Download Adapting to Life in the Sea

Key Concepts
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The evolution of the amniotic egg gave reptiles a great reproductive advantage.
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The Asian saltwater crocodile lives in estuaries and is adapted to life in the marine
environment.
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Sea turtles have streamlined bodies and appendages modified into flippers.
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Sea turtles mate at sea and lay eggs on the same beaches where the females hatched.
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Sea turtles may migrate long distances between their breeding grounds and their
nesting beaches.
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The marine iguana of the Galápagos Islands is the only marine lizard.
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Sea snakes are mostly found in the shallow coastal waters of the Western Pacific
and Indian oceans where they feed on fish and fish eggs.
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Shorebirds are adapted for finding food in shallow water and sand.
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A variety of bird species including, gulls, pelicans, and tubenoses are adapted to
feeding on marine organisms.
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Penguins are the birds most adapted to life in the sea.
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Many marine reptiles and birds are endangered by human activities.
Marine Reptiles
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Ancestors of modern reptiles appeared about 100 million years ago.
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Reptiles adapted for success on land, then used the same characteristics to return to
the sea
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Modern-day reptiles include:
– crocodilians
– turtles
– lizards
– snakes
Amniotic Egg
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An amniotic egg is covered by a protective shell
– amnion
– yolk sac
– allantois
– chorion
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Amniotic egg allowed longs development with less risk of predation
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Copulatory organs allow efficient internal fertilization
Physiological Adaptations
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Advanced circulatory system
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Kidneys are efficient in eliminating wastes while conserving water
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Skin covered with scales and lacking glands decreases water loss
Marine Crocodiles
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Largest living reptiles
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Feed mainly on fishes
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Drink salt water and eliminate excess salt through salt glands on their tongues
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Lives along the shore, where it nests
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Females reach sexual maturity at 10 – 12 years of age, males mature at ~ 16 years.
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Elevated nests contain 40 – 60 eggs, incubation period is ~ 90 days
Communicate with calls or barks
Good navigational skills
Sea Turtles
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Seven species inhabit world’s oceans
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Adaptations to life at sea
– protective shells that are fused to the skeleton
• outer layer composed of keratin
• inner layer composed of bone
• carapace
• plastron
– leatherback turtle lacks shell
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Adaptations to life at sea
– shell is adapted for buoyancy/swimming
– fatty deposits and spongy bones add buoyancy
– front limbs are modified into large flippers
– back limbs are used for steering and digging nests
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Behavior
– generally solitary, interact for courtship
– remain submerged (up to 3 hrs) while at sea
– alternate between feeding and resting
– sleep on the bottom under rocks or coral
– in deep water, sea turtles can sleep on surface
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Feeding and nutrition
– have a beak-like structure instead of teeth
– green sea turtle is the only herbivore
– leatherback sea turtles adapted to eat jellyfish
– salt consumed are eliminated as tears
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Reproduction
– courtship
– nesting
– female can lay several clutches of eggs
– development and hatching
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Turtle migrations
– migrate hundreds to thousands of km
– females return to beaches where they were born to nest
– many hypotheses explaining method for sea turtle navigation over long
distances:
• utilize smell and taste as well as auditory cues
• sense angle intensity of earth’s magnetic field
• use sun
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Sea turtles in danger
– beach erosion/alteration
– artificial lighting near nesting beaches
– sea turtles are killed when trapped in fishing nests
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turtles are hunted by humans
dogs, cats and raccoons dig up nests and prey on eggs
Marine Iguana
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The only marine iguana is in the Galápagos Islands
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Most are black, some mottled red and black
– absorption of heat
– high body heat allows swimming and feeding in cold water
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few predators but vulnerable to feral predators
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Feeding and nutrition
– herbivores with snout for grazing on seaweed
– some dive at high tide to feed on algae
– excess salt excreted by specialized glands
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Behaviors
– good swimmers
– intruders are attacked when they enter territory
• rarely result in serious injury
Sea Snakes
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Descendants of lizards
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Adaptations to life in the sea
– scales
– tail
– nostrils
– single lung
– exchange gases through the skin
– can lower metabolic rate to use less O2
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Feeding and nutrition
– eat mainly fish, fish eggs and eels
– salt excreting gland
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Reproduction
– 3 oviparous species, others are viviparous
– congregate to mate
– have two penises - hemipenes
– gestation from 4 to 11 months
– can swim at birth
