Lecture Test 2 Flashcards
How old is our planet estimated to be?
Around 4.5 billion years old
From which subclass did mammals arise?
Synapsida
Approximately how many years ago did synapsids first appear?
About 320 million years ago
What subclass led to turtles and has no holes in the skull?
Anapsids
Pleasaurs are extinct marine reptiles are part of the which subclass?
Uriapsids
Which subclass led to lizards and snakes and has two holes in the skull?
Diapsids
What structural feature of skulls is used to classify these subclasses?
Holes in the skull for muscle attachment
What are the two different orders into which Synapsida split?
- Pelycosauria
- Therapsida
What characteristics define Pelycosauria?
- More primitive
- Smaller temporal opening
- Reptilian-like teeth
- Homodent dentition
- Multiple bones in jaw
- Smaller dentary
What defines Therapsida?
- Advanced mammal-like reptiles
- Large temporal opening
- Differentiated teeth
- Much larger dentary
Which group within Therapsida technically gave rise to mammals?
Cynodontia
In the 140 million years from the late Paleozoic to the early Mesozoic what were the changes seen in fossil records that indicated a shift to becoming mammals
• Enlargement of the temporal opening
• Transition from 1 occipital condyle to 2
•Maxillary and palatine bones extend posteriorly and medially
•Dentition becomes heterodont
• Dentary bone become larger other bones reduced
• Ribs are reduced
•Limbs move under body
•Reduction in carpal and tarsal bones
Underlaying themes to these changes are improving ability to process food and increase mobility
What is the significance of the enlargement of the temporal opening in early mammals?
Greater muscle attachment for chewing
This adaptation facilitated more efficient food processing.
How did the transition from one to two occipital condyles affect early mammals?
Allowed for more precise movement
This change improved head mobility.
What structural change occurs in the maxillary and palatine bones of early mammals?
They extend posteriorly and medially
This separates the nasal cavity from the oral cavity, aiding in simultaneous chewing and breathing.
What does heterodont dentition indicate about early mammals?
A wider range of specialized food
This adaptation allows for more diverse diets.
What happens to the dentary bone in early mammals?
It becomes larger while other bones are reduced
This change contributes to a stronger jaw structure.
What is the effect of reduced ribs in early mammals?
Increased flexibility of movement
This adaptation enhances agility and mobility.
How does moving the limbs under the body benefit early mammals?
Reduces energy demand for movement and increases stamina
This change supports more efficient locomotion.
What change occurs in the number of carpal and tarsal bones in early mammals?
Reduction from 2, 3, 4, 5, 3 to 2, 3, 3, 3, 3
This reduction increases dexterity in limb movement.
Why do they need more food?
They had to become nocturnal to avoid becoming prey, they are starting to evolve endothermy which is calorically expensive, and other physiological changes are assumed to be happening but are not preserved in fossil records.
Physiological changes include metabolism, lactation, endothermy, and reproduction.
When do you say they became mammals?
Currently considered Monophylic Monotremes included.
Monophyly refers to a group of organisms that share a common ancestor.
How small were the smallest dinosaurs compared to mammals?
The smallest dinosaurs were 10 times the size of mammals at the time.
This highlights the significant size difference between early mammals and small dinosaurs.
What were the three feeding guilds of early mammals?
- Multituberculates - herbivores
- Triconodants - carnivores
- Pantotheres - omnivores
These groups are determined by jaw structure and teeth.
What hypothesis did Jeff Lang propose about dinosaur extinction?
Dinosaurs went extinct because an asteroid altered temperatures, resulting in all eggs becoming one sex except those that buried eggs, which allowed mammals to become dominant.
This hypothesis suggests environmental changes directly influenced reproductive success.
What percentage of calories go towards keeping endotherms warm?
95%
What are the two mechanisms to determine diet by skull?
- Where your jaw articulates vs where your occlusal surface
- Tooth structure: hypsodont, bunodont, etc.
What does ‘form follows function’ imply in the context of tooth structure?
Tooth structure is adapted to the dietary habits of the animal.
What is the base locomotion pattern for mammals known as?
