Lectures 3 and 4 Flashcards
Evolutionary Transitions: Jaw Joints and Ear Bones - Early Amniotes
Had 7 bones in lower jaw, including angular and articular
Jaw joint = articular and quadrate
Stapes was already used in sound transmission from external ear, through middle ear, to inner ear
Stapes = columella of other tetrapods
Evolutionary Transitions: Jaw Joints and Ear Bones - Mammals
The jaw was remodeled during the evolution of mammals from non-mammalian synapsids
Only dentary comprises the lower jaw
Jaw joint = dentary and squamosal
2 bones that were formerly part of the jaw joint now incorporated into the middle ear - the articular and quadrate
Mammal Reproduction
Tied to virtually every structural, physiological, and behavioral adaptation of an individual or species
Is of great antiquity (i.e. evolved early)
- Mammary glands
- Milk for nourishing newborn
- Close mother-young bond
- Viviparity evolved later
Male Anatomy
Male Reproductive System:
Testes (male gonads)
-Produce gametes to females
Penis (intromittent organ)
-transport gametes to females
-Internal fertilization
ALL mammals use an INTROMITTENT ORGAN
Spermatogonia undergo spermatogenesis during breeding season
Spermatogenesis is continuous in mammals where there is no breeding season
Saves energy for animals with breeding seasons to only undergo during that time
Reproductive System: Male
Testes may stay internal permanently
Testes may be suspended outside the body cavity in thin-skinned scrotum
- Migrate out of the body cavity at birth permanently
- Migrate out at sexual maturity
- Allows cooling away from the warm body cavity
- Sperm development is hindered by high temperatures
For good spermatogenesis, needs to be COOLER than body temp (98.6); cooer environment descended outside of body, so sperm development is hindered by higher temperatures
Variationin Baculum Morphology
The Baculum is the penis bone (AKA ospenis) found in SOME mammals
Carniverons (dogs, cats, raccoons, seals, sea lions, bats, rats, some primates)
Single bone that supports the penis in intromission
Up to 18” long in Walruses
Female Anatomy
Females Must:
- Manufacture gametes (ova)
- Receive and transport male sperm to the ova
- Nourish developing young during gestation
Females responsible for more than males
Gestation is species-dependent: Anywhere from a couple of weeks to 22 months
Females must ALSO:
- Undergo parturition (birth - or egg laying in monotremes)
- Provide energy-rich milk (lactation)
- Provide protection and support after lactation
Strategy of male mammals: Mate with as many females as possible to spread as many genes as possible
Strategy of females: Be picky about males, need to produce very fit young, mate with males that are most fit
Female Anatomy: Monotremes
Subclass Prototheria
Duplex uterus
-Right and left uteri enter urogenital sinus
Cloaca present
Cloaca: Single opening that empties digestive, urinary, and reproductive tracts
Cloaca is ANCESTRAL trait
Female Anatomy: Metatherians
In addition to paired uteri, they have paired cervices
Pair of uteri enter into vaginal sinu
Duplex cervis (2 cervices)
2 vaginas
-Male metatherians have a forked, biphid penis
Common urogenital sinus
Birth occurs through pseudovaginal canal
In a lot of species, there is NOT a central birth canal; form a pseudovaginal canal just before birth
Female Anatomy: Eutherians
Fallopian tube would enter either left or right uterus
Retain paired ovaries
May retain paired cervix and uterus (duplex) or uteri may be fused (simplex or bicornuate)
-Uteri fused at some point (usually proximally)
Single vagina
Diverged ~300Mya
Amniotes are named for the major derived character of the clade _______, which contains specialized membranes that protect the embryo
Amniotic egg
Amniotic Egg: Allantois
Function: Waste deposit
Disposal sac for certain metabolic wastes produced by the embryo
The membrane of the allantois also functions with the chorion as a respiratory organ
Amniotic Egg: Amnion
Function: Floating environment PROTECTS egg
The amnion protects the embryo in a fluid-filled cavity that cushions agains mechanical shock
Amniotic Egg: Chorion
Function: Gas exchange with environment
The chorion and the membrane of the allantois exchange gases between the embryo and the air. oxygen and carbon dioxide diffuse freely across the shell
Amniotic Egg: Yolk sac
Function: Nutrients
Contains the yolk, a stockpile of nutrients. Blood vessels in the yolk sac membrane transport nutrients from the yolk into the embryo. Other nutrients are stored in the albumen (“egg white”)
