Blue Shark Ariel Nelson evolution

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Blue Shark Ariel Nelson

-Sharks have existed for over 350 or 400 million years. They evolved over 100 million years before the dinosaurs did. This was long before people evolved. Most fossil evidence of early sharks is from fossilized teeth and a few skin impressions. Cladodonts, primitive sharks, had double-pointed teeth, were up to 6 feet (2 m) long lived about 360 million years ago (mya); they ate fish and crustaceans.

- Megalodon (Carcharodon megalodon) was an ancient, meat-eating shark, living between 25-1.6 million years ago; it is extinct. It was over 40 feet (12 m) long, but this is only an estimate from fossil teeth that have been found. Its teeth resemble those of the great white shark but are almost 3 times larger; these teeth are each the size of a person's hand!
- (OF ALL SHARKS): Sharks have existed for over 350 million years. They evolved over 100 million years before the dinosaurs did. This was long before people evolved. Most fossil evidence of early sharks is from fossilized teeth and a few skin impressions. Cladodonts, primitive sharks, had double-pointed teeth, were up to 6 feet (2 m) long, ate fish and crustaceans, and lived about 360 million years ago (mya). The earliest-known primitive shark remains are fossil "scales" that date from about 420 million years ago, during the early Silurian. The earliest shark genera are Mongolepis, Polymerolepis, and Palaeospondylus. Other early sharks included Orthacanthus, Hybodus and Megalodon. Modern forms of sharks evolved during the Jurassic period, about 150 mya; this was the time of the giant dinosaurs like Brachiosaurus.

Evolution of Sharks - Enchanted Learning Software. (n.d.). ENCHANTED LEARNING HOME PAGE. Retrieved September 21, 2011, from

5. Carcharhiniformes (Ground Sharks) are the largest, most diverse and widespread order of sharks. Dating from the Jurassic period (160-200 mya) the ground sharks are comprised of around 247 species in 8 families; catsharks (Scyliorhinidae), finback catsharks (Proscylliidae), false catsharks (Pseudotriakidae), barbeled houndsharks (Leptochariidae), houndsharks (Triakidae), weasel sharks (Hemigaleidae), requiem sharks (Carcharhinidae), and hammerhead sharks (Sphyrnidae).

These shark species inhabit cold to tropical seas, intertidal to deep water and pelagic open ocean. Their physical appearances can be quite different; from the Daggernose shark (Isogomphodon oxyrhynchus) to the Great Hammerhead (Sphyrna mokarran), however all have 5 gill slits, 2 dorsal fins (with one exception; the aptly named “Onefin catshark” Pentanchus profundicolus) and anal fins.

Reproductive strategies are also very varied both the catsharks and the finback catsharks are oviparous (egg laying) and ovoviviparous with typically 1-2 eggs or live pups per litter, false catsharks are ovoviviparous (2-4 pups per litter), oophagous (meaning “egg eating” pups feed off eggs produced by the ovary whilst inside the uterus, 2 pups per litter), viviparous (pups nurtured via a placental connection, 7 pups per litter), the barbeled houndsharks reproductive method is unknown, houndsharks are ovoviviparous (2-52 pups per litter) and viviparous (2-20 pups per litter), the exact method in weasel sharks is unknown but they do bare 1-4 live young, requiem sharks are ovoviviparous (10-80 pups per litter) and viviparous (1-135 pups per litter) and hammerhead sharks are viviparous (30-55 pups per litter). . . . Shark Evolution and Classification. (n.d.). . . . Home . Retrieved September 21, 2011, from

Google Images. (n.d.). Google. Retrieved September 21, 2011, from

Sharks are known to be an ancient creature, with fossils from some of the oldest sharks dating back as far as 450 million years. Before they could swim, they were known to crawl on land, eventually merging into the sea in order to move more effectively. Their evolution is one that has led to several species, sizes and structures that are linked to the pre-historic animal. From the evolution of sharks, are also various kinds of these animals that exist. These are divided according to the shapes and features that are present in the animal. Features such as the fin, spine, nose and body shape help to determine the type of shark that is seen. For example, a white shark will have their mouth behind their eyes and will have a fin towards the front and towards the back. An angel shark, on the other hand, will have several fins that are along the spine as well as a flat nose with the mouth underneath.
Facts and Information about Sharks. (n.d.). Facts and Information about Sharks. Retrieved September 21, 2011, from


  1. Science Resource Center

    1. Weigh 33 kilograms

    2. 30 kilograms less than those 5 decades ago

    3. Humans eat all the large fish and then the smaller fish have to breed creating smaller fish over time

Menna, J. D. (n.d.). Science Reference Center: OCEAN PREDATORS LOSE THEIR BITE. EBSCO Publishing Service Selection Page. Retrieved September 21, 2011, from

