Why do marine animals have fins?

Why do marine animals have fins?

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Why do Marine animals have fins.

It is more efficient to use fins than feet, hooves, or other similar body parts. It is the same reason that you can swim faster while wearing flippers. Having a larger surface area allows animals to push against more water, so that they have more force when swimming. Here is a picture of the bones in a dolphin fin. They are extremely similar to the bones in a hand, because dolphins evolved from land animals that had individual fingers.

Amphibians like frogs and salamanders have webbed feet, which is a "compromise" between feet and fins. These feet allow them to push against water with more power, since they have webbing instead is separate fingers. It also allows them to grip the ground on land, since their fingers can move independently of each other.

Dorsal fins also aid in stability. Many marine animals and mammals are fusiform (torpedo-shaped) to reduce drag in the water and make locomotion easier. Without fins for stability, primarily dorsal fins, it would be difficult for animals to orient upright in the water without rolling. The dorsal fin actually increases lateral drag (rolling side to side) to provide this stability. Check out this reference for more information

Marine Science B- Unit 1: The Ocean and Its Populations

Part 1 - Please watch the following video and answer the questions that follow.

Edith Widder: Glowing life in an underwater world

1. On her first open-ocean dive in the Santa Barbara Channel, Widder says she dove down to 880 feet and turned off her lights. Explain why she did this. (1 point)

2. If you happen to be on a ship and go to use the bathroom at night without turning on the light, why does Widder explain you might think you are having a "religious experience"? (1 point)

3A. Why are most people who are studying bioluminescence today focused mainly on the chemistry behind it? (1 point)

3B. What does the Nobel Prize have to do with this? (1 point)

4. What makes bioluminescence an important factor of survival for so many animals? (1 point)

5A. Why is Widder dissatisfied with the way we explore the ocean? (1 point)

5B. What are the two main ways we learn about what lives in the ocean that she describes in the video? (pick 2) (2 points)

Part 2 - Please watch the following video and answer the questions that follow.

David Gallo: Underwater astonishments

1. Gallo spends his short talk examining amazing underwater creatures and pointing out their adaptations. He mentions two squid that are fighting. What part of his description of these squid is an adaptation? (1 point)

Marine Pollution

Marine pollution is a combination of chemicals and trash, most of which comes from land sources and is washed or blown into the ocean. This pollution results in damage to the environment, to the health of all organisms, and to economic structures worldwide.

Biology, Ecology, Earth Science, Oceanography

Water Pollution

Pollutants are dumped into the ocean. This waste affects the daily life of fish and other marine creatures.

This lists the logos of programs or partners of NG Education which have provided or contributed the content on this page. Powered by

Marine pollution is a growing problem in today&rsquos world. Our ocean is being flooded with two main types of pollution: chemicals and trash.

Chemical contamination, or nutrient pollution, is concerning for health, environmental, and economic reasons. This type of pollution occurs when human activities, notably the use of fertilizer on farms, lead to the runoff of chemicals into waterways that ultimately flow into the ocean. The increased concentration of chemicals, such as nitrogen and phosphorus, in the coastal ocean promotes the growth of algal blooms, which can be toxic to wildlife and harmful to humans. The negative effects on health and the environment caused by algal blooms hurt local fishing and tourism industries.

Marine trash encompasses all manufactured products&mdashmost of them plastic&mdashthat end up in the ocean. Littering, storm winds, and poor waste management all contribute to the accumulation of this debris, 80 percent of which comes from sources on land. Common types of marine debris include various plastic items like shopping bags and beverage bottles, along with cigarette butts, bottle caps, food wrappers, and fishing gear. Plastic waste is particularly problematic as a pollutant because it is so long-lasting. Plastic items can take hundreds of years to decompose.

