Narwhals

Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
Class Mammalia
Order Artiodactyla
Infraorder Cetacea
Parvorder Odontoceti
Family Monodontidae
Genus Monodon
Species monoceros

The Narwhal lives in the arctic circle, off Greenland, Canada, and Russia. During the summer, Narwhals stick closer to shore, in shallow water. In winter, they head out to deeper water, under the ice. They breathe through cracks in the ice. Narwhals range from about 14-18 feet in length, with males usually being larger than females.

Narwhals mature at about 8 years old, and have a gestation period of 14 months. Their fecundity is low. They give birth to only one calf at a time, and calves are raised by their mothers for more than a year. Narwhals have a specialized diet, eating Halibut, Cod, and Squid. Major predators of the Narwhal include Orcas, Polar Bears, and Greenland Sharks.

Narwhal tusks have many uses. The tusk has millions of nerve endings, which seems to indicate that it is used as a sensory organ. They might also be used for communication between individuals. Narwhals have also been observed using their tusks to stun fish. Narwhals also have small, vestigial teeth. They also seem to like swimming upside down. During the Middle Ages, many europeans believed that the Narwhal's tusk had magical properties. Some tusks in the 1500s were worth as much as some castles! Narwhals may be the origin of the unicorn myth. Rarely, there are individual narwhals who have two tusks. There is an exhibit on narwhals at the National Museum of Natural History.

The closest relative of Narwhals is the Beluga whale. The ICUN lists Narwhals as having the Least Concern status. Their population appears to be stable, if not increasing. However, climate change and the loss of Arctic sea ice may pose a danger to them.

The Evolution of Ancient Whales

Indohyus lived about 50 million years ago. It had long legs designed for walking on land, and a long tail. But it also had several adaptations that distinguish it from the other small mammals of the time, like a thick, bony covering over the inner ear, and thicker bones so that it could wade on the bottom of rivers.

Ambulocetus natans lived 49 million years ago. It had webbed feet, and a streamlined body plan to help it swim. It is believed that it still wasn't a very good swimmer, and that its adaptations for water dwelling inhibited its movement on land. So it is believed to be an ambush predator, like modern crocodiles.

Rodhocetus lived about 46 million years ago. It had many more adaptations for living in water, such as having its nostrils on top of its head, unfused sacral vertebrae so that it could flex its body up and down for locomotion, and webbed feet. It also had some holdovers from its landlubbing ancestors, including differentiated types of teeth, and well developed hind limbs.

Basilosaurus cetoides looked a lot like a modern whale, with an elongated, streamlined body, hindlimbs that were vestigial, a blowhole, flippers, and even a tail fluke. But on the other hand, it still did have hindlimbs, as vestigial as they were, and it also had differentiated teeth. Basilosaurus was an apex predator in its day, about 40 million years ago.

Dorudon atrox lived 40 million years ago. It had many of the same adaptations that the modern day whales do, such as a tail fluke, blowhole, and a streamlined body. But it also had vestigial hindlimbs, a strange flipper/hand combo, and differentiated teeth. However, it was these creatures, not the seemingly more advanced Basilosaurus, that would give rise to modern day whales.

Finally, below is a modern Blue Whale (Balaenoptera sp.). It has many of the adaptations handed down by its ancestors, such as a streamlined body plan, a flexible spine, a blowhole, flippers, and a tail fluke. However, it has a few things that set it and other modern whales apart from their predecessors. Its hindlimbs are completely absent, it has only a single type of dentition, and it is a filter feeder (though not all modern whales have this feeding strategy.)

Stellar's Sea Cow

Kingdom Animalia

Phylum Chordata

Subphylum Vertebrata

Class Mammalia

Order Sirenia

Family Dugongidae

Genus Hydrodamalis

Species gigas

Stellar's Sea Cow was more closely related to dugongs than manatees, though it was a separate genus from the modern day Dugong itself. It lived in the Bering sea, stretching from Alaska to Kamchatka. They could reach lengths of over 30 feet, and weighed up to 8,800 pounds! It is believed they grew this large to avoid the ill effects of the cold waters in the north, and to protect against predators.

The Stellar's Sea Cow was algivorous, feeding mainly off of kelp. It had no known natural predators. But humans were the major predator of the Stellar's Sea Cow, from 1741-1768, and hunted them to extiction.

