#4: Mammals

Question 1

Fossil record for mammals

Answer 1

very complete

Beginning of Tertiary, 70 MYA started age of mammals, coinciding with the extinction of many reptiles.

Question 2

Synapsid branch

Answer 2

Amniotes diverged 320 MYA during carboniferous era.

Question 3

Synapsid skull

Answer 3

Possesses:

1.one lateral temporal opening allowing for advanced muscles for diverse diets

Question 4

What is nature of evolutionary lineages

Answer 4

IT branches; not linear

Question 5

The KT boundary

Answer 5

divide between Cretacious & Tertiary eras wherein the former dinosaurs die out and mammals started to thrive

Question 6

Characteristics of ancient mammalian ancestors

Answer 6

1. more vertical limbs than reptiles
2. possess a synapsid skull vs diapsid skull in reptiles
3. seperation of moracic and abdominal cavity
4. possession of mammary gland
5. probably ectothermic
6. oviparous
7. no fur

Question 7

Characteristics of typical mammal

Answer 7

1. endothermic
2. fur
3. vivaparity (nourishes the embryo inside the body)

Question 8

Characteristics of therapsids

Answer 8

1. hindlimbs directly beneath the body, moved parellel to long axis
2. seperation of trunk into thoracic and abdominal regions
3. Breathing mechanisms similar to mammals
4. most became extinct; only few cynodont therapsids survived

Question 9

First true mammals

Answer 9

Jurassic era

mostly nocturnal

Question 10

Later cynodonts

Answer 10

smaller
mammal-like with hair and endothermy
specialized teeth
changes in middle ear/brain improved hearing/olfaction

Question 11

Additional characteristics of mammals

Answer 11

1. mammary glands
2. sweat, sebacaceaous, scent glands (all epidermal in origin)
3. diaphragm
4. three middle ear ossicles
5. Four-chambered heart
6. large cerebral cortex

Question 12

Subclass: Protheria

Answer 12

Monotremes
Oviparous, w/ cloaca present
ie duck-billed platypus, spiny anteater
Only mammals that lay eggs

Question 13

Subclass: Theria consists of what two infraclasses?

Answer 13

Metatheria & Eutheria

Question 14

Infraclass: Metatheria

Answer 14

Characteristics:
Marsupials
1. Viviparous w/ short gestation period; young often premature
2. marsupium (protective pouch) covers mammary glands; young feed & complete development inside it
3. ie opposums, kangaroos, koalas, wombats

Question 15

Infraclass: Eutheria

Answer 15

Characteristics:

1. Placental mammals.
2. Born at advanced stage of development after nourishment in uterus
3. Placenta: structure thru which maternal and fetal circulatory systems exchange nutrients & wastes thru diffusion
4. Elephants, manataees, anteaters, shrews, bats, otters, horses, giraffes, whales, rabbits, lemmings, monkeys

Question 16

External structure of mammals

Answer 16

1. Skin: epidermis & dermis; protects, regulates temp, helps in sensory perception, excretion
2. Hair is keratinized derivative of epidermis; composed of dead cell and periodically molts. Aid in sense of touch; may be modifed into vibrissae (whiskers); traps air, provides insulation
3. Sebaceous glands of hair follicles lubricate, waterproof skin. Sweat glands release water for cooling and salt excretion
4. Scent glands: secrete pheromones for territorial behavior
5. Mammary glands: milk in females

Question 17

Skull and teeth

Answer 17

1. One bone of lower jaws allows jaws to close together.
2. Secondary palate separates nasal & oral passages; allows breathing while chewing
3. Specialized teeth for different functions and diet (heterodont); reptilian teeth uniformly conical (homodont)
4. Milk teeth develop into permanent teeth
   5.

