Kingdom Animalia Subkingdom Eumetazoa Bilateria Phyla … 3A/Bio... · 2016-08-26 · •Some had hook-like teeth –Cartilaginous or bony ... – Large coelom ... •Rays dorsoventrally

Kingdom Animalia Subkingdom Eumetazoa

Bilateria Phyla Hemichordata & Chordata

Professor Andrea Garrison Biology 3A

Illustrations ©2014 Cengage Learning unless otherwise noted

Text ©Andrea Garrison 2014

Phylum Hemichordata

• Acorns worms (hemi = half; chorda refers to chordates)

• Marine • Sedentary

– Live in U-shaped tubes in sand or mud

• Muscular proboscis • Collar • Elongated trunk • Coelomate • Deuterostomes

2 Hemichordata and Chordata

Phylum Hemichordata

• Share some of the chordate traits – Pharyngeal gill slits

• Trait of chordates • Cilia create water flow in mouth

and out through gill slits – Suspended particles caught

for food – Respiration

– Dorsal nerve cord • Also have reduced ventral

nerve cord

– Rudimentary structure similar to notochord

• DNA evidence indicates more closely related to echinoderms


Phylum Chordata

• Coelomate

• Deuterstomes

• Share common chordate characteristics at some point in their life – Notochord

– Postanal tail

– Dorsal hollow nerve cord • Dorsal to notochord

– Pharyngeal gill slits

– Segmented muscles in body wall


Phylum Chordata

• 3 subphyla

– Invertebrate chordates

• Lack vertebrae

• Small, marine suspension feeders – Use pharyngeal gill slits for feeding and respiration

• Subphylum Cephalochordata

• Subphylum Urochordata

– Vertebrate chordates

• Subphylum Vertebrata


Subphylum Cephalochordata

• Lancelets (28 species)

• Chordate characteristics as adults

• Warm, shallow marine waters

• Sedentary

– Burrow into sand

– Filter feeders


Suphylum Urochordata

• Tunicates (Oura = tail); aka sea squirts

• Chordate characteristics as free-swimming larvae – Lose nerve cord, most of

notochord and tail in adults • Pharynx with gill slits

remains

• Larvae settle and metamorphose into sessile filter-feeding adults

Hemichordata and Chordata 7

Suphylum Urochordata


Subphylum Vertebrata

• All common chordate characteristics present at some point during life – Fish keep them throughout life

• Possess endoskeleton (usually bone) – Cranium (well-developed cephalization)

– “Notochord” broken into vertebrae • Protects nerve cord

• Possess neural crest

• Large, well-developed brain



• Skeletal structure – Axial skeleton

• Vertebral column – Vertebrae protect nerve

cord

• Cranium – Protects brain

– Appendicular skeleton • Girdles and appendages

w/joints • Anterior pectoral girdle

– Attach bones of forelimbs to axial skeleton

• Posterior pelvic girdle – Attaches bones of hind

limbs to axial skeleton



• Neural crest – Tissue from ectoderm

• Has been called 4th germ layer because of its importance

– Develop next to early nervous system

– Later cells scatter throughout body

• Large brain with 3 regions – Forebrain – Midbrain – Hindbrain



• As we study the vertebrate classes, we see development of derived traits – Variety in body form and function

• Evolutionists hypothesize these changes due to mutations in homeotic genes – control rate of development of certain body part(s) – Influence size and location of body part(s) – Hox gene complex felt to play a large role in

vertebrate evolution • More advanced vertebrates have more copies of the

complex


Hox Genes & Vertebrate Evolution


Vertebrate Phylogeny


Early Vertebrates (Now Extinct)

• Agnatha (a = without; gnath = jaw)

– Lacked jaws • Some had hook-like teeth

– Cartilaginous or bony skeleton

– Conodonts soft-bodied

– Ostracoderms heavily armored • Sucked mud into mouth


Early Vertebrates (Now Extinct)