Stellar's Sea Cows were described as monogamous, and as being quite protectiive of their young.

Stellar's Sea Cows were bouyant, and could not dive, unlike their dugong cousins.

Stellar's Sea Cows fasted during winter, due to the lack of kelp.

In Sea Cow specimens, no "hands" are found. Some believe that this means the Stellar's Sea Cow gradually lost its hand bones over time.

While most modern sirenians are grey in color, Stellar's Sea Cow was a dark brown, with the occasional white splothces.

Stellar's Sea Cows had no teeth but instead had bony plates for grinding kelp.

Georg Wilhelm Steller discovered Hydrodamalis gigas in 1741. The native peoples of the area had already reduced their population to a very small number, about 2-3,000. Russian whalers on their way to Alaska hunted the Stellar's Sea Cow for its meat and its blubber. By 1768, a mere 27 years after its discovery, the last of the Stellar's Sea Cows died out.

The Stellar's Sea Cow was a fascinating creature, having survived the Holocene epoch, the last ice age, and native hunters until finally being slain by europeans in the eighteenth century. It serves as a reminder of how delicate many of are ocean's creatures really are, and as a warning of what could happen to the remaining sirenians in the future, if we do not protect them. They are all endangered.

Morphed -- When Whales Had Legs -- National Geographic Cetacean Evolution

1. What helped Phillip Gingerich decide what kind of fossil he had found?

Gingerich discovered a Sygmoid Process, a part of the structure of the inner ear, that is unique to whales.

2. Why does Pakicetus go into the water in the first place?

The climate changed to arid conditions, and as the planet warmed, marine life flourished, while many of the common prey items of Pakicetus on land went away.

3. What was the problem in the water for Pakicetus?

One of the main problems facing Pakicetus was predation. Pakicetus was still far away from being an efficient, streamlined swimmer like modern whales. It most likely had to paddle like a dog, making it an easy target for Crocodilians.

4. According to Hans Thewissen, how has Pakicetus adapted to life in the water?

Tail develops muscles and flattens like that of an otter. Back legs shorten and widen to act like flippers. The body becomes more streamlined.

5. Thewissen named the new species Ambulocetus natans, which means-------?

Ambulocetus natans means "The walking and swimming whale."

6. How do they know if it lived in the sea full time?

In order to tell wether Ambulocetus lived permanantly in the oceans, you have to determine if it could have drunk seawater. A land animal wouldn't be able to handle the extra salt, while a marine animal could.

7. It really drank...?

Ambulocetus natans drank freshwater.

8. Ambulocetus vanishes from the -------------- 49 million years ago

49 million years ago, Ambulocetus vanishes from the fossil record.

9. How has the new species adapted to living in water?

A shorter, more powerful neck for better diving; rear legs widen and become more flipper-like; tail develops muscles.

10. The key to Rotocetus success in the ocean is linked to its organ of balance in the inner ear. It is much smaller in whales, allowing it to be acrobatic and agile enough to avoid predators.

11. Basliosaurus lived in the shallow Tethys sea 39 million years ago. What does Basilosaurus mean?

Basilosaurus means "King lizard." (When first described, scientists thought it was a Mosasaur.)

12. What adaptations does Basilosaurus have?

Exceptional eyesight; Improved underwater hearing; long thin body shape to hunt in shallow water.

13. Even though Durodon is much smaller than Basilosaurus, what may have helped it survive?

It is believed that Durodon might have travelled in pods.

14. 36 million years ago, ----------------- died out. why?

Basilosaurus died out 36 million years ago. The climate was cooling, causing sea levels to drop. Basilosaurus was adapted to hunting in shallow waters, and due to the loss of its habitat, it had to try and dive, which it was not designed to do.

15. ------------------- is the whale that gives rise to modern whales.

Durodon survived to become the lineage that would give rise to today's whales.

16. 30 million years ago Megalodon ate Durodons. What did Durodons do that helped them survive?

Durodon migrated northwards over time, to escape Megalodon.

17. How have modern whales adapted to deep diving?

Modern whales can control the flow of blood to their hearts and brains.

