18-19: Mammal origins, Primates Flashcards
What sets mammals apart from other animals?
Endothermy and homothermy- generate own heat, maintain temperature
Have a placenta (in eutherians) and mammary glands
Heterodony- teeth not all in the same shape
Secondary palate- way of breathing whilst chewing
Enlarged brain
How many extra holes in the skull do mammals have?
1 on each side
What is 1 extra hole on each side called?
Synapsid
When did ‘mammly’ type things occur?
End of Triassic- the start of the dinosaurs
When did mammly things diversify?
Cretaceous
What allowed the diversification of mammals?
The extinction of the dinosaurs
Synapsida features
From the Permian Single opening between skull roof and cheek Large canine-like teeth Strong, arched palate Eg. Pelycosaurs
Therapsida features
From mid-Permian to Triassic
Expansion of jaw muscles- to chew
Less sprawling gait, more upright
Expansion of cerebellum
Cynodonta features
From triassic to mid-Jurassic Well developed post-canine teeth Changes in jaw Jaw bones change to ear bones Complete secondary palate- can chew and breathe at the same time Endothermic
Early mammalia features
Late Triassic to present
First evidence of hair- doesn’t fossilise well, could have been earlier
Mammary and skin glands
Teeth when growing, shed and have second set when adult
Closer to modern form
Mammalia features
3 ear ossicles
Modified vertebrae
Long bones
Enlarged neopallium (part of brain for sensory perception, cognition, language)
What are theria?
Most of the modern mammals- eutherians and marsupials
Have modifications of the braincase
What are eutherians?
Give birth to developed offspring
What are marsupials?
Undeveloped offspring are kept in pouches
Evolution of the jaw joint
Reduction in the number of bones
It is stronger to have fewer bones
Needs to be strong for chewing
Jaw bones become ear bones
Features of the mammal palatte
Soft palate separates
The epiglottis stops food going down the airway
Would be better to have nose underneath mouth- evolution is not perfect
Amphibian palatte features
Big bony plate
No separation of airway from the oesophagus
Therapsid reptile palatte features
Partial bony layer
A bit of separation
Mammal palatte bony layer
Completely jointed
Characteristics of the modern mammal
Hair- can be evolved into spines Sweat, scent, mammary glands 3 ossicles (malleus, incus, stapes) Usually 7 vertebrae in neck- birds have as many as they need Heterodont- lots of different shapes of teeth 4 chambered heart Non-nucleated, biconcave red blood cells Males are heterogametic (XY) Milk from mammary glands
Mammal hair features
Made of keratin
Usually 2 layers- dense, soft underhair, course guard hair
Varied colours that can change by seasons for camoflague
Sweat gland examples
Eccrine- cooling
Apocrine- reproductive
Scent gland uses
Marking
Communication
Teeth argument
Success of mammals is due to the range of teeth?
What teeth do mammals have?
4 types: 3 Incisors 1 Canine 4 Premolars 3 Molars (on each side) They have these on both upper and lower jaws
Mammal diets
Insectivorous Herbivorous Ruminants Carnivorous Omnivorous Can have special teeth for diet
Insectivore digestive system
Short intestine
No caecum
Ruminant herbivore digestive system
4 chambered stomach with large rumen
Long small and large intestine
Non-ruminant herbivore digestive system
Simple stomach
Large caecum
Carnivore digestive system
Short intestine and colon
Small caecum
Herbivore =
long gut, takes more time to digest vegetation
Flight in mammals
Eg. northern flying squirrel
Gliders
Help us see the process of where flight came from
What is echolocation?
Frequency modulated pulses directed in a narrow beam
Allow them to ‘see’
Reproduction forms
Monotremes- lay eggs (ancestral form)
Marsupials- pouched, viviparous
Eutherians (placentals)- viviparous, lessaltricial
Internal fertilisation
Placenta features
Needs to cope with nutrients and waste crossing inside the body
Membrane system
Which type of mammal produces offspring the quickest?