• Gnathostomata (gnath = jaw; stom = mouth)

– Jaws • Upper jaw fixed in place

• Mouth inflexible

– Spiny shark related to extant bony fishes


Extant Vertebrate Groups

• Not all Agnatha and Gnathostomata are extinct • Superclass Agnatha—hagfishes and lampreys • Superclass Gnathostomata—jawed vertebrates

– Class Chondrichthyes—sharks, rays – Class Osteichthyes—bony fish – Tetrapods

• Class Amphibia—frogs, toads, salamanders • Class Reptilia—lizards, snakes, turtles, crocodilians • Class Aves—birds • Class Mammalia—mammals


Typical Vertebrate Organ Systems • Other vertebrate characteristics

– Large coelom • Organs held in place with mesenteries

– Well-developed muscles – Closed circulatory system

• #heart chambers related to ectothermy or endothermy

– Well-developed digestive system – Well-developed respiratory system

• Gills if aquatic • Lungs if terrestrial

– Well-developed excretory system • Kidneys • Ammonia, uric acid or urea

– Well-developed reproductive system • Dioecious • Egg development

– Oviparous – lay eggs – Ovoviviparous – embryo with large yolk, develop in oviduct, young born live – Viviparous – young nourished by mother via “placenta”, born live

• As we go through vertebrate groups, we’ll see adaptations in these systems


Superclass Agnatha

• Lack jaws, scales • Cartilaginous skeleton • Hagfishes

– Release lots of mucus

• Lampreys – Ectoparasites

• Cylindrical body • Branchial pouches

– Gill filaments attached to walls of pouch

• No paired fins (lack stability in water) • 2-chambered heart

– Ectothermic • low O2 needs

• Excrete ammonia – Immediately diluted in water

• Oviparous – Large larvae

• 3-7 yrs as larvae in freshwater

– Hagfish possess both sex systems initially, but only one matures


Superclass Gnathostomata Class Chondrichthyes

• Sharks, rays (khondros = cartilage; ikhthys = fish)

• Cartilage skeleton

– Bony fishes present in fossil record prior to this lineage splitting off

– Loss of bone derived trait

• Most marine predators

– Teeth derivatives of epidermis (true of all verts)



• Movable jaws

• Rays dorsoventrally flattened

• Spend time on bottom

• Feed on benthic invertebrates

– Teeth designed to crush shells


Anatomy of a Female Shark


2 dorsal fins caudal fin

2 pelvic fins

2 pectoral fins

lateral line

Spiracle --incurrent flow

Gill slits (5 or 7) --excurrent flow


• Sharks – General fish-like external

anatomy • Adapted to living in water

• Paired fins provide stability

– Skin with dermal teeth

– Poor eyesight

– Other senses well-developed • Electroreceptors on head

• Lateral line picks up vibrations in water

– Large, oily liver aids buoyancy

– Excrete ammonia



• Sharks

– Teeth develop in whorls and move forward as teeth lost

– Internal fertilization • Oviparous or ovoviviparous

• Males have claspers

– Transfer sperm to female


Superclass Gnathostomata Class Osteichthyes

• Bony fish (oste = bone; ichthy = fish)

• Most abundant vertebrates • Freshwater, marine • Bony skeleton

– Elaborate modifications of jaws for different feeding styles

• Gills in common chamber protected by external operculum

• Mucus covering retards bacterial growth and smoothes water flow

• Excrete ammonia


Modified by A. Garrison


• Appendages are fins

– Supported by thin bony rays

• Ray-finned fishes

• Most abundant fish group

-OR-

– Supported by internal bony skeleton and muscles

• Fleshy-finned fishes

• Less diverse than ray-finned fishes

• Ancestors of tetrapods


Modified by A. Garrison


• Ray-finned fishes

– Very diverse

– Articulated fins • Stability

• Ability to brake and turn

– Scales

– Many with swim bladder • Fill with gas from blood

for buoyancy

– Oviparous or ovoviviparous



• Fleshy-finned fishes – Coelacanths marine

– Lungfishes freshwater • Have gills and lungs

– Lungs supplement gills respiration when O2 content low in Australian species

– Lungs collect O2 during dry season, when they are dormant in mucus –lined burrow in dry mud in African and South American species