18. Today, there are more than 80 whale species.

19. The Grey Whale can swim more than 12,000 miles in an annual migration.

20. Orcas can reach speeds of 34 miles per hour.

21. Bowhead whales can live for over 200 years.

Analyzing a Scientific Article and a Project on Bird Beaks

The first part of my assignment was to read a scientific article and answer some questions about it:

1. What 3 reactions do shorebirds usually have to the presence of humans?

a. Watching the humans

b. Walking away from approaching humans

c. Flying over to an undisturbed section of beach

2. What is the potential consequence of these reactions?

Abandonment of the sections of beach with humans, including foraging areas

3. What does foraging mean?

Foraging is searching for food.

4. How many beaches were studied and where were they located (general area)?

13 beaches in Ventura County, CA

5. How often was data collected? What affected the number of days between surveys?

a. once per month

b. Tides

6. What 3 things were counted during surveys?

a. Shorebirds

b. People

c. Dogs

7. Over what period of time did the entire study take place?

June 1994-May 1997

8. What were the total counts of birds, humans, and dogs during this time?

Birds: 22,087, from 23 different species

Humans: 3,629

Dogs: 528

9. Define the following:

Mean: the average, derived by adding up all the numbers and then dividing by the number of terms

Standard Deviation (SD): a number that indicates the variance between two values

Range: the difference between the lowest and highest values of a data set

10. What assumption did the researchers make about the relationship between shorebird abundance and the presence of humans/dogs?

That the number of shorebirds would be directly affected by the number of humans and dogs.

11. Was this assumption correct? Why or why not?

It was not correct. There are other factors that could affect the result, including the physical characteristics and conditions of the habitat and the availability of prey.

12. What were some reasons other than human/dog use that might affect the number of shorebirds on a particular beach?

Physical characteristics of the habitat, such as the slope of the beach and the height of the waves, as well as the availability of prey.

13. Which beach had the largest mean number of shorebirds? Of humans? Of dogs? Which had the least for each? Looking at the entire data set for Table 1, does there appear to be a correlation between the abundance of shorebirds, humans, and/or dogs? Explain your answer.

Ormond 1 has the largest mean number of shorebirds; Marina beach has the largesr number of humans, and Silver Strand has the most dogs. Hobson beach had the fewest birds; Deer Creek had the least amount of people, and Ormond 2 and 3 had the fewest dogs. There do seem to be fewer shorebirds at beaches with lots of humans.

From the fact that there were more shorebirds on beaches with few people, I would infer that there is a correlation of some sort. However, there is a lot of variation in the data, and there could be more than one reason for the correlation. Correlation isn't causation.

14. Looking at the data for the 3 Ormond Beach sites, what did the researchers think about the possible relationship between shorebird abundance and human presence?

The researchers concluded that the population of birds at the Ormond Beach sites was due to a consistently low human population.

15. Did the researchers find that the number of shorebirds was impacted by the presence of humans/dogs? Was this the result they expected when they started this study?

The researchers came to the conclusion that the presence of humans affected the shorebird population, while the number of dogs had little effect, which surprised the researchers due to the dogs being frequently observed chasing the shorebirds.

16. What problems with their approach do the researchers admit to?

Counts were conducted only once a month, from Monday through Friday. Meaning that there was no accounting for weekend fluctuations, or for an increase in people on holidays.

17. What would you have done differently to create a more scientifically accurate study?

I would conduct counts once per week, and alternate between counting on weekdays and weekends. Also counts should be conducted at the same time of day, to avoid inconsistencies.

The second part of my assignment was to do a project showing the difference is the beaks of birds with different feeding strategies.

Surface skimmers fly right above the surface of the water and stick their elongated lower jaw under the surface of the water, snapping up any fish unlucky enough to be in their path.

Examples: Black skimmer (Rynchops niger); African skimmer (Rynchops flavirostris.)

A scything beak is used by wading birds to pick small prey items out of the mudflats.

Examples: Pied Avocet (Recurvirostra avosetta) American Avocets (Recurvirostra americana.)

Aerial fishers have a sharp, spear like beak, perfect for quickly striking and stabbing their prey.

Examples: Pied Kingfisher (Ceryle rudis) Great Blue Heron (Ardea herodias.)

A pursuit fisher actively chases after its prey, instead of ambushing it. The bill is wider than an aerial fisher's, and often has a hook at the end for grabbing slippery fish.

Examples: Great Cormorant (Phalacrocorax carbo); Flightless Cormorant (Phalacrocorax harrisi.)

Pelicans are famous for dip netting. Dip netters swallow a large gulp of water, then drain off the water, leaving behind fish, small crustaceans, and other such food items.

