Campbell Biology 14 Chapt 34 Part Ii

Front 1

Gnathostomes

Back 1

Vertebrates with jaws

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Derived characteristics of Gnathostomes

Back 2

Hox genes duplicated. Single set in chordates became 4 which contributed to jaw evolution as well as other features:

Enlarged forebrain with enhanced sense of smell and vision

Jaw was created from skeletal rods that supported slits

Lateral line system in aquatic animals (sensing vibrations in water)

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Early gnathostomes

Back 3

Paired fins and tail over time stiffened by bony structures (fin rays) allowing thrust and steering.

Faster swimming also due to more efficient gas exchange system in gills (the slits that were no longer needed for suspension feeding)

Placoderms: “plate skin”

Acanthodians

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Chondrichthyans

Back 4

Skeleton composed of cartilage with some calcium

Sharks, rays, and relatives

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Oviparous

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Lay eggs that hatch outside the mothers body

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Ovoviviparous

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Retain fertilized eggs in oviduct.

Nourished by egg yolk.

Develop Into young and are born after hatching inside uterus

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Viviparous

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Young develop within the uterus

Receive nutrients through mothers blood through a yolk sac placenta, or absorb nutrient-fluid from the uterus or by eating other eggs

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Osteichthylans

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Ray-finned And lobe fins (bony fish)

Belong to clade: gnathostomes

Have ossified endoskeleton with a hard matrix of calcium phosphate

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Operculum

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4 or 5 pairs of gills located in chambers covered by a bony flap

Helps fish Breathe by water in through the mouth, then pharynx and out btw the gills through muscle contraction of chambers

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Swim bladder

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An air sac that helps fish maintain buoyancy equal to the surrounding water (gas exchange btw blood and swim bladder help with changing pressure swimming deep or shallow)

These arose from lungs (opposite of what Darwin thought)

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Ray finned fish (actinopterygii)

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Nearly all aquatic osteichthyans

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Lobe-fins

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Other major lineage of osteichthyans

Only 3 lineages today: coelacanthis (actinistia), lungfish (dipnoi), and tetrapods(includes human)!

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Tetrapods

Back 13

“Four feet” are a part of gnasthostomes

From lineage of lobe-fins

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Derived characteristics of tetrapods

Back 14

Head separate from body by a neck

Pelvic bones attached to hind legs fused to backbone

Pharyngeal clefts become ears, glands, and other structures instead of gills

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Origins of tetrapods

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Coastal wetlands home to lobe-fins

Used oxygen to breathe air due to shallow water and used fins to “walk” across bottom

Tilaalik: had fins, gills, lungs, covered in scales, and ribs

Had same pattern: humerus, ulna radius and so on.

Had pelvis

Front 16

Amphibians

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3 Clades: salamanders (tailed), frogs (tail less), caecilians (legless)

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Amniotes

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Tetrapods including reptiles and mammals

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Derived characteristics of amniotes

Back 18

Amniotic egg

Have rib cage to ventilate lungs (as opposed to throat based amphibians that breathe through their skin)

Having a rib cage may have helped to eliminate breathing through their skin, thus forming skin that can conserve water

Front 19

Amniotic egg

Back 19

4 membrane parts:

1. the amnion (shock absorber), 2. the chorion (exchange gases btw embryo and air, 3. the yolk sac (nutrients) 4. allantois (disposal sac for waste

From tissue layers that grow out from embryo (extraembryonic membranes)

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Phylogeny of amniotes

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Back (Definition)

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Reptiles

Back 21

Clade that includes: tuataras, lizards, snakes, turtles, crocodilians, birds, plsiosaurus, ichthyosaurus

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Shared derived characteristics

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Scales that contain keratin like human nails protect skin

Lay shelled eggs on land (shell keeps eggs from drying out)

Some are ectothermic, birds are endothermic

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Ectothermic vs endothermic

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Ecto: absorb external heat as their main source of body heat. A reptile can live in less than 10% food energy

Endo: maintain body heat through metabolic activity

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Origin of reptiles

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Diapsids: hole on each side of head, created 2 lineages

1. Lepidosaurs: tuataras, lizards, snakes, monosaurs

2. Archosaurs: turtles, crocodilians, pterosaurs, dinosaurs

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Archosaurs

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Pterosaurs: first of flapping flight

As small as humming birds and as big as 11m wing span

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Dinosaurs (archosaurs)

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Had a group of theropods (T-Rex) ancestor of birds

Some were ectotherms, some were endotherms

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Lepidosaurs

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Consist of

1. tuatara (exist only on islands due to rats eating their eggs), grow to be over 100

2. Lizards, squamate: small to large (16 mm to 3 m)

3. Snakes: descended from lizards, can move by gripping ground with belly scales or waves of lateral bending pushing snake forward, noneardrums but sensitive to ground sensations, also have heat sensing organs btw eyes to locate warm animals

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Turtles (archosaurs)

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Do not have holes and were once thought to be diapsids, but new evidence shows holes in earlier turtles.

Shell with upper and lower shields fused to vertebrate, clavichord, and ribs. Shell was acquired over time (earlier had lower shell only)

Could not retract head early on but evolved to vertical or horizontal movement

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Crocodilians (archosaurs)

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Earliest were small quadrupeds with long slender legs

Some crocodilians grew up to 12 m long and are dinosaurs

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Birds (archosaurs)

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Almost every feature of their anatomy has been modified in their adaptation to flight

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Derived characteristics of birds

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Adaptations that facilitate flight like weight saving (lack urinary bladder and females have one ovary, gonads are small and they are toothless to make head lighter)

Feathers: made of beta keratin (like in scales and nails)

Wings attached to strong breast bone for flapping (some are made more for soaring)

Endothermic. Some use fat to retain heat

4 chamber heart allows for oxygen and nutrients

Good eyesight and color vision (larger portion of brain)

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Origin of birds

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Belong to theropods (dinosaurs)

Feathers developed before flight

Archaeopteryx earliest bird: teeth, clawed fidgets, wings and long tail

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Ratites

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Order of birds includes:

Ostrich, rhea, kiwi, cassowary, and emu

All flightless birds (sternal keel is absent and breast are small)

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Penguins make up another order of bird

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Flightless but “fly in water” so have large breasts muscle