This trash poses dangers to both humans and animals. Fish become tangled and injured in the debris, and some animals mistake items like plastic bags for food and eat them. Small organisms feed on tiny bits of broken-down plastic, called microplastic, and absorb the chemicals from the plastic into their tissues. Microplastics are less than five millimeters (0.2 inches) in diameter and have been detected in a range of marine species, including plankton and whales. When small organisms that consume microplastics are eaten by larger animals, the toxic chemicals then become part of their tissues. In this way, the microplastic pollution migrates up the food chain, eventually becoming part of the food that humans eat.

Solutions for marine pollution include prevention and cleanup. Disposable and single-use plastic is abundantly used in today&rsquos society, from shopping bags to shipping packaging to plastic bottles. Changing society&rsquos approach to plastic use will be a long and economically challenging process. Cleanup, in contrast, may be impossible for some items. Many types of debris (including some plastics) do not float, so they are lost deep in the ocean. Plastics that do float tend to collect in large &ldquopatches&rdquo in ocean gyres. The Pacific Garbage Patch is one example of such a collection, with plastics and microplastics floating on and below the surface of swirling ocean currents between California and Hawaii in an area of about 1.6 million square kilometers (617,763 square miles), although its size is not fixed. These patches are less like islands of trash and, as the National Oceanic and Atmospheric Administration says, more like flecks of microplastic pepper swirling around an ocean soup. Even some promising solutions are inadequate for combating marine pollution. So-called &ldquobiodegradable&rdquo plastics often break down only at temperatures higher than will ever be reached in the ocean.

Nonetheless, many countries are taking action. According to a 2018 report from the United Nations, more than sixty countries have enacted regulations to limit or ban the use of disposable plastic items.

Pollutants are dumped into the ocean. This waste affects the daily life of fish and other marine creatures.

How do marine animals use sound?

Many marine animals rely on sound for survival and depend on unique adaptations that enable them to communicate, protect themselves, locate food, navigate underwater, and/or understand their environment. They may both produce sounds and listen to the sounds around them.

Sounds are particularly useful for communication because they can be used to convey a great deal of information quickly and over long distances. Changes in rate, pitch , and/or structure of sounds communicate different messages. In particular, fishes and marine mammals use sound for communications associated with reproduction and territoriality. Some marine mammals also use sound for the maintenance of group structure.

Dolphins, such as these common dolphins (Delphinus spp.), travel in large groups, therefore, sound is important for communication to maintain group structure. Photo courtesy of NOAA/NEFSC.

Similar to sonar systems on ships, some whales use sound to detect, localize , and characterize objects. By emitting clicks, or short pulses of sound, these marine mammals can listen for echoes and detect objects underwater. This is called echolocation . Some whales and dolphins use echolocation to locate food. They send out pulsed sounds that are reflected back when they strike a target. The analysis of the echoes helps the animals determine the size and shape of an object, its location, whether it is moving, and how far away it is. Echolocation is an effective way to locate prey and also helps whales and dolphins analyze their environment.

Toothed whales, such as these orcas, use sound to locate prey. Photo courtesy of NOAA/NMFS.

Many species of fish and aquatic invertebrates also use sound. Fishes produce various sounds, including grunts, croaks, clicks, and snaps, that are used to attract mates as well as ward off predators.

Big eye scad, a tropical fish, produce sounds using their pharyngeal teeth. These sounds are often heard when a fish is captured and may function to ward off predators. Photo courtesy of John E. Randall.

