Lecture 11 Flashcards
What percentage of UK mammals are in decline?
25%
Give 4 defining features of mammals
. Mammillary glands
. Hair
. Specialised teeth
. Skull type
What is an amniote?
A tetrapod (4 limbed vertebrate with a membrane shelled egg: Egg with a membrane (waterproof) that allows gas exchange
What are the 4 types of amniote skull types?
. Anapsid
. Synapsid
. Diapsid
. Euryapsid
Describe the amniote skull type anapsid and give examples
Has no temporal fenestra
Turtles- orbit at angle and no secondary hole
Describe a synapsid amniote skull and give an example
Has a single fenestra
Mammal-like reptiles
Describe a diapsid amniote skull and give examples
Double fenestra
Lizards/ snakes
What defines the nodes in a cladogram?
Synapomorphies- shares derived character states
Describe pelycosaurs (when they lived, what they were)
. Abundant terrestrial forms in late Carboniferous/ early Permian (320-265 mya)
. Herbivores and carnivores with primitive heterodonty
. Relatively long limbed with parasagittal gait= when opposite limbs move together (compared to other reptiles)
. Elongated neural spines on vertebrae (weight-bearing)
. Dorsal sail: temperature regulation device?
. Basic tail= not as well defined
. Competition= carnivore —> sharp teeth for ripping
. 1 metre in length
. 150 kilos
What is meant by a parasagittal gait?
When opposite limbs move together
Describe therapsids (when they lived, their build)
. Worldwide occurrence in late Permian (249 mya- came later than the others) before the break-up of Pangea- roamed all the land mass—> wide spread
. Longer-limbed, more upright stance, rib number reduction, diaphragm
Describe Cynodonts (cynognathus crateronotus) (habitat, diet, looks)
. Cynognathus was a very fast and fierce hunter. It had a very large and powerful head, up to 40cm in length, filled with incisors, canines and cheek teeth made for a carnivorous diet. It is likely it was warm-blooded despite being classified as a reptile
. Lived in temperate woodlands of Sphth America, South Africa and Antarctica during the Triassic period when this area made up the south of the continent of Gondwana
. Main food source were herbivorous reptile therapsids (so it is a secondary consumer)
. Small, reduction in lumber ribs (gone in us as we only have thoracic ribs)
Why do we only have thoracic ribs and not lumber ribs?
Because we have a diaphragm that allows us to be able to expand and contract our lungs
What do lumber ribs do?
Maintain pressure within the body allowing early mammals to breath properly (ability to take deep breaths)
What is a zygomatic arch? What does this along with a sagittal crest allow? Give an example of a species that has this
The formation of the cheek bone from the top of the ear along the top.
This along with a Sagittarius crest allows really strong muscle development allowing for really strong jaws to form as in large carnivores e.g. badgers- very strong bite
What are defining nodes in cladograms called?
Synapomorphies
What is the difference between the late and early cynodonts?
Their cheek teeth- precursors to our molar teeth
What is a cusp point?
Where teeth collide when they slot into each other
What does the change in cheek teeth between late and early cynodonts mean for the cynodonts?
Allows the animal to have a shearing point and a crushing point and this variation in the teeth opens up a huge variation in the diet- the teeth fit against each other which allow you to chew
What are semi-circular canals in your ear/ how do they work/ what do they do?
They act as a gyroscope and if they move in a particular direction then the brain interprets which way up you are by the movement of the liquid
What is the cochlea in the ear filled with?
Fluid and hairs
What is the endolymph in the ear (of a mammal)?
Liquid moves and determines which way up you are
What is embryology?
Looking at embryos developing
What does mammal embryology show? (Bones)
Homologies: articulations=malleus, and quadrate=incus (so the bones that where in the jaw but aren’t in mammals jaw are because they have moved to form part of the ear derived from the same origin/ common ancestry but they have a different function)
What makes characters homologous
Common ancestry (without the necessity for similarity of function
What is Ontogeny recapitulates phylogeny?
The idea that while watching something develop you will see it go right through its ancestry form (not true because the same embryo can develop in different ways)
