A STUDYGUIDE bY Andrew Fildes · PDF filePlanet Earth is a BBC production with five episodes in the first series ... focussing on key species or relationships in each ... Planet Earth

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A STUDYGUIDE bY Andrew Fildes

9

Overview

Planet Earth is a BBC production with five episodes in the first series (episodes one through five) and six episodes in the second series (episodes six through eleven). Each episode examines a specific environment, focussing on key species or relationships in each habitat; the challenges they face; the behaviours they exhibit and the adaptations that enable them to survive. Recent advances in photography are used to achieve some spectacular ‘first sights’ – in particular, stabilised aerial photography gives us remarkable views of migrating animals and the techniques used by their predators to hunt them.

As the series examines pristine environments where possible, they are often extreme. These are the parts of the world where few humans have chosen to live as the climate and landscape is too challenging, too difficult and dangerous. The plants and animals that do survive here have made some spectacular adaptations in forms and behaviour to live in these far reaches of the planet.

The series is suitable for middle secondary students studying Science and SOSE, and for senior secondary students of Biology, Environmental Science and Geography.

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Episode Nine: Shallow Seas

The continents are fringed by con-tinental shelves, waters up to 200 metres deep that may stretch out hun-dreds of kilometres before plunging to the abyssal depths. While they are less than ten percent of the world’s ocean areas, they hold the vast majority of marine life because this is where we find the breeding and feeding grounds.

This episode of Planet Earth ranges from the remarkable biodiversity of the tropical coral reefs to the rich polar feeding grounds, using the migration of a humpback whale mother and calf as an example to demonstrate the dif-ference between the marine environ-ments available to them. Why would the mature whales choose to starve themselves for half the year and what drives them to migrate thousands of miles along the coasts of Australia and other continents? On the way they may pass the great coral reefs like the Great Barrier Reef, the largest organic structures on earth and yet built by some of the smallest organisms. A symbiosis between coral polyps and algae creates rich gardens in other-wise barren tropical marine deserts, especially in Indonesia where the most diverse reefs in the world exist. Hunting packs of sea snakes work in harmony with carnivorous goatfish to flush out prey from coral crannies in astonishing scenes filmed in detail for the first time.

Away from the reefs and out on the sands, camouflage and concealment are the key to survival but the huge sea cows, dugong, can graze the sea-grass meadows safely. However the fish find that even the extreme shal-lows are no guarantee of safety when dolphins are intelligent enough to learn

to hydroplane in inches of water.

The whale has raised her calf to the stage where it can begin to feed itself and she’s starving, so it’s time for the journey south to the great summer feeding grounds. As the waters become colder and rougher, the nutrients are stirred up from the ocean floor by cold currents, providing food for the phytoplankton algae and seaweeds, food to power the richest

marine environments on earth. The massive quantities of new green life support invertebrates like jellies and krill, food in turn for small fish and squid. Now the large fish and mam-mals like dolphin and seals can survive on the dense food resources and even starfish pursue each other across the ocean floor in time-lapsed mass hunts, suddenly made thrilling by the speed of the camera.

(Timings Are ApproximATe)

Episode 9: Shallow Seas Time Log

Intro 00:00 - 01:20

Humpback Whale and Calf 01:20 - 03:40

Great Barrier Reef 03:40 - 05:30

Indonesian Coral Reef 05:30 - 09:20

Sea Snakes and Goatfish 09:20 - 12:25

Life on the Sands 12:25 - 13:25

Seagrass Grazers - Dugongs 13:25 - 15:20

Dolphins - Shallow Hunting 15:20 - 19:20

Bahrain Cormorants 19:20 - 21:45


Algal Bloom and System 23:45 - 26:57

Sea Mammals Hunting 26:57 - 28:45

Kelp Forests 28:45 - 30:35

Starfish Hunts (time lapse) 30:35 - 32:45

Seals, Stingrays and Squid 32:45 - 35:45

Seals and Sharks 35:45 - 39:15

King Penguins 39:15 - 41:25

Predatory Seals 41:25 - 44:00


Shearwaters and Whales 44:50 - end

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In some places such as the Cape of South Africa, the cold currents create permanent feeding grounds where squid are taken by fur seals which in their turn fall victim to huge, acrobatic great white sharks. But the seals themselves can be murderous predators as we see on Marion Island in the ‘roaring forties’ where the fur seals have learned to catch and kill the homecoming king penguins on the gravel beaches of their rookeries.