The life history of many coral reef fishes includes a pelagic larval stage that metamorphoses to the juvenile stage. Late stage larvae and transforming juveniles need to reach suitable reef habitats to mature. There is some evidence that underwater reef sounds may be detected by coral reef fish (and invertebrate) larvae guiding them to coastal areas and allowing them to identify suitable settlement habitats [1] Simpson, S., Meekan, M., McCauley, R. and Jeffs, A. (2004) Attraction of Settlement-Stage Coral Reef Fishes to Reef Noise. Marine Ecology Progress Series, 276, 263&ndash268. [2] Mann, D., Casper, B., Boyle, K. and Tricas, T. (2007) On the Attraction of Larval Fishes to Reef Sounds. Marine Ecology Progress Series, 338, 307&ndash310. [3] Vermeij, M.J.A., Marhaver, K.L., Huijbers, C.M., Nagelkerken, I. and Simpson, S.D. (2010) Coral Larvae Move toward Reef Sounds. Vollmer, S., Ed., PLoS ONE, 5, e10660. [4] Simpson, S.D., Meekan, M.G., Larsen, N.J., McCauley, R.D. and Jeffs, A. (2010) Behavioral Plasticity in Larval Reef Fish: Orientation Is Influenced by Recent Acoustic Experiences. Behavioral Ecology, 21, 1098&ndash1105. [5] Kennedy, E.V., Holderied, M.W., Mair, J.M., Guzman, H.M. and Simpson, S.D. (2010) Spatial Patterns in Reef-Generated Noise Relate to Habitats and Communities: Evidence from a Panamanian Case Study. Journal of Experimental Marine Biology and Ecology, 395, 85&ndash92. . Different coastal habitat types have been found to produce different ambient sounds over short distances.

The larvae of some coral reef fish species like these damselfish, may use sound to locate suitable settlement areas. Image credit: NOAA.

Little research has been done on marine invertebrates that produce sounds. However, several marine invertebrates, including spiny lobsters and fiddler crabs, have been found to produce sounds for defensive and courtship purposes. Some marine invertebrates use sound for other purposes. The cleaner shrimp announces itself as a cleaner and advertises its services by clapping one pair of its claws when reef fish approach.

Cleaner shrimps identify themselves as a &ldquocleaner&rdquo and advertise their services to reef fish by clapping their claws (chelipeds). The hungrier the shrimp, the more clapping it does. In this video, one can watch a cleaner shrimp (small, transparent animal at center) clap/signal to reef fish swimming nearby.
Video by Lucille Chapuis, University of Western Australia

Additional Links on DOSITS


  • Radford, C. A., Stanley, J. A., Simpson, S. D., & Jeffs, A. G. (2011). Juvenile coral reef fish use sound to locate habitats. Coral Reefs, 30(2), 295&ndash305.
  • Radford, C., Stanley, J., Tindle, C., Montgomery, J., & Jeffs, A. (2010). Localised coastal habitats have distinct underwater sound signatures. Marine Ecology Progress Series, 401, 21&ndash29.
  • Simpson, S. D., Meekan, M. G., Jeffs, A., Montgomery, J. C., & McCauley, R. D. (2008). Settlement-stage coral reef fish prefer the higher-frequency invertebrate-generated audible component of reef noise. Animal Behaviour, 75(6), 1861&ndash1868.
  • Simpson, S. D., Radford, A. N., Tickle, E. J., Meekan, M. G., & Jeffs, A. G. (2011). Adaptive avoidance of reef noise. PLoS ONE, 6(2), e16625.
Cited References
⇡ 1 Simpson, S., Meekan, M., McCauley, R. and Jeffs, A. (2004) Attraction of Settlement-Stage Coral Reef Fishes to Reef Noise. Marine Ecology Progress Series, 276, 263&ndash268.
⇡ 2 Mann, D., Casper, B., Boyle, K. and Tricas, T. (2007) On the Attraction of Larval Fishes to Reef Sounds. Marine Ecology Progress Series, 338, 307&ndash310.
⇡ 3 Vermeij, M.J.A., Marhaver, K.L., Huijbers, C.M., Nagelkerken, I. and Simpson, S.D. (2010) Coral Larvae Move toward Reef Sounds. Vollmer, S., Ed., PLoS ONE, 5, e10660.
⇡ 4 Simpson, S.D., Meekan, M.G., Larsen, N.J., McCauley, R.D. and Jeffs, A. (2010) Behavioral Plasticity in Larval Reef Fish: Orientation Is Influenced by Recent Acoustic Experiences. Behavioral Ecology, 21, 1098&ndash1105.
⇡ 5 Kennedy, E.V., Holderied, M.W., Mair, J.M., Guzman, H.M. and Simpson, S.D. (2010) Spatial Patterns in Reef-Generated Noise Relate to Habitats and Communities: Evidence from a Panamanian Case Study. Journal of Experimental Marine Biology and Ecology, 395, 85&ndash92.

