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%%Permian (270 MYA)%%
%%crocodile-like%% early amphibian
%%aquatic%% & %%terrestrial%%
had some structural %%features%% that would %%appear%% in %%later%% reptiles
</p>
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%%middle-late Permian (240-230 MYA)%%
3ft, 5-10 lbs
%%wide V-shaped boomerang head%%
possibly used to %%navigate strong currents%%
facilitated rapid opening for %%suction-gape feeding%%
</p>
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%%30%% spp.
characteristics
reproduction
why “mole salamanders?”
</p>
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characteristics
distribution
reproduction
lay %%eggs%% in %%water%%
eggs --> %%gilled larvae%%
partial transformation into %%red efts%% (2-3 years)
reach sexual maturity and %%spend life in water%%
distribution
diet
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~300 spp.
characteristics
reproduction
diet
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%%4%% genera, %%23%% spp.
characteristics
distribution
reproduction
diet
</p>
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heat exchange with environment occurs via
</p>
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%%max%% & %%min%% voluntary can be %%highly variable%%
%%tropical mean%% temps is %%higher%% than %%temp%%
%%snakes & lizards%% tend to have %%highest body temps%%
warmest to coolest
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response to %%temp extremes & environmental cues%%
can occur in %%3 different forms%%
Scaphiopus: active 1 month/year in Arizona
Thamnophis: active 4 months/year in Manitoba
dormancy forms explained
hibernation
freezing tolerance
%%ice%% crystals %%destroy%% cells & %%extracellular fluid freezes%% & %%dehydrates%% cells
%%few%% spp. can do this (Pseudacris crucifer <3)
use %%cryoprotectants (glycerol or glucose)%%; replace water in cells with antifreeze
estivation
eastern spadefoot, Scaphiopodidae
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%%penetration of sperm & fusion of male & female pronuclei%%
%%many%% sperm can reach the egg, but %%only one%% will penetrate it
2 types
external
internal
external
internal
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asexual reproduction
Hybridogenesis: progeny only %%transmits female chromosome; all female populations%%
Gynogenesis: diploid/triploid egg only %%activated by sperm; no male chromosomes incorproated into embry%%
only female offspring
fathers from 5 specific spp.
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any form of %%post-egg laying parental behaviour%% that increases %%offspring survival%% at some %%expense of parent%%
most %%amphibs show no parental care%% aside from %%nest construction%%
represented by a variety of behaviours
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Exotrophic
Metamorphosis
Paedomorphosis
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%%addition%% of enw tissue %%in excess%% oif what was lost in damaged tissue
two types
embryonic
juvenile
==GROWTH IN AMPHIBIANS IS INDETERMINATE/NEVER-ENDING==
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intervals ==(periodicity & not age)== are important
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%%prevents desiccation%% & contamination by %%environmental pathogens%%
creates own %%aquatic environment%%
by %%folding & curling%%, reptile embryo can be %%very long%%
3 extraembryonic membranes are formed (no need to know function)
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Asexual
parthenogenesis
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pre-depositional
post-depositional
live-bearing
20% of all lizards & snakes
ovoviviparous
viviparous
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2 growth pulses
embryonic
juvenile
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