Chapter 29: Vertebrates/Chordata

What is the body plan and embryonic development type of chordates?

bilateral deuterostomes

How many germ layers do chordates have, and what type of coelom?

triploblastic eucoelomates

What type of digestive system do chordates have?

complete digestive system

What excretory system do chordates possess?

kidneys to remove metabolic waste

What type of nervous system do chordates have?

brain with a central nervous system

What types of respiratory systems are found in chordates?

gills, lungs, skin

What are the five defining characteristics of all vertebrates?

notochord, hollow dorsal nerve cord, pharyngeal slits, post-anal tail, endostyle/thyroid gland (may only be present during embryonic development in some)

What is the notochord?

flexible, rod-shaped structure derived from mesoderm tissue; located dorsal to digestive tube, ventral to nerve cord; rigid support and muscle attachment sites

Does the notochord persist into adulthood?

in true vertebrates, replaced by vertebral column (spine) in adults, present during all embryonic stages

What is the hollow dorsal nerve cord and what is its origin?

hollow tube derived from ectoderm; dorsal to notochord; develops into brain and spinal cord

What are pharyngeal slits and their function?

openings in pharynx, connect external environment; aquatic vertebrates, water enters mouth and exits through this

What do pharyngeal slits develop into in aquatic vertebrate fishes?

gill supports in jawless fishes

jaw supports in jawed fishes

What do pharyngeal slits develop into in land vertebrates?

parts of ear, tonsils, thymus

What is the post-anal tail?

posterior tail that extends beyond anus; contains skeletal and muscular components

What functions does the post-anal tail serve in aquatic and terrestrial species?

aquatic - locomotion

terrestrial - balance

What is the post-anal tail reduced to in humans and great apes?

coccyx (tailbone)

What is the endostyle?

mucus-producing tissue on floor of pharynx

What does the endostyle produce and what does it develop into?

substance similar to thyroid hormones; develops into the thyroid gland in most vertebrates

Which two chordate clades are invertebrates?

cephalochordata (lancelets) and urochordata (tunicates/sea squirts)

What characteristics do adult cephalochordata have?

all five defining chordate characteristics

What characteristics do larval urochordata have?

all five defining chordate characteristics

Which chordate characteristics do adult urochordata retain?

only pharyngeal slits and endostyle

What is subphylum vertebrata craniata?

largest group of chordata, with cranium and vertebral column

Do all bilateral animals have a cranium?

no, almost all have a head, but not a cranium

What are the chordate characteristics of craniata?

all five defining chordate characteristics

What major novel evolutionary adaptation defines vertebrata craniata?

vertebral column (spine), irregularly shaped bones joined together to form backbone

What happens to the notochord in vertebrata craniata embryos?

vertebral segments replace notochord in adults

What are agnathostomes?

animals with no jaw

Which two classes are agnathostomes?

myxini (hagfish), petromyzontidae (lampreys)

What are gnathostomes?

animals with jaws

What two main groups do gnathostomes divide into?

fishes and tetrapods

What are tetrapods?

animals with four limbs; amphibians, reptiles, birds, mammals

How are tetrapods further divided?

amphibians and amniotes

What defines amniotes?

animals with eggs that contain extraembryonic membranes (yolk, amnion, chorion, allantois); adapted to terrestrial life

What animals are amniotes?

mammals, birds, reptiles

Which group has the greatest number of species in subphylum chordata?

fishes

Where do the earliest vertebrates live?

in sea

Are fishes sessile or active feeders?

active feeders; even filter-feeding fish actively swim

How old are agnathostomes?

550 million years old; still extant

What do agnathostomes lack?

hinged jaws, paired lateral fins, scales, internal ossification

Do agnathostomes and gnathostomes have a cranium?

Yes

What type of feeders are Myxini (hagfish)?

scavengers; blind but have sensory barbels around mouth; rasp pieces of food from dead animals using keratin teeth on cartilage base

What kind of cranium do Myxini have?

cartilaginous cranium

What supports the body of Myxini?

notochord (no vertebrae)

What type of lifestyle do Petromyzontidae (Lamprey) have?

parasitic (ectoparasites)

What kind of body parts does a Petromyzontidae have?

cranium, eyes, cerebellum, simple vertebrae

How do Petromyzontidae feed?

suction mouth with rasping tongue

What fins do Gnathostomes have that are considered novel traits?

paired pectoral fins and paired pelvic fins; enable accurate and nimble movement

What did the evolution of hinged jaws and paired fins allow fish to become?

active feeders

What are the two main classes of Gnathostomes?

chondrichthyes and osteichthyes

What type of fish are in class chondrichthyes?

