Lecture 1 Flashcards
Define phylogeny
Phylogeny refers to the evolutionary history of a taxonomic group of organisms. It shows the relationships between groups of organisms (taxa) particularly the differences and similarities among them.
What is a node on a cladogram?
A hypothetical common ancestor
What are fossils?
Remains of the bodies or behaviour of extinct organisms
What percentage of species do fossils represent?
only represents about 3% of the species that lived, at best
What is the hardest substance in the body?
Enamel (it is 98% mineral).
The size of the ________ is closely related to the size of the organism.
Size of the teeth is closely correlated with the size of the organism.
What is a synapomorphy?
It is a shared derived trait
The shape of teeth is directly related to the physical properties of what?
Shape of teeth is directly related to the physical properties of the primary food stuff.
Why do big terrestrial organisms have bones?
If you’re big and you don’t have any bones then your muscles don’t have anything to pull against. It works in the water with big animals because water supports them but on land you need bones to move around! Your bones act as levers
How can we see where muscles were attached by looking at a fossilised bone?
Muscles leave scars on the bones so we can see where muscles were attached by look at the shapes of bones and the marks on bones.
Name the two types of bone.
Endoskeleton and Ectoskeleton
Name the two parts of the skull
Cranium and mandible
Name the two functions of the skull
1) To house the sense organs and brain
2) Ingestion and mechanical processing of food
Why are the sense organs housed near the mouth?
The mouth is the most important part of the body because that’s where the energy goes in so this is why the sense organs are housed near the mouth!
Name the two sections of the postcranial skeleton and what they are made up of
1) Axial skeleton: vertebrae and ribs
2) Appendicular skeleton: limbs and limb girdles
What is taphonomy?
The study of the laws of fossilisation.
What is the essential element of fossilisation?
Burial
Provide the key steps for fossilisation
1) Death
2) Burial
3) Fossilisation
4) Exposure
5) Discovery
Name the four primate derived features
Grasping hands and feet
Forward facing eyes
Nails instead of claws
Large brain for body size
Grasping hands and feet are also known as what?
Divergent hallux and pollex
What is the name of the bone which can indicate whether an animal had nails, claws or hooves?
distal phalanx (singular) or phalanges (plural).
Flat distal phalanges = nails!
What does propinquity of descent mean?
Relatedness; who is more closely related to who
If two organisms share the same trait then it is likely that their ________ ________ will also have that trait.
If two organisms share the same trait then it is likely that their common ancestor will also have that trait.
How do we decide if a trait is derived?
Outgroup analysis
What does parsimony mean?
Parsimony is a philosophical term meaning choose the simplest explanation because that is most likely to be true.
What does Encephalisation mean?
enlargement of the brain.
What is convergent evolution?
onvergent evolution is the process whereby organisms not closely related (not monophyletic), independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.
Primates have a __________ auditory bulla.
petrosal auditory bulla
Why is the auditory bulla in primates called a petrosal auditory bulla?
The bulla in primates is called the petrosal auditory bulla because it grows as an outgrowth (during development) of the petrosal temporal bone. Other animals have an auditory bulla but they are constructed from different bones.
What is the dental formula of extant primates?
2.1.3.3
What is the dental formula of the primitive placental?
3.1.4.3
Why are synapsids called synapsids?
They only have one cranial opening
What is the stem group of synapsids?
Therapsids (mammal-like-reptiles)
What kind of teeth do dinosaurs, lizards and snakes have?
Dinosaurs, lizards, snakes etc. have conical teeth that don’t touch (occlude) each other so they can’t chew. They can rip but they can’t chew.
What are the triangular teeth (such as therapsids developed) called?
tribosphenic
In therapsid teeth, how many cusps were on the lower and upper teeth?
6 cusps on the lowers and 4 on the uppers.
What is the plural of bulla?
Bullae
What is a plesiadapid?
Primitive adapid
Why are crania rare in the fossil record?
Because the bones are really thin so most of the time they turn to dust
Why is /Purgatorius/ thought to be a primate? And why is it likely yo not be one?
Considered to be earliest primate because of the low rounded cusps on its teeth. This is associated with being frugivorous so this could be convergence; they could be eating lots of fruit just like primates.
However, it has a dental formula of 3.1.4.3 so its only link with primates is reduced molar cusp height.
What is a stem group?
A fossil group that has some but not all of the characteristics of the extant or crown group.
What are the distinguishing features of strepsirrhines?
Tooth comb and grooming claw.
List two primitive conditions that strepsirrhines have
An orbit that is open at the back and separate right and left frontal bones
What type of hole in the temporal bone for arteries to enter is primitive?
Primitive condition is to have both the promontory and stapedial.
What kind of hole in the temporal bone do haplorhines have?
The promontory branch.
Adapids are related to __________. Omomyids are related to _____________.
Adapids related to strepsirrhines
Omomyids related to haplorhines