  1. Evolution of Sharks

    1. Large pelagic, indigo colored, sleek shark w/ pointed fins, pointed snout, and large eyes

    2. Indigo colored but color may differ

    3. Sleek tarped body-graceful swimmer

    4. Elongated caudal fin(tail) provides swimming power as the tail moves from side to side

    5. Grow up to 12.5 feet or 3.8 meters long

    6. Among fastest swimming sharks (possibly one of the fastest fish); can leap out of the water-estimates range from 22 mph to 60 mph for speed (not enough experiments to accurately give estimation on speed)

    7. Teeth- pointed and serrated: enable them to catch slippery squid/fish

      1. Teeth in rows which rotate into use when needed: the first row used to catch prey, other rows rotate in when a tooth or teeth become lost, broken, or worn down.

    8. Diet: mostly squid but will eat anything- scavenger as well

    9. Found in open waters (pelagic) and found worldwide

    10. Classification:

      1. Kingdom: Animalia (animals)

      2. Phylum: Chordata

        1. Subphylum: Vertebrata (vertebrates)

      3. Class: Chondrichthyes (cartilaginous fish)

        1. Subclass: Elasmobranchii (sharks and rays)

      4. Order: Carcharhiniformes

      5. Family: Carcharhinidae

      6. Genus: Prionance

      7. Species: glauca

Evolution of Sharks - Enchanted Learning Software. (n.d.). ENCHANTED LEARNING HOME PAGE. Retrieved September 21, 2011, from

  1. Open Ocean-things that help them survive (adaptations)

    1. Gills

      1. Inner margin of each gill has fingerlike gill rakers that prevent prey from escaping out of the gill slits

      2. Can eat smallest creatures-shrimp, krill, anchovies, pelagic salps, etc.

    2. Teeth

      1. Slender tipped/serrated in both jaws; upper have overlapping bases and are broader than the lowers

        1. Arrangement allows them to catch slippery-bodies prey that can be swallowed low or to tackle larger food sources

        2. Mostly eats squids and schooling fish

    3. Eyes

      1. Well developed to help detect faint bioluminescence stimulated by prey movement or from specialized light-producing organs of the prey itself

      2. Also use electroreception for detection

    4. Movement

      1. Sonic telemetry studies have revealed that Blue Sharks employ several hunting strategies, each characterized by distinct short-term movement patterns. Off Santa Catalina Island, California, from March to early June, Blue Sharks move inshore at night and offshore during the day. Beginning around midnight, the sharks move into shallow waters off Santa Catalina and feed on small schooling fishes – principally Northern Anchovies (Engraulis mordax) – returning to offshore waters by dawn. In contrast, from June to October, Blue Sharks remain offshore day and night, where they feed heavily on pelagic squids. From December through February, Blue Sharks also move inshore at night to take advantage of incredibly rich feeding provided by the winter mass spawnings of Market Squid (Loligo opalescens). Thus, at least off Santa Catalina, circadian and seasonal movements of Blue Sharks are strongly correlated with movement patterns of their prey.

      2. Telemetry studies conducted off New England, from Georges Bank to Cape Hatteras, have shown that Blue Sharks regularly move up and down in the water column. These vertical oscillations are most pronounced during daylight hours and smaller in amplitude at night, when they are confined to depths near the thermocline. Several theories have been advanced to explain the functional significance of this behavior, but most of them strike me as overly convoluted. Since similar vertical oscillations have been recorded in other large open ocean fishes – including tunas, billfishes, and sharks – I suspect that these movements may simply be an expedient way of searching a wide section of the water column.

      3. Three lines of evidence support my theory. All of the fishes in which similar movement patterns have been recorded – including the Blue Shark – feature large, well-developed eyes. Underwater lighting can be tricky, characterized by flickering light and subdued contrasts of light and shade. Moving up-and-down through the water column may help visually scan for potential prey. A glint of underwater sunlight or shadow that remains fixed as the hunter shifts depth could betray the presence of potential prey. Further, since oceanic water masses tend to stratify by density, odors that may signal an injured or dead animal tend to be smeared horizontally between water layers of similar density. Thus, swimming continually through as many strata as possible maximizes a predator’s chances of detecting an attractive scent. Lastly, an entire community of fishes, squids, and other creatures rises from the mesopelagic zone at night and remains near the surface until shortly before dawn, when it retreats en masse to the twilight depths. This might explain why the vertical oscillations of Blue Sharks are more confined at night, since remaining above the thermocline would probably maximize encounters with potential prey from the mesopelagic. Thus, the up-and-down movements of Blue Sharks in the western North Atlantic may represent a simple but effective hunting strategy

  2. Open Ocean: Blue Shark . (n.d.). ReefQuest Centre for Shark Research Home. Retrieved September 21, 2011, from

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