Embryological development involves all evolutionary history of the ancestors.
Trait that is homologous within a group but not limited to that group. (ancestral character state) Ex. Vertebrae in zebras, cheetahs, and monkeys have very distant ancestor, so not able to shed light on phylogenetic relations.
Evolutionary state unique to a particular species and its descendants, so can be used as a defining character (derived character state) Ex. Jaws
Apomorphy shared by two species, or shared derived character state.
Must unite ALL descendants of common ancestor (based on synapomorphies)
Character shared by different species, but not present in their common ancestor. Ex. Can't trace fins of dolphins and sharks back to their common ancestor.
Analogy vs. Homology
-Birds and bats did not inherit wings from common ancestor (analogy) -Birds and bats did inherit forelimbs from common ancestor (homology - comes from same evolutionary/embryologic origin)
Convergent evolution shapes...
Convergent evolution definition:
analogous organisms indep. evolve similar traits as a result of having to adapt to similar environments or ecological niches.
new species formation without branching of the evolutionary line of descendants
1. Mammary Glands/other skin glands 2. Hair 3. Viviparity, etc. 4. Highly developed cerebral cortex 5. Skeletal develop. limited to early life 6. Heterodonty & develop. of sec. palate 7. Single jaw bone & 3 inner ear ossicles 8. Efficient respiratory and circulatory systems
Reduced in mammals with blubber and many sweat glands.
Developing placenta in mother where barrier is between fetal and maternal circulation. Having live birth instead of eggs.
Skeletal Develop. Info:
Better working joints. Ex. Antelope running hours after birth.
Having various different teeth. Secondary palate develop. with bony separation b/w mouth and nasal cavities so can breathe while chewing.
Efficient systems info:
4 chambered heart (only other that has this are aves/birds)
Which characteristics are related to homeothermy?
Hair, Heterodonty & develop. of sec. palate, efficient respiratory and circulatory systems
Shrews (<2g), Blue Whale (>90,000,000g - 100ton), Elephant (5,000,000g)
How long have mammals been around?
>200mya in Triassic period of Mesozoic Era -Have been dominant terrestrial vertebrates for 60my
Diversity of Mammals:
-1,100 genera (5,500 species) of LIVING mammals -2,000 genera of extinct mammals -30 orders, 159 families (Just 2 orders have 3,400 spp.) -Compared to: 10,000 birds, 6000 reptiles, 5000 amph., 32,000 fishes, >5000 dung beetles
Mammalian skeletal features:
-Simplified, lighter, fusion of many elements, loss of other elements, more completely ossified. -More flexible, allowing greater range of movement.
What do only mammals have on ends of long bones?
Growth discs. -Diaphysis (main bone), Epiphyseal cartilage (young mammals on ends of long bones), and epiphysis
Bicipital (2 headed) -artic w/ vertebral column
All mammals have 7. -Exceptions: Manatee and 2-toed sloth has 6, giant anteater has 8, 3-toed sloth has 9.
Skull in mammals vs. reptiles:
-Reptiles had solid temporal shield, but Therapsids had large fenestrum (hole) in temporal shield, which enlarged until leaving only zygomatic arch and sagittal crest. -Underneath shield reptiles had separate, cartilaginous braincase (fully ossified in mammals)
Rearrangement of chewing muscle attachments:
-Zygomatic arch- origin of masseter muscle -Sagittal Crest- origin of temporalis muscles -Lambdoidal ridges- origin of temporal and cervical muscles
Opening/hole/passage of nerves; blood vessels ("canals" for cranial)
4 Types of Heterodont Teeth:
-Incisors -Canines -Premolars -Molars
set in socket (alveoli)
molars never replaced 1)Brachyodont 2)Hypsodont
low crowned; enamel covered; found in meat-eaters or soft plant food -enamel then dentine -cement on bottom
hi crowned; associated with herbivores, especially folivores -cement, enamel, dentine (young) -cement outside, then enamel, w/ pools of dentine -some rootless and ever growing
top of tooth
on side towards tongue
towards inside of cheek of lips
Parts of teeth:
-enamel -dentine -cement
-lower teeth set in dentary -upper I in premaxillae -C,P,M set in maxillae
Exceptions to heterodonty:
1. Baleen Whales: Baleen plate originates from maxillary
-primitive (shrews) vs. specialized (bats, anteaters, aardvarks)
fish-eating -otters, pinnipeds, toothed whales, fishing bat and cat
dogs, raccoons, bears, opossum, chimps
vampire bat blood
bats, honey opossum
-resins (gums and saps of trees) -marmosets, sugar gliders
walrus, sea otter
-feces dung beetles, rabbits
How vampire bats process blood:
-kidney absorbs water rapidly, excrete copious amounts of dilute urine until light enough to fly, kidney function changes to make urine more concentrating again
Caching is also called:
Two types of hoarding:
Gray Squirrel -create many different food caches (nuts)
-red squirrel (middens of pine seeds) -woodrats (fossil middens in caves of dry climate western deserts (seeds)) -Pika (survives off hay pile)
Carnivores have smallest caecum and colon, but longest small intestines > Omnivores > Herbivores
related to metabolic rate relative to body size -large mammals live slower, small mammals liver faster and shorter -Harbor seal (18-20bpm) vs. shrew (1300 bpm -eats 3-4x its body weight); elephant eats 1% of body weight
-water -lipids -di and tri-saccharides -casein -albumin -salts -carbohydrates
Cows and humans have 3.7% fat, seals have >40% fat
early milk; hi in protein and contains antibodies
1. White adipose tissue 2. brown fat
White adipose tissue:
-subcutaneous -used for energy STORAGE and INSULATION -desert species and hibernating species- localized in tail and inguinal region
-non-shivering thermogenesis -concentrated in interscapular and inguinal regions, has lower melting point -good source of metabolic water
Complete separation of pulmonary (oxygenated) and systematic flow (de-oxygenated) -erythrocytes are biconcave discs and lack a nucleus (enucleate)
made in bone marrow -surplus stored in spleen -destroyed in liver -excreted in feces
-like birds -'negative pressure breathing with muscular diaphragm -diaphragm lowered by expansion of ribcage during inhalation and raised by contraction of ribcage during exhalation -pressure applied to lungs via intrapleural fluid
O2 and CO2 diffuse across these tiny pockets -single-cell layer of epithelium -from air into/from capillaries
1 degree oocytes
-female is born with complete set of these inside protective and nourishing follicles -arrested at end of meiosis I -400,000 in humans
-completed cyclically starting at puberty -the follicles rupture (ovulation) to release secondary oocyte
When is actual OVUM produced?
