10/18/12 1 Figure 34.14 The origin of tetrapods Phylum Chordata Now we move to reptiles (Class Reptilia) and birds (Class Aves), then on to marine mammals (Mammalia). These are all re-entry animals – they re- entered the marine environment to exploit niches there. With birds we see the advent of true endothermy. Nekton •Free swimmers •Tend to be large •The birds, reptiles and mammals breathe air, and are all re-entry animals •They have various adaptations for thermoregulation, breeding, osmoregulation, and movement that evolved in response to their re-entry into an aquatic environment •MANY are K selected, which makes them susceptible to exploitation, invasive species etc. •Genetic bottlenecks – what’s this? Nekton adaptations •r vrs. K selection reproductive strategies •Breeding on land •Migrations •Staying warm (endotherms) •Osmoregulation (salt and water balance) Adaptations of marine mammals •Hair! •Internal mammary glands •Heat retention (blubber /fur) – endotherms •Respiratory rates-decreased •High blood volume •Fusiform bodies •K-selected •Good vision (generally) •The role of acoustics •Counter current heat exchange •Tend to get large (why?) •Some have delayed implantation (embryo) Counter current heat exchangers revisited •Blood in the arteries runs deep (not near the surface) •As it passes by cooler veins, it gives up some of its heat, warming up the veins. •In this way, heat can be ‘trapped’ within areas where it is needed
Transcript
10/18/12
1
Figure 34.14 The origin of tetrapods Phylum Chordata
Now we move to reptiles (Class Reptilia) and birds (Class Aves), then on to marine mammals (Mammalia). These are all re-entry animals – they re-entered the marine environment to exploit niches there. With birds we see the advent of true endothermy.
Nekton • Free swimmers
• Tend to be large
• The birds, reptiles and mammals breathe air, and are all re-entry animals
• They have various adaptations for thermoregulation, breeding, osmoregulation, and movement that evolved in response to their re-entry into an aquatic environment
• MANY are K selected, which makes them susceptible to exploitation, invasive species etc.
• Genetic bottlenecks – what’s this?
Nekton adaptations
• r vrs. K selection reproductive strategies
• Breeding on land
• Migrations
• Staying warm (endotherms)
• Osmoregulation (salt and water balance)
Adaptations of marine mammals
• Hair! • Internal mammary glands • Heat retention (blubber/fur) – endotherms • Respiratory rates-decreased • High blood volume • Fusiform bodies • K-selected • Good vision (generally) • The role of acoustics • Counter current heat exchange • Tend to get large (why?) • Some have delayed implantation (embryo)
Counter current heat exchangers revisited
• Blood in the arteries runs deep (not near the surface) • As it passes by cooler veins, it gives up some of its heat, warming up the veins. • In this way, heat can be ‘trapped’ within areas where it is needed
10/18/12
2
Order Sirenia: Manatees and dugongs
4 species: 3 Manatees and 1 dugong
There used to be the Steller’s Sea Cow – extinct now
?
Dugongs: Dugong dugon
Natural history of Dugongs
Live over 70 years, K-selected Sexually mature between 10 and 18 years! 13-15 month gestation Nurse for another 14 months Leave mom when mature!
IUCN redlisted (close to extinction) Southeast Asia, Africa, Australia
Monophyletic (closely related to) elephants First appeared about 56 million years ago Eat seagrass
Sirenia Manatees Trichechus
Natural history of Manatees
Live over 60 years, K-selected Sexually mature between 10 and 18 years! 12-13 month gestation Nurse for another 18 months
IUCN redlisted (close to extinction) Amazon, West Africa, West Indian 45 meter long intestines!
Monophyletic (closely related to) elephants First appeared about 56 million years ago Eat seagrass and mangroves and over 60 species of plants
10/18/12
3
Boat strikes
Other threats: red tides, habitat degradation, hunting, pollution
Cetaceans (order Cetacea): whales and dolphins
Evolution Feeding and reproduction Conservation status Natural history Physiology 3 families of Mysticetes 6 families of Odontocetes
Archaeoceti Most Archaeocetes had hind limbs – terrestrial life They evolved from From Artiodactlyls – even toed ungulates: pigs hippos, camels. Most likely ancestor were hippo-like (about 65mya)
Its thought that Archaeocetes re-entered the water about 55 MYA
Basilosaurs emerged from the Archaeocetes, about 34mya. They were truly aquatic
Basilosaurus
Two suborders of Cetaceans Mysticetes: baleen whales 3 families: Balaenidae, Balaenopteridae, Eschrichtiidae
The only whales to feed on the bottom (on benthic amphipods)
Mysticetes Are LARGE Are endangered Are K-selected Undertake long migrations (most) Feed with baleen in a variety of ways Are not particularly social…
We looked at three families
Remember those blow holes?
Odontoceti • Teeth • Smaller (ex. sperm whale) • Highly social • Sophisticated sonar • deep divers • One blowhole • Predators • short or no migrations • temperate/tropical
