A STUDYGUIDE BY ANDREW FILDES 4 www.metromagazine.com.au www.theeducationshop.com.au Overview Planet Earth is a BBC production with five episodes in the first series, and a second series to follow in 2007. Each episode examines a range of environments, 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, stabilized aerial photography gives us remarkable views of migrating animals and the techniques used by their predators to hunt them. The series is suitable for middle secondary students studying Science and SOSE/HSIE, and for senior secondary students of Biology, Environmental Science and Geography. SCREEN EDUCATION 2 Episode Four: Caves selves in one of the most dangerous to protect the formations and the envi- sports around. Half flooded sea caves ronment of the cave, this is one of the The Caves episode begins dramatically in New Zealand provide haven for first detailed views we have had of this as a man hurls himself into the void of huge shoals of fish every night while amazing cave and possibly the last. the Cave of Swallows in Mexico. We nocturnal fish emerge from the cave soon realize that he is a base jumper each night in their turn. Web Resources and we watch as he and his friends parachute down into the largest cave Many cave dwellers have special Deer cave shaft in the world, 400 metres deep. abilities to make life in the dark pos- – http://www.ecologyasia.com/ Caves are one of the least explored sible, just as the bats and swiftlets use news-archives/2002/jul-02/ places on Earth and we rarely venture echolocation (sonar). A cave snake thestar_20020727_1.htm deep into them. If we do, we find that catches bats as they fly past by sens- Cave formation many animals and organisms have ing their thermal image and striking. – http://www.reec.nsw. made their home in the dark. Some animals choose to stay deep edu.au/2002/stu7-12/ in the dark for life and have changed cave%20ecosystems%20V3/ In New Zealand, tiny glow-worms hang irreversibly as a result. Troglobytes caves/textcave/4acavelf.htm from the roof of caves creating a galaxy like cave angel fish in Thailand who – http://dwb.unl.edu/Teacher/NSF/ of tiny, blue ‘stars’ in the eternal night. hang on to walls, feeding on bacteria C01/C01Links/rville.k12.mo.us/ The reality is less romantic as they in waterfalls; blind, white salamanders Cave/caveForm1.html are luring cave insects into the sticky which must detect even the slightest Remipedes strands of mucus that they dangle as movement to catch food; blind crabs – http://www.tamug.edu/ traps. Most large caves like those seen that pick through the debris to find any cavebiology/fauna/remipedes/ here are formed in the limestone that organic material to eat. There are the S_tulumensis.html covers ten percent of the land, lime- fish that live in the acidic waters of the Snottites stone that was once part of the seabed. Villa Luz sulphur cave and the colonies – http://www.nasa.gov/vision/ Acidic water literally dissolves the rock of bacteria on the walls, extremo- universe/solarsystem/cave_slime. to produce sometimes awe-inspiring philes, that exude sulphuric acid. Life html chambers such as Deer Cave in Bor- adapts to any environment it seems. Extremophiles neo, home to three million small bats. – http://www.astrobiology.com/ All the energy in the cave is brought in Finally we enter the most beauti- extreme.html by the bats – the enormous mound of ful cave system ever discovered, so droppings beneath their roost which is fragile that even scientists have to Species list literally seething with life. Swarms of seek permission to enter. Lechuguilla cockroaches feed on the guano and in the USA has walls covered with • Cave Glow-Worm – Arachnocampa anything else that falls from the roof, exquisite and delicate structures of luminosa (larva) dead or alive. The bats leaving the cave gypsum crystals up to six metres long. • Wrinkle-lipped Bat – Chaerenphon at twilight form an immense rolling As film crews are normally excluded plicata swarm which is promptly attacked by • Cave Cockroach – Pycnoscelus falcons and bat-hawks. The walls of the Episode 4: Caves Time Log striatus cave are also home to swiflets, small • Giant Cave Centipede – There- Intro 00:00 - 01:00 birds that use a similar echolocation upoda decipiens technique to the bats to find their nests Cave of Swallows 01:00 - 03:15 • Rufous-bellied Eagle – Hieraaetus in the dark. These are the bird’s nests New Zealand Glow-Worm 03:15 - 07:08 kienerii that are harvested for gourmet soup by Ha Long Bay 07:08 - 08:15 • Peregrine Falcon – Falco peregri- local villagers, hanging on to ropes and nus Deer Cave 08:15 - 12:25 makeshift ladders high above the cave • Bat Hawk – Machaerhamphus floor to collect the precious little cups. Bat Hunting 15:50 - 17:05 alcinus Cave Swiftlets 17:05 - 20:30 • Remipede – Speleonectes tulumen- In the Yucatan region of Mexico, there Limestone Formation 20:30 - 23:20 sis are no surface rivers or lakes, only a • Demoiselle (Damsel) Fish – Chro- Yucatan Cenotes 23:20 - 30:00 massive 500km network of flooded mis dispilus caves below the surface. Any rainfall Poor Knight Islands 30:00 - 30:55 • Cave Racer Snake – Elaphe taen- SCREEN EDUCATION sinks into the limestone rock and Cave Python and Bats 31:35 - 33:45 iura becomes part of these subterranean Troglobytes 35:35 - 37:25 • Texas Cave Salamander – Eurycea rivers. Just as with the base jumpers, troglobytes Villa Luz Acid Cave 37:25 - 44:15 this is an irresistible lure to adventur- • Belize White Crab – Typhlopseudo- ers, cave divers who explore and map Lechuguilla Cave 44:15 - 48:00 thelphusa acanthochela the system at enormous risk to them- (TIMINGS ARE APPROXIMatE) • Cave Mollies – Poecilia sphenops 3 1 Blackline Master | Planet Earth | Episode 4: Caves Viewing Questions SCREEN EDUCATION 4 1a 1. How deep is the shaft of the Cave of Swallows? 2. How do glow-worms catch insects? 5. How much of the rock on earth is limestone? 6. How are caves formed in limestone? 3. What makes a glow-worm glow? 7. How many bats are in Borneo’s Deer Cave? SCREEN EDUCATION 4. What is limestone? 8. What eats bat droppings? 5 1b 9. Why do people collect the bird’s nests? 12. What is a cenote? 10. What is a stalactite? 13. Why is cave diving so dangerous? 11. How is a stalagmite different? SCREEN EDUCATION 14. Why do demoiselle fish sleep in the sea caves? 6 1c 15. How do the cave snakes ‘see’ the bats? 18. What lives in the cave water? 16. What is a troglobyte? 19. What hangs from the cave walls? 20. What mineral forms the crystals of Lechuguilla? SCREEN EDUCATION 17. Why is the water white in Villa Luz cave? 7 2 Case Study | Planet Earth | Episode 4: Caves 'Closed' Ecosystems SCREEN EDUCATION 8 2a 'Closed' Ecosystems are Open Ecosystems. But in a few come from to start up the system? cases, it is difficult for organisms to The main source is the droppings The caves featured in this episode enter or leave – an isolated pond or of the bats and birds. They leave are unique in many ways. They con- oasis, for instance, or a cave. In one, the cave to eat outside and excrete tain entire and isolated ecosystems species are restricted by their need of inside the cave, providing food en- in which many odd species have water. In the other, by their ability to ergy for small invertebrate omnivores adapted to suit the habitat niches live in the dark. These odd examples like cockroaches, the grazers of the available. Some caves contain spe- are almost Closed Ecosystems – no cave. They are detritivores (detritus cies that are only found in that one system can be completely closed but = waste). Larger invertebrates like place and the ecosystem must have these come close. centipedes then eat the cockroaches been developing for millions of years while micro-organisms break down in that one isolated place for these In a normal ecosystem, the sun the cockroach wastes. It is estimated endemic species to develop. powers the growth of green material that the bats eat up to 10,000kg of which is then eaten by herbivores insects every night, bringing that Most ecosystems do not have and so on. Photosynthesis is the driv- energy into the cave. In more sealed boundaries that are easy to define. ing force. However, in the cave the caves, water flowing through may Animals and plants stray over any sun does not penetrate and nothing bring food sources like bacteria. border that we draw on a map. They grows, so where does the energy Research Activities • Draw a food web of Borneo’s Deer Cave, based on the following information. » Bats and swiftlets – eat insects outside, excrete inside » Cockroaches – eat bat dung » Centipedes and whip scorpions – eat cockroaches » Cave cricket – eats bird eggs and nestlings » Cave racer snake – eats bats and swiftlets Troglobytes and The true troglobytes who never leave Extremophiles – Extremophilic or- Extremophiles the dark are often strangely adapted. ganisms are usually eukaryotes and Animals like fish, salamanders and simple animals which have adapted Troglobyte – animals that live in crabs will often lose the pigment in to live in extreme environments. and never leave the cave. They are their skin and eyes as there is no These include the snottite bacteria in often specially adapted for life in the value to being coloured and their eyes the film which get their food from the dark and could not survive in a sunlit serve no purpose.