at moment of fertilization
Cause of cyclicity:
oscillation of horomones (estrogen and progesterone) via the hypothalamic pituitary axis
gonadotropins (FSH and LH)- production of 2 degree oocyte (master endocrine gland)
a) measures photoperiod (some mammals seasonal breeders) b) interprets some sexual stimulus (some rodents and carnivores are induced ovulators) c) send continuous oscillation of nervous impulses (mice and rats have 4 day estrous cycle that constantly repeats all year - female in estrous when ovulating; humans take longer because of buildup of endometrium, which is then sloughed off if no fertilization and implantation)
Where does fertilization occur?
in oviduct (Fallopian tube)
secretes progesterone (pregnancy hormone) that keeps embryo alive before and after implantation -embryo eats its way into endometrium to form placenta (no direct circulatory connection)
* dies if no zygote/embryo- HCG (chorionic gonadotropin)
-Spermatogenesis -no cyclicity except in seasonal breeders
In most male mammals testes are...
abdominal during non-breeding season and descent into scrotum for breeding. -testes must recrudesce (grow 1000s of times) for breeding
Alternative reproductive strategies:
-delayed fertilization (sperm storage in female oviduct) -delayed implantation (blastocyst suspended in oviduct) -delayed development (post-implantation; bats and carnivores)
-penile morphology can be highly specific due to reproductive isolation -Insectivora, Chiroptera (bats), Primates, Carnivora, Rodenta
4 types of Uteri:
-Duplex -Bipartitc -Bicornuate -Simplex
-fully separate horns -Rodents, Lagomorphs, Aardvarks, Hyraxes
Cetaceans, most carnivores
insectivores, some bats, primates, MOST OTHER orders
Some bats, primates, edentates
Brain in Therapsids:
mammal-like reptiles -developed neopallium (outer covering of gray matter) -this becomes expanded to cerebral cortex in mammals
Cerebral cortex has:
new control center, greater behavorial integration; convolutions correlate with intelligence
Allows communication between two hemispheres of brain found only in placental mammals
reflective layer in retina (causes eye shine at night)
Most highly developed sense in mammals:
bats, insectivores, toothed whales
lower than we can hear -elephants, baleen whales -long wavelengths and carry further than ultrasound
loss of bone of temporal shield -more freedom of movement of jaw adductor muscles -decreased weight of skull -associated with complete ossification of braincase -areas of low stress from jaw muscle not needed
Reptiles have what types of bones connecting dentary and skull?
Quadrate and Articular (In ears of mammals)
Jaw Joint theories:
1) Greater efficiency of chewing through improved bracing 2) Smaller therapsid jaw bones (posterior) already transmitting sound waves to ear
Cynodont Jaw improvements:
-first to have masseter muscle b/w zygomatic arch and dentary -increased transverse movement, increased bite force, more focused -decreased size/importance of front, increased cheek teeth
ADVANCED ONES HAD BOTH REPTILIAN AND MAMMALIAN JAW JOINTS
-small carnivorous therapsid 1st glenoid fossa of squamosal -jaw joint articulation that included quadrate and articular bones along with squamosal and dentary bones -lumbar ribs reduced to vertebral process -many changes throughout vertebral column -Ilium shifted forward, publis/ischium shift posteriorly
-HIGHLY SUCCESSFUL -first mammalian herbivores (small) that survived for 100my -highly apomorphous lower cheek tooth -smooth cerebrum (not intelligent) -declined over 20my from competition with therians (marsupials and placentals)
developed trigon (Hadrocodium)
developed talonid -angular process of dentary (Hadrocodium)
-plate tectonics -volcansim -glaciation (cyclic)
-seaway from arctic ocean to gulf of mexico divided N.A. east from west -Pangea broke up in Jurassic, Gondwana in Cretacous
Mammals took advantage when dinousaurs went extinct -Biodiversification of angiosperms, increase insects, increase insectivore mammals and other mammals
-Gigantism (co-evolutionary arms race b/w predator and prey) Cope's Law -process of getting bigger decreases genetic variability -Climate change and first human contact (game drives, fires)
-Between Borneo and Sulawesi islands -discont. in species distributions
-combines Nearctic and Palearctic -Talpidae, red fox, elk, wolverine, brown bear
Restricted ranges of convergent evolution:
-Endemic: found only there because evolved there -Relictual: used to occur more broadly, but went extinct elsewhere -Ex: meadow vole only found on Fl. gulf coast but used to be elsewhere
Causes of relictual:
-Vicariance: some geographic/climate event isolated population (Pleistocene relicts) -Dispersal: colonists after long migration (bat)