Lecture 16 + 17 (BIO-2040)

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

Skin evolution of Ostichthyes

primitive fish had a dermal (heavy) armour. This has replaced with thin scales for advanced mobility

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

Alligators & Crocidiles (Diapsids)

23 species

• largest living reptile

• all tropical except american alligator

• known to leave eyes, nostrils, and ears above the water

• can live 70yrs

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