For each tool in the table, decide which of those four questions it can answer. Write ✓, ✗ or "partly" in each cell, then complete the last column.
| Tool | (a) depth | (b) bottom material | (c) salinity & temp at 50 m | (d) life | Its main limitation |
|---|---|---|---|---|---|
| Wax on a weight and line | |||||
| Piano wire sounding | |||||
| Dredger on a steam winch | |||||
| Nansen / Niskin bottle | |||||
| CTD | |||||
| Sonar | |||||
| Satellite imaging | |||||
| ROV or submersible |
Analysis
- Complete Table 2.1. 12
- Which one tool would you choose if you could take only one, and why? There is no single right answer — the marks are for the justification. 4
- Expand the abbreviation CTD, and explain how an instrument measures salinity without collecting any water. 4
- Sonar can map thousands of square kilometres of sea floor. Explain why marine scientists still lower dredges and bottles at all. 4
- CAPS says scuba and submersible craft "made areas of the ocean more accessible for humans". Explain how that is a different kind of advance from a better sampling bottle. 4
- Two World Wars accelerated ocean instrument development. Explain why governments funded it, and name the technology the source gives as the example. 4
Aim
To describe the discovery of the coelacanth and to evaluate what a single specimen does, and does not, prove.
Supplied data — the timeline
| When | What happened |
|---|---|
| ~66 million years ago | The last coelacanth in the known fossil record. The group is assumed to have died out. |
| December 1938 | Marjorie Courtenay-Latimer, curator of the East London Museum, finds an unrecognised 1.5 m fish in a trawler's catch taken off the Chalumna River mouth. She cannot preserve the soft parts. She sketches it and writes to a specialist. |
| Early 1939 | Prof. J.L.B. Smith, a chemistry lecturer and ichthyologist at Rhodes University, identifies it as a coelacanth — a lobe-finned fish known only from fossils. He names it Latimeria chalumnae. |
| 1939–1952 | Smith searches for a second specimen for fourteen years, distributing reward notices along the East African coast. |
| December 1952 | A second specimen is found in the Comoros. Smith is flown there in a military aircraft authorised by the Prime Minister. |
| 1997–98 | A second living species is identified in Indonesia — Latimeria menadoensis. |
| 2000 | Coelacanths are found in South African waters again, in the submarine canyons off Sodwana Bay, at roughly 100–150 m. |
Analysis
- Name the two people central to the 1938 discovery and state what each contributed. 4
- Why was the coelacanth so surprising? Refer to the fossil record in your answer. 4
- The soft internal parts of the first specimen were lost. Explain why that mattered so much that Smith spent fourteen years looking for another. 4
- A newspaper writes: "The coelacanth has not evolved for 66 million years." Explain why that statement is wrong. 4
- Another writes: "Scientists have found the ancestor of all land animals." Explain why that is also wrong, and state the more accurate relationship. 4
- The reasoning question. Before 1938, scientists said coelacanths were extinct — and they had a fossil record covering 66 million years to back it up. Were they being unscientific? Argue your answer, and state what the episode teaches about absence of evidence. 6
- Coelacanths live in the submarine canyons off Sodwana Bay. Using Topics 2 and 3, name the biogeographic zone that is in, and the sea-floor feature they shelter in. 3
Aim
To find out what equipment marine scientists use and what a marine sciences career actually involves — by visiting an institution, or by working from the supplied described visit and interview.
Method
- If you can go: a museum, aquarium or science centre with a marine section works. In the Eastern Cape, Bayworld in Gqeberha is the obvious one; the East London Museum holds the coelacanth story from Investigation 3. Complete Table 4.1 from what you see.
- If you cannot: use the described exhibit and interview below. They are written to carry exactly what CAPS asks the visit and the talk to deliver.
- Either way, complete both tables and answer the questions.
Supplied — a described research-vessel exhibit
The centrepiece is a CTD rosette, and it is bigger than people expect — a metal frame about the height of a person, ringed with a dozen grey cylinders. Each cylinder is a Niskin bottle, open at both ends on the way down, closed by command at a chosen depth. In the middle of the frame sits the CTD itself, a cluster of sensors recording conductivity, temperature and depth continuously as the whole assembly descends. A winch cable runs from the top.
Beside it, a box corer — a steel box on a heavy frame, driven into the sea floor to bring back an undisturbed block of sediment with its layers intact. Next to that, a plankton net: a long fine cone with a collecting jar at the tip, exactly like the one built in Topic 17.