Examples: Brown Pelican (Pelecanus occidentalis); American white pelican (Pelecanus erythrorhynchos.)

Marine Reptiles Across the Ages

Around 312 million years ago ("MYA"), Amniotes developed adaptations that would keep them alive on land at all stages of their life cycle, allowing them to colonize the interior of the continents, and diversify into many groups, including reptiles. Chief among these was the amniotic egg, which had internal membranes to keep the embryo moist on dry land and allow for gas exchange from the air rather than the water. One would assume that reptiles had left the sea for good. But this is not the case. Below, I will discuss five different species of marine reptiles, each with different adapttions for life in the sea.

Nothosaurus lived in the Triassic period, about 240 MYA, and was small compared to some of the later marine reptiles, about the size of a seal. It still had a very reptilian body plan, but there were some key differences. Its feet were webbed, its tail was muscular, for swimming, and it had pointy, thin teeth designed for holding on to slippery prey. It is believed to be only semi-aquatic. Although not as impressive as some of the later marine reptiles, it is important, because something like Nothosaurus was the ancestor of the mighty plesiosaurs.

Metriorhynchus lived in the late Jurassic period, about 167 MYA. It was a crocodyliform, and had salt glands for excreting excess salt, flippers, and a finned tail. It is known to have scavenenged Leedsichthys, a massive fish, and was probably also a predator. It had long, slightly curved, conical teeth.

Elasmosaurus lived about 80 MYA, during the late Cretaceous period. It was fully aquatic, and had flippers, a short tail, a small head, and of course its defining feature: a neck longer than its body and tail combined. It probably hunted schools of fish. They were probably viviparous, i.e., had live birth. (There are fossils of other species of plesiosaur with fetuses.)

Tylosauruss was an apex predator. It had multiple rows of teeth, a long tail with a fin at the end, paddle like flippers, and scales (most marine reptile skin impressions that we have are smooth). Tylosaurus was a squamate, related to snakes and lizards, though the scientific community is still debating whether it is more closely related to snakes (because of adaptations like its extensible jaw), or lizards. It lived in the late Cretaceous, about 80 MYA.

Archelon was a magnificent chelonian, reaching up to 12 feet in length. It had many of the adaptations of modern sea turtles, including large flippers for swimming, a leathery carapace instead of a hard shell, and a robust beak for crushing shells. It likely ate mollusks and crustaceans. It lived in the late Cretaceous, about 70 MYA.

"The End of the Line" Documentary Film

My assignment this week was to watch the film "The End of the Line" and answer questions about it:

1. Fishermen in Newfoundland, Canada had been experiencing declining cod harvests for years when a sudden change was announced in 1992. What was the change? Mark it with a line on the graph.

A moratorium on cod fishing until 1994

2. What was the economic impact on Newfoundland of this decision? Did the stocks of Atlantic Cod recover?

40,000 people lost their jobs overnight. The cod recovered only slightly.

3. In 2001, records showed that local stocks of fish were down worldwide. Yet, records of harvests indicated that fish were being taken at record rates. What was actually happening?

China was falsely reporting inflated statistics.

4. Stocks of Bluefin tuna have dropped by 80%. What reasons are given for this and other population declines seen in commercial fish?

There are too many boats, and not enough fish.

5. Why is Bluefin tuna particularly at risk?

The Bluefin Tuna's flesh is widely sought after and makes fishermen a lot of money.

6. List the recommended quota limit for Bluefin tuna, the recovery limit (so stocks could replenish), thequota set by the politicians, and the actual estimated catch.

Recovery Limit – 10,000 tons

Recommended Limit – 15,000 tons

Established Quota – 29,500 tons

Actual Catch - 61,000 tons

7. The documentary alleges that the Japanese corporation Mitsubishi is hoarding tons of frozen Bluefin tuna. Why would they?

Greed. Once there are no more Tuna left to catch, they can sell the frozen stocks at whatever price they demand.

8. Why are native fishermen having such a difficult time making a living along the West coast of Africa?

Because the European boats are using massive industrial scale fising boats, leaving the natives almost nothing.

9. What species of marine animals make up “bycatch”? What percent of total catch does this make up?

Bycatch makes up one tenth of the total catch, and consists of Turtles, Seabirds, Sharks, and Dolphins.

