Question & Answer Session
Here I'll try to answer some of the questions that browsers have submitted, a couple of things to remember :
- To make sure you don't miss out, do some extra research too, there's lots of great books out there and I can't cover everything (though i'll try).
- Check your facts, I'll try my best to make sure everything is right, but I'm an engineer not a shark biologist , though I read a lot about sharks and dived with, seen many and worked with quite a few.
- Don't just copy what I write down, use my page as a resource by all means, but chances are your teachers also come and read this site, so they'll recognise any copying ;-) besides I write in a fun, informal way and often messy way (when I'm in a hurry), not something that would be good for a report so you will have to still do some work, bad luck ;-)
- Anything I write will mostly be based on the prevailing accepted scientific theory of evolution, remember too that many people believe that God created everything as it is and many believe that God created life and life evolved (that evolution was God's) plan.
So this site will talk about natural selection and evolution as its the accepted theory with the most evidence (but not perfect). However we will also deal with creation theory. More information on all three theories will be given later on, my aim is that both alternatives will get their voice to fit in with many schools' curriculums e.g. Muslim Schools or Christian Schools, everyone must make their own mind up.
Ok that said lets get on with it :
I got an email from Noella in Hampshire, England (part of Great Britain). She's almost 10 years old and likes sharks. She has to make a presentation of 2-4 minutes on animals and how they have adapted to their changing environment / habitat. She'd like to make her talk about sharks and asked for help finding information .
Well, I'll do what I can!
First though, since its only 2-4 minutes, don't try to say to much, stick to a few basic facts showing how sharks are adapted to their different environments!
The problem for me is that there are LOADS of ways that sharks have adapted over millions of years.
I'll try and suggest some ideas that might help, pick and choose just a couple of examples that will last you 2-4 mins.
Sharks have been around for hundreds of millions of years, during this time they've been able to evolve and fine tune their design to fit into the wide range of habitats that they live in.
Most people's idea of a shark looks like a great white shark like my friend Crunch here....
He can grow up to 24ft long, he's designed by nature to be fast and sleek in order to be able to ambush seals, dolphins and fast moving Tuna.
There are 2 types of adaptations that animals have :
- Physical Adaptations - Their bodies have adapted over millions of years in a way that helps them to do something special.(or some people believe they were given these adaptations by God - Called creationism.)
- Behavioural Adaptation - They learned to do something special or figured it out. E.g. some chimpanzees use sticks as tools to catch and eat termites from inside their nest, other chimps which never learned this don't do it.
So what adaptations does Crunch as a Great White shark have ?
Crunch lives in the Cold waters off California, he has several physical adaptations that help him live there. Most people think of California as being a place of warm sunny beaches, mostly they're right , however even in South California where its sunny the water is cold as the sea water there is fed by a current from Canada and Alaska. Sharks like all fish, reptiles and amphibians are cold blooded, this means their body temperature is at the same temperature as their surroundings, mammals and birds are warm blooded, this means they can keep their body temperature warmer or cooler than the surroundings so they don't overheat or cool too much. Keeping the blood and the muscles warm means that they can use their muscles more effectively.
Muscles work more effectively at a warmer temperature and can work longer before getting tired.
So what does this have to do with crunch ? Lots!
Great Whites and their Cousins the Mako sharks have evolved a way to keep their blood warmer than the surrounding water. Animals that can do this are called "Pokoliotherms". The way they keep their blood warmer is that blood vessels going away from the heart carrying blood that is warmer passes right next to the blood vessels coming back to the heart with cooler blood. The heat in the warm blood passes to the cool blood conserving heat inside the body. This allows great whites and makos to swim faster and for longer than their cousins that can't do this.
Another physical adaptation is the great white's shape, see how he's streamlined like a torpedo, his tail fin is the same on the top and on the bottom, he's designed to be sleek and streamlined to swim effortlessly in open water. Other sharks we'll see are designed more for living on the bottom.
Again another physical adaptation is the colour of Great White's and most open water sharks, have you noticed how they are dark on top and light underneath ? Well fighter planes are painted a similar way (except for some of the more modern fighters that fly higher, they're grey all over to be harder to see).
Think of a Spitfire in WWII, they were painted green and brown on top and light blue or grey underneath. This is so that to fighters above them they were hard to see against the colour of the ground so hopefully might not be seen and attacked from above. Yet from below looking up it would be hard to see the blue underside of the plane against the blue sky, this means that the spitfire might go unseen and can pounce on the enemy from above.
Well for great whites and other sharks it works the other way around, the dark blue on top of the sharks merges with the dark blue of the sea below, this means that a seal or a dolphin might not see the shark below until he's close enough to swim up quickly and pounce. This colouring is called countershading.