Copyright © 2002-2021 University of Rhode Island and Inner Space Center. All rights reserved.

Internal Physiology


The skull of the Mysticete is bow-shaped, while the Odontocete skull is compact and has a parabolic dish shape. The Mysticetes' bow-shaped skull is adapted to accommodate its baleen. The skull shape also suggests that Mysticete probably do not possess any echolocation capabilities. The thickness of the Odontocetes' skull is adapted for its unique feeding requirements. The compact, thick skull provides a large base for muscles to anchor, allowing for the power needed to catch prey. The parabolic dish shape of the Odontocete skull is believed to play a large part in the echolocation abilities of the Odontocete.

The spinal cord of the Odontocete is much thicker than that of the Mysticete relative to size. This seems to again be related to feeding practices. Mysticetes do not have to move quickly to catch their prey. They feed on slow moving creatures such as plankton or krill. Mysticetes also have no natural predators to outrun. As they do not need to move quickly, they do not require an extensive muscle mass. Odontocetes, however, have predators they must outrun as well as prey they must chase and catch. Both of these activities require a large muscle mass. Once again, a larger bone surface area would accommodate a more extensive muscle mass.

Blood Pressure

While diving a dolphin&rsquos heart rate drops as low as 12 beats per minute, conserving oxygen while submerging. When resurfacing, a dolphin&rsquos heartbeat can skyrocket to 120 beats per minute. If this fluctuation occurred in a human, he/she would probably have a stroke. A dolphin, however, is able to handle the quick change in blood pressure because of a special adaptation called the retia mirabilia. The retia is a tissue found underneath the ribcage, between the blowhole and dorsal fin area. It consists of a dense mass of blood vessels that act like a sponge. The arteries in a dolphin feed into the retia, rather than going directly to the brain. The diverted blood flow saturates the vessels within the retia, like a sponge, when a dolphin&rsquos heart rate is high. The retia then controls the flow of blood to the brain, maintaining a consistent flow, no matter how much blood is contained in its vessels. Thus, the retia acts as a buffer, protecting against a surge of blood during high blood pressure, and against a lack of blood flow during reduced heart rates.


One of the characteristics of mammals is the ability to bear live young and nurse them for a period of time. Dolphins put a large amount of energy into raising their young, which stay with them an average of three to six years. (More information about the reproductive and maternity cycles of the bottlenose dolphin may be found in the Dolphin Research Center Maternity Information File.)

Respiratory System

Dolphins breathe air directly into their lungs via the blowhole. Dolphins and whales can also use their blowhole to create sounds. Odontocetes have only one nasal opening, or blowhole, at the surface of the skin. They do have two nasal passages underneath the skin, but the septum does not rise all the way to the surface.

Mysticetes have two nasal openings, or blowholes, at the surface of their skin. The septum rises all the way to the surface of a Mysticetes skin. Whalers could actually identify whales from afar by their blow. Odontocetes have a blow that shoots straight up, while Mysticete blows fountain out. In a sperm whale, only the left nasal passage rises to the surface. The right nasal passage circles around inside the head and is speculated to be associated with sound production.

Cetaceans do not breathe through their mouths at all. In fact, the trachea and esophagus are completely separated with the aid of an organ called the goose beak. The goose beak is an evolutionarily modified larynx that bridges the gap between the nasal passages and the trachea, and is designed to keep anything but air out of the lungs. It is a cartilaginous organ that sits unattached, but tightly fit, inside the sporacular channel found in the skull underneath the blowhole.

