Zoology Final Exam (BIO-2040)

Unique Characteristics of Chordates

1. Dorsal nerve cord

2. notocord

3. pharyngeal pouches/slits

4. post-anal tail

Dorsal Hollow Nerve Cord

• Other phyla have solid nerve cords

• central nervous system (brain and spine)

Notochord

• flexible, dorsal structure rod

• axis for muscle attachment, locates below nerve cord

• it persists in early chordates

• replaced by bones in vertebrates

Pharyngeal slits

similar to that of hemichordates

• originally for filter feeding, now adapted for feeding/respiration

Endostyle

A gland intimately associated with paryngeal slits, it produces mucus to trap food particles

Muscular post-anal tail

• usually related to segmented musculature

• primarly for propulsion

• works with notochord/vertebrates

• best developed in fish at larval or adult stages

Later Chordates

Craniata

Cephalochordata

• about 23 species

• have all 4 chordate characteristics

• 5-15cm in length

Cephalochordata Locomotion

• use notochord and segemented muscles

Cephalochordata Feeding

• mouth pulls in water, goes through pharyngeal slits, food trapped by mucus, water goes into the atrium then out

Urochordata

• tunicates or sea squirts, about 3,000 species

• name from “tunic”

• look like barrets and have prominent brachial basket

• most are solitary

Urochordata Adult

• gill slits remain

• notochord and tail disappear

• nerve cord becomes reduced

Urochordata feeding

Water circulation

• Incurrent Siphon → Pharynx → atrium and out

Craniata

• vertebrate (mostly)

• notochord replaced by spine

Craniata Innovation

• formation of living endo-skeleton

• not heavy, made from calcium phosphate

Craniata unique thing

They are made from calcium phosphate

lamprey

• has cranium but only rudimentary vertebrate

• marine and freshwater (most parasitic)

Hagfish

• has cranium no vertebrate

• all marine

• slime eel

Gnathostomatha origin of jaw

from modification of first gill arch

→ first arch become main jaw

→ second arch became main support

→ first gill slit is reduced

Have cranium and well formed vertebrate

Gnathostomatha include

• fish

• amphibians

• reptiles

• birds

• mammals

Fish Classes

1. chondrichtyes (shark and ray)

2. Osteichthyes (bony fish)

Chondrichtyes

• about 850 species

• skeleton made of cartilage bones

• includes shark, ray and skates

Chondrichtyes key characteristics

• heterocercal tail

• placoid scales

• exposed gill slits

• large pectoral fins

• ventral mouth

Chondrichtyes general morphology

• sharks have jaws with rows of teeth they regrow frequently

• mouth opens to pharynx and gill slits

Chondrichtyes locomotion

• streamlined body for speed swimming 

• strong heterocercal tail and large pectoral fins

Chondrichtyes sensory organs

• great vision with enlarged view feilds

• olfactory system able to detect 1 part/ 10 billion

• lateral line to detect vibrations

Class Mammalia

hairy vertebrates with mammalia glands

subclasses of Mammalia

• monotremes

• theria

infraclasses of theria

• marsupials

• eutherian

Prototherians

monotremes

• very low diversity

• lay eggs

• platypus and echidna

• no nipples

• have a pouch for newborns and large cloaca

Metatherians

marsupials

• give birth to underdeveloped kids

• have a pouch

• kangaroos and tasmanium devil

• short gestation and long lactation

viviparous

give birth

oviparous

lay eggs

Eutherians

placentals

• over 90% of animals

• all babies have hair

• viviparous and have placenta

• short lactation and long gestation

four advanced social behaviours of eutherians

1. vocal communication

2. development of heirachys

3. friendship and sexual behaviour

4. high learning ability

Ostichthyes

• bony fish

• main type is teleosts (96% of all fish forms)

• most diverse vertebrate

5 key characteristics of Ostichthyes

1. Cycloid/ Ctenoid scales

2. operculum cover gills

3. small pectoral fins

4. The mouth is terminal

5. homocercal tail

Adaptive Radiation of Ostichthyes

• mouth & jaws have adapted to many shapes and feeding modes

key adaptation of Ostichthyes

• a swim bladder that grew from the gut to help position them in the water

• A lateral line was perfected as a sensory organ

Paedomorphosis

retension of juvenille traits in the adult

Highland fish adaptions

large gills for low oxygen

intertidal fish adaptation

loss of the swim bladder

deep sea fish adaptation

lack colour and develop a fishing pole

Commercial Importance of Ostichthyes

due to their variety and abundance, people have a strong dependancy on fishery resources

aquaculture may provide much of the protein but it relys on fishing

Subsistence fishing

by natives, local-scale fishing

Commercial fishing

most people, large-scale fishing

New Density Habitat

• Air is 50x less dense then water

• solution → added size and strength to limbs

New habitat is dry/hot

• air means desiccation risk and breathing outside the water

• solution → lungs instead of gills

Characteristics of transition creatures (amphibians)

