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Mammals Flashcards

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1
Q

Evolution of mammals within synapsids

A
  1. Pelycosaur (first tetrapods in terrestrial habitats that were widely spread)
  2. Derived pelycosaur
  3. Therapsids
  4. Cynodont (derived therapsids)
  5. Mammal
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2
Q

When did mammals appear

A

During the very end of the Triassic and probably descended from cynodonts

Early mammals appeared around 205 mega around the same time as dinosaurs

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3
Q

Synapsid trends

A

-gradual and coordinated modification of trains that reflect increased energy intake and expenditure (increased metabolic rate)

-axial and appendicular skeletons
-skull, jaw and teeth

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4
Q

Pelycosaurs

A

-resemble reptiles
-sprawling limb posture
-lumbar ribs
-long, heavy tails m-fine shaped teeth

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5
Q

Therapsids include what

A

Include basal forms and derived forms called cynodonts

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6
Q

Changes in the skeleton when we compare the therapsids with pelycosaurs

A
  1. Limbs becoming longer, more slender and increasing held under the body
    -more erectile stance
    -loss of lumbar ribs (cynodont)
    -increased Dorso-ventral flexion
    -reduced tail (cynodont)
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7
Q

Why is losing the lumbar ribs so important

A

Mammals developed a diaphragm which suggests an increased metabolism and respiratory rate

Absence of ribs would give the animal the ability to flex in the dorsal-ventral direction

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8
Q

Changes in the skull, jaw and teeth from pelycosaur to therapsids

A

-larger dentary, other jaw bones reduced
-increased heterodonty
-multi-cussed teeth (cynodonts)
-secondary palate (cynodonts)
-nasal turbinate bones (cynodonts) that increase surface area inside the nose.

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9
Q

Further Modifications from cynodonts to early mammals

A

-Two bones of mandible (articular and Quadrate) shrank and separated to become part of the middle ear-malleus and incus)
-dentary-squamosal jaw joint now used
-molars with cusps (chewing surface)
-diphyodont teeth (two sets): indicates suckling -two sets of teeth over lifetime

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10
Q

Traits of early mammals

A

-higher metabolic rates
-oviparous
-probably endothermic with film coat of hair
-mammary glands

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11
Q

Were mammals small during dinosaur times

A

Not just small; shrew-like animals that creeped in shadows of dinosaurs.
-were diverse forms from terrestrial carnivores to aquatic mammals to squirrels like gliders.

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12
Q

Monotremes

A

Mammals that still lay eggs

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13
Q

Mesozoic mammals

A
  1. Earliest mammal is called Morganucodon-small, nocturnal, insect/eating mammal
  2. Monotremes
  3. Multituberculates
  4. Therians
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14
Q

Multituberculates
Characteristics

A

-flourished in Cretaceous
-survived and recovered after KPg
-extinct 34 mya

-rodent like
-filled similar niches: burrowing, grazing and arboreal
-first grass eating mainly

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15
Q

Therian animals

When did they expand

A

Includes marsupials mammals (metatherians) and placental mammals (eutherians)

-expanded after KPg extinction

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16
Q

Are monotremes and marsupials related?

A

Not closely

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17
Q

The therian mammals includes _____ and _____

A

Placental
Marsupial

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18
Q

Monotremes
-oldest fossil
-where do current species live

A

Jurassic from Australia

Australia, new guinea, Tasmania

Includes platypus and 2 echidna

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19
Q

Monotremes reproduction

-Traits shared with reptiles
-traits shared with other males

A

-true cloaca
-long, filiform sperm
-oviparous: 10-11 day inculcation, artificial young

-lactation (4-7 months): mammary glands
-hair (fur)

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20
Q

Weird trait of monotremes

A

-Electroreception to find prey (on beak)

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21
Q

Marsupials make up what percent of worlds mammals?

Where do they live?

A

6%

Australia/ Tasmanian/ N and S America

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22
Q

Evolutionary history and dispersal of marsupials

A
  1. NH origin: diverged from placentals 175mya
  2. N. America to South America (60-80mya)
  3. South American-> Antarctica-> Australia (55mya)
  4. Modern lineages appeared in Australia 20-40 mya
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23
Q

Marsupial traits compared to placentals

A

-lower Basal metabolic rate at 35.5° vs 36-38°
-50% have marsupium (pouch)
-limited range in body size (2g to 66kg)
-difference in placenta, gestation and length of lactation