Question 18

adult mammals teeth

Answer 18

4 kinds: 
1. anterior incisors for gnawing
2. canines for tearing
3&4. premolars, molars for chewing
Mammalian species have characteristic numbers of each, described by dental formula

Question 19

Nutrition and Digestion

Answer 19

classified into:

Carnivores (fox), omnivores, insectivores (mouse), herbivores

Question 20

Ruminant Herbivores

Answer 20

Enlarged cecum (pouch w/ microorganisms) for digesting cellulose
Ruminants possess extra stomach before actual stomach, used to ferment plant-based matter prior to digestion (ie deer)

Question 21

Non-ruminant herbivore

Answer 21

Simple stomach, large cecum

ie rabbit

Question 22

carnivore

Answer 22

Short intestine & colon, small cecum ie fox

Question 23

insectivore

Answer 23

shore intestine, no cecum ie common shrew

Question 24

Circulation, gas exxchange

Answer 24

1. Four chambered hearts with seperate pulmonary & systemic circuits
2. Placenta allows diffusion of nutrients, gases and wastes bet fetal & maternal blood supplies w/out mixing
3. Seperation of nasal & oral cavities & long snouts: increased surface area for efficient gas exchange
4. inspiration & expiration occur by expanding & contracting volume of thoracic cavity using a muscular diaphragm

Question 25

Temperature regulation

Answer 25

1. Heat production by shivering thermogenesis (muscle activity w/ little movement & non-shivering thermogenesis (metabolism). 2. Changing peripheral blood flow 3. insulation 4. countercurrent heat exchange systems (hands and feet) 5. Controlled hypothermia (ie hibernation where hypothalamus slows down the metabolic, heart and respiratory rates. 6. Evaporative cooling from sweat glands or respiratory surface.

Question 26

Excretion and Osmoregulation

Answer 26

1. excrete urea (water soluble, cannot be excreted in semi-solid form like uric acid) so leads to some H2O loss 2. Water also lost thru sweat glands and respiratory surfaces 3. Kidneys reabsorb H2O, produce concentrated urine 4. Several behavioral & physiological mechanisms to reduce water loss. Low protein diets reduce urea production; metabolic oxidation of carbs makes H2O

Question 27

Reproduction & development

Answer 27

1. Highly developed viviparity. Allows females to roam but expends > energy. 2. Most females undergo estrus cycle when sexually receptive; mediated by hormonal changes that stimulate maturation and release of ova. Uterus also changes to prepare for receiving developing embryos. 3. Monestrus: bears; diestrus (domestic dogs); polyestrus (rats)

Question 28

Monotremes

Answer 28

1. oviparous 2. nourishment through yolk 3. ie platypus

Question 29

Marsupials

Answer 29

1. nourish come from uterine milk (a primitive placenta) 2. short gestation period, long lactation period 3. ie kangaroo

Question 30

Eutherians

Answer 30

1. embryo implanted into uterine wall 2. nourished thru placenta 3. ie human

Question 31

Primates

Answer 31

1. Late Cretaceous Era, 65 MYA 2. Insectivores were probable ancestors 3. Arboreal, diurnal habits favored color vision 4. Eyes on front of head, providing overlapping view, depth perception 5. Center of gravity shift to hind limbs 6. sensitive foot and hand pads for exploration 7. Medial digits of hands opposable to allow grasping.

Question 32

Suborders of primates

Answer 32

1. Lemurs & bush babies | 2. Tarsiers, New & old world monkeys, gibbons, apes (gorilla, chimpanzee, orangutan, humans)

Question 33

Evolution of hominins

Answer 33

1. First apes 25 MYA 2. 5-7 MYA, Hominids diverged from other apes when African apes became terrestrial, and upright posture provided better view and freed the hands. 3. Bipedal locomotion w/ changes in skeleton and skull (ie curved vertebral column, shorter pelvis, reduction in size of jaws, teeth, etc.)

Question 34

First Hominid: Australopithecus (Lucy) 4 MYA

Answer 34

show pelvis and leg structure typical of bipedalism

Question 35

Six Homo species, starting to appear 2.5 MYA

Answer 35

Homo sapiens, arising in Africa 195K years ago.