Sometimes it is necessary to administer fluids and medications to a dolphin via a stomach tube. The elasticity of a dolphin&rsquos throat tissue, combined with the separation of trachea and esophagus make the tubing process quite easy. This process is quite uncomfortable for a human due to the epiglottis and a gag reflex. Humans and other mammals have a gag reflex to protect their lungs from swallowing foreign objects into the trachea from the mouth. Dolphins have no gag reflex, since the trachea and esophagus are completely separated. So, this procedure does not bother a dolphin.

Digestive System

A dolphin has a three chambered stomach, similar to an ungulate (cow or deer), pointing further to its evolution from a terrestrial ancestor. Since dolphins do not chew their food, the mastication of their meal is taken care of in their first or fore stomach. The majority of digestion is processed in the main stomach or second chamber. The last section of their stomach, the pyloric stomach, takes care of the remainder of their digestion prior to the contents emptying into the intestinal region.

Renal System

In making the change from terrestrial to aquatic living, cetaceans needed a way to accommodate for the higher salinity of their environment. Unlike human kidneys, which are just two singular renules (or balls), dolphins have two kidneys with multiple renules. These renules all function as separate kidneys which help filter out the higher amount of salt content they must deal with in their daily environment.

Dolphins also have a very small bladder, which causes them to urinate frequently. Dolphins can be taught to give a urine sample on command for medical purposes.

How does oil impact marine life?

Following an oil spill, there are specialists and veterinarians to deal with oiled wildlife. These experts are trained on how to clean oil from animals, rehabilitate them, and return them to the environment.

Oil destroys the insulating ability of fur-bearing mammals, such as sea otters, and the water repellency of a bird's feathers, thus exposing these creatures to the harsh elements. Without the ability to repel water and insulate from the cold water, birds and mammals will die from hypothermia.

Juvenile sea turtles can also become trapped in oil and mistake it for food. Dolphins and whales can inhale oil, which can affect lungs, immune function and reproduction. Many birds and animals also ingest oil when they try to clean themselves, which can poison them.

Fish, shellfish, and corals may not be exposed immediately, but can come into contact with oil if it is mixed into the water column — shellfish can also be exposed in the intertidal zone. When exposed to oil, adult fish may experience reduced growth, enlarged livers, changes in heart and respiration rates, fin erosion, and reproduction impairment. Fish eggs and larvae can be especially sensitive to lethal and sublethal impacts. Even when lethal impacts are not observed, oil can make fish and shellfish unsafe for humans to eat.

Animal Adaptations in the Ocean

Students review what animal adaptations are, identify marine animal adaptations in a photo gallery, and predict how types of adaptations vary with ocean habitats.

Portuguese man-of-war

Portuguese man-of-war invertebrates dangle poison-bearing tentacles.



1. Introduce or review the concept of adaptations.
Write the word adaptation on the board. Ask students to define this word as it relates to animals. Ask:

  • Why do animals have special adaptations to their habitats?
  • What examples of animal adaptation can you think of near where you live?
  • What types of adaptations in marine animals have you previously learned about?

Encourage students to think about adaptations in marine animals related to obtaining food, providing camouflage or safety from predators, or dealing with changes in temperature, salinity, pressure, lack of sunlight, and need for oxygen.

2. Have students identify animal adaptations in a National Geographic photo gallery.
Show students the photo gallery and have them take turns reading aloud the captions as the class looks at each photo. Ask students to identify information about adaptations in each caption. For those captions that do not include adaptation information, challenge students to find visual evidence of adaptation. For example, needlefish travel in schools to protect themselves from predators their color and size help them blend into their surroundings. Portuguese man-of-wars have air bladders that allow them to float on or near the surface of the ocean. These communal organisms use their air bladders like sails, allowing wind to move them through the water. The green sea turtle’s shell protects it from predators.

3. Have students make predictions about ocean habitats.
Ask students to predict how different ocean habitats might affect the animal adaptations seen there. Ask:

Why do most species have five digits on their hands and feet?

