Biodiversity 8: The mammals Flashcards
Describe the key features of the class mammalia
Endothermic vertebrates
Possess hair made of keratin, with fat = insulation
Skin glands inc mammary (modified sweat gland)
4 chambered heart → needed to support high metabolic rate
Describe some anatomical features of mammals
Limbs carried beneath body
Synapsid skull (1 fenestra) with large braincase
Jaw consists of a single bone
Ear comprises 3 ossicles derived from jaw bones
Describe the 2 types of mammalian hair
Thin soft under hair - insulation
Thick long guard hair - protection
Give some examples of modified mammalian hair and their functions.
Porcupine quills → protects against predators
Pangolin scales →protects against predators and water loss
Puma whiskers → sensory
Rhino horn → matted hair, protection
What are mammalian ossicles originally made from?
The bones originally in the jaw of the reptiles = malleus and incus
Why is having 3 ossicles an adaptation?
Sound detection and distinction much more evolved
What are the 4 types of mammalian teeth?
Incisors
Canines
Premolars
Molars
What are incisors used for?
cutting, shearing
What are canines used for?
In which mammals are they found?
piercing, ripping (absent in herbivores, dominant in carnivores)
What are premolars used for?
slicing, crushing
What are molars used for?
grinding (bone or coarse vegetation)
What is the dental formula?
I-C-P-M
What is the dental formula in placental mammals?
3-1-4-3/3-1-4-3
What is the dental formula in humans?
2-1-2-3
Which adaptations allowed Mesozoic mammals to survive the extinctions of the Cretaceous and radiate?
hair and fat provide insulation
Describe the prototheria
‘one opening’
Reptilian characteristics:
Egg laying (egg is reptilian in structure)
Cloaca
Mammalian characteristics:
Hair
Mammaries
What are the 2 forms of prototheria?
Platypus
Echidna - spiny anteater
Describe the platypus
aquatic life
Webbed feet, thick fur, no ears
Bill for feeding on invertebrates (convergent evolution)
Find prey using electric pulses
Describe the echidna
Long snout
Sticky tongue
Heavy claws
Describe the metatheria
Egg contains yolk, shell membrane
Embryo nourishes mostly by yolk then placenta later on
Short gestation, young altricial <1% mother weight
Young are completely dependent on mother for 1st month
Young have strong forelimbs and claws, climb into marsupium (pouch) where mammaries are located
E.g Koalas, Virginia Opossum, Red Kangaroo
Which clade do marsupials belong to?
Metatheria
Which clade do placental mammals belong to?
Eutheria
Describe the Eutheria
al mammals - Eutheria
Complete development in uterus
Most extant orders originated 50-70 mya
Phylogenetic relationships between orders are difficult to resolve as they radiated rapidly
What are the 4 major lineages in the Eutheria?
Afrotheria e.g elephants
Xenarthra e.g sloths
Laurasiatheria e.g moles, bats, cats
Euarchontoglires e.g rabbits, mice
Give some examples of species that belong to afrotheria
Elephants
Manatees and dugongs
Give some examples of species belonging to xenarthra
Sloths, anteaters, armadillos
- have reduced or no teeth
Give some orders belonging to laurasiatheria
Insectivores - moles, shrews, hedgehogs
Bats
Carnivores - cats, dogs, seals
Cetaceans - whales, dophins
Artiodactyles - sheep, pigs, deer
Perissodactyls - horses, rhinos
Which order is considered the most primitive of the Laurasiatheria
Insectivores
Describe carnivores specialised dentition
Specialised for piercing (incisors) and slicing (carnassial pair)
Describe the artiodacytes
sheep, pigs, deer
Even toed ungulates
Bunodont or selenodont teeth
Elaborate ruminant stomach to digest cellulose (e.g cows chew twice)
Weaponry evolved in many
- Tusks
- Antlers
- Horns
Describe the Perissodactyls
horses, rhinos
Odd toed ungulates
Lophodont grinding molars and incisors for cropping vegetation
Simple single stomach
Which orders belong to Euarchontoglires?
Lagomorphs
Rodents
Describe the lagomorphs
Rabbits, hares
2 pairs of rootless incisors
Rootless molars, high crowned (hypsodont)
Describe the rodents
Most specious mammals
Rootless incisors, hypsodont molars
Most pass food twice (caecotrophy)
