A structure found in two (or more) different species, but derived from a common ancestral structure is said to be HOMOLOGOUS in those species. The structure may or may not be used for the same function in the species in which it occurs.

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a structure that serves the same function in two species, but is NOT derived from a common ancestral structure

(ex. wing of bird vs. wing of bumble bee)[image]

look alike but may or may not be homologous or analogous

(ex: eye spot look-a-like on a fish)

heriditary modification of phenotype that increases adaption & help for survival

hereiditary modification of phenotype that allows organism to meet a new environmental challenge before it even exists

Relatively differnet organism that are different but b/c live in similar habitat ad similar lifestyles look similar but distantly related.

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(child-form) when a decented species looks like an immature or larvel form of its ancestor.

(ex: leapord frog: instead of morphing into a frog, they do not metamorphize and contain sperm and egg and create a zygote, thus creating tadpoles that will never become full frogs)

Asymmetry- not same on both sides (ex sponges)

Radial symmetry- have a top or bottom, either one is oral or ab-oral surface[mirrored sides] )[image]

metamerism: all segments look identical (metameres) ex: arthopods, worms

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forlimb- pectoral

hindlimb- pelvic

limb closest to body- proximal

limb farthest from body- distill

explains corse of evolution of particular group.

[phylogenetic systematics: identify monophyletic (ancestor and all of his decendents) groups]

Speciation with geopgraphical speciation

(ancestoral speciation probably stil exists)

Taxonomy-  apply NAMEs to certain groups (ex: cats, lions b/c they both have retractable claws)

Systematics- apply to a Group

Based on phenotype, groups, orders, phyla

(looking for shared characteristics)

[ex: (vertebrates: Ambhibians, reptiles, birds, mammals) charactersitics similar- recent common ancestor]

group organisms based on ancestors in common

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Monophyletic group:  ancestor and all its decendents

Paraphyletic group: common ancestor, but not all of its decendents

Polypeletic group: 2 groups of oganisms that don't share recent common ancestor

[image]Origins of chordates: virtually no fossils since beggining of time, no bones.

apomorphic charc: inverted body axis

- Subphylum Urochordata

-Subphylum Cephalochordata

-Subphylum Craniate (Vertabrata)

(mollusks[octopus, squid], annelids[leeches, worms], and arthropods[crayfish, spiders]) develop so that the first opening in the embryo is the mouth (protostome = first mouth).

-bilaterally symmetrical, have three germ layers, the organ level of organization, the tube-within-a-tube body plan, and a true coelom.

-Spiral Cleavage

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1. Notochord-  A long flexible rod that supports the body and runs along the dorsal axis of the body in the future position of the vertebral column, 1st skelatal stucture,important inducer,
   
2. Dorsal hollow nerve cord- a Nerve cord that goes with bilateral animals, and eventually developed into the spinal cord and nerve system, most invertebrates have solid nerve chord
   
3. Pharygeal slits-  In chordate embryos, slits that form from the pharyngeal clefts and communicate to the outside, later developing into gill slits in many vertebrates, phyryn part of alimentary canal [tube goes from mouh to anus]
   
4. Muscular Post-anal tail- A support for the sinal column

 (as exemplified by the echinoderms[starfish] and chordates[humans]) develop the anus first, then the mouth at the other end of the embryo

-radial cleavage[image]

-acorn worm (live in soil and mud with strong cranial probiscus, pharyngeal slits, stomochrord  which stiffens to be the probiscus, more or less dorsal nerve core, and ventral nerve core)

-use filter feeding (Water entered through the mouth and then passed through the gills where food particles were strained out.)

-Sea Angel- attached to sea bottom (sessile)

-Sea Squirts (sessile filter feeders) larval form called "tadpole larva"

-has pharynx with slits, dorsal hollow nerve cord, notochord, tail (but adult form doesnt have all these)

-Larvacea (spend entire life time in larval form, dont go thru metamorphosis, but still reproduce)

apomorphic charac.- Cranium

Oldest sedimentary rocks formed in Paleozoic era have fossils of conodonts  (layers of rocks)

-Rock distinctive for rock formed in certain era

[conodonts have good guide fossils b/c known for there hard teeth that showed up]

-most primitive craniates [no jaws (suction/filter feeders), most have no paired fins]

-Ostracoderms: (bone-skin) no jaws, no paired fins, alot of bony plates in skin to protect them from predators

-Cyclostomes: (living member of Agnatha) hag fish [very soft body, cartilage cranium] and lamprey eels [some parasites & some filter feeders] lampreys have a larval form called ammocoetes larva.

-have jaws (new lifestyle, now can be predators or use jaws to make nest), made from one of the 2nd/3rd pharyngeal arch and pharyngeal arch behind become support

-paired fins/appendages

-Most Primative are placoderms (big boney plates) existed in paleozoic era, ~15 ft. long, went extint maybe b/c too heavy so sank down.

-optic pedicel (structure in eye that supports eye ball), jawed

ex: placodermi (primative jawed big on bottom of sea)[image]

-cartilege fish, ex: shark, rays, catfish.