On the wall, a cutaway of the SA Agulhas II: wet and dry laboratories, a moon pool through the hull, helicopter deck, reinforced bow for breaking ice, and berths for around 100 scientists and crew. A caption notes it services South Africa's Antarctic and sub-Antarctic research bases.
In a case near the door, the older instruments: a Nansen bottle from the 1930s, brass and heavy; a lead sounding weight with a hollow underside where the wax went; and a coil of piano wire on a wooden drum.
Supplied — a described interview with a marine scientist
Dr N., a fisheries biologist, 14 years in the job.
What do you actually do all day? "Most of it is data. I get maybe three weeks of sea time a year, and the rest is processing what we brought back and arguing with it. People imagine the job is diving. The job is spreadsheets, with occasional diving."
What did you study? "Maths and Physical Sciences at school — you cannot get in without them. Then a BSc with zoology and statistics, honours, a masters. The statistics turned out to matter more than anything else I took."
What equipment do you use most? "A CTD rosette, trawl nets, and a laptop. The laptop by a very long way."
Hardest part? "Telling people things they do not want to hear. If the stock assessment says the quota should come down, that is somebody's income. You have to be certain, and you have to be able to show your working — which is why the method matters so much."
Best part? "Being on deck at 3 a.m. when the net comes up and nobody yet knows what is in it."
Advice? "Learn to write. The science is half of it. The other half is making someone act on it."
Results
| Instrument | What it collects or measures | Old or modern? |
|---|---|---|
| Question | What you found out |
|---|---|
| School subjects required | |
| Qualifications after school | |
| Proportion of time in the field vs at a desk | |
| Equipment used most often | |
| Hardest part of the job |
Analysis
- Complete Table 4.1 with five instruments. 10
- Complete Table 4.2. 5
- The exhibit puts a modern CTD rosette in the same room as a lead sounding weight with wax on it. Explain what the two have in common, and what changed between them. 4
- The scientist says the job is "spreadsheets, with occasional diving". Does that make marine science less interesting? Give your own view, with a reason. 3
- The scientist names statistics and writing as the two most useful skills. Explain, using Topic 5, why each one matters to a marine scientist. 4
- "You have to be certain, and you have to be able to show your working." Explain how that connects to the errors-in-thinking grid on the topic page. 4
Memo — worked answers and mark allocation (does not print)
Total: 118 marks — Investigation 1: 27 · Investigation 2: 32 · Investigation 3: 29 · Investigation 4: 30.
Investigation 1 — wax on a weight and line
- Q1 (4): Supplied data: (2.5+2.6+2.5+2.7+2.6) ÷ 5 = 12.9 ÷ 5 = 2.58 m (3). Difference from 2.40 m = +0.18 m (1).
- Q2 (4): Too deep (1). The rope stretches under the weight's load, so the length paid out is greater than the true vertical distance (2) — an over-estimate every time, not a random error (1).
- Q3 (4): The angled readings were much deeper still — 3.1 and 3.3 m against a true 2.40 (1). An angled line is the hypotenuse of a triangle, so it is always longer than the vertical depth (2). A current does exactly this to a real sounding line, and the error grows with depth (1).
- Q4 (3): A smear of fine grit and a leaf fragment — a few dozen grains (2), representing only the few square centimetres the weight actually struck (1).
- Q5 (4): Depth: the rope stretches and the current drags it, so the reading is unreliable and biased deep (2). Sample: only what sticks to a lump of wax from one point of impact, so it may not represent the surrounding sea floor at all (2).
- Q6 (5): Piano wire does not stretch (2). It fixes the stretch error (1). It does not fix current drag — an angled line is still too long (1) — and it does not increase the sediment sample size at all (1).
- Q7 (3): Each sounding takes minutes even in a swimming pool; at ocean depths it meant lowering and winching back kilometres of line, up to 8 hours for one reading (2). One ship could manage a handful a day, in one place, in good weather (1).
Investigation 2 — the sampling ladder
- Q8 (12): Wax/line: depth ✓(poorly), material partly, water ✗, life ✗. Piano wire: depth ✓, material partly, water ✗, life ✗. Dredger: depth ✗, material ✓, water ✗, life ✓. Nansen/Niskin: depth ✗, material ✗, water ✓, life partly (plankton). CTD: depth ✓, material ✗, water ✓, life ✗. Sonar: depth ✓✓, material partly (hardness from echo strength), water ✗, life partly (fish shoals). Satellite: depth ✗ (surface only), material ✗, water partly (surface temp), life partly (surface chlorophyll). ROV: all four ✓. Award for reasoned cells; "partly" with a reason is worth as much as a tick.