• Use lobbed fins to move from puddle to puddle



1 caudal fin

1 or 2 dorsal fins

1 anal fin

2 pectoral fins

operculum

2 pelvic fins

385 MYA—Moving to Dry Land

Advantages

• Plenty of food – Land plants, invertebrates

• Environment rich in oxygen

• Lack of predators

Hurdles • Avoiding desiccation

– Gills – Moist skin – Eggs

• Reproducing without shedding eggs/sperm into water

• Storage of excretory wastes requires non-toxic waste

• Air offers less body support than water

• Sensory structures often collapse out of water


Moving to Land—Evolutionary Developments

• To avoid desiccation – Lungs replaced gills

• Don’t collapse or dry out in air

– Tough dry skin replaced moist skin • Skin cells filled with keratin and lipids

– Creates waterproof covering

– Amniotic egg replaced typical aquatic egg and larval development • Membranes protect embryo and allow

gas exchange and excretion of wastes • Shell is porous and allows gas & water

exchange with environment

• To fertilize egg without water, requires internal fertilization (copulation)



• To avoid toxic wastes issues

– Fish excrete ammonia • Toxic; requires lots of water to

flush from tissues

– Terrestrial vertebrates often excrete uric acid • Less toxic, requires less water to

flush from system



• To provide more body support

– Stronger vertebral column

– Sturdier girdles

– Rib cage to protect internal organs

• Tetrapod



• To provide sensory information

– Tympanum picks up vibrations in air

– Stapes transfers vibrations to inner ear

Hemichordata and Chordata; photo by Carl D. Howe; http://commons.wikimedia.org/wiki/File:North-American-bullfrog1.jpg http://creativecommons.org/licenses/by-sa/2.5/deed.en

34

Superclass Gnathostomata Class Amphibia

• Frogs, salamanders, etc. (Amphi = of both kinds; bios = life)

• Tetrapod • Vertebrate characteristics • Adult with lungs • Not free from water

– Moist skin absorbs water when needed

– External fertilization; oviparous • Jelly-coated egg; not amniotic

– Larval development • Tadpole larva w/gills

• Large mouth, small teeth – Swallow prey whole – Nostrils and respiratory tract open

into oral cavity



• Adults carnivorous, juveniles herbivorous

• Circulatory system w/3-chambered heart – 2 atria, 1 ventricle – Mix oxygenated and

deoxygenated blood – OK—ectothermic, so low

energy needs

• Excrete urea (toxic) – Spend time around water

• Cloaca – Empties intestine, reproductive

ducts, excretory bladder



• Order Anura – Frogs, toads

• Order Caudata – Newts, salamanders

• Order Gymnophiona – Caecelians – Tropical – Legless burrowers – Bony scales embedded in

in skin – Internal fertilization – ovoviviparous


Phylogeny of Terrestrial Tetrapods (Amniotes)


Superclass Gnathostomata Class Reptilia

• Lizards, snakes, turtles, crocidilians (reptil = to crawl)

• Fully terrestrial – Dry skin

• Keratinized scales or dermal bones covered by epidermis

– Internal fertilization • Copulatory organ

– Amniotic egg • Oviparous or ovoviviparous

– Lungs throughout life cycle – Excrete uric acid

• cloaca

• Well-developed teeth – Various types – If venomous, it travels down groove or canal

in fangs

• Imperfect 4-chambered heart – Hole between ventricles – Perfect 4 chambers in crocodilians – Ectothermic


Superclass Gnathostomata Class Reptilia

• Order Testudines – Turtles

• Shell of bone covered by keratin

• Vertebrae attached to inside of dorsal shell

• Order Squamata – Lizards and snakes

• Order Crocodilia – Crocodiles and alligators

• Order Aves – Birds—closely related to

Crocodilia—so they are reptiles?