10. Which trophic level of fish is hunted in the Coral Triangle?

Tertiary Consumers

11. What impacts have been observed at Chesapeake Bay as a result of selective hunting like this?

The population of Cownose rays exploded.

12. Atlantic Cod in Newfoundland occupied a similar level on theecological pyramid – how has their absence impacted the food web?

There are now large populations of Lobsters, as well as jellyfish. algae and worms.

13. Describe four ways that fishing in Alaska is more tightly controlled and regulated, thus preventing a collapse of their fishing stocks.

Alaska keeps control of how many fishing boats are in their waters. They drive away boats without proper liscences. They have scientifically derived quotas, and they enforce the 200-mile limit. They give fisherman a limited time to fulfill their quota.

14. What is Marine Stewardship Council (MSC) certification?

It is essentialy a certificate of sustainibility.

15. What is the problem with fish farming or aquaculture? How many kilos of anchovy are needed to produce a kilo of salmon? What would be a better option for consumers?

Fish farming uses wild fish to feed the farmed fish and kills more than it produces. Five kilograms of anchovy per one kilogram of salmon. It would be better just to eat the anchovies.

16. What are marine reserves? How do ecosystems respond once an area is declared a reserve?

Marine reserves are areas where no commercial fishing is allowed, which often leads to popularion recovery.

17. (a) What percent of the ocean would need to be reserves to maintain sustainable fishing stocks? (b) What percent is currently part of a reserve?

(a) 20-30%.

(b) Less than 1%

18. Are ocean fish as we are harvesting them a renewable or nonrenewable resource?

Nonrenewable. They can't replace themselves at the rate they are being caught and killed.

19. Bottom-trawling is frequently mentioned in the documentary as one of the worst, most damaging forms of commercial fishing. Explain why.

Trawling not only targets the Fish, but it also targets the entire ocean floor ecosystem by destroying habitat.

20. According to the documentary, 50% of Atlantic Cod is caught illegally. One quote given is “every other cod in your plate is stolen – from you.” Is this accurate? Are the oceans a commons area?

The oceans are all interconnected, and what somebody does on one side of the ocean can affect the entire ecosystem, so they are a common area. Overfishing is a global problem.

21. If a gourmet restaurant were to put dishes with endangered mammals on the menu – such as orangutan or lions, it would be a huge public scandal. Why isn’t there a similar reaction to endangered fish?

Because by the time a fish gets on to a consumer's dinner plate, it no longer looks like a fish. People don't really sympathize with fishsticks. And most people don't even know what species are endangered. And we have a pro- cute furry mammal bias that doesn't apply to fish, which many people see as primitive or strange by comparison.

Bony Fish Body Plans

Threre are three major body types in bony fish: Fusiform, Compressed, and Depressed.

I used Tinkercad software to build a digital 3D-model of each type.

A Fusiform body plan is streamlined, elongated laterally, with a long, muscular tail. This body type is helpful for predators to catch their prey, and for prey to try and escape. A good example of this would be a Sailfish (Istiophorus albicans).

A Depressed body plan is squahed vertically, like a pancake. This is advantageous to benthic dwellers, such as Hogchokers (Trinectes maculatus), who need to be able to grab food from the sea floor, and to hide from predators.

A Compressed body plan is flattened laterally, and is useful for maneuverability. and for hiding in tight spaces, like in a coral reef. One example is the Angelfish (Pterophyllum sp.)

Here are all 3 shapes together from several angles, for comparison.

Sharkwater

My assignment this week was to watch the filim "Sharkwater" and answer questions about it.

Shark Myths

1. Why are sharks so hard to photograph?

They often feel threatened by humans and avoid us.

2. What prey defenses have evolved in fish in response to predators like sharks?

Schooling, camouflage, speed, size, and communication

3. What strategies are given for repelling sharks in the black and white film?

Sounds, a stream of bubbles, shredding paper to confuse the shark.

4. According to the documentary, elephants kill more people than sharks. Why then, do people fear sharks so much more?

Psychological revulsion to a "cold monster of the deep".

5. What conditions around the Galapagos Islands of Darwin and Wolf make them so favorable for the hammerhead sharks?

Undersea currents bring plankton, which attracts creatures that eat the plankton, which attracts hammerheads.

6. What two additional senses do hammerhead sharks have that humans do not?

Lateral lines and electromagnetic detection.

