Zoology Exam IV

Arthropoda + Animal Behavior + Echinodermata + Chordata

Phylum Chordata: 3 Living Subphyla

Urochordata, Cephalochordata, Vertebrata

Phylum Chordata: Major Groupings

“Agnatha”, Gnathostomata,Tetrapoda, Amniota

Supraclass “Agnatha”

jawless fish

• class myxini - hagfishes

• class petromyzontiformes - lampreys

Group Amniota

Class “Reptilia” - reptiles

• subclass anapsida

  • order testudines - turtles & tortoises

• subclass diapsida

  • order sphenodonta - tuatara

  • order squamata - lizards & snakes

  • order crocodylotarsi - alligators & crocodiles

  • order ornithischia - bird hipped dinosaurs

  • order saurischia - lizard hipped dinosaurs

Class Aves - birds

Class Synapsida

• order pelycosauria - early mammal like reptiles

• order therapsida - late mammal like reptiles

subclass mammalia - mammals

• infraclass prototheria - platypus & echidnas

• infraclass metatheria - marsupials

• infraclass eutheria - placental mammals

Supraclass Gnathostomata

jawed vertebrates

• class placodermi - placoderms

• class chondichthyes - sharks, skates, rays, & chimeras

• class acanthodii - acanthodians

• class “actinopterygii” - ray finned fishes

• class “sarcopterygii” - fleshy finned fishes

Superclass Tetrapoda

Class Amphibia - amphibians

• order labyrinthodontia - labyrinthodonts

• order anura - frogs & toads

• order urodela - salamanders & newts

• order gymnophiona - caecilians

Urochordata

tunicates, sea squirts, & salps

Cephalochordata

lancets & amphioxus

Vertebrata

fishes, amphibians, reptiles, birds, & mammals

Pharyngeal Gill Slits

Phylum Chordata Synapomorphy

• Effect: Allows water to flow through the body, picking up food

• Innovation: More efficient food capture

Endostyle

Phylum Chordata Synapomorphy

• Effect: Produces mucus to pick up food

• Innovation: More efficient food capture

Post-Anal Tail

Phylum Chordata Synapomorphy

• Effect: Further isolates muscles of locomotion of the gut

• Innovation: Specialized locomotion

Notochord

Phylum Chordata Synapomorphy

• Effect: Stiffens body so muscles bend rather than telescope

• Innovation: More efficient locomotion

Dorsal Hollow Nerve Cord

Phylum Chordata Synapomorphy

• Effect: Allows cerebrospinal fluid to diffuse nutrients to larger brain & spinal cord

• Innovation: Bigger body size

Caenorhabditis elegans

• phototaxis: react (move due) to light

• photophobia: don’t like light - move away

Horse Fly

• thermotaxis: react to heat

• thermophilic: like heat - move towards

Lumbricus terrestris

• vibrotaxis: react to vibrations

• vibrophobia: don’t like vibrations - move away

Ground Squirrel

communication

• tonal: changing tone changes meaning

Dolphins

communication + cognition

• invent new moves together

Crows & Jays

problem solving + intelligence

• use/make tools

Rhesus Monkeys

choice + preference

Karl Von Frisch (1886-1982)

studied honey bee communication

• translated meanings to the waggle dance

Niko Tinbergen (1907-1988)

“father of modern ethology”

• observed birds feeding fish

Genetic vs Learned - 3 Methods

• deprivation & learning experiments

  • isolate young

  • behavior exhibited = genetic, not = learned

• interbreeding experiments

  • interbreed species w/ different behaviors

  • offspring display mixed behaviors = genetic, not = learned

• gene knockout experiments

  • identify & mutate a gene possibly responsible for behavior

  • behavior changes = genetic control

Ultimate Questions - Why?