Ambulatory (Plantigrade)
Which animals are examples of ambulatory locomotion?
- Bears
- Opossums
- Shrews
- Mice
What are the characteristics of ambulatory animals?
- Pentadactyl
- Metacarpals and metatarsals are not fused
- Ankles and wrist permit movement in several planes
What does cursorial refer to in terms of locomotion?
Running
Which animal is known as the fastest cursorial animal?
Pronghorn antelope or cheetah
What are the themes associated with cursorial locomotion?
- Increase mobility and length of stride
- Generally restricted to larger terrestrial species
- Typically ungulates and carnivores
- Distal joints to the pelvic and pectoral girdle are restricted to movement in a single plane
- Musculature in legs reduced
- Reduction or complete loss of clavicle
What is the formula for speed in relation to strides?
Speed = number of strides / time x length of stride
How does the cheetah increase its top speed?
By not having a clavicle and being able to arch its back, increasing top speed by 6 miles an hour.
Which muscles are more powerful in a cheetah?
Back muscles are more powerful than leg muscles.
What does ‘cursorial digitigrade’ refer to?
Walking on toes, examples include dogs and cats.
What characterizes ‘cursorial unguligrade’ locomotion?
Walking on toes with a hoof, fused cannon bone, and spring ligament.
What is the function of the spring ligament in cursorial unguligrade animals?
Acts like a rubber band to provide more energy.
What are the three characteristics of jumping in animals?
- Hind legs are generally elongated and more muscular than front legs
- Stocky appearance with center of gravity shifted posteriorly
- Many have a longer tail for balance.
What is ‘saltatorial jumping’?
Jumping on all fours, examples include rabbits and jumping mice.
What is ‘ricochetal jumping’?
Jumping using only the hind feet, example includes kangaroos.
What anatomical feature aids kangaroos in ricochetal jumping?
Convergence of the spring ligament.
What does the term ‘amphibious’ refer to?
Spending equal amounts of time on land and in water
Examples include beavers and muskrats.
List two characteristics of amphibious animals.
- Increase in the thickness and quality of hair which water cannot penetrate
- Tail modified to aid in propulsion
What is fimbriation in relation to amphibious animals?
A stiff fringe of hair between toes in some animals such as water shrews
This adaptation aids in swimming.
What does ‘aquatic’ mean?
Spends most time in water but only comes to land to reproduce
Examples include walrus and seals.
Define ‘Pinnipedia’.
Marine mammals
This group includes seals, sea lions, and walruses.
List three characteristics of aquatic animals.
- Body mass is mostly interior
- Tail reduced or absent
- Bony elements of their hands or feet are supported in a paddle-like fin or flipper
Marine
Never leave water examples whales, dolphins, manatees
What are marine adaptations
• Nostrils on dorsal portion of skull
• Nostrils can close with valves
• Skull is telescoped - parts of skull compact and parts streched out
• Body form is fusiform in shape to reduce drag or increasing laminar flow - the smoothness of the movement of water over a surface
• Hairless (with very little hair- whiskers)
• Skeleton greatly modified
• posterior appendages are gone
• tail moditied, fluke for propulsion
• forelimbs stablization and steering
Fossorial
Underground example moles
Fossorial adaptations:
• body tends to be fusiform in shape
• legs tend to be short
• pectoral girdle (large) greatly modified for digging
Moles can 36 times ther body weight
• Strong front limbs
• Fur has no nape
• Auditory and visual senses vestigial or absent
• Olfactory and tactile senses increased
• Vibrisae on tails and butt (moles)
laminar flow
the smoothness of the movement of water over a surface
What is the definition of graviportal?
Dictated by weight, with legs like pillars
Examples include elephants and hippos.
What are two characteristics of graviportal animals?
- Ulna and radius as well as tibia and fibula same size
- Fiberous disc under toes acts as a cushion to reduce pressure
What does arboreal refer to?
Spending most of the time in trees, two examples sloths and squirrels
Arboreal sloths characteristics
• spend the majority of their time upside down
• shoulder girdle strong
• Number of ribs increased to support internal organs
• Additional vertebrae totaling 9 more flexible neck
• senses greatly reduced
What are 3 key features of squirrels (Arboreal)?