Eutherians- main advantage
But marsupials more flexible- can ditch baby in pouch if no food around
Joey in pouch, egg in body
Primate limb
Nails rather than claws
Grasping hands and feet
Upright body posture
Retained a lot of primitive features- hands/feet
How many digits?
5- a pentadactyle limb
This is the ancestral form
Primate hand adaptations
Adapted to grasping
Many don’t have a thumb
Which primate does have claws?
The marmoset
A secondary derivation that has re-evolved
Primate teeth/diet features
Ungeneralised teeth
Some have a tooth comb
Eat a generalised diet
Have incisors, canines, premolars, molars
What are tooth combs?
Where incisors point forwards
Eg. in lemurs for grooming
Old world monkey teeth
Have big canines
Aye-aye teeth
A madagascan lemur
Has huge protruding gnawing teeth
Primate senses, brain and behaviour features
Short snout Large eyes Big brains Flexible behaviour Extended infant care Large social groups
What is the only nocturnal monkey?
The owl monkey
Features of the proboscis monkey
Can enlarge nose for sexual display
Makes a noise
Like to swim
Example of a monkey with a prehensile tail
Red spider monkey
What is a prehensile tail?
Can grasp objects
What are primates split into?
Strepsirhini
Haplorhini
Features of Strepsirhini
Wet, dog-like nose
Split lip
Whiskers
Features of Haplorhini
No split lip
Dry noses
What do tarsiers belong to?
Haplorhini, as they have dry noses, but are also said to be prosimians
Haplorhini split into
Platyrrhini- flat noses
Catarrhini- round noses
Tarsiiformes- tarsiers
Lemuriformes are split into
Lorisoidea
Lemuroidea- madagascan lemurs
Catarrhini are split into
Cercopithecoidea- old world monkeys
Hominoidea- great and lesser apes
What are the old world monkeys called?
Cercopithecoidea
What are the great and lesser apes called?
Hominoidea
When do we think primates began to appear?
After dinosaurs, but no fossils
See properly in oligocene
When does fossil evidence say the earliest hominins appear?
6mya
What are hominins?
Human-type
Bipedal (walked on two legs)
Small canines
Vertical face
What are hominids?
All human/ape like ancestors
What did the common ancestor look like?
Not like a chimp
No idea!
Miocene hominins
6.5mya (Miocene) Part of skull found Gorilla-like? Very human-like from the front Don't know if its part of the human lineage
6mya (Miocene)
Part of femur suggests that they were bipedal
Pliocene hominins
4.5mya
Chimpanzee ancestor
Not enough evidence to confirm bipedality
3.5mya
Skull of an offshoot from the main human lineage?
Australopithecus- lots of them!
3-1.5mya
Huge teeth for eating tough vegetation?
What were Australopithecines?
From Africa, found in 2 places
In south african caves, good preservation but difficult to date
In east africa, can date but not good preservation
Relatively small brain
Pleistocene hominin
Homo habilis Earliest homo species! Earliest stone tools Similar to Australopithicus but bigger brain Quite small, sexual diamorphism Just in Africa
What was homo erectus?
1.8mya to 200,000 ya Nariokotome Boy- skeleton of adolescent Long, low skull with broad base Prominent brow ridges Large posterior teeth Apart from skull, looks human Originated in Africa, but have been found outside
What are Neanderthals?
Found in Neander valley, Germany All over Europe Bigger brain than modern humans Tools not as advanced Not separate species- we have lots of Neanderthal DNA
Neanderthal features
Lack of chin
Projecting mid-face
Large cranial capacity
Low forehead
Anatomically modern human features
Definite chin
Small anterior teeth
Small brow-ridges
Vertical forehead
What was homo floresiensis?
Found on island east of Java 18,000 ya Very small brain 1m tall Related to homo erectus Stone tools
What were the Denisovans?
Finger bone found in Siberia
Genetically distinct from modern humans and Neanderthals