7. How many humans have been killed by hammerhead sharks?

Zero

Long Line Fishing

8. List the fish found in the long line recovered by the film crew.

Sailfish, Dorado, Sharks, and Tuna

9. Explain why sharks are not equipped to tear flesh from animals larger than them. What causes moast human deaths from shark attack?

A shark's teeth are not designed for tearing flesh. Most shark related deaths are caused by blood loss.

10. As illustrated by the book Moby Dick, people used to be afraid of whales. How have public perceptions of whales changed since then.

People have come to see them in a new light as beautiful.

11. What does Captain Paul Watson and the Sea Shepherd Conservation Society do to protect whales and sharks from illegal fishing?

They intervene directly to provide enforcement of fishing and whaling regulationsm and treaties, sometimes at the request of governments, sometimes on their own. They sometimes ram whaling ships..

12. The Sea Shepherd caught the Varadero I, an illegal shark fishing boat. Why didn't the fishermen stop on orders from the ship? What are shark fins used for?

The fishermen would lose their ship, their fishing license, and their profits. Shark fins are used to make shark fin soup, which is seen as a status symbol in some Asian cultures.

13. What is the basis for the belief that shark fins have medicinal properties?

Sharks appear to be more resistant to disease, though there is no scientific basis for this. Some people think eating their fins will give them the shark's power to resist disease.

14. How did the Varadero I eventiually escape? Why was the crew of Sea Shepherd arrested?

Varadero agreed to follow Sea Shepherd to port, but they called the Guatemalan authorities and lied about what happened, saying the Sea Shepherd people tried to kill them. They paid off corrupt officials. Sea Shepherd was ordered to disengage, and the crew were charged with attempted murder.

15. Upon their return to the Galapagos Islands, the crew comes across fishermen hunting sea cucumbers. One of them was badly afflicted with the bends. What causes this sickness? Why weren't they returning to shore for treratment?

The bends are caused by rapid differential in pressure: diving too deep and surfacing too quickly. The fisherman did not want to return to shore because they would lose time and money.

16. Why did fishermen want long-line fishing legalized on the Galapagos Islands?

So that they could fish for sharks.

17. Overall shark population is estimated to have declined by ____.

90%

18. Explain how a decline in top predators like sharks can affect producers like plankton.

Plankton feeders are eaten by sharks When sharks decline, the plankton feeders increase their population and eat up more of the plankton, which provide most of our oxygen..

19. As Rob Stewart returns to Costa Rica, he was concerned about being arrested or caught by the mafia. What did he discover was happening there instead? What change was brought about in part because of public pressure?

Protests against finning and in favor of conservation were happening. Public pressure made long lining in the Galapagos illegal again.-More than 100 countries have banned shark finning.

For my assignment, I also had to look up the status of several shark species featured in the film:

A. Scalloped Hammerheads (Sphyrna lewini) often gather together in large groups, which makes them easy targets for fishermen. They have a long age of maturity, which means their population will not be sustainable, because they can not replace themselves as quickly as they are being killed. They are endangered.

B. Whale shark (Rhinchodon typus) fins are highly valuble, and juveniles are easy targets. It is estimated that there is a more than 50% decline in whale shark populations worldwide. They are also classified as endangered.

C. Carcharhinus longimanus, or the oceanic whitetip shark, is a common victim of by-catch. Although their population is declining, they have not reached endangered levels yet, and are classified as vulnerable.

Constructing an Elasmobranch Dichotomous Key

This is my attempt at a dichotomous key for sharks, rays and skates.

1. Is the body Fusiform or Depressed?

a. if depressed--------->2

b. if fusiform------------>5

2. Are the pectoral fins attached to the head?

a. yes ----------------->3

b. no-------------------> Order Squatiniformes (Angel Sharks)

3. More than one dorsal fin?

a. yes------------------>4

b. no------------------->Order Myliobatiformes (Manta and Sting Rays)

4. Produces electricity?

a. yes------------------>Order Torpediniformes (Electric Rays)

b. no------------------->Order Rajiformes (skates)

5. Number of gill slits

a. more than five------->Order Hexanchiformes (Frilled, Six Gill and Seven Gill Sharks)

b. five----------------->6

6. Eye position

a. in front of mouth---->7

b. behind the mouth----->Order Orectolobiformes (Carpet Sharks)