- Elongated body
- Sharp and well-developed claws
- senses well-developed
Brachiation (Arboreal specialization)
example gibbons
• Arm over arm, branch to branch swinging
• Pollex is not well developed better for hooking branches
• Well-developed friction pads
• Senses well-developed
• binocular vision
Gliding (Arboreal specialization)
• developed flaps of skin which increase surface area
• tails flattened
Flying (Arboreal specialization)
•Fight is enhanced for both slow flight and maneuverability
• Wing extension of the skin
• Thrust offset drag (fingers of bats)
• Lift created by inner part of wrist/arm
What is Bernoulli’s principle and how does it aids in flight
with increased velocity equals decreased pressure
Shape of wing cause the air flowing over wing increases speed results in decrease in pressure while the air flowing under the wing has high pressure causing it to lift up
What is aspect ratio?
Length to width of a wing
Length creates speed and thrust while the width creates the lift
What does wing loading refer to?
Weight of body on wing
What adaptions or ways do bats have/do to aid with flight
Bats have flaps like airplanes by changing shape of wings by rolling wrist or ankles to change the aspect ratio.
Bats have keeled sternum for greater muscle attachment
Bats dont have hollow bones like birds because of enucleated erythrocytes and need bone marrow so they have thin bones
Every mammal starts life on mothers milk after that there are various strategies called
Feeding guilds:
a diet of plant material
Herbivorous - example ungulates
eats just foliage/ leaves
Folivorous - example some sloths and primates
eating fruit
Frugivorous - example fruit bats
grain/seed eating
Granivorous - example Kangaroo rats
nectar eating
Nectivorous - example some bats
diet of colonial insects such as ants and termites
Myrmecophagous
diet of meat from vertebrates
Carnivorous
both plant and meat eating
Omnivorous
diet of hardshell chitinous animals usually invertebrates
Durophagus - example grasshopper mouse
insect eating
Insectivorous -
fish eating
Piscivorous -
diet of blood
Sanguinivorous - 3 vampire bats
Describe the process of digestion and the different structures of the digestive tact in order
First step of processing food is mastication where breakdown food
Digestion - chemical breakdown of food
pyloric sphincter - valve at end of stomach
small intestine - aborbs nutrients, 20ft in humans
Appendix - Cecum in herbivores the site of microbial fermentation
Large intestine - water absorbtion, 6ft in humans
What is the only animal that can digest plant material cellulose with cellulase?
Silver fish
What type of organisms do herbivores have a symbiotic relationship with to break down plant material?
Protists and bacteria
What are the two forms of herbivores’ symbiotic relationships?
- Foregut fermenters
- Hindgut fermenters
What characterizes foregut fermenters?
Stomach is highly modified and becomes the site of fermentation
What characterizes hindgut fermenters?
Fermentation process happens after absorption in the cecum
Coprophagy is common in hindgut fermenters
What is coprophagy?
Eating their own feces to absorb the fermented material
Which animal is an example of a hindgut fermenter that participates in coprophagy?
Rabbits
How many chambers do foregut fermenters like cows typically have?
4 chambers
True or False: Foregut fermenters are less efficient than hindgut fermenters.
False
Fill in the blank: Foregut fermenters can be more efficient and eat _______ than hindgut fermenters.
less
What is the digestive system characteristic of insectivores?
Has short intestine and no cecum
Insectivores primarily consume insects and have adapted their digestive systems accordingly.
What are the main features of a carnivore’s digestive system?
Short intestine and colon, small cecum
Carnivores are adapted for a meat-based diet, which requires efficient digestion.
What is the digestive system structure of nonruminant herbivores?
Simple stomach, large cecum
Nonruminant herbivores typically consume plant materials that require different digestive processes.
Describe the ruminant herbivore digestive system.
4-chambered stomach with large cecum, long small and large intestine
Ruminants are specialized to digest fibrous plant material through fermentation.