The migrations have come to an end as the humpbacks reach the polar seas and can now gorge themselves on up to three tonnes of krill each day, one of the worlds largest animals fattening itself for the coming year on one of the smallest. They only have a couple of months to lay down the fat reserves they need for the com-ing year. In the Aleutian Islands south of Alaska, five million shearwaters (mutton birds) have made the epic flight from Australia to exploit the northern krill swarms. Recent falls in abundance of krill threaten these great systems and migrations.

Species List

Humpback Whale – Megaptera novae-angliae

Pygmy Seahorse – Hippocampus denise

File Clam – Ctenoides alesBanded Sea Krait – Laticauda colub-

rinaYellow (or Gold) Saddle Goatfish

– Parupeneus cyclostomusBluefin Trevally – Caranx melampygusVeined Octopus – Octopus marginatusOriental Flying Gurnard – Dactyloptena

orientalisJawfish – Opistognathidae spp.Wonderpus Octopus – Wonderpuss

spp.Green Turtle – Chelonia mydasSea grasses – Zostera spp.Dugong – Dugong dugonBottlenose Dolphin – Tursiops trun-

catusSocotran Cormorant – Phalacrocorax

nigrogularisSalps – Salpa fusiformisComb Jellies – Ctenophora spp.Krill – Euphausiid spp.South American Sea Lion – Otaria

flavescensDusky Dolphin – Lagenorhynchus

obscurusGiant Kelp – Macrocystis pyriferaPurple Sea Urchin – Strongylocentro-

tus purpuratusSunflower Star – Pycnopodia helian-

thoidesBrittle Star – Ophiothrix spiculataSand Dollar – Echinarachnius parmaChokka Squid – Loligo vulgaris rey-

naudiiShort-tail Stingray – Dasyatis brevi-

caudataRagged Tooth Shark – Carcharias

TaurusGreat White Shark – Carcharodon

carchariasCape Fur Seals – Arctocephalus pusil-

lusKing Penguin – Aptenodytes patagoni-

cusSouthern Elephant Seal – Mirounga

leoninaSubantarctic Fur Seal – Arctocephalus

tropicalisShort Tailed Shearwater – Puffinus

tenuirostris griseus

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Blackline Master | Planet Earth | Episode 9: Shallow Seas

Viewing Questions

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11 What are ‘continental shelves’ and how deep are they?

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2 What percentage of the world’s oceans are they?

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3 Where do the humpback whales breed?

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4 Why do the whales go there to breed and mate?

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5 How much milk does the whale calf need each day?

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6 What organisms build the great offshore reefs?

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7 How do algae help the corals feed?

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8 Why do the snakes hunt with the large predatory fish?

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9 Where are the largest sea grass meadows in the world?

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10 What huge animal grazes on them?

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11 How do the West Australian dolphins catch fish in the

shallows?

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12 What plant drives the marine ecosystem in spring and

summer?

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13 What is the most abundant animal on the planet?

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14 What kind of plant is the giant kelp?

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15 Which small animal kills the kelp towers?

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16 What eats the squid in the Benguela current?

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17 Which is the smaller of the sharks that predate seals

and squid?

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18 Which penguin lives on Marion Island?

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19 Where do the shearwaters in Alaska come from?

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20 How much krill can a humpback whale eat each day?

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Discussion Questions | Planet Earth | Episode 9: Shallow Seas

Ecosystems

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Discussion Questions

1. Mutualism is a form of symbiosis – a relationship where both species benefit. So is the hunting behav-iour of the snakes and fish. How common are these relationships in nature?