The condition of having no more than five fingers or toes--in this context, 'most species' means a subgroup of jawed vertebrates--probably evolved before the evolutionary divergence of amphibians (frogs, toads, salamanders and caecilians) and amniotes (birds, mammals, and reptiles in the loosest sense of the term). This event dates to approximately 340 million years ago in the Lower Carboniferous Period. Prior to this split, there is evidence of tetrapods from about 360 million years ago having limbs bearing arrays of six, seven and eight digits. Reduction from these polydactylous patterns to the more familiar arrangements of five or fewer digits accompanied the evolution of sophisticated wrist and ankle joints--both in terms of the number of bones present and the complex articulations among the constituent parts.

Early evolutionary experiments in hexa- or octodactyly (that is, creatures having six or eight digits) were associated with rather simple limb skeletons, much like those present in the flippers of modern whales and dolphins. This might provide a functional clue about one of the reasons for digit number reduction, which is related to the functional demands of simple "walking" limbs. Unlike paddles, such limbs have to provide purchase on a range of substrates, provide the platform for an efficient push-off and allow some rotation relative to the lower and upper limb bones as the rest of the body travels onward. In the very few instances of secondarily evolved polydactylous limbs from the fossil record, the phenomenon is associated with aquatic taxa. The classic instance of this is in the paddles of ichthyosaurs, extinct fishlike marine reptiles that lived more than 65 million years ago.

Is there really any good evidence that five, rather than, say, four or six, digits was biomechanically preferable for the common ancestor of modern tetrapods? The answer has to be "No," in part because a whole range of tetrapods have reduced their numbers of digits further still. In addition, we lack any six-digit examples to investigate. This leads to the second part of the answer, which is to note that although digit numbers can be reduced, they very rarely increase. In a general sense this trait reflects the developmental-evolutionary rule that it is easier to lose something than it is to regain it. Even so, given the immensity of evolutionary time and the extraordinary variety of vertebrate bodies, the striking absence of truly six-digit limbs in today's fauna highlights some sort of constraint. Moles' paws and pandas' thumbs are classic instances in which strangely re-modeled wrist bones serve as sixth digits and represent rather baroque solutions to the apparently straightforward task of growing an extra finger. Patterns of six (or more) digits can be achieved by laboratory-based developmental manipulations, some of which concern changes in gene activity that probably reflect transformations involved in the fin-to-limb evolutionary transition. Here might lie another part of the reason for the prevalence of five: pleiotropy, or the multiple effects of genes upon more than one physical characteristic. For instance, Hand-Foot-Genital syndrome is a rare condition in which, as the name implies, the genito-urinary tract and the limbs are malformed. Crucially, the genes responsible are within the set of those involved in digit number and patterning. Therefore, although this tells us nothing directly about the significance of digit number, it indicates something important about developmental stability: the mechanisms involved in patterning the tips of our limbs include those involved in our reproductive success. Thus, tweak at your peril.

Why do marine animals have fins? - Biology

Project title or topic of activity

The Convergent Evolution of Marine Fish and Whales

Author(s): Andy Lam

Date: Fall 1999

Summary of Activity
50-100 words

The purpose of this activity is to enlighten young minds about the similarities and differences between fish and whales. Many of the similarities are a product of convergent evolution, animals from different lineages that evolve similar morphological and physiological characteristics because they endure the same environmental contraints. While explaining the differences, it is important to highlight the different physiological adaptions to cope with the same conditions.

General description or introduction
The scientific principles that the activity is founded on.

Although fish and whales come from different lineages they share many morphological characteristics as well as some behaviors. When organisms are forced to face the same abiotic and biotic pressures, some organisms evolve to resemble others living in the same environment. This concept is known as convergent evolution. This activity attempts to uncover some of those similarities as well as differences between fish and whales.

Background information

Before jumping into the similarities it is more important at first to recognize the differences.