• based on microeconomic theory

• underlying assumption - particular behavior should benefit fitness (beyond costs):

  • increased mating (individual fitness - direct passage of genes)

  • increased food

  • increased inclusive fitness - family are more successful due to individual efforts

Types of Costs (Grouse)

energetic: use energy in displays

risk: not paying attention to predators

opportunity: not using time to feed/drink

Proximate Questions - How?

underlying mechanisms of behavior

• genetic vs learned

  • nature vs nurture

  • evolutionary vs non-evolutionary

widow birds

runaway sexual selection

• females prefer males w/ abnormally long tail feathers

  • males struggle to fly - easier prey

irish elk

runaway sexual selection

• males had extremely large antlers that females preferred

  • antler size possibly meant males struggled to survive - likely resulted in extinction

stalk-eyed flies

runaway sexual selection

• males w/ more distance between eyes is preferred by females

manakin birds

runaway sexual selection

• males have increasingly long & elaborate mating dances - moonwalk

  • dances can involve other males

Female Behaviors

females are choosy - QUALITY over quantity

• greater investment of energy

• often raise young alone

• maternity is guaranteed

Male Behaviors

males are more “liberal” - QUANTITY over quality

• low investment of energy

• often provide no parental care

• paternity not guaranteed

monogamy

type of pair bond - albatrosses

• 1 male & 1 female

• mate for life beginning at maturity (18-20 years)

• will not find another mate after 1 dies

  • very rare

polygamy

1+ mate over a season

promiscuity

multiple males & females - bonobos

• mate w/ multiple individuals during season

• no specific mating pairs

  • males mate w/ males, females, & self

polygynous systems

lekking, female-dense polygyny, & resource-defense polygyny

polyandrous system

polyandry - extremely rare

polyandry

jacanas - 1 female & many males

• female lays eggs & male cares for chicks - initially take turns but female goes off to start new nest

• females fight over males - larger, compete, have 4-5 mates

  • female has many males protect her nests

  • many nests likely due to crocodile predation

lekking

grouse & pufferfish - 1 male w/ multiple females

• females watch dances & choose male based off it - join their harem

  • female chooses a mate based on qualities

  • female chooses male w/ other females

female-defense polygyny

lions - 1 male defends 2+ females

• females have strong bond & stay together

  • males are satellites & defend territory when females come into heat

  • male is just only available mate in area - females aren’t really attracted to them

  • males protect females against males

resource-defense polygyny

elephant seals - 1 male controls territory/resources/females

• males arrive early to breeding grounds & claim territory/resources

• females have to come to land to give birth & immediately go into heat after

• females don’t really find males attractive - simply go into their territory for resources

  • males protect resource females need

Urochordates structure

tunicates, sea squirts, ascidians, salps

• synapomorphy: notochord in tail only

• filter feeders

Cephalochordates structure

amphioxus & lancets

• synapomorphy: notochord extends over head & w/out vertebrae

• filter feeders

chordate fossil origin: pikaia

cambrian

• best candidate for a long time

chordate fossil origin: haikouella

cambrian

• preserved soft anatomy

• endostyle tbd

  • has all features of modern cephalochordates

  • best modern candidate

chordate fossil origin: conodonts

cambrian → triassic

• chordate features: true bone & enamel

rhombencephalon

back section of tripartite brain

• basic function

mesencephalon

midsection of tripartite brain

• conduit of information between both parts

prosencephalon

front section of tripartite brain

• higher thought/function

Neurulation

leads to the development of the central nervous system, starting around 21 days postfertilization in humans

• involves primary neurulation for neural tube closure & secondary neurulation for spinal cord formation at lower levels

vertebrate origins

cambrian - 550 MYBP

• step 1/4

evolution of jaws

silurian - 430 MYBP

• step 2/4

invasion of land

devonian - 350 MYBP

• step 3/4

development of amniotic egg

carboniferous - 325 MYBP

• step 4/4

Composite Theory

evolution of jaws

• gills of all fishes supported by a skeletal system called the branchial arches

  • initial role: pharyngeal pumping

  • later role: seizing prey & take bites

Invasion of land by vertebrates

predator avoidance hypothesis - out of water & away from predators

dry pond hypothesis - water ways dried up

terrestrial resource hypothesis - more food available on land

water→land FEEDING challenge

• suction (-/intraoral pressure) → lingual (tongue) feeding

water→land INTEGUMENTARY challenge

• scales → thick, keratinized skin

water→land CIRCULATORY/RESPIRATION challenge

• gills → lungs

• low → high blood pressure

water→land SKELETAL challenge

• vertebrae not interlocking

  • could not handle gravity

• fins not feet

  • nothing to stand on

• pectoral girdle braces head

  • head connected to chest - no neck

• pelvic girdle not connected to spine

  • legs not connected to spine - no locomotion under pressure from gravity

amniotes

4 double layered extra-embryonic membranes (round)