- Unique type of tail: heterocercal tail (upper lobe of tail fin is longer then the bottom) vertebral column extends to upper tail, this type of tail pushes fish up (helps in lift, unlike placodermi)

Ways how got off the ground:

1) using the lift from the heterocercal tail

2) heavy bone with light cartilage

3) small scales in the skin instead of bony called placoid cells (liek our teeth)

[image]

4) enormous liver w/ oil which weighs less then water

2 GROUPS  of

Chondrichthyes

1) Elasmobranchi (Shark & rays)

-plate gill slits (arches of gills that protect gills)

2) Holocephal (rat fish)

-apomorphic charc.: autostyli [only one where upper jaw is fused to the skull]

- operculum: flap that covers gill

terminal mouth (mouth at tip of head)

a) Acanthodii

b) Osteichthyes

Ap.Ch: "Spiney sharks" (fins)

- known only by fossils

(bone-fish) Ap. Ch: Air Sac [put enough air in air sac to make them self neutrally buoyant]

- gas bladder, lung, swim bladder: reduces weight to keep from sinking

-evagination of alimentary canal

1) physostomous- pimative air sach retains connection to alimentary canal, have to swim to top surface and take gulp of air. use as lung as well as buoyancy compensator

2) physoclistous- nomadic duct lose, glandular structures that add or remove gas from gas bladder.

1) Actinopterygii (ray-fin)

2) Sarcopterygii (lob-fin)

(ray-fin) fin supported by thin rays

  A) chondrostei- snout nose made of cartiledge (primative fishes) -heterteocercal tail (big bony tail to detter thing from eating it, physostomous air sac, thick ganoid scalesm position of paired fins (pectoral-low on side, & plevic- close to anus)

    B) neopterygii- ex. paddle fish, reed fish. modified tail that is not hetereocercal (doesn't go upward much)

          a) holosteii - modified muddfish, thinner scales

          b) teleostii- 25,000 species, 2 GROUPS:

                 i) soft ray: cycloid scales fin (primative), physistomous many, no spin in fin ex. sardine or sucker fish.

                 ii) spiney ray:  more advanced, Ctenoid scales (help keep cote of mucus on skin, very thin help in weight reduction.

(lob- fin) fin supported by thick fleshy lob

A) Dipnoi- lungfish, have larvel forms which then metamorph.

B) Actinistia- Coelacanthis (extinct) paired lobe fins that extend away from its body like legs,  hinged joint in the skull, an oil filled- a notochord, thick scales common only to extinct fish.

C) Rhipidistia- ancestor to amphibians we know today, labryrinthodont type of tooth, some have bones in their pectoral and pelvic bones homologous to proximal (arms and hand) like tetrapod

Ap. Char.-four feet, legs or leglike appendage (finger's & toes)

- earliest are amphibians (frogs, toads, salamanders), reproduce in water, only embryonic membranes they have is Yolk Sac

Group: Lissamphibia (no scale on skin, slimy)

1) Anura (frogs and toads) smooth skin

2)Urodela (salamanders) smooth skin and have tails

3) Apoda (no appendages) (Sicilians) worm like but have jaws

source of nutrition: Yolk sac

-eliminate waste nitrogenic waster(simply diffuse in H2O- amniote [prevents desication- Amnion]

-respiratory organ

- all craniates have a yolk sac

Amniota

- amniotic membrane called amnion, thus free from producing in water

- anamniote: craniote that doesnt have  amnion

- amniota: adapted to living on land because have membrane that eclosed egg in water already (allantois- another membrane around that stores or moves the waste so doesnt poison embryo)

1) Sauropsida: (include reptiles and birds) homodont, suborbital fenestra

2) Synapsida: (mammals & immediate ancestor of them) hetrodont, single temporal fenstra

homodont (all teeth look exactly the same)

-Suborbital Fenestra (window)- holes in skull & sometimes lower jaw, can help in weight reduction (allows for muscles to get big or attach)

- Parareptilia- (turtles) no temporal fenestrae (anapsida)

- Eureptilia- diapsida (b/c 2 temp fenestrae)

     -Lepidosaurs (lizard & snakes) overlapping scales & pleurodont (teeth in inner surface of bone in groove)

     - Archosaurs (crocodiles, allig., and birds) nonoverlapping scales, theocodont (teeth in socket) & have anteorbital fanestra (window in front of orbital)

heterodont (all teeth look different)

Sauropsida->Eureptilia->

Archosaurs->Dinosauria

-Perforate (windowed depression help them bipedal)

-acetabulum (depression for head of femur)

-hipbone [composed of 3 fused bones illium (forms joints with screm, ishium, pubis)]

a) Saurischia (lizar-hip)- pubis bone points up, carnivores, modern day birds (Aves- ap. charc: feathers; endothermic (warm blooded); have pygostyle (Support tail) & heeled sternum (breast bone) to provide surface for flight muscles; beak no teeth.

b) Ornithischia (bird-hip)- pubis bone points down, ischium point toward tail. Herbivorous (plant-eating), birds pelvic girdle shape, but Aves originated in Saurischia.

-Ap. Charc.- hair, Mammory glands, single lower jaw bone [unlike Sauropsida who had Articular (lower jaw bone) & Quadrate (upper jaw bone)] the jaws were restructures on Mammals

-All Synapsida have ear bone, Stapes, Mammals have 3 ear bones [Malleus, incas, stapes]. sound waves follwed thru Jaw to ear.

1) Monothermata (Protheria)- (one-opening) oviparous, have cloaco (suer chamber end of Caudal. Teria- viviparous (have placenta) but a subdived cloaca to different parts.

2) Metatheria- Marsupial (kangaroos) only 1 in N. America (platypus), less efficient placenta choriovitelline placenta.

3) Eutheria- "placental" mammals, better developed for nourishment. Placenta called chorioallantoic placenta, pushes against & fuses w/ membrane & lining