1) streamlined body shape
2) dorsal and pectoral (flippers) fins. Dorsal fins provide stability. Pectoral fins and flippers most likely derived from the arms of land animals.
3) very efficient gas exchange. Fish utilize a countercurrent system of gas excxhange where the blood in the gills flow in the opposite direction to the water. Deoxygenated blood from the body flows opposite of the oxygenated water producing a more efficient from of gas exchange. Whales can take in extemely large breaths in a short amount of time. Compared to humans fin whales take half the time to fill their lungs with air but a whale breathes in 3,000 times more air. Cetaceans hold their breath in order to get as much oxygen as they can. As much as 90% of the oxygen is exchanged during each breath in contrast to 20% in humans.
4) ability to breathe while feeding. Some cartilaginous fish are equipped with spiracles located on the top of its snout. These spiracles take in water for those fish (especially sharks) while it has prey in its mouth. Remember most sharks need to keep their mouths open while moving in order to breathe. Whales have blowholes located near the top of its head. Not only can a whales eat and breathe at the same time but also take quick breaths while jumping out of the water.
5) strong tail muscles for propulsion. Sharks and tunas have much red muscles and especially myomeres. These mucles are very strong and can propel some fish up to 50 miles per hour or more.
6) cryptic coloration and countershading. Skates and Stingrays develop cryptic coloration to camoflage themselves with the sea floor. Killer whales are dark with peculiar white patches to breakup its outline to prey. Both fish and whales utilize countershading as a way to hide itself in open waters. The dark dorsal side matches the ocean floor while the light underside blends in with the light shining from above.
7) migration. Schooling fish and certain cetaceans travel through the same migration routes year after year.

Credit for the activity

Estimated time to do the activity

Goal A

understand fundamental differences between fish and whales

Goal B

understand how different kinds of animals can evolve similar features and behaviors because they endure the same conditions

Goal C

understand the different physiological adaptions that different animals develop

Two content standards that this lesson plan covers:

  • A small poster that shows how fish use countercurrent to fully reoxygenate doxygenated blood.
  • A sample of Shark "eggs" to show
  • A picture of a whale giving live birth and pointing out it is born tail first to prevent drowning.
  • Show shark teeth and dolphin bones. Ask why there are no shark bones.
  • Pictures and diagrams that show the actual shapes of a killer whale, a baleen whale, a shark and a tuna. Note their steamlined bodies. Even add that seagulls and seals have also this kind of body shape. Note the fins and their development from the arms of land animals (or did they lead into arms?).
  • For an activity to prove that fin shape aids in propulsion battery operated plastic dolphins can be purchased. Break off the tips of one of the dolphins flippers and have the two race. In theory the dolphin with the wider fins should come out ahead every time. Also these dolphins are countershaded. Although not as popular as they used to be these dolphins can still be purchased through
  • Point out countershading in killer whales.
  • point out cryptic color for skates or rays.
  • A map that shows migration routes of different fish and whales.

Step-by-Step Procedure for the Activity

This activity is for fifth to eighth graders in groups no larger than eight to keep tham attentive.

Images, work sheets, additional web pages

Items for discussion or conclusion

Are their animals that have deleoped similarities to man because of common environmental restraints

2nd question

Can you really say that fish are more better suited for the ocean than marine mammals?

3rd question

Will one day fish invade land?


Fish and mammals develop differently form one another. But if you were to put these animals under the same environmental contraints, after many years of evolution, they may develop many of the same characteristics.

Beyond the Activity
Further activities which relate to and extend the complexity of the experiment.

Work Schedule

Marine biologists doing fieldwork often have the least conventional work schedules. Depending on the nature of the research, fieldwork might demand long hours and irregular intervals of time. Marine biologists who are teaching might also have class schedules or office hours that require working evenings.

How to Get the Job

Marine Careers and Conservation Job Board offer listings for opportunities in marine biology.


Working as a professor at a university with a marine biology program is one of the best routes to a career doing research.


Fisheries or state and national park programs with access to waterways are possible career paths for marine biologists.

Watch the video: 50 Years of Marine Mammal Captivity in 4 Minutes. CAPTIVE. TakePart (August 2022).