cartilaginous jawed fish; sharks, rays, skates; marine; breathe through gills

What is the typical diet of Chondrichthyes?

mostly carnivorous, some filter feeders

What type of skin do most Chondrichthyes have?

abrasive skin covered with placoid scales

What sensory abilities are well-developed in Chondrichthyes?

acute sense of smell, ability to detect electromagnetic fields (Ampullae of Lorenzini), lateral line to detect water vibrations

Describe the general body shape of Chondrichthyes?

dorsolaterally flattened with unequal sized fins

What is the structure of gills that helps with respiration?

thin tissue filaments with extensive folding to increase surface area

Why is increased surface area important in gills?

ensures enough oxygen absorbed from oxygen-poor water

In which direction does oxygen-poor blood flow in relation to water flow across gills?

countercurrent (opposite) to water flow

How does oxygen move from water to blood in gills?

oxygen diffuses from water (high concentration) to oxygen-poor blood (low concentration)

How is carbon dioxide removed in gills?

diffuses from blood (high concentration) to water (low concentration)

What type of reproduction do Chrondrichthyes have?

sexual reproduction with internal fertilization

What are the three reproductive modes in Chondrichthyes?

viviparous, oviparous, ovoviviparous

What does viviparous reproduction involve in Chondrichthyes?

egg sac with embryo attaches to mother's oviduct and embryo gets nutrition from mother; live birth

What does oviparous reproduction involve in Chondrichthyes?

laying eggs that hatch outside mother's body; eggs covered in leathery egg case; embryo nutrition comes from egg yolk

What happens during ovoviviparous reproduction in Chondrichthyes?

fertilized eggs develop inside mother's body, hatch in utero, born alive; nutrition comes from egg yolk, some species' embryos cannibalize siblings

What type of skeleton do Osteichthyes have?

true osseous (bony) skeleton, NO cartilage

What kind of scales cover Osteichthyes?

overlapping scales

What habitats do Osteichthyes live in?

marine and freshwater

What are the dietary types of Osteichthyes?

carnivorous, herbivorous, omnivorous

How do Osteichthyes respire?

gills

What organ helps Osteichthyes control buoyancy?

swim bladder

What sensory system do Osteichthyes have to detect vibrations?

lateral line system

What is the general body shape of Osteichthyes?

Vertically flattened with mostly equal sized fins.

How do Osteichthyes reproduce?

sexual reproduction with external fertilization

Do Osteichthyes exhibit parental care?

little to no parental involvement or care

How many chambers does a fish heart have?

Two chambers: one atrium and one ventricle.

What type of circulatory system do fish have?

single circuit circulation

Describe the blood flow in a fish's circulatory system?

blood flows from heart > gills > body > back to heart

What happens in the atrium and ventricle of a fish heart?

atrium—deoxygenated blood from body enters

ventricle—pumps blood to gills

Why are amphibians called "dual life"?

have both aquatic and terrestrial life stages

What is amphibians' dependency related to reproduction?

require water for reproduction with external fertilization and embryo development

What are three types of amphibians?

frogs, salamanders, and caecilians

What evolutionary novel trait do amphibians have as vertebrate tetrapods?

four complex limbs

What is unique about the hind limbs of some salamanders?

hind limbs can be reduced in some species

What is unique about the hind limbs of caecilians?

they lack it

Describe the skin of amphibians?

moist and permeable; absorbs water

What type of respiration do amphibians use?

lungs, skin, mouth, gills (only in axolotls and larvae)

How are amphibians' senses?

can see color, frogs and toads have well-developed hearing while salamanders do not

What is the diet of amphibians?

carnivorous

How do amphibians regulate body temperature?

ectotherms; basking in sun or on warm surfaces, seeking shade or water to cool; no need for metabolic activity

What type of development do amphibians undergo?

complete metamorphosis (larval stage > metamorphosis > adult stage)

Which amphibian species retain their larval stage as adults?

axolotls

What are the larvae of frogs and toads called?

tadpoles

What feeding strategies do tadpoles use?

filter feeders or predators

What are key features of tadpoles?

gills, long-finned tails, no limbs

What major changes occur during tadpole metamorphosis?

lose tail and gills, develop four limbs, fully hinged jaw, digestive system, eardrum, and lungs

How many chambers does an amphibian heart have?

Three chambers: two atria and one ventricle.

What happens when blood enters the ventricle in amphibians?

oxygenated and deoxygenated blood mix before mixture is pumped out to the body

What type of circulatory system do amphibians have?

double circuit: blood flows from heart > lungs/skin > heart > body

What is the one subclass of amphibians?

lissamphibia; three orders