7. Anal fin?

a. no------------------->8

b. yes------------------->9

8. Does it have ventral gill slits and a dramatically elongated snout that resembles a saw blade?

a. yes------------------>Order Pristiformes (Sawfish)

b. no------------------->Order Squaliformes (Dogfish and Cookie Cutter Sharks)

9. Does it have different types of teeth in the front and back of its jaw?

a. yes------------------>Order Heterodontiformes (Horned Sharks)

b. no------------------->10

10. Do its eyes have nictitating membranes?

a. yes----------------->Order Charcariformes (Tiger, Bull, and Hammerhead Sharks)

b. no------------------>Order Lamniformes (Sand Tiger, Thresher, Megamouth, Basking, Mako, Goblin and Great White Sharks)

Prehistoric Sharks

Falcatus lived in the Carboniferous period, around 325 Million Years Ago ("MYA"). It was probably piscivorous (meaning it ate fish), and lived in deeper waters, which is why it has such large eyes. The most obvious feature of this shark was its long, forward pointed spine. However, specimens of Falcatus can be found without this spine, and it does not appear to have any specific purpose.

So what could it be? Well, since it is found on only some specimens, scientists have concluded that the spine was for mating purposes, most likely as a display. This is a great example of sexual dimorphism, common among many animals today.

Edestus lived in the late Carboniferous. It was related to Helicoprion, and had strange, outward curving tooth whorls that looked like a giant pair of scissors. It probably ate soft bodied animals, and attacked using a vertical thrashing strike.

Hybodus lived throughout the mesozoic era, approximately 260 to 66 MYA. Unlike some of the previous animals, these were generalists. They had two different types of teeth: sharp teeth for grasping prey, and rounded teeth, which could crush hard shells. They most likely ate whatever they could find, and that is probably why they lived for so long. Another adaptation that helped them to survive was long spines on their dorsal fins. These were probably used for defense.

Squalicorax lived during the late Cretaceous period (approximately 105 to 65 MYA). This shark looks a lot likee a modern shark. Its teeth were definately those of a predator, and we also find its teeth in fossils of other animals, includinng turtles, Mosasaurs, and even Hadrosaurs (duck billed dinosaurs)!

And now we get to Megalodon. Megalodon lived from the early Miocene to the late Pliocene (approximately 23 to 2.6 MYA), making it the most recent of these sharks to swim the seas. it was a massive predator, reaching about sixty feet in length. It would have eaten mainly small whales, which were common in the southern oceans at the time. Scientists believe that the whales began to adapt to northern climates and migrated, but megalodon could not adapt to follow their major food source, which likely explains its extinction.

Here is my attempt to estimate Megalodon's size:

And here is my measurement, which shows I was a bit off in my estimate:

I used a 120 inch, or ten foot, tape measure, and marked off each 10 foot distance with chalk.

This is a lifesize 3D model of a megalodon tooth. I created it with Tinkercad software.

It is 18 cm long (approximately 7 inches), which is about as big as they come.

And this is a fossil megalodon tooth that my mom gave me:

Chordate Evolution

My assignment was to "[c]reate a project that shows the evolutionary developments that helped to lead to true vertebrates in the following animals. Begin with the most primitive, and work your way up to the most advanced.

Amphioxus

Hagfish

Hemichordates

Lampreys

Tunicates"

Hemichordates came first, and they had two of the distinguishing features of chordates: gill slits and a dorsal nerve cord. (They also had a ventral nerve cord.)

Next came the Tunicates, or at least their larvae. They have the dorsal nerve cord and pharyngeal gill slits, like their predecessors, but they also have something new: the notochord. Thus, they have three of the four distinguishing chordate characteristics. However, most of these features are lost when they become adults, leaving only the gill slits behind.

Amphioxus was the first organism to have all four chordate features as an adult. The fourth chordate feature is a post-anal tail.

The hagfish was the first agnathan, and just barely scrapes across the boundary to vertebrates. Though more advanced than amphioxus, its spine (derived from the notochord) was a single cartilaginous rod, and it has no jaw.

The next step was the Lamprey. It had all the chordate features, plus fins, and individual vetebrae.( It still no jaw, though.)

Marine Invertebrate Safari

These photos are mostly from a recent family trip to the Georgia Aquarium. My mom took lots more photos of the whale sharks, skates and rays than of marine invertebrates, though, so a couple of pictures are from an earlier trip to the New York Aquarium.