• yolk sac: nutrition

• chorion: separates embryo & environment - respiration

  • receives O2

• allantois: respiration & waste storage

  • transfers O2 between embryo & chorion

• amnion: protects embryo & prevents water loss

  • blue-red-red-yellow/blue

anamniotes

1 double layered extra-embryonic membrane (pear-shaped)

• yolk sac: provides nutrition

  • blue-red-yellow

splanchnocranium

jaws & gills

dermatocranium

outer shield + teeth/palate?

chondrocranium

brain case

anapsid

w/out holes/arches behind orbit

• testudines & basal tetrapods

  • small muscles → weak bite

diapsid

2 holes/arches behind orbit

• upper arch: postorbital + squamosal

• lower arch: jugal + quadratojugal

• non-testudine reptiles & birds

  • bigger muscles → powerful bite

synapsid

1 hole/arch behind orbital

• lower arch: jugal + quadratojugal

• mammal-like reptiles & mammals

  • bigger muscles → powerful bite

hypocercal

upper lobe smaller than lower lobe

• lives in lower water column

• tail morphology → pushes down

diphycercal

lobes same size & connect at end of tail

• swimbladder ?

homocercal

lobes same size

• swimbladders regulate vertical position

hyper/heterocercal

upper lobe larger than lower lobe

• lives in upper water column

• tail morphology → pushes up

epidermal scale

reptile - thick keratinized epidermis

dermal denticle

teeth skin - chondrichthyans

• enamel + dentine + pulp

ganoid scale

gar - diamond shaped

ctenoid scale

goldfish - cone shaped

cycloid scale

herring - silvery & round

shark hunting senses

hearing: 1000-2000 m

smell: 200-500 m

lateral line: 100-200 m

• senses movement using waves in cupula

vision: 10-80 m

ampullae of lorenzini: 0-5 m

• jelly filled sensory pore

pitcher plant frog

raise young in pitcher plants that collect water to keep young hydrated

poison arrow dart frog

tadpoles suction to parents back as they travel to wet locations to keep hydrated

marsupial frog

tadpoles live in pouch of skin on back of parent - keeps young hydrated + safe

suriname toad

hole toad ☹

darwins frog

keep young in stomach + don’t eat - keep young hydrated & safe

midwife toad

keep young on back end & travel to wet locations to keep young hydrated

snake feeding

• lower jaws: swing out laterally & jointed in the middle

  • left/right lower jaws joined by elastic tissue at the bottom

• upper jaws: mobile & move independently

  • bring food into mouth/throat

feather anatomy

• calamus - sticks into skin

• rachis - central tether for vanes

• vane - individual extensions

  • barbs + barbules + hooklets

    • barbules & hooklets lock together like velcro

Origin of flight in birds

• tree-down hypothesis

• ground-up hypothesis

ground-up hypothesis

• bournoulli’s effect helped early birds climb/speed

• used wings + speed to gain altitude up trees

tree-down hypothesis

• baby birds have clawed wings for climbing

• tail + teeth + other features made early bird VERY heavy so true flight was unlikely - glided down from trees

Bernoulli’s principle

wings must have camber

• faster flow over wing → low pressure

• slower flow under wing → high pressure

  • generates lift - normal force

secondary palate

2 plates of bone separate mouth from brain

• advantage: breathe while eating & possibly protection from sharp prey (unlikely)

complex ear

3 middle ear bones/ossicles

• malleus, incus, & stapes

• advantage: low + high frequencies

heterodonty

teeth are differently sized/shaped w/ different functions

• incisors/canines - biting & premolars/molars - chewing

• advantage: breaks down food

Subphylum Myriapoda

• class chilopoda: centipedes

• class diplopoda: millipedes

Class Pyncogonida

sea spiders

• body greatly reduced

• carry eggs

Class Merostomata

horseshoe crabs

• walking legs act as gnathobase

• carapace covers tagmata

aposematic coloration

bright colors - dangerous/warning

cryptic coloration

environmental colors - try to hide/disguise