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Amphibians
- Includes frogs, toads, salamanders, and caecilians
- Two stages in lifecycle
- Begin life adapted to an aquatic
- environment (e.g., tadpoles have gills)
- Mature into semi-terrestrial adults with
- lungs
- Most adults respire through lungs and
- moist skin
- Most have four limbs
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Amphibian Reproduction
- They reproduce sexually using external
- fertilization
- The male sperm swim to the female eggs
- Eggs are protected from drying by a jelly-like coating
- Larvae, such as the tadpoles of some
- frogs and toads, develop in water
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Amphibians Require Water
- Their skin must be kept moist to avoid
- desiccation when out of water
- Lungs do not provide enough oxygen, skin supplements O2 via diffusion
- Their breeding behavior and use of
- external fertilization requires water
- Sperm must swim to eggs
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Amphibian Groups
- Frogs and toads undergo metamorphosis
- from aquatic tadpoles into terrestrial adults
- Salamanders have lizard-like bodies with
- four legs and a long tail
- Begin as aquatic larvae with gills that
- may be retained in adulthood
- others metamorphose into terrestrial
- adults
- Caecilians are limbless burrowing
- amphibians
- they have small eyes and limited vision
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Vertebrates: Reptiles
- Evolved from an amphibian ancestor about
- 250 million years ago
- Reptiles include lizards, snakes,
- alligators, crocodiles, turtles, birds
- They respire exclusively through lungs
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Reptile Adaptations to Land
- “Improvements” over their amphibian
- ancestors
- Tough scaly skin that resists water loss
- Internal fertilization
- Three- or four-chambered hearts
- separates oxygenated and deoxygenated
- blood more effectively
- More efficient lungs than amphibians
- Do not use skin as a respiratory organn
- Shelled, amniotic egg
- Protects the embryo in a liquid-filled
- membrane, or amnion
- Allows reptiles to live away from water
- Skeleton provides better support and more
- efficient movement on land than do those of amphibians
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Snakes and Lizards
- Both groups mostly predators
- Adaptations of snakes to predatory lifestyle
- Special sense organs that track prey by sensing body temperature
- Some have venom that is delivered through hollow teeth
- Snakes have a jaw joint that permits the snake to swallow prey
- much larger than its hea
- Lizards are generally small, eat insects or inverts
- Some can be large, e.g. Komodo dragon
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Crocodiles and Alligators
- Aquatic, warm waters
- Nostrils on top of head permit breathing while submerged
- Strong jaws, pointed teeth for crushing and tearing prey
- Extensive parental care (within reptiles this is unique to crocs)
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Turtles
- Occupy many habitats
- Box-like shell that is fused to the vertebrae, ribs, collarbone
- No teeth- use beak to eat plants or animals
- Leatherback turtle is the largest
- Some have long migratory routes for
- nesting
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Birds
- Appear in the fossil record 150 million years ago
- Distinguished from other reptiles by feathers, which are highly specialized reptilian scales
- Modern birds retain scales on their legs, which is evidence of
- evolution from common reptile ancestor
- The earliest known bird is Archaeopteryx (~150mya)
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Adaptations for Flight
- Feathers provide lift, control, insulation
- Hollow bones reduce the weight of the skeleton
- Bird reproductive organs shrink considerably during non-breeding periods
- Females have a single ovary
- The nervous system provides coordination and balance for flight, acute eyesight
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Mammals
- Appeared in fossil record
- ~250 mya
- They did not diversify and dominate terrestrial habitats until the dinosaurs became extinct (~65 mya)
- Produce milk from mammary glands
- Endothermic with high metabolic rates
- Four-chambered heart
- Most have hair that protects and insulates
- Most have limbs for running rather than crawling
- They have sweat, scent, and sebaceous
- (oil-producing) glands, which are not found in other vertebrates
- The mammalian brain is highly developed
- Mammals have unparalleled curiosity and
- learning ability, allowing them to alter their behavior based on experience
- This increases their chances of survival in a changing environment
- Mammals have extended parental care after birth
- This allows some mammals to learn extensively through parental guidance
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Mammal Groups
- Monotremes
- Egg-laying mammals
- Marsupials
- Embryos develop in protective pouch
- Placental mammals
- Embryos develop in uterus where they are
- nourished by a placenta
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Montromenes
- Includes only three species
- Platypuses forage for food in the water and eat
- small vertebrate and invertebrate animals
- Echidnas (anteaters, 2 species) are
- terrestrial and eat insects and worms they dig out of the ground
- All lay leathery eggs rather than giving birth to live young
- The newly hatched young are nourished from milk secreted by the mother
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Marsupials
- Includes the opossums, koalas, kangaroos, wallabies, wombats, and the Tasmania devil
- Embryos begin development in the uterus of the female
- Gestations may be only a few weeks
- Young are born at a very immature stage and must crawl to pouch to nurse
- Some species spend a year or more in the pouch
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Placental Mammals
- Ubiquitous
- Diverse group including such animals as bats, moles, whales, seals, primates, etc.
- Rodents account form almost 40% of all mammal species
- Uterus contains a placenta that
- functions in gas, nutrient, and waste exchange between mother
- and embryo(s)
- Young are retained in the uterus for their entire embryonic development
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Bats: Flying Mammals
- Adaptations for feeding on specific foods such as nectar, fruits, insects
- Most are predators and hunt frogs, fish, flying insects, or blood that they obtain from the skin of sleeping mammals or birds
- Echolocation to catch flying prey
- Wings are adapted “hands”
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