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Sea snakes and humans
– venom is toxic
– rarely bite humans
– eaten in Japan
Seabirds
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250 of 8,500 bird species live near or in the sea
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Seabirds feed in the sea
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Some spend months away from land
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Types of seabirds:
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shorebirds
gulls and their relatives
pelicans and their relatives
tubenoses
penguins
Adaptations for Flight
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Homeothermic
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High rate of metabolism
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Strong muscles, quick responses and coordination
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Advanced respiratory system with 4-chambered heart
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Excellent sight and hearing and large brain
Adapting to Life in the Sea
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Large amounts of salt are consumed
– salt glands remove excess salt
– tears have high salt concentration
Shorebirds
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Oystercatchers
– oystercatchers use long, orange bills to slice through adductor muscles of
bivalve molluscs, pry limpets off rocks, crush crabs and probe mud
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Plovers
– have short, plump bodies
– nests in depressions or hollows on the ground
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Turnstones
– heavyset birds, with upturned bills used like crowbars to turn over stones and
beach debris
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Sandpipers
– feed on small crustaceans and mollusks in sand
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Curlews
– long-billed curlew uses bill like a forceps to extract shellfish from their
burrows
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Avocets and Stilts
– have long legs and necks and slender bodies
– avocets wade through shallow water, moving beak the water
– stilts probe the mud for small animals
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Herons, egrets and bitterns
– widespread
– skinny legs and long necks
– most stand still and wait for prey
– some stalk prey or frighten prey into motion
Gulls and Their Relatives
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Gulls have webbed feet and oil glands
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They are not true ocean-going birds
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Have enormous appetites but are not selective feeders
Relatives of gulls include terns, skuas, jaeger birds, skimmers and alcids
Gulls
– herring gulls are the most widespread
– feeding
• noisy, aggressive, efficient predators and scavengers
• may drop prey to break the shell open
• highly successful at finding food
– nesting
• highly gregarious; gather in large colonies
• not picky about nesting sites or materials
• both sexes assist in incubating 2-3 eggs
• chicks hatch in 3-4 weeks
• not uncommon for only 1 out of every 5 hatchlings to survive
Terns
– small birds with brightly-colored bills and forked tails
– hunt by plunging into the water; will steal food
– usually gregarious nesters
Skuas and Jaegers
– very aggressive omnivores and predators
– “hawks” or “vultures” of the sea
– jaegers will pursue other birds to steal their prey
Skimmers (scissorbills)
– pupils that are vertical slits and a
– lower jaw protruding farther than the upper bill
– fly over water and create ripples that attract fish
Alcids - include auks, puffins and murres
– look like penguins but are related to gulls
• convergent evolution
• ecological equivalents
– nesting and reproduction
• alcids gather in dense, cliff side colonies
• both parents care for 1 pear-shaped egg
– parental care of the young
• young murres plunge into the water to be joined by the parents
• alcid parents spend most of their time gathering food for chicks
• adult puffins abruptly leave chicks to learn to swim after 6 weeks of
constant care
Pelicans and Their Relatives
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Pelicans, gannets, boobies, cormorants, darters, frigatebirds, tropicbirds
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Have webs between all 4 toes
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Upper mandible is hooked in pelicans, cormorants and frigatebirds
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Many are brightly colored, or have head adornments
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Pelicans
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large birds preferring warm latitudes and estuary, coastal and inland waters
require a large fish population
feed just under the water’s surface
• gular pouch
Boobies
– dive into the sea from 18-30 m up to fish
– numbers of eggs may reflect food supply
Cormorants
– lack oil glands, must periodically dry their wings
Frigatebirds
– lightweight body and near 2 m wingspan
– cannot waterproof their feathers
– hence they feed by skimming surface with their bills
– pursue/attack other birds to steal prey
Tubenoses
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Petrels, albatrosses and shearwaters
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Tubular nostrils on their beaks
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Glands secrete concentrated salt solution
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Glands in stomachs produces oil used for feeding hatchlings and defense
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Albatrosses
– gliders with wings nearly 3.5 m long
– most live in the Southern Hemisphere
– usually come to land only to breed
– elaborate courtship displays precede mating
– 1 egg is incubated by both
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Petrels
– small birds with long legs with fluttering flight
• feed with legs extended and feet paddling rapidly
• form long-term pair bonds for breeding
• live only in year-round cold water
• spot prey from the air, dive, and pursue prey by “flying” underwater
Penguins
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Swift swimmers
– streamlined
– flat, webbed feet for steering
– leap from the water to breathe
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Eat fishes, squid and krill
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Eaten by leopard seals and killer whales
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Female emperor penguin lays 1 egg, which the male incubates while she feeds
– egg sits on his feet, covered by a fold of skin
– male can feed the chick
– crop
– both parents help
– by summer, the chick can feed itself,