What does the term ‘Artiodactyla’ refer to?
Even-toed ungulates, foregut fermenters
This order includes animals like cows, pigs, and deer.
What is ‘cud’?
Plant material already swallowed and digested
Cud is regurgitated by ruminants for further chewing.
What is the process of ruminating?
Chewing cud to increase its surface area
This process aids in the digestion of fibrous plant material.
List the groups of Artiodactyla.
- Non-Ruminating with 3 chambered stomach (Includes hogs and hippos)
- Ruminating with 3 chambered stomach (Includes camels, mouse deer)
- Ruminating with 4 chambered stomach (Includes giraffes, antelope, deer, cow, goats, sheep)
These groups are categorized based on their digestive system structures.
What are the four chambers of a cow’s stomach?
- Rumen
- Reticulum
- Omasum
- Abomasum
These chambers work together to digest food in ruminants.
Which is the biggest chamber of a cow’s stomach?
Rumen
The rumen can hold up to 35 gallons in cows.
What is the function of the reticulum in a cow’s stomach?
Wringing out liquid
The reticulum helps separate solids from liquids.
What is the primary function of the omasum?
Absorbing and holding area
The omasum plays a key role in the absorption of nutrients.
What begins in the abomasum?
digestive enzymes start digestion material which includes the products the microorganism are producing
What are the three products produced by microorganisms in the rumen?
- FFA (free fatty acids)
- Nitrogen
- Vitamins
These products are beneficial for the animal’s nutrition.
How many bacteria are typically found in 1 gram of content in the rumen?
50 billion bacteria
How many protists are found in 1 gram of content in the rumen?
1/2 million protists
What is the special adaptation in calves?
Esophageal groove - when head is lifted up it by passes the first 3 fermentation chambers and goes straight into the abomasum to start digestion
What is the definition of oviparous?
Oviparous refers to animals, like monotremes, that use yolk for nutrition.
What does viviparous mean?
Viviparous refers to most mammals where the fetus gets nutrition from placental attachment, not yolk.
Define ovoviviparous.
Ovoviviparous animals have fetuses that get nutrition from yolk in an egg but hatch in the female’s body, resulting in live birth.
What are the significant benefits of viviparous reproduction?
High fetal survival rates and often extended postpartum care.
Describe R-selected species.
R-selected species exhibit low parental care, examples include rodents and rabbits.
What characterizes K-selected species?
K-selected species provide parental care, including humans and mammals as a group.
What are the reproductive characteristics of marsupials?
• Females reproductive tract has got 2 canals, and there is not a single vaginal opening. There are 2.
• In some cases they have 2 cervix and a separate uteruses and can have offspring in the right uterus growing at a differental rate than the one in the left uterus
• Gestation period is short 1-7 weeks max but generally 1-4 weeks
• Dynamic Alternative
• Long lactation period.
• Can have 3 offspring in different stages at one time
• typically have chorizo-vitelline placental attachment
Fill in the blank: Marsupials typically have _______ placental attachment.
chorio-vitelline
What is the most important and distinctive feature of Therian reproduction?
The placenta is probably the most important and distinctive feature of Therian reproduction although technique not unique to Therian reproduction.
List the four functions of the placenta.
- Anchor the fetus to the uterus
- Provides nutrients and excretes waste (metabolic)
- Bring in oxygen and expels CO2
- Produces hormones - regulate both fetus and the mother
Is the placenta maternal or fetal tissue?
Fetal tissue
What connects the placenta fetal tissue to maternal tissue
The umbilical cord
What is chorio-vitelline?
Chorio-vitelline - the blastocyst does not implant deeply into the uterine mucosa. There is a little bit of wrinkling to increase surface area. The embryo is nourished by uterine milk which limits the amount of nutrition
What are the 3 problems with the chorio-vitelline placenta?
3 problems with chorio-vitelline:
1. Mechanical weakness, it is barely attached to the uterine wall
2. Inefficiency in nutrient exchange
3. Immunosuppression issue
Eutherians Reproductive features:
• 1 litter at at ime
• Placenta well-developed
• Chorio-allantoic
Chorio-allantoic
Chorio-allantoic - the blastocyst adheres to the uterus and is going to sink fairly deeply into the uterine wall. Very quickly villi grow out and push pretty fair into the endrometrium. As a response the uterus becomes highly vascularized. This all creates a substantial amount of surface area.
