Reptiles Flashcards
When did the reptiles arise?
Palaeozoic era during the Carboniferous period (310 - 320 MYA)
What is the first-known reptile called?
Hylonomus
Reptiles are classified in ____ orders.
___ orders are extinct.
___ orders remain - ~10000 species
(1) 16
(2) 12
(4)
What are the 4 remaining orders?
- Rhynchocephalia (1 species)
- Chelonia (341 species)
- Crocodilia (25 species)
- Squamata (9,671 species) ; Amphisbaenia (188 species); Sauria (lizard - 5,987 species); Serpentes (snake - 3,496 species)
The importance of skull fenestration. What type of animals have:
One skull opening (lateral temporal opening)?
Two openings (dorsal and lateral temporal openings)?
No opening?
(1) Mammals
(2) Reptiles and Birds
(3) Amphibians & Reptile-like amphibians
What is meant by CLADISTIC CLASSIFICATION?
(based on common ancestry)
- Splits the diapsids into three major lineages:
Lepidosauria (Tuatara, modern snakes & lizards)
Archosauria (extinct dinosaur lineages, crocodilians & birds)
______ have lost their skull fenestration and now have an _______ skull.
(1) Chelonians
(2) anapsid
Name at least 3 differences between reptiles and amphibians.
Briefly describe
- Reptilian skin is dry and scaly, limits water loss; Stratum corneum (dead cells) are permanent in reptiles resulting in moulting; Beta-keratin is more rigid
- Amniotic egg: allows embryo to bypass the aquatic stage of amphibians; AMNION: fluid-filled sac that surrounds and cushions the developing embryo. CHORION: outermost layers, allowing gas exchange. ALLANTOIS: excreted wastes from embryo. YOLK SAC: nutrient-rich food supply for the embryo
- Reptilian jaws are more powerful; the openings in the skull (fenestration) provide additional surface area for MUSCLE ATTACHMENT allowing greater pressure to be exerted. With the exception of TURTLES, which have a horny beak (sometimes serrated), all reptiles possess TEETH and many of them have them on both the palate and the jaw.
- Most reptiles have HOMODONT detinition: PARTIAL HETERODONTY occurs in snakes (i.e. fang) and a few lizards
- Orientation of limbs: In most reptiles, the appendages are ROTATED TOWARDS THE BODY; the long axis of the limbs lie MORE PARALLEL to the body’s main axis; the angle between the upper and lower limbs is reduced; LIMBS ARE STRAIGHTER –> provides BETTER SUPPORT FOR THE WEIGHT OF THE BODY and make GREATER AGILITY and SPEED possible
- Reptiles have INTERNAL FERTILISATION and so, males have a COPULATORY ORGAN
- Reptiles REPRODUCTIVE LIFE HISTORIES; most species are OVIPAROUS
Briefly describe the amniotic egg.
- Calcium-impregnated shell that prevents the evaporation of fluids inside but allows gas exchanges
- Large quantities of yolk –> allows embryo to attain a relatively advanced state of development before it hatches; NO METAMORPHOSIS
Briefly describe the characteristics seen in the three different amniote reproductive strategies.
OVIPAROUS: Shell present; Embryo grows OUTSIDE the shell; Food comes from the EGG; Seen in Birds, Reptiles, Few Mammals
OVOVIVIPAROUS: Shell present; embryo growth INSIDE the shell; Food comes from the EGG; Seen in REPTILES
VIVIPAROUS: No shell; embryo grows INSIDE mother; Food comes from the MOTHER; Seen in MAMMALS, few Reptiles
Briefly describe the viviparous squamous cells
Exhibit placentae formed by the appositions of maternal and embryonic tissues
What is parthenogenesis?
TRUE parthenogenesis is the complete absence of male contributions - NO SEXUAL REPRODUCTION
Only 0.1% of all vertebrate species do this - it is VERY RARE
Show the different sexual chromosomes seen. Distinguish which are male and which are female
XY/XX (Male/Female): seen in most reptiles with sexual chromosomes & mammals
WZ/WW (Male/Female) : Few reptiles & birds
Are all offspring that are created through parthenogenesis female?
NO
Briefly describe temperature dependant sex determination
- Temperature of nest affects rate of embryonic development
- Excessive high/low temperatures can be lethal
- Sex determination by temperature of developing eggs is wide spread in turtles, all crocodilians and many lizards; In turtles HIGH temperatures result in LARGER individuals which are usually FEMALE; In some lizards this is the opposite, High temperature = males
- Viviparous lizard selects sex of embryos; Influence of gestation temperature on the sex ration; Mothers can choose the sex of offspring via basking behaviour.