Intro to Amniotes & Reptiles Flashcards
1
Q
How did they go from sea to land?
A
- Amphibian development is linked to water
Shell-less eggs
Thin, moist skin
Often gilled larvae - An ancestor of amniotes evolved an egg that is better adapted to dry terrestrial conditions
2
Q
What are Amniotes?
A
- Monophyletic group within vertebrata
- Includes
Nonavian reptiles
Birds
Mammals - Amniotic membrane around the embryo
- Lack gilled larvae
- Internal fertilization
- Lay eggs on land or retained within the mother
3
Q
What are anamniotes?
A
- Vertebrates that lack an amniotic membrane
- Informal group that includes fishes and amphibians
- Tend to lay their eggs in water
- Smaller, slower growing embryos compared to amniotic egg of same size
4
Q
Are eggs in water or on land?
A
- In general Amniotic egg is a terrestrial egg Anamniotic egg is an aquatic egg - Exceptions Some amphibians lay their eggs on land (moist environment) Even fish can lay their eggs on land
5
Q
What are the adaptations of Amniotes?
A
1) Amniotic egg
2) Thicker and more waterproof skin
3) Rib ventilation of the lungs
4) Stronger jaws
5) High-pressure cardiovascular systems
6) Water-conserving nitrogen excretion
7) Expanded brain and sensory organs
6
Q
Explain the amniotic egg
A
- Has four extra embryonic membranes Amnion Chorion Allantois Yolk sac
7
Q
What is the amnion?
A
- Encloses embryo in fluid (aqueous medium for growth)
- Cushions embryo
8
Q
What is the chorion?
A
- Surrounds the entire egg and is highly vascularized
- Participates in gas exchange
- In most mammals, it contributes to the placenta
9
Q
What is the allantois?
A
- Participates in gas exchange and stores metabolic waste (uric acid) in birds and nonavian reptiles
- Role in development of the placenta in most mammals
10
Q
What is the yolk sac?
A
- Also found in anamniotes (tend to be larger in amniotes)
- Stores nutrients
- In marsupials and placental mammals the yolk sac doesn’t store yolk, but contributes to the placenta
11
Q
What is the shell?
A
- Many amniotic eggs have a shell
Eggs of some lizards, some snakes, and most mammals lack a shell - Shell is mineralized but often flexible
- Provides mechanical support
- Semipermeable barrier
Allows passage of gases but limited water loss (especially in birds)
12
Q
Explain their waterproof skin
A
Amphibians
Thin, moist skin to permit effective gas exchange
Vulnerable to dehydration and physical trauma (on land)
Amniotes Change is skin morphology Thicker, tougher, more waterproof Few use skin for respiration Protected by hair, feathers, scales
13
Q
Explain their rib ventilation of the lungs
A
- Amniotes have better developed lungs than amphibians
Reflects an increase in metabolic demands and a reduced ability to breathe through skin - Amphibians use positive ventilation breathing
Amphibians push air from oral and pharyngeal cavity into lungs - Amniotes use negative ventilation breathing
Expand thoracic cavity to pull air into lungs
14
Q
Explain their stronger jaws
A
- Fish jaw is designed for suction feeding
Have teeth but don’t chew - Tetrapods have tongue and strong jaw
Amphibians and some reptiles have teeth but don’t chew (swallow prey whole)
Mammals have strong jaw adapted for mastication (chewing)
15
Q
Explain their high pressure cardiovascular system
A
- Adaptive for terrestrial organisms
Higher metabolic needs
Heart must pump blood uphill
- Heart is segmented
Fish: 2 chambers
Amphibians & most nonavian reptiles: 3 chambers
Birds & mammals: 4 chambers
16
Q
Explain their water conserving nitrogen excretion
A
- Most aquatic organisms (ammonia)
Toxic at relatively low concentrations - must be diluted with water (not adaptive for dry terrestrial environments) - Mammals (urea)
Concentrated in the kidneys, reduces water loss - Birds and nonavian reptiles (concentrated uric acid)
Bladder receives diluted urine
Water and many salts are resorbed in the bladder
Voided as a semi-solid mass of uric acid
17
Q
Explain their expanded brain and sensory organs
A
- All amniotes have a relatively large brain
Particularly birds and mammals - Better integration of sensory information
- Better control of muscles during locomotion
18
Q
What is the traditional definition of class Reptilia?
A
- Includes snakes, lizards, tuataras, crocodiles and turtles
- Also extinct groups: dinosaurs, plesiosaurs, pterosaurs, early mammal like reptiles
- This is a paraphyletic group because it doesn’t include birds
19
Q
What is the modern definition of Reptilia?
A
- Includes nonavian reptiles and birds
- Crocodiles and birds belong to a clade within Reptilia called Archosauria
Also includes the extinct dinosaurs
20
Q
What are non-avian reptiles?
A
- Some use tongue for smell
- Swallow enormous prey
- Skin is dry and soft
- Snakes: one of the most common fears among adults
21
Q
What is the class Reptilia?
A
- Order Testudines (turtles)
- Superorder Lepidosauria (tuataras and Squamata)
- Archosauria (crocodiles and birds)
22
Q
What are the general characteristics of non-avian reptiles?