2. How many of the large animals that we see in this episode are actually mammals rather than fish? Why is this and what adaptations are required?

3. Every ecosystem is powered up by the production of green material (producers) – grass on earth and algae in the ocean and freshwa-ters. Is this in fact true?

4. We tend to assume that tropical waters are much more diverse and richer marine environments. Why is this an illusion?

5. Dugongs feed on the sea grass meadows around sub-tropical Australia. What are the greatest threats to this endangered mam-mal?

Extension Tasks

Try collecting and preserving examples of local algae and small seaweeds – details here: http://en.wikipedia.org/wiki/AlgaeTerms like symbiosis, commensal-ism, mutualism, parasitism and others represent a whole spectrum of relationships between plants and organisms. Investigate the precise differences and prepare a presentation or report with classic examples of each type.Draw up a table or a visual presen-tation (poster) that shows the food webs of the polar habitat during the spring and summer feeding season.Investigate the possible reasons for sudden decline in the krill populations and the effect that this might have on the planet’s marine ecosystems.

Algae

Algae are simple living aquatic organ-isms, often floating, that capture light

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energy through photosynthesis, using it to convert inorganic nutrients into organic matter like other green plants. Algae range from single-cell floating organisms to multicellular organisms, some with fairly complex form and (if marine) called seaweeds. All lack leaves, roots, flowers and other organ structures that characterize higher plants. They are the powerhouse of the marine environment as we see in this episode and are at their richest in cool waters which are far richer in the upwelling nutrients (such as phos-phates). These nutrients are brought to the surface by cold currents from the seabed where they have settled over millions of years. Most fisheries in the world are based on the productivity of offshore cold currents. In contrast, tropical waters have high biodiversity (more species) but far lower biomass (quantities of fish and other life). Alga species seen in this episode range from tiny single cells that live inside coral polyps through to the massive bull kelp towers.

Although algae seem to be simple �

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plants, they actually span more than one domain, including both eukaryota and bacteria (blue-green algae – cy-anobacteria), as well as more than one kingdom, including plants and protists, the latter being thought more animal-like (see protozoa). Therefore algae are not a single evolutionary line, but a level of organization that may have developed several times in the early history of life on earth. They are per-haps the most important ecosystem producer on the planet, rivalling the role of grass in land-based systems.

All algae have photosynthetic ma-chinery ultimately derived from the cyanobacteria, and produce oxygen as a byproduct of photosynthesis. It is estimated that algae produce about 73 to 87 per cent of the net global production of oxygen – which is avail-able to humans and other terrestrial animals for respiration.

Algae are usually found in damp plac-es or bodies of water and are common in terrestrial as well as aquatic envi-ronments. However, terrestrial algae are usually rather inconspicuous and far more common in moist, tropi-

cal regions than dry ones, because they lack vascular tissues and other adaptations to live on land. Algae can endure dryness and other conditions only in symbiosis such as with a fun-gus like lichen.

The various sorts of algae play significant roles in aquatic ecology. Microscopic forms that live suspended in the water column – called phyto-plankton – provide the food base for most marine food chains. In very high densities (so-called algal blooms) these algae may discolour the water and outcompete or even poison other life forms, especially in their blue and red forms – so-called red tides for instance. Seaweeds grow mostly in shallow marine waters. Some are used as human food or harvested for useful substances such as agar (a thickener used in foods and products like sham-poo) or fertilizer. The study of marine algae is called phycology or algology.