1. Reproduction remains confined to water or very moist habitats

2. small eggs, mostly unprotected, normally deposited in masses

3. moist and permeable skin (ectothermal)

4. skeleton and limbs grow stronger

Amphibian classification

1. Apoda

2. Caudata

3. Anura

Apoda

• no legs

• few cm - 1.5m long

• all tropical (160 species)

• most blind as adults breath by skin and lungs

Apoda Reproduction

• internal fertilization

• eggs are lay on water or moist ground near water

• tadpole larva with gills

Unique features of Apoda

• having internal fertilization

• being blind as adults

Caudata life cycle

• always external fertilization, eggs laid in jelly masses

• larva have gills that turn to lungs as an adult

Anura

• no tail

• diverse and distributed

• metamorphosis

Anura Reproduction

• external fertilization

• eggs in water

• tadpoles with gills morph into adults with lungs and skin

Amplexus

the female lays eggs and the male attatches to her back to add sperm, this is a hug, not copulation

Differences between frogs and toads

frogs → smooth skin, pointy nose, long legs, live close to water, bright colours

toads → rough skin with warts, broad nose, short legs, explore far from water, dull colours

Reptiles

• more dominant in the dinosaur era

• mostly ectotherms

4 adaptation of Reptiles

1. egg with amnion

2. well adapted to dessication

3. copulatory organ

4. upgraded jaw + skeleton

Egg with amnion

A thin membrane with fluid that protects the embryo

well adapted to desiccation

• skin with scales: heavier, thicker, and non-permeable

• also excrete highly concentrated urine to prevent water loss

Copulatory Organ

• Internal fertilization is now mandatory

• The cloaca holds reproductive organs

How are Reptiles classified

based on the presence and number of temporal openings in skull

Classification of Reptiles

Anapsids → no Temporal opening

Synapsids → one temporal opening

Diapsids → two temporal openings

Anapsids

• turtles

• about 300 species

• oviparous

Anapsids shell

distinctive feature, evolved for protections

dorsal carapace + ventrral plastron

carapace = vertebrate and ribs fused

Land Turtles

can retract head, have strong walking legs

Sea Turtle

cannot retract head, limbs become flippers

Synapids

several extinct reptiles

• therapsids → ancestor of mammals

Diapsids

• most were dinosaurs

• there are 4 main living groups

Lizards (Diapsids)

• detach tail

• some are huge

• can camouflage

Snakes (Diapsids)

• 2,700 species

• derived from lizards

• boas and phytons are most primitive

• known for vemon

Neurotoxins

stop breathing and heartbeat

Hemotoxins

cause blood clots

reptiles with feathers

• birds

• The Archaeopteryx → a fossil of a transitional creature, a reptile with bird characteristics

Main innovations of birds 

1. feathers

2. fly skeleton and muscles

3. temperature regulation 

4. respiration

5. reproduction and behaviour

Feathers

• distinctive features

• derived from reptile scales

Flight feathers

strong; cover and support wings

Contour Feathers

weak; keep and regulate heat

Pneumatized

bones are porous, strong but light-weight

skeleton and flight muscles of birds

• vertebrate fused to ribs, with a sternum and a keel for flight muscle

• skull is fused into one peice; jaws lack teeth

Endothermic

body generates it’s own heat

Homothermic

body maintains a constant temperature

bird respiration and air sacs

well-developed lungs and blood irrigation.

• air sacs that serve as a reservoir of fresh air

Reproduction and Behaviour

well developed brain for flight, balance, hearing, and visual systems

• behaviour and visual displays

Imprinting 

young-parent recognition

shared features of arthopoda and annelida

1. arthropod-like cuticle

2. un-jointed legs

3. partial segmentation

Echinoderms

spiny skin animals

marine with penta radial symmetry

penta radial symmetry of echinoderms

secondary adaptation

1. ancestors were all bilateral

2. larve were all bilateral

Unique water vascular system of echinoderms

• the amburarcral system

• internal system with radial canals connected to out-pockets of body wall

• involved in multiple roles

madreporite

a dorsal plate with tiny canals that handle water pressure

Papulae

dermal gills of the coelom that help with excretion and gas exchange

• Most solids are expelled via the mouth, fine excretion is done by these

Pedicellaria

claw-like structures, keep surface clean for papillae

Radiation of Echinoderms

• starfish

• brittle stars

• sealillies

• sea cucumbers

• echinoids

Class Asteroidea

• a central disk surrounded by 5+ arms (with organs in them)

• ossicles of the endoskeleton protrude as blunt spines

• a keystone predator

Asteroidea movement

using podia or tube feet

Asteroidea feeding

• by double stomach (pyloric and cardiac)

• cardaic stomach emerges through the mouth to digest prey

Asteroidea sexual reproduction

gonads located on each arm

Asteroidea asexual reproduction

be regeneration of arms, they do this often