?

Superclass Gnathostomata Class Aves

• Birds (aves = bird) • Descendants of bipedal

dinosaurs • Fully terrestrial tetrapods

– Dry skin – Lungs (small) – Scales – Internal fertilization (no

copulatory organ; juxtapose cloaca)

– Amniotic egg – Excrete uric acid

• Cloaca



• Forelimbs modified as wings

• Scales

• Feathers (= modified scales)

• Well-developed digestive system – Crop for food storage, 2 part

stomach includes gizzard (gravel to grind food)

• 4-chambered heart – Double circuit

– Endothermic • High O2 needs



• Modifications for flight – Streamlined body shape

– Feathers • Developed from reptilian

scales

– Lightweight • Fewer bones in limbs;

lightweight

• Bone marrow replaced with system of air sacs attached to respiratory system but not used for O2

• No excretory bladder



• Modifications for flight (cont.) – Bones fused for strength

• Bones of cranium; lumbar vertebrae; pelvic & pectoral girdles to vertebrae;

– Large sternum for attachment of flight muscles

– Wing muscles large, attach to sternum on ventral side of body • Lowers center of gravity • Improves aerodynamics

– Muscles at base of tail control feathers important for flight


Superclass Gnathostomata Class Mammalia

• Humans, dogs, cats, rodents, etc (mamm = breat; al = pertaining to)

• Derived from reptilian ancestor (different from birds)

• Fully terrestrial tetrapods – Dry skin – Lungs – Internal fertilization

(copulatory organ) – Amniotic egg – Excrete urea

• different



• Integument with 2 layers – Epidermis and dermis

• Hair or fur – Hair follicle developed

from epidermis

– Sensory whiskers, bristles modified hairs

• Mammary glands – Derived from epidermis

• Movable eyelids

• External ears



• Skeleton

– 7 cervical vertebrae

– Limbs and girdles adapted for lifestyle • Fast runners

– Reduced clavicle and #toes

• Climbers

– Stronger clavicle, limbs elongated



• Teeth and digestive system vary with diet – Herbivores eat lots of cellulose

• No enzymes to break it down • Long digestive tract w/bacteria to

break it down • Inefficient, so eat lots of food

– Insectivores • Eat insects • Digestive system specialized to

break down chitin – Strong gastric enzymes – Stomach lined with tough

epithelium

– Carnivores eat more protein • Easier to digest • Shorter digestive tract • Fewer meals • Premium on intelligence



• Highly developed brain – Convolutions to increase surface

area

• 4-chambered heart – Endothermic

• High O2 needs

• Reproduction – Dioecious – Internal fertilization – 3 types

• Monotremes – Oviparous

• Marsupials – Viviparous; young develop

partially in uterus, then born to grow in pouch attached to teat

• Placentals – Viviparous; young develop fully

in uterus


General Vertebrate Pattern

• Ectotherms

– Agnatha

– Chondrichthyes

– Osteichthyes

– Amphiba

– Reptila

• Endotherms

– Aves

– Mammalia

– BUT what about . . .


A Very Unusual Vertebrate

• Endothermic mesopelagic fish – Opah (Lampris guttatus) – Produces heat by flapping

pectoral fins – Retains heat using counter-

current heat exchangers in gills • Warm blood from heart runs

alongside cooler blood from gills to heat it before the blood goes to body

– Distributes warm blood to heart and rest of body

Hemichordata and Chordata; photo: NOAA 51

Documents

Kingdom Animalia Subkingdom Eumetazoa Bilateria Phyla … 3A/Bio... · 2016-08-26 · •Some had hook-like teeth –Cartilaginous or bony ... – Large coelom ... •Rays dorsoventrally