Types

prokaryotic algae

Cyanobacteria have been included

among the algae, referred to as the cyanophytes or blue-green algae (the term ‘algae’ refers to any aquatic organisms capable of photosynthesis though some recent work on algae specifically exclude them). Cyanobac-teria are some of the oldest organisms to appear in the fossil record dating back to the Precambrian, possibly as far as about 3.5 billion years. They are thought to be the oldest organisms on earth still living in the form of stro-matolites in Western Australia (http://en.wikipedia.org/wiki/Stromatolites). Ancient cyanobacteria likely produced much of the oxygen in the Earth’s atmosphere.

eukaryotic algae

All other algae are eukaryotes and conduct photosynthesis within mem-brane-bound structures (organelles) called chroloplasts containing DNA. The exact nature of the chloroplasts is different among the different lines of algae, and some members are no longer photosynthetic. Some retain plastids, but not chloroplasts, while others have lost them entirely.

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Case Study | Planet Earth | Episode 9: Shallow Seas

Algae and symbiosis

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Algae and symbiosis

Algae are both very fragile and very adaptable so many microscopic spe-cies have survived by entering into relationships with other species. Some even invade the tissues of fish (like carp) to survive.

In symbiotic relationships, the algae supply photosynthates (organic sub-stances) to the host organism which in turn provides physical protection or a moist environment to the algal cells. The host organism derives some or all of its energy requirements from the algae. The example seen in this Planet Earth episode is that of algae living in

corals. The common sybioses are:

• Corals – algae known as zooxan-thellae are symbionts with cor-als. Typical amongst these is the dinoflagellate symbiodinium, found in many hard corals. The loss of symbiodinium, or other zooxan-thellae, from the host is known as coral bleaching and causes death of the reef area. Corals typically filter feed at night, sifting parti-cles from the water but the algae also photosynthesise during the daylight hours, providing the corals with food during the other half of the day.

• Sponges – green algae live close

to the surface of some sponges, for example, breadcrumb sponge (halichondria panicea). The alga is thus protected from predators; the sponge is provided with oxygen and sugars which can account for up to eighty per cent of sponge growth in some species.

• Lichens – a fungus is the host, liv-ing on bare rock or tree bark usu-ally with a green alga or a cyano-bacterium as its internal symbiont. Both fungal and algal species found in lichens are capable of liv-ing independently, but the relation-ship allows them to invade new habitats, too dry for the algae and too low in nutrients for the fungus. 11

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This study guide was produced by ATOM [email protected]

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3Viewing Questions

1 The shallow areas around conti-nental coasts down to 200m

2 Eight per cent3 Whales migrate to breed in warm

tropical seas4 There are few predators and the

waters are calm5 500 litres6 Coral polyps7 By providing food during the day-

light hours8 They’re too slow without assist-

ance9 Shark Bay, Western Australia10 The Dugong11 Hydroplaning12 Marine algae13 Krill14 An alga15 Purple sea urchins16 Seals and stingrays

17 The ragged toothed shark 18 King penguin19 Australia20 Three tonnes each day

Discussion Questions

1 Endless examples but students might like to consider the nature of their relationships with their pets – or with the organisms that infest their own intestines.

2 Seals, whales, dolphins, dugongs. They appear to have returned to the water as there were abun-dant food resources there but the physical adaptations required were extreme including loss of limbs, huge fat reserves, seasonal behav-iour patterns. However many are still gregarious – they form tribes or herds.

3 Almost exclusively. There is some

evidence that volcanic vents, ‘smokers’, in the deep ocean can support an ecosystem without it – but every dark system, even dark ones like caves, require a depend-ence on growing plants.

4 Tropical waters are low in nutri-ents and algae-coral reefs are the exception as they can protect and exploit algae but they are like oa-ses – the exception – and the rest of the environment is an underwa-ter sand desert.

5 Destruction of seagrass areas by recreation like boating, by pollu-tion and injuries to animals by boat propellers are serious problems.

BBC and Planet Earth are trade marks of the British Broadcasting Corpo-ration and are used under licence. Planet Earth logo © BBC 2006. BBC logo © BBC 1996.

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A STUDYGUIDE bY Andrew Fildes · PDF filePlanet Earth is a BBC production with five episodes in the first series ... focussing on key species or relationships in each ... Planet Earth