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24
Q

Placenta

A

Temporary organ formed by the interaction of embryonic and maternal structures

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25
Difference in placental and marsupial mammals extra-embryonic membranes
Parts of extra-embryonic membranes interact with maternal structures to form a temporary organ called a placenta. Placenta of marsupials: -Choriovitelline placenta: enlarged yolks sac fused with chorion. Weak attachment to uterine wall. Blastocyst does not sink deep into endometrium, no villi Placenta of placental mammals: -Chorioallantoic placenta: all placentals and few marsupials have it. Blastocyst sinks deeply into endometrium, placenta developed from chorion and Allantois membranes, chorionic villi project into endometrium to increase surface are for gas exchange.
26
Chorioallantoic placenta function
1. Nutrient and gas exchange -maternal and fetal circulation are in close contact but not fused: substances move between them larger by diffusion -maternal blood provided O2 and nutrients and removed CO2 and waste from infants blood 2. Produces substances to suppress maternal rejection 3. Produced hormones to support pregnancy 4. Fetus spends longer in uterus and is more developed at birth
27
Incubation, gestation and lactation of marsupials and placentals
Marsupials: -brief gestation (weeks) -highly altricial young -long lactation Placentals: -long gestation (varies based on body mass) -short lactation -developed today young at birth: altricial in rodents and carnivores, precocial in ungulates
28
Of marsupials and placentals, who spends more overall time (gestation and lactation) with dependent offspring
Marsupials Invest little into gestation, but more into lactation
29
Reproductive timing usual order of events
Estrous Ovulation Mating Fertilization Implantation of blastocyst Development of embryo Parturition (birth)
30
induced ovulation
The act of mating induced ovulation Common in rabbits, Felids, camels and rodents
31
Bat reproductive timing strategies
Sperm storage before ovulation Delayed development after implantation
32
Delayed implantation
Development of blastocyst stops after fertilization and waits to be implanted. In bears, weasels, seals, insect eaters, rodents and kangaroos
33
Delayed implantation reasons
Obligate: synchronize birth with seasonal cycle Facultative: food availability
34
Integument and derivatives function
Protective layer between animals and environment: repels heat, water, physical attack, microorganisms, conserves heat and moisture Unique mammalian derivatives of epidermis serve different functions: insulation, communication, locomotion, nourishment (mammary glands)
35
Types of glands
Sebaceous glands -most associated with hair follicles -secrete sebum (oil) that helps to keep skin and hair moist and waterproof Sweat glands -secrete water for cooling -secrete moisture on palms of feet for traction Scent glands -modified sebaceous or sweat glands
36
Scent gland purpose
Used to mark territory Males use it to attract females Males use it to destroy competing males Deter enemies
37
Mammary glands
Specialized epidermal glands -functional only in females -number and location of glands vary -protein and fat content varies by species and with age of infant
38
Hair-epidermal derivative keratin Types
Palage: overall coat -guard hair -underfur: soft and heat trapping -molt: juvenile or annual Modified guard hairs -vibrissae -quills -spines
39
Horns and antlers
Only found in ungulates (hooves animals) -True horns in sheep and goats have an inner core of dermal bone and a keratin sheath. They grow continually and produce a single horn -Antlers found in cervidae (deer family) shed annually, thin layer of epidermal velvet covers growing dermal bone, branched
40
Claws, nails and hooves are derived from what
Epidermis Keratin
41
Claws
Cover dorsal and part of ventral side of digit. Shared with reptiles and birds
42
Nails
Only on dorsal surface, accompanied by increase in nerve endings at tip of digits. Mostly in primates
43
Hooves
In ungulates Point of contact with ground
44
Modifications for running lifestyle
-Increased limb length to increase stride length -elongation of distal limb segments -change in foot posture
45
Plantigrade Digitigrade Ungulates
Plant heel and palms on the ground as they walk Plant their phalanges on the ground and raise the heel and metatarsals off the ground Stand on their toes or hood
46
Jumping lifestyle body modifications
-centre of gravity shifts posterior -long hind limbs, feet -larger tail for balance -kangaroos, rabbits, jumping rodent
47
Arboreal lifestyle body modifications
Tree climbing mammals grip the tree with claws or with sensitive digits Often have long tails for balance Wide range of movement in their limbs and feet
48
Gliding life style modifications
Skin membrane called patagium Not powered flight. They glide down from higher up
49
Among mammals, only ____ have powered flight
Bats Elongated fore arm and phalanges Thin sheet of skin (patagium)
50
Fossorial or burrowing life style body modifications Subterranean mammals
-short, strong limbs -long claws -tubular body form -some use teeth to dig (large incisors) -poor sight -well developed hearing -vibrissae (tactile receptors)
51
Star nose mole adaptations
- 22 fleshy appendages with 25000 Eimers organs: sensory receptors used to explore environment and find prey. -bubble bowling behaviour to sleep when under water
52
Swimming lifestyle types
Amphibious: use terrestrial and aquatic Semi-amphibious: most of the time in the water but use land to mate Fully aquatic: never move to land