- Q9 (4): Any tool, well argued (4). The strongest case is the ROV/submersible — the only one that answers all four — but a case for sonar on grounds of coverage, or a CTD rosette on grounds of routine value, earns full marks if reasoned.
- Q10 (4): Conductivity, Temperature, Depth (2). Salt dissolved in water splits into ions, which carry electric current — so the more salt, the better the water conducts, and conductivity can be converted to salinity (2).
- Q11 (4): Sonar returns shape, not composition or biology (2). Only a physical sample tells you what the sediment is made of, what lives in it, or what the water chemistry is (2).
- Q12 (4): A better bottle improves the quality of a sample fetched from a distance (2). Scuba and submersibles put a human or robot in the place itself, so you can choose what to look at, watch behaviour, and see context a sample destroys (2).
- Q13 (4): Not curiosity — political power and territorial dominance of "ocean territory" (2). The example given is sonar, to map the seafloor (2).
Investigation 3 — the coelacanth
- Q14 (4): Marjorie Courtenay-Latimer — spotted, rescued and sketched the unrecognised fish and sought an expert (2). J.L.B. Smith — identified it as a coelacanth and named it (2).
- Q15 (4): Coelacanths were known only as fossils (1), with none in the record for about 66 million years (1), so the group was assumed extinct (1) — finding a living one contradicted that directly (1).
- Q16 (4): The skin and skeleton show what it looked like, but almost every biological question — how it breathes, reproduces, digests, how the fins are built internally — needs the soft anatomy (3), and that had been discarded (1).
- Q17 (4): Nothing stops evolving (1). The fossil record was silent, which is not the same as the animal being unchanged (2), and modern coelacanths differ from the fossil ones (1).
- Q18 (4): It is not an ancestor (1) — it is a surviving relative of the lobe-finned lineage from which land vertebrates arose (2), a cousin rather than a grandparent (1).
- Q19 (6): A good answer says no, they were not being unscientific (2): they drew the best conclusion the evidence supported, and being open to revision is exactly what science requires. It then states the lesson — absence of evidence is not evidence of absence (2) — and notes that the conclusion should have been held as provisional rather than settled, especially for a deep-sea group nobody could sample (2). Accept a well-argued opposite case that engages with both points.
- Q20 (3): The Natal BGZ (Sodwana is south of St Lucia) or the Delagoa BGZ if the learner places it further north — accept either with reasoning (2). The feature is a submarine canyon (1).
Investigation 4 — the visit and the talk
- Q21 (10): Two marks per instrument. From the described exhibit: CTD rosette (conductivity, temperature, depth, continuously — modern); Niskin bottle (a water sample from a chosen depth — modern); box corer (an undisturbed block of sediment with its layers — modern); plankton net (plankton from a known volume — both); Nansen bottle (water at depth — old); lead sounding weight with wax (depth and a few sediment grains — old); piano wire (depth, accurately — old).
- Q22 (5): Maths and Physical Sciences to matric; BSc then honours and masters; roughly three weeks at sea a year against the rest at a desk; a CTD rosette, trawl nets and a laptop; telling people things they do not want to hear.
- Q23 (4): Both are trying to answer the same two questions — how deep, and what is down there (2). What changed is accuracy, volume and continuity: one point of contact and a smear of grit, against a continuous profile and a dozen bottles in a single lowering (2).
- Q24 (3): Any defended view (3). Full marks need a reason, not just an opinion — e.g. the analysis is where the discovery actually happens, or conversely that the fieldwork is what makes the analysis meaningful.
- Q25 (4): Statistics: results have to be shown to be reliable and not chance, which is the validity and reliability work from Topic 5 (2). Writing: an investigation that is not communicated changes nothing, and the report is the outcome CAPS assesses (2).
- Q26 (4): The errors-in-thinking grid is about people believing what suits them (1). "Show your working" is the defence — transparent, repeatable method means a conclusion can be checked by someone who disagrees (2), which is exactly what stops a funded scientist quietly reporting what the funder wants (1).
Marking note. Q9, Q19 and Q24 have no single right answer. Mark the reasoning, not the position — a well-argued minority answer is worth full marks.