My assignment was to do a photo safari of marine invertebrates, and identify their phylum and what features identify them as belonging to that phylum. I was supposed to identify them down to class or order if I could, and create a cladogram showing their evolutionary relationships.

In this first photo, we have two different creatures. First, there's a Sea Star, of the Phylum Echinodermata, Class Asteroidea. You can tell this by its pentaradial symmetry, its spiny skin, and by the thick attachments of its arms to the central disk. There is also an anemone in this photo, Phylum Cnidaria, Class Anthozoa. It has the radial symmetry and tentacles of a cnidarian, but it is sessile as an adult and has a polyp body form.

This second photo of anemones is of the bubbe tip anemone Entacmaea quadricolor of the phylum Cnidaria, Class Anthozoa.

This is some sort of clam, in the Phylum Mollusca, Class Bivalvia. It has two shells.

Here is a table coral. It is a Cnidarian (phylum), Anthozoan (Class), Sclereactinian (Order) coral. I know this since it is part of a larger reef structure, which are made by scleractinians.

This is a moon jelly, Aurelia aurita. Because it has radial symmetry, and tentacles with stinging cells, it must be a cnidarian. And due to its round bell with tentacles all along the rim, it has to be a member of class Scyphozoa, i.e., a true jellyfish.

Pictured here is a Japanese sea nettle, Chrysaora pacifica. It is also a Cnidarian, and a Scyphozoan, for the same reasons as above.

This is a Japanese Spider Crab, scientific name Macrocheira kaempferi, of the Phylum Arthropoda, Subphylum Crustacea, Class Malacostraca, and the Order Crustacea. I can tell that it is an arthropod based off its jointed legs, and that it is a decapod because it has ten legs.

This is a Nautiloid. It is from Phylum Mollusca, Class Cephalopoda. This is evident by its soft body with multiple tentacles, and its siphon for jet propulsion, as well as the fact that it has a shell.

This is a sea fan, a soft coral, from phylum Cnidaria, Class Anthozoa, Subclass Octocorallia.

It has a sessile polyp body form as an adult, lacks tentacles or an osculum, spongeocoel, or ostia, so it isn't an anemone or a poriferan, and must be a coral. It does not have a hard calcium carbonate skeleton, so it is a soft coral.

This is a sea urchin, of the Phylum Echinodermata and the Class Echinoidea. I can tell this because of the spiny skin, and the Aristotle's Lantern that is clearly visible.

This is a white striped cleaner shrimp, Lysmata ambonensis. Phylum Arthropoda, Subphylum Crustacea, Class Decapoda, which I know because of its ten, jointed limbs and hard carapace/exoskeleton.

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This is a sea snail, of Phylum Mollusca, Class Gastropoda. it has a radula, a soft foot, and a helical shell with one opening.

The second part of my assignment was to create a cladogram showing the evolutionary relationships between the animals I chose.

Sea Star Water Vascular System

The water vascular system starts with the Madreporite, where water enters the body. The water is then funneled into the starfish's core through the Stone canal, which then flows into the Ring canal. The ring canal distributes water around the center of the organism, where it then enters one of the radial canals. The radial canals take the water from the center of the creature all the way down the arms, into the ampulla, where it can then be used for locomotion, by hydraulically moving the tube feet, and assist in feeding (also with tube feet).

Crustacean Life Cycles

CRABS: The crab life cycle consists of a stage called a Zoea, which is usually planktonic. Zoea look nothing like adult crabs. They are transparent, have elongate, shrimp like abdomens, and have long spines protruding from their backs. Over time, they change into the Megalops, which has more of the adult crab features, including claws, though the abdomen still trails out behind them. As they mature, the abdomen retracts under the body, officially entering the juvenile stage. After that point, they mostly grow bigger, with minimal physical changes, until they reach reproductive maturity.

SHRIMP

The shrimp's life cycle undergoes many stages. It starts with a small, feathery, planktonic larva called a Nauplius. Over time, the Nauplius elongates, and turns into a Zoea, at which point its appendages begin to specialze, and mouth parts develop. It then undergoes a the Mysis stage, when the swimmerets and walking legs are distinguished fom each other. It then grows, through the juvenile stage, before finally becoming an adult.

LOBSTER:

The Lobster life cycle is much more linear, with a series of stages that progress over the course of several weeks. Then there are no physical changes for months, only size increase until reproductive maturity.