6 subgroups of Chorio-allantoic
comes down to the extent that the maternal and fetal blood supplies are separated (6 layer to 1 layer)
Why it’s important to not share blood?
• Different blood types
• Different dna create a immune rejection response
• Fetus don’t have immune system yet infection passed through blood would kill the fetus
What are the two categories of afterbirth placenta expulsion?
- Deciduate
- Non-deciduate
Deciduate involves tearing away of the uterine part where the placenta is attached, causing scarring. Non-deciduate involves villi pulling out with minimal scarring.
Define Deciduate in the context of placenta expulsion.
Part of the uterus where the placenta is attached is torn away, scarring occurs.
This type of expulsion results in more extensive tissue loss.
Define Non-deciduate in the context of placenta expulsion.
Villi pull out of the uterine wall, leaving basically no scars.
This is mainly found in the least intimate connections.
Term for villi are distributed throughout the entire placenta attachment
Diffuse
Term for evenly spaced groups or patches of villi
Cotyledonary
Term for continuous band of villi
Zonary
tend to be common in carnivores (raccoons)
Term for one or two disc shaped areas of villi
Discoidal
(monkeys, humans)
What is the difference between uteri of Monotremes, Metatherians, and Eutherians
Monotremes - no uterus, egg laying
Metatherians - uterus heart-shaped, lateral vaginal canal
Eutherians - somewhat simpler but 4 different designs: Duplex, Bipartite, Bicornuate, simplex
What is a Simplex uterus?
Fallopian tube, big uterus, cervix and birth canal example: human
Simplex uterus typically has a single cavity.
What characterizes a Bicornuate uterus?
Body of uterus not as large as simplex uterus, horns of uterus large, examples carnivores
Bicornuate uterus has two distinct horns.
What is a Bipartite uterus?
Lack of common uterus space, just two horns, example: cetaceans
Bipartite uterus is characterized by two separate uterine horns without a central cavity.
What defines a Duplex uterus?
Fallopian tubes, 2 different cervix, example: rabbits, rodents
Duplex uterus has two separate cervices and often two uterine cavities.
What are Estrous cycles?
All female mammals except higher primates (humans + great apes) copulation is restricted to a certain period of time, during a certain portion of the reproductive cycle
Estrous cycles dictate the timing of fertility and mating behavior.
What happens during the Estrous?
There’s a significant behavioral shift in the female, usually when they will either initiate or tolerate copulation
This phase is marked by increased sexual receptivity.
What are the phases of the Estrous Cycle?
- Proestrous
- Estrous
- Medestrus
Each phase has distinct hormonal and physiological changes.
What occurs during the Proestrous phase?
Building up prelude to breeding, hormonal changes, highly vascularized uterus
This phase prepares the body for potential mating.
What is the significance of the Estrous phase?
Usually when ovulation occurs
This is the peak period of fertility in the estrous cycle.
What happens during the Medestrus phase?
After if mating fails, regression of hormones, uterus shrinks
This phase is characterized by the body returning to a non-receptive state.
Spontaneous ovulation steps
- Ovulation
- Copulation
- Fertilization
- Implantation
- Gestation
- Parturition
- Lactation
Example: humans
Induced ovulation steps:
- Copulation
- Ovulation
- Fertilization
- Implantation
- Gestation
- Parturition
- Lactation
Example: Cats
Delayed ovulation sleps:
- Copulation
- Delay
- Ovulation
- Fertilization
- Implantation
- Gestation
- Parturition
- Lactation
Example: Bats
Delayed implantation steps:
- Ovulation
- Copulation
- Fertilization
- Delay
- Implantation
- Gestation
- Parturition
- Lactation
Example: Bears
What is the term for delay that occurs after implantaion
Embryonic Dipause marsupials such as kangaroos - Delay after implantation
