Vertebrates 2 - Amphibians

ostei vs chond meaning

osteichthyes - boney

chond - cartilage

Swim Bladder - who, function, similar to…

*key innovation of boney fish

• flotation device (neutral buoyancy)

• regulate gas

• homologus to tetrapod lungs (lung is the synapomorphy…one became swim bladder other more developped lung)

two mechanism of gas regulation with swim bladder

• gulp air from surface and ‘burp out’ to sink down

• gland in bladder that regulates gas internally

Why Tetrapod moved to land

• devonian droughts (~400 mya)

  • high competetion

  • low dissolved o2

• new food resources on land … no predators (insects were there)

3 water and 1 land differences

• avaible water and moisture and o2 in water

• stability of temp in water

• density of medium (kept shape of blobfish) in water

• move UV radiation outside

Advantages of Resperating Terristrially

• air has higher o