Lecture Exam 2 Material Flashcards
How does the rate of front-limb evolution differ between eutherians and metatherians?
Much faster in eutherians than metatherians. There is not much diversity between metatherians front-limbs because they are born with such short gestation times and come out poorly developed. The crawl they must do in the pouch contrains the evolution of front-limbs.
Difference between eutherian and metatherian blastocysts
In metatherian blastocysts, trophoblast doesn’t surround the entire embryonic tissue and there is less fusing of trophoblastic cells into the syncytio-trophoblast. The estrous cycle is not halted in metatherian embryoblasts like it is in eutherian embryoblasts because there is not signaling by chorionic gonadotropins to the corpus luteum. This causes marsupials to have short gestation periods and give birth to insanely altricial young.
Understand how reproduction differs between eutherians and metatherians
Gestation periods in metatherians rare much shorter than in eutherians. Metatherians have a much longer overall period from conception to weaning and a higher percentage of time spent lactating. Since lactation is about twice as energetically costly than gestation, eutherians experience a lower energy cost of reproduction and, therefore, have a competitive advantage over metatherians
Neonatal ossification difference between eutherians and metatherians.
Neonatal ossification in metatherians is not as defined in comparison to eutherians. There is mostly ossification seen in just the oral region of metatherians.
Difference between brachydont and hypsodont teeth. What animals exhibit these teeth?
Brachydont: low crowns, omnivore
Hypsodont: high crowns, herbivores
Know the terms incisors; premolars, and molars: what are each used for?
Incisors: croppers and nippers canines (puncture and hold)
Premolars: slice and grind
Molars: slice and grind
Is evolutionary tendency for mammals to gain or lose teeth? Know how incisors, premolars, and molars are gained or lost.
Tendency to lose teeth rather than gain teeth.
Incisors: posterior lost first
Premolars: anterior lost first
Molars: posterior lost first
Know terms lingual, labial, anterior, and posterior
Lingual: Side of teeth facing tongue
Labial: side of teeth facing lips
Anterior: front teeth (usually incisors and canines)
Posterior: back teeth (usually premolars and molars)
Know the terms: Dilambdodont, secodont, bunodont, selenodont, lophodont, selenolophodont
Dilambdodont: two triangular shaped transverse ridges on molars (seen in shrews)
Secodont: teeth with sharp cutting edges (seen in carnivores)
Bunodont: often brachydont. Have rounded cusps for crushing and grinding (seen in most monkeys and pigs)
Selenodont: when lophs are isolated and crescent-shaped (often seen in deer)
Lophodont: teeth with cusps that form continuous ridges (often seen in elephants)
Selenolophodont: intermediate of selenodont and lophodont teeth in terms of loph organization (seen in rhinos)
What is a carnassial pair?
The last upper premolar and first lower molar. Used in carnivores for shearing
What is the most common species concept and how does it define a species?
Biological species concept: a group of populations that is reproductively isolated from other groups. There is no gene flow between species.
What are pre- and post- zygotic isolating mechanisms?
Prezygotic: geography may separate sets of populations and prevent interbreeding
Postzygotic: hybrid breakdown where hybrids are fertile but less fit than either parental species
How is the biological species concept tied to allopatric speciation? What is meant by allopatric speciation?
The biological species concept is tied to allopatric speciation because the two species produced become reproductively isolated. Allopatric speciation is when an ancestral species becomes separated by some form of barrier and undergoes divergence until the two species become reproductively isolated.
Understand the evolutionary and phylogenetic species concepts. List pro’s and con’s.
Evolutionary species concept: a group of populations with its own evolutionary tendencies and a unique evolutionary fate
Phylogenetic species concept: a group of populations that are diagnosable from other such groups
Pro’s: applicable in cases of allopatry and doesn’t rely on reproductive isolation
Con’s: over-recognizes diversity and a lot of incongruence among characters
Understand the genealogical concordance species concept. What are pros and cons?
A group of populations that are diagnosable using more than 1 concordat character.
Pros: useful in allopatry and does not emphasize reproduction and also very predictive
Cons: most rigorous of the species concepts and ignores hybridization and underestimates diversity
How is lift generated?
Lift is generated by the difference in pressure between the wings upper surface and lower surface. The pressure must be lower on the upper surface and increasing on the lower surface in order to be lifted upwards. An airfoil is a curved surface on the wing, favorable for lift.
Why is it more difficult to maintain flight at low speeds?
Is it more difficult to maintain flight at low speeds because the magnitude of lift depends on the differential in velocity.
How do bats generate lift at low flight speeds?
- Increase camber/curvature: increases differential in speed of airflow across upper surface in relation to lower surface
- Increase angle of attack: even symmetric airfoil can generate lift this way
- Leading edge flaps: promotes laminar flow at low speeds and also supplies camber
Laminar vs. turbulent flow
Laminar flow is smooth and consistent while turbulent flow can be irregular and chaotic
What is meant by wing loading and aspect ratio? How do they relate to bats?
Wing loading is body weight/surface area. The lower the wing loading, the easier it is to overcome the force of gravity. Bats typically have low wing loading. Aspect ratio is length/width. Low AR = short and broad wings and high AR = long and narrow wings.
