SDSU Bio 101 Exam 3 Ekdale

Hemichordata

acorn worms (free living) and pterobranchs (colonial, live in tubes)

Enteropneusta

acorn worm that uses the mucus coated proboscis for locomotion and feeding

Pterobranchia

Small, colonial, live in collagen tubes

Suspension feeders, catch food in mucus coated tentacles and have a small shield shaped proboscis

Main regions of bodies of Hemichordata

Proboscis, collar, trunk

How do you distinguish hemichordate "worms" from other "worms"?

The acorn worm has a collar while the earthworm has a clitellum, the earthworm moves through peristalsis, the hemichordate has a proboscis, the earthworm has metameric segmentation

3 major clades of Chordata

cephalochordata (lancelets), urochordata (tunicates), vertebrata (animals with backbones)

5 major synapomorphies of chordata

Notochord, Dorsal hollow nerve chord, Pharyngeal slots or pouches, endostyle, muscular and postanal tail

Notochord

A flexible but non-compressible rod that supports a chordate's back- modified as intervertebral disks in adult humans

dorsal hollow nerve cord

Constitutes the central nervous system (brain and spinal cord)

Pharyngeal slits/pouches

Open to the outside, function in feeding (non-vertebrates) and respiration (e.g. gills); contribute to ear and neck in terrestrial vertebrates

Endostyle

Pouch in the throat with mucus to trap food; develops into thyroid gland in vertebrates (regulates energy use)

Muscular, postanal tail

Functions in locomotion of the body

Cephalochordata

(= "head cord") Includes lancelets, amphioxus, suspension feeders, live half buried in sand, segmented muscle blocks: myomeres

Urochordata

(= "tail cord") Includes tunicates ("sea squirts"), suspension feeders, gregarious or solitary, metamorphosis: motile larvae with tails, sessile adults lack tails

Neural Crest Cells

Cells along the sides of developing nerve cord, migrate to other regions of the body to form specific structures, including regions of face and nerves

Vertebrata

(= "vertebra bearing") includes cyclostomes (jawless fish - hagfish and lampreys) and gnathostomes (jawed vertebrates - sharks, bony fish, amphibians, reptiles, mammals)

Synapomorphies of Vertebrata

Vertebrae, bone and cartilage, myoglobin, pineal organ, lateral line system, neuromast

Vertebrae

bone or cartilage surrounding the spinal cord

Bone and Cartilage

Connective tissue for support and protection

Cartilage - flexible connective tissue with collagen in hard matrix

Bone - rigid connective tissue that is mineralized (calcium carbonate)

Myoglobin

Colored protein in muscles that stores oxygen

Pineal Organ

Endocrine gland in brain, sensitive to light, secretes serotonin (regulates circadian rhythm)

Lateral Line System

Detects motion in water (like tadpoles, as babies they have the lateral line system because they spend that part of their life in water)

Neuromast

Specialized mechanoreceptive organ

Cyclostomata

(= "round mouth") includes Myxini (hagfish) and Petromyzontida (lampreys) - jawless fishes, monophyly is supported mostly by DNA, only weak anatomical support

Myxini

(= "slimy") includes hagfish or "slime eels", marine scavengers - feed from the corpses of dead animals, produce slime as defense mechanism, knot themselves during feeding and cleaning

Petromyzontida

(= "stone sucker") Ectoparasites - ring of teeth in mouth scrapes hole in side of fish to suck blood

Adults are parasitic but larvae are suspension feeders

How do hagfish and lampreys differ in their feeding behavior? How are they similar?

They both have round mouths and are jawless. Myxini are marine scavengers while Petromyzontida are parasites.

Does everything that is considered a "fish" form a monophyletic group?

No

Conodonts

jawless vertebrates with mineralized mouthparts

What is the significance of the evolution of mineralized tissues (i.e., bone) in vertebrates?

Mineralization of tissue is associated with a transition in feeding mechanism (suspension to scavenger/ predator). Some early vertebrates developed defense armor covering various amounts of their bodies

What is the prevailing hypothesis for the origin of jaws?

jaws developed from skeletal support of pharyngeal slits (anterior gill arches)

Gnathostomata Synapomorphies

Jaws - grab prey

Paired appendages - chase prey

Claspers - internal fertilization

Chondrichthyes

cartilaginous fish, includes sharks, skates and rays, and ratfish, cartilaginous skeleton in living species

Osteichthyes

bony fish, two major clades: Actinopterygii (ray finned) and Sarcopterygii (lobe finned)

Osteichthyes synapomorphies

Operculum - covers gills for protection (gills function in gas exchange)

Air sac - lungs or gas bladder

Actinopterygii

(= "ray fin") fin rays in appendages, extremely diverse, includes humans

Sarcopterygii

(= "fleshy fin") two major clades: Actinistia and Choanata, synapomorphy: internal limb bones (strengthens the limb)

Choanata

two clades: Dipnoi (lungfish) and Tetrapoda (amphibians, reptiles, mammals), synapomorphy: internal nostril

Tetrapoda

(= "four feet") terrestrial vertebrates, two clades: amphibia (frogs, salamanders, caecilians) and Amniota (mammals and reptiles)

Tetrapoda synapomorphies

Limbs with fingers and toes for terrestrial locomotion, Double circulation of blood with a three-chambered heart