53
Whale evolution
Animal that resembles deer!!! Hind limbs lost Forelimbs became flippers Tail fluke Nostrils posterior and dorsal Ear modified to localize sound Loss of hair Echolocation Baleen
54
Modern whales
1. Toothed whales (Odontoceti) -pursuit predators -echolocation -dolphins, beluga, narwhal, spermatids whale 2. Baleen whales (Mysticeti) -filter-feeders -blue, grey, humpback
55
Homodont teeth Heterodont
Most fishes and reptiles All the teeth are the same Mammals and whales (secondarily heterodont) Teeth are varied
56
Carnassial teeth
Last premolar of upper jaw and first molar on bottom jaw Used to shear meat
57
Herbivores dentition, muscle and gut
-incisors to clip vegetation -cusps modified into grinding ridges (cheek teeth) -diastema between incisors and cheek teeth Large masseter muscles for side to side chewing Complex digestive system and long intestinal tract Fermentation chamber with microbes to digest cellulose (in stomach, colon or cecum)
58
Gnawing herbivores
Rodents, rabbits and some marsupials Same adaptation as other herbivores but with ever-growing incisors
59
Carnivores dentition, muscles and gut
-Large canines (seize prey) -shearing teeth (carnassial) Large temporalis rise to seize prey and hold jaws closed Short intestine with a small or no cecum (food digests rapidly)
60
Convergence of carnassial teeth
The Tasmanian devil, a marsupial predator also had molars modified to shear prey
61
Insect eaters dentition, and gut
Numerous sharp teeth to pierce and crush insects Short intestine, no cecum
62
Digestive tracts of two types of herbivores
Non/ruminant- use their Colons and cecums as fermentation chambers Ruminant-special stomach chambers for fermentation
63
Mammal brains: Expansion of _______
Neocortex (cerebral cortex) = six layers of gray matter that cover the cerebrum Specific regions correspond to function
64
Bird vs mammals brains
Different but equivalent parts of brain integrate information Mammals: cerebral cortex Birds: pallium
65
Olfaction in mammals
-Chemoreception occurs as air passes over olfactory receptors in epithelium in nasal passages -complex nasal turbinates in many mammals increase surface area for olfactory epithelium -increased number of olfactory genes compared with other vertebrates
66
Flehmen testing and vomeronasal organ
Flehmen or lip curl testing is done in breeding season by male ungulates to pick up a females urine and expose it to the vomeronasal organ. This is done to assess whether a female is in estrous or not.
67
Hearing in mammals
Pinna: external ear -focuses sound on tympanic membrane (ear drum) -assists in locating sound -pinnae lost in some groups (whales)
68
Vision in mammals
-colour vision well-developed in other vertebrates (birds, fishes, reptiles) -capacity to perceive colour probably reduced in early mammals due to more nocturnal lifestyle
69
Nocturnal vision
1. Rod cells - sensitive to wide range of wavelengths of light. Results in large number of rod cells that are sensitive to low light levels but do not provide much visual acuity. 2. Tapetum lucidum-mirror reflects back image onto retina 3. Large curved lens
70
Colour vision in mammals
Monochromatic Dichromatic: most mammals, 2 cone cells types Trichromatic: 3 cones, primates, some marsupials, humans
71
Tactile mammals
Sensitive digits (primates, raccoons) Vibrissae (whiskers) Eimers organs (star-nosed mole)
72
What is a primate?
1. Arboreal: grasping extremities, sensitive digits, nails, improved vision 2. Large brain 3. Monkeys and apes have acute daylight Vision: trichromatic 5. Eat fruit, seeds and foliage 6. Slow reproduction: increased parental care, delayed sexual maturity, one infant/cycle, long life span
73
Habitat of most primates
Mostly tropics Exception: snow monkey and humans
74
Two lineages of primates
Haplorrhine Strepsirrhine
75
Haplorrhine characteristics
Simple or dry nosed -tarsiers, monkeys and apes -almost all diurnal except tarsier and night monkey -most are highly social
76
Strepsirrhine characteristics
Wet nosed -lemurs, lorises, galagos -longer rostrum with wet “doggy” nose -smaller brain -most nocturnal -some solitary
77
New world monkeys
Platyrrhini Monkeys living in central and South America
78
Prehensile tails
Monkeys that can hang from their tail Only south and Central American monkeys
79
Old world monkeys
Asian and African monkeys (Catarrhini) Terrestrial and arboreal forms Apes, orangutan, gorilla, chimps and humans Single young, long lactation (2-4 years), delayed maturity All endangered except humans
80
Humans (Hominins): Genus Homo
-Bipedal -Larger brains -Reduced Sexual Dimorphism -Multi-male, Multi-female communities -Extent of culture differs form apes (use of tools, language)
81
Significant events in Human Evolution
6.6 mya-last shared common ancestor with chimpanzees 3.7-3.0 mya- Australopithecus 2.4-2Mya-Genus Homo appeared in Africa with larger brains than other early humans 3mya - 25,000 ya- different honk in species lived at the same time, including members of Genus homo and Australopithecus
82
Homo sapien time frame
Modern humans 200,000-100,000 ya: living in Africa Reached max brain size 100,000 years ago, increased cultural artifacts (50,000ya) Other homo spp. went extinct by 25,000 ya
83
Pleistocene extinctions
13,000-8000ya Mostly affected large mammals (>10kg) Wooly mammoth, saver-toothed cats, camels, wooly rhinos, giant ground sloths Caused by human migration leading to over killing and or climate change

Vertebrates (7 decks)

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