12. Mammals Flashcards
Gymnophiana
Snake looking amphibian with no legs
Live in soil and substrate of streams
Predator, eat small invertebrates
Poorly understood, because there have been found few fossils. They are also hard to find, because of the place they live. They occur in Tropical forest of South America, Africa and South-East Asia
Gymnophiona skin
They have a smooth and colorful skin.
It´s covered in muscus glands, which helps them with burrowing.
Some of them produce toxins.
Caecilians tentacles
Is used for chemosensory, because most of the adults are blind.
Amniota
Its a bigger clade that includes monophyletic groups like mammals, reptiles and birds.
To main lines:
Sysnapsida - mammals
sauropsida - reptiles and birds
Amniote eggs
An egg there has internal membranes which make the embryo able to breath and still conserve water. Called the amniotic cavity.
Mammals have an umbilical cord.
The eggs needs internal fertilization.
What selection pressures produced the amniotes in contrast to amphibians?
The amniotes needed to survive in drier environments.
Adaption
- The yolk of the egg was bigger
- Leathery or hard shell
- Allantois, which is a channel (yolk-looking thing) for respiration and disposal of waste in the egg.
- Kidneys and intestines there retain water more efficient.
How did the skull change?
Large openings in the side of the skull, made the skull lighter.
Stronger jaws, which made their bite stronger.
Whay is a synapsid?
Synapsids were the first monophyleitc group to spread out.
They are confused with reptiles. They are not reptiles.
They walk on land.
ectothermic
Therapsida characteristic
Replaced the early synapsids after the Permian-Triassic extinction event.
Limbs underneath the body
Teeth like modern mamals
Somewhere endothermic
Parental care of the young
Cyndontia
Subgroup of Therapsids
Carnivores and herbivores
Number of jaws bones was reduced in some of them evolved hearing.
Mammals come from this clade, cyndontia.
laid eggs, later evolution to mamals, which didn´t
The nocturnal bottleneck
Was ar herbivores, which was mostly nocturnal, because they lived at the same time as the archosaurs.
The archosaurs was the ancestor of dinosaurs.
consequences of the nocturnal bottleneck evolution?
They evolved teeth, which was meant to capture and crush insects.
small bodies, thermal insulation (fur) and tempeture regulation, was necesary for nightlife.
hearing and smell was inhanced
vision and whiskers (knurhår)
thermoregulation
Cynodonts were probably endothermic with fur. Which means they gained heat internally and used the fur for thermo.
Different kind of temperature regulation
Ectothermic: obtaining heat external
Endothermic: obtaining heat internal
Homothermic: maintaining constant body temperature.
Poikilothermic: Differs in temperature
