Personal Work Sample (ACE)

Hi Readers, the following is an Ace which I had done for term 3. Hope you like it. In the rubrics I have no idea what "personal work" really meant so I assume it is Ace, something that I had done. Hope you like it :D

Adaptation of Sharks

What are sharks?
Sharks are a type of fish with a full cartilaginous skeleton and a highly skeleton and streamlined body. Did you know the earliest known sharks date from more than 420 million years ago, before the time of the dinosaurs. Scientist has only found 440 species of sharks. Ranging from small-sized dwarf shark to the enormous whale shark, which can grow up to approximately 12 metres (39 ft 4 in) and which feeds only on plankton, squid and small fishes by filter feeding. Sharks are found in all seas and are common down to depths of 2,000 metres (6,562 ft). Most sharks lived in the ocean but some sharks like the bull shark can live in fresh water too. All sharks breathe through 5 to 7 gill slits and they do not have scales but a toothed-like skin which enable them to shark faster.
Firstly, what is adaptation?
- The evolutionary process whereby a population becomes better suited to its habitat. This process takes place over many generations, and is one of the basic phenomena of biology.
- A feature which is especially important for an organism's survival and reproduction.
- Produced in a variable population by the better suited forms reproducing more successfully, that is, by natural selection.

Sharks’ adaptation to the world around them/ Biotic Factors
- Sharks have a large oily liver and light cartilaginous skeleton, unlike fish that have a swim bladder to regulate buoyancy. These adaptations allow the shark to control their buoyancy in water. With an oil filled liver instead of a swim bladder, sharks are able to make fast changes in depth without having to wait for gas pressure to be equalize, which is a necessary adaptation for pursuing preys in the depth of the surface to 100m. Did you know that even though sharks’ cartilage is about half as dense as bone and the liver constitutes up to 30% of their body, sharks still have to keep on swimming or they would sink. To prevent sinking, the sharks employ dynamic lift to maintain depth. Some sharks such as Sand Tiger sharks store air in their stomachs, using it as a form of swim bladder. However, certain shark species, such as the nurse shark, are capable of pumping water across their gills, allowing them to rest on the ocean bottom.
- Most sharks have streamlined body, which are torpedo shape; this will enable the shark to swim faster so as to pursue prey. Also, the shark have a tailfin with a longer lobe, which is necessary as it provides a downward driving force to balance forward lift caused by the pectoral fins and flat ventral surface of the snout.
- All sharks have dermal denticles, which feel like sandpaper. This will channel the surrounding water to produce laminar flow, which lowers friction, making the shark hydrodynamic. With the shark having lesser water resistance, the shark is able to swim much faster, allowing it to hunt for its prey easier.
- Another adaptation of many predatory shark species have a nictitating lower eyelid, such as the Tiger Shark, which slides across the eyeball allowing the shark to protect its most vulnerable organ at the time of the attack. However, some sharks like the great white shark, do not have the nictitating eyelid. Instead of using the eyelid, they roll their eyes backwards, preventing injuries in their eyes from the threshing of prey.
- A sharks’ most important sense is smell. It is so powerful that sharks are able to niff a tea spoon of blood in an Olympic size pool, sharks can smell up to 100m or more. Once the shark identifies the scent, it will start swimming. The sharks’ natural swimming motion of moving its head back and forth provides further assistance in determining where the scent is coming from. With each movement, the snout picks up more water for the shark to analyze, and the shark is able to tell whether it’s coming from the right or left nares. This helps them determine which way to swim. The shark’s nose may work so well because it does not have to do anything else. Shark use their nose just for smelling and the sharks’ sense of smell is not connected to its mouth so sharks often do not know how something is going to taste until they have taken a bite. With this keen form of smell, sharks are able to locate weak, injured and old preys, making it easier for the shark to hunt for its prey.
- Sharks have probably the most efficient teeth in the animal world as they are able to remove tissues/flesh up to 10kg or more from their prey from just a single bite. The teeth are arrange in rows, which moves up when those that are in used are damaged or lost in the struggle with the prey. This process will last a life-span, meaning to say that the sharks will continuously have teeth. It was said by some researchers that sharks can lose up to 5000 teeth per life time. Their teeth also get replaced by bigger teeth as they get bigger. The bite-force of a shark can be enormous, with a large force of 18 tons per square inch. Different teeth have different functions. The Mako’s and Sand Tiger’s have fang-like teeth for seizing and holding their fast moving prey, in which the prey is swallowed whole. In another case, the Great White Shark have large triangular teeth for cutting large cunk of flesh from its prey.
Abiotic Factors
- Salinity. Sharks tend to live in salty water, however there are still sharks that are able to live in fresh water, such as the bull shark.
- Temperature. For every shark, there is a different amount of temperature for the shark to survive. Great white sharks live in water where the temperature is between 12°C and 25°C (54°F to 78°F), while nurse sharks tend to stay in warm waters.

Habitat
The approximate 500 different shark species can be found in all of the oceans and the vast majority of the seas throughout the world. Because water covers an enormous percentage of the earth’s surface, this implies a significant number of animals inhabiting its depths. There are a small number of shark species that are able to live in freshwater rivers and lakes as well. Most sharks live between the water’s surface and 2000 metres down. It is rare to find sharks living at 3000 metres or more below sea level, but it has been witnessed, such as the goblin shark. Sharks tend to prefer the shallower continental shelf areas. This is because these are the areas at which rivers deposit nutrients into the oceans. These nutrients feed the marine lives in this water from a cellular level, which, in turn, feed larger and larger species. The chain continues until it reaches predators such as sharks and even human beings, who feed off fish, crustaceans and molluscs.