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Transcript of Dolphins
Anya H. Priya C.
The earliest ancestors of dolphins were most likely land and shallow water animals, which evolved to become deeper water animals.
Scientists think the ancestry of modern dolphins is from early cetaceans, such as the indohyus.
Modern Species versus Intermediate Species
This is the indorses, which is believed to be one of the oldest ancestors of cetaceans (dolphins, whales, etc).
Environmental Conditions Influenced Evolution:
Adaptations of modern species + environmental changes
Modern Relatives & Their Adaptations
Response to Environmental Changes: Temperature Increase
The Bottlenose Dolphin Today
Over time, the ancestors of the common bottlenose dolphin, adapted to have blowholes to suppy oxygen, no hind legs, and slick blubber to insulate them in colder water temperatures.
The Atlantic bottlenose dolphin is closely related to other species of dolphins, such as:
Stenella frontalis, the Atlantic spotted dolphin
Orcinus orca, the killer whale (it actually belongs to the dolphin family!)
Timeline of Evolution
Indohyus, a mostly land animal
Paklecetus, a semi-aquatic animal
Ambulocetus, which starting to look more like a water animal
Rodhocetus, saltwater habitat
Dorudon, which had a blowhole and very small hind legs
Orcodontes, the dolphin, which uses ecolocation to hunt
Mystecetes, today's whales
Inshore vs. Offshore Atlantic Dolphins
Most Atlantic bottlenose dolphins live inshore, where the water is warmer. These dolpins have a lighter grey appearance, because they don't need to absorb as much heat.
The Atlantic bottlenose dolphins that live offshore have a darker grey appearance to absorb heat, have shorter fins and beaks since they migrate less than inshore dolphins.
Orcas have black backs to camoflauge from above with the dark color of water, and white undersides to blend in with light from below.
Orcas use clicks and whistles to communicate, just as other dolphins do.
Orcas are the largest animals of the dolphin family.
Tursiops Truncatus Classification
Family: Delphinidae (dolphin)
Species: Tursiops truncatus
The body of the bottlenose dolphin has changed over time to survive their environment, (ex: the extensions of it to the middle ear for hearing + echolocation to locate prey)
Now dolphins' ears have became adapted for hearing ultrasonic frequencies beyond human range
Present-day dolphins have blowholes to help them acquire oxygen from above water easily.
Lengths of legs shortened
Thicker skin to retain heat
Larger tails for greater thrust while swimming
Echolocation to find prey in water
If the temperature of the water the bottlenose dolphins live in were to increase by 10 degrees:
Dolphins with darker skin would get too hot.
Dolphins wth lighter skin would be unaffected and pass on their genes, or
A mutation could occur, resulting in a dolphin having lighter skin, which would allow it to remain cool and pass on its genes.
Dolphins would move offshore towards the cooler, deeper water.
Atlantic Spotted Dolphin
This species of dolphin has spots to help camoflage in its shallow(er) water environment; light rays, sea foam, and the spots all look similar.
The spotted dolphin has a slimmer body than the bottlenose dolphin, which makes it a more agile swimmer.