A
- Ectothermic
- Tetrapods
Two paired limbs
However, limbs vestigial or absent in many - Body covered in keratinized epidermal scales
- Usually dioecious
Some lizards produce by parthenogenesis - Parental care typically absent
Except in crocodilians - No larval stage
23
Q
What is keratin?
A
- Fibrous structural protein
- Very tough material
- Found in reptiles, amphibians and mammals
Hair, horns, claws, hooves, scales, shells, feathers, beaks, quills - Analogous function to chitin
24
Q
What is chitin?
A
- Nitrogenous polysaccaride
- Very tough material
- Found in arthropods, molluscs, annelids
Setae of annelids
Arthropod exoskeleton
Mollusc radula
Cephalopod internal shell
Fish scales
25
Q
What is the order Testudines (Turtles)?
A
- Enclosed in shell
Dorsal carapace
Ventral plastron (breastplate) - Outer layer composed of keratin
- Inner layer composed of bone
- Bony layer is a fusion of ribs, vertebrae and other bone
- Unique among vertebrates (turtle limbs are located inside the ribs)
26
Q
Explain the reproduction of the Testunides
A
- Oviparous
- Internal fertilization
- All turtles (even marine) bury shelled, amniotic eggs in the ground
- Once nest is constructed, it is abandoned
27
Q
What are the Lepidosauria?
A
Squamata
Lizards
Monitors
Snakes
Tuatara
Lizard like animals
Endemic to New Zealand
28
Q
Explain the Squamata
A
- Lizards and Snakes
- Comprise 95% of known living non-avian reptiles
- Characteristic features
Body covered with scales
Kinetic skulls
29
Q
What is the kinetic skull?
A
- Skull specializations for swallowing large prey
- Snake skulls even more kinetic than lizards
- Major factor that enabling diversification of snakes and lizards
30
Q
What are lizards?
A
- A paraphyletic group
- Familiar animals such as geckos, iguanas, skinks, monitors, chameleons
- Most have four limbs
A few are completely limbless - Moveable eyelids
31
Q
What are the general characteristics of lizards?
A
- Ectothermic (like nearly all non-avian reptiles)
Adjust body temp by moving among different microclimates - Few species in cold climates
Few opportunities to warm up - Successful in warm climates with low productivity
Because of the energy savings associated with being ectothermic
32
Q
What are snakes?
A
- Monophyletic group
- Limbless
- Vertebrae are shorter, wider, and more numerous than other tetrapods
- Differ from lizards in several ways:
No moveable eyelids (snakes eyes covered by a translucent cap)
No external ear openings (internal ears only hear sounds in a limited range of low frequency)
Skull even more kinetic than lizard skull (larger range of motion)
33
Q
What is the difference between a limbless lizard and a snake?
A
- Different common ancestor
- Lizards have moveable eyelids, snakes don’t
- Lizards have ear openings, snakes don’t
- Snake skull is more kinetic
34
Q
How do snakes capture prey?
A
- Kinetic skull
Skull bones are loosely articulated
Two halves of the lower jar are joined only by muscle and skin - Jaws have posterior facing teeth that anchor prey and slowly move it in
- Snakes can swallow very large prey (several times their own diameter)
- Tracheal opening is extended forward between the mandibles (to breath)
35
Q
How do snakes smell?
A
- All snakes and some lizards use their tongues for smell
- Employ Jacobsons organ
Paired organs located in roof of mouth
Line with olfactory epithelium - Forked tongue flicks through air collecting scent molecules
- Draws past Jacobson’s organ
- Also have olfactory areas in the nose (less well developed)
36
Q
What are the Tuataras?
A
- Lizard like animal
- Endemic to New Zealand
2 living species
Sole survivors of a lineage that diverged from lizards and snakes - Endangered species
Threatened by non-native species
Slow reproduction rate (10-20 years to reach sexual maturity and they produce eggs once every 4 years) - Share burrows with petrels (a burrowing sea bird)
37
Q
What are crocodilians?
A
- Alligators and crocodiles
More closely related to birds than others
Non-avian reptiles - Elongated, robust, well-reinforced skull and massive jaw musculature
- Wide gape and powerful closure
- Teeth are replaced (like sharks)
38
Q
Alligators vs Crocodiles
A
- Alligator head and jaws are wider and shorter than crocodiles
- Alligators teeth are less visible with mouth closed
39
Q
What is the reproduction of the crocodilians?
A
- Oviparous
- Female lays 20-50 eggs and buries them in sand
- Extensive parental care:
Female guards eggs
Opens nest when hears vocalizations of the hatchlings
Young are guarded by mother for 2 years after hatching - Incubation temp determines the sex ratio of the offspring
Low nest temp produces only females
High nest temp produces only males
Opposite pattern from turtles
40
Q
What is the temperature-dependant sex determination (TSD)?
A
- Genetic sex determination in most snakes and lizards and some turtles
Z/Z=male, Z/W=female
Same system used in birds - Temperatuer dependent sex determination (no sex chromosomes) in all crocodilians, most turtles and some lizards and snakes
41
Q
Example of TSD in turtles
A
- Low temp produces males
- High temp produces females
- Very small range of temperatures will produce both males and females from a single brood