Great Whites have evolved (or been designed by a higher being) to hunt fast moving marine mammals and big fish such as :
- Sea Lions
All of these guys can move REALLY fast, if the shark is seen before he can pounce, chances are the intended victim can escape by outmanouvering the shark.
In some parts of the world such as the mediterranean Great Whites must hunt Dolphins and Tuna in open water, to do this they sneak up from below using their colour scheme to get close without being seen, once close enough underneath they can pounce quickly and catch their prey.
However in California, Australia, New Zealand and South Africa Great Whites live around Seal , Sea Lion and Penguin (South Africa) colonies. In two of these places South Africa and California and only in special parts of certain islands Great Whites have been observed jumping fully out of the water.
Why only in these special places ? Well its thought that the shape of the bottom is just right, there is a deep area close to the seal colony where the sharks can come in deeper over a rocky bottom (where their colour hides them, unlike a sandy bottom where they would easily be seen).
Further out to sea the seals relax a little, also close inshore they relax, however as the seals / sea lions come in over that particular area they dive and move quickly, not stopping if they can help it. However sometimes they forget, or when the babies leave the beach they don't know to do this.
Anything that lingers over this area risks having a Great White pounce on it, because the water is deeper there the sharks get more of a run up, so they can move fast enough to hit their prey faster, often by the time they hit the seal they are moving so fast they jump out of the water. This is something they seem to have learned to do.
What about other sharks and other adaptations :
This is Donti, he's a horn shark, he also lives in California like Bob. Sometimes Angel sharks will try to eat these guys. However he has horns in front of each of the fins on his back, sometimes these help them to escape since he gets lodged in the throat of the angel shark.
Notice also that both these bottom dwelling sharks have brown colouration and spots to help them stay camoflauged on the bottom. Also see that they have more stubby shapes to lie on the bottom. Donti can actually walk along on the bottom using his fins, another adaptation, also he has a tail that is larger on top than on the bottom, better for resting on the sea bed.
This is gingly, he's a nurse sharkAll sorts of sharks have different teeth adapted to eat different foods, sharks such as gingly, that live on the bottom and eat small fish, crabs, lobsters, shellfish have many small teeth for grabbing and crushing. The teeth shown below are from a Zebra shark, which has a similar lifestyle to gingly and similar teeth, they come from an auction site on the internet.
So teeth are another big adaptation that sharks have to their lifestyles, the shapes of their teeth are geared to the types of food they eat.
They also constantly grow their teeth, they have between 5 and 7 rows that constantly shed and regrow. This is not specific to the shark, all sharks do this.
How else are sharks adapted to different lifestyles, as we've already seen they come in many shapes and sizes (Only about 4% of sharks are big, most are between 6" to 12 foot, the average shark is actually just about 2.5 ft, hardly the monsters from jaws.) from small sharks such as Donti the horn shark to massive sharks like great whites and whale sharks!
Wait, i haven;t mentioned Whale sharks yet!
These guys are the biggest fish in the sea yet they eat only plankton and tiny fish, they wander the sea with their mouths open straining the tiny animals that are plankton. This is Auger the whaleshark he can grow up to 50ft but only eats tiny animals...
Interestingly the second biggest fish in the sea is the Basking shark (only slightly smaller) and they can be found around the UK.
Why is this character called Auger ?
Well one of the biggest oil platforms in the world is in the Gulf of Mexico and run by Shell, its called Auger, one day the crew saw a whale shark feeding around the platform, so they decided to do a practice safety boat drill, they stopped several yards away from the shark, and he came right up to the boat to look. Apparently the shark has come back many times, so now they call him Auger! Why does he come around the rig ? Big structures out at sea attract all sorts of life which start to grow over the structure and form an artificial reef, Auger is probably finding shoals of plankton and small fish around there at thte right times of year.
Check out these photos.
How is he adapted ?
well he has large pectoral fins (like wings) to give him lots of lift. He has a very wide head, his mouth is right at the front and is the width of the head so he can swim around with it open like a bucket scooping up plankton! He also has a huge , powerful tail, he doesn't use much energy to get around.
The writing on the boat says ALsafe 550, this means it is 5.5m long which is ~18.5ft long, this fella is still young! He could easily be TWICE this size.
Well there's LOADS more that could be written and I will write a page on this stuff later, hopefully a little more concisely, however its 11:41 pm now and I must be up at 6 am! So I hope this helps you talk about adaptation for 4 mins - To sum up there are many adaptations, here are a few in summary :
- Shape - Body, Tail, fins
- Teeth Shape
- Feeding style