Challenges of the water to land transition

Respiration - lungs, internal nostrils

Support and movement - strengthen pectoral and pelvic; vertebrae modified for support and flexibility

Senses - e.g. hearing vs lateral line system

Reproduction - occurs in water for most amphibians, metamorphosis in amphibians; amniotes have specialized eggs

Advantage of terrestrial lifestyle

Reach sunlight, avoid competition, find food, access to atmospheric O2, possibly escape predators

Tiktaalik roseae

Fish or tetrapod, it represents the transitional form between fish and tetrapods. ~375 million years old (discovered in 2004)

Amphibia

Three major clades: Anura (frogs and toads), Urodela (salamanders and newts), Apoda (caecilians)

synapomorphy: smooth skin with glands (mucus and poison)

Anura

(= "no tail") most diverse clade of Amphibia, frogs and toads, have vocal pouches and buccal pump for respiration and vocalization, most species are oviparous and use external fertilization

Urodela

(= "conspicuous tail") salamanders and newts, most metamorphose with aquatic larvae and terrestrial adults, most are oviparous and use internal fertilization

Apoda

(= "no feet") caecilians, limbless burrowers with reduced eyesight, internal fertilization, viviparous, species now are limbless, live in tropics

Oviparous

egg laying

Viviparous

producing living young (not eggs)

Paedomorphism

Juvenile characteristics in adults, seen in some species of urodela

Amniota

(amnion bearing) includes reptiles and mammals, temporal openings (windows inside of skull), amniota have overcome water dependence (in reproduction)

3 types of temporal openings

Anapsid skull - no windows; turtles

Diapsid skull - two windows; lizards, crocodilians, snakes

Synapsid skull - one window; mammals

Name Amniota / key synapomorphy

amniotic egg - a membrane in egg that surrounds the fetus

Amniotic egg

major function is protection (from drying)

Amnion - fluid filled sac that cushions embryo

Allantois - waste disposal from embryo

Chorion - gas exchange between air and embryo

Yolk sac - contains yolk (food supply) and blood vessels for nutrient transport

Shell - protection; allows gas exchange; leathery or calcified

Other synapomorphies of amniota

internal fertilization, kidneys and large intestines are modified for water retention, rib cage ventilation, sternum and well developed ankle bones

Reptilia

three major clades: testudines - turtles and tortoises

Lepidosauria - Squamata (lizards and snakes), Sphenodon (tuatara)

Archosauria - Crocodylia (crocs and alligators), Aves (birds, lineage of dinosaurs)

Reptilia synapomorphy

overlapping scales (protection, but also water retention), feathers are modified scales

Testudines

(= "shell") turtles and tortoises, characterized by a bony shell, beak, no teeth, oviparous

Testudines diagnostic features

bony shell - carapace (dorsal/back), plastron (ventral/belly side) formed through fusion of vertebrae and ribs

shell has keratin scutes overlying bone

Temperature sex determination

in reptiles, some species of testudines, sex determination is by temperature

low temperatures = males

high temperatures = females

Lepidosauria

(= "scaly lizard") Squamata - lizards, snakes

Sphenodon - tuatara

diapsids (two temporal openings/windows)

Lepidosauria synapomorphies

Kinetic skull, caudal autonomy, keratinized scales

Caudal autonomy

Ability to lose tail, predator can eat tail, but rest of lizard survives, tail eventually regenerates but never completely, ability lost in some squamates (e.g. snakes, monster lizards)

Kinetic skull

jointed and movable skull, allows animals to eat large prey (move the upper jaw up)

Squamata

(= "scaly") lizards and snakes, fringe-toed (helps them run on sand), some have cryptic coloration (helps them blend in)

diversity in feeding (wait and watch, seek and search)

synapomorphies: forked tongue, hemipenes

Hemipenes

in males, paired copulatory organs; male alternate during copulation

Forked tongue

used to detect chemicals in the air (smell)

Sphenodon

(= "wedge tooth") tuataras, lizard like, but not lizards, cloacal kiss, internal fertilization and oviparous, key feature: parietal (third) eye (light sensitive; pineal organ)

2 species in islands off of New Zealand

Serpentes

carnivorous, limbless (some have vestigial pelvic girdles), no external ear - detect ground vibration, highly kinetic skull, some venomous

3 types of venom

Hemotoxin - attacks cardiovascular system

Cytotoxin - targets specific tissues and muscles

Neurotoxin - attacks the brain and nerves

Archosauria

(= "lead lizards) diapsid reptiles, two living clades: Crocodylia and Aves

Archosauria synapomorphies

Four chambered heart - separates blood and increases oxygen delivery

Nest building and parental care - enhances the survival of offspring

Secondary bony palate

Endothermy

Legs held under body

Secondary bony palate

internal nostril positioned posteriorly; allows breathing during eating

Dinosaurian

Erect posture in which legs are held straight under the body - increases stamina and allows the animal to run and breathe more easily

Living birds are members of...

Birds evolved from Saurischians (lizard like hip evolved into modern bird hip), theropods were carnivorous, gave rise to birds

Dinosaurs: ectothermic or endothermic

most evidence points towards endothermy.

1. fossils in polar regions

2. birds are endothermic

3. limbs under body - vigorous locomotion (internal regulation needed)

4. bird like respiratory system in saurischians

evidence for ectothermy

1. dings lack respiratory structures found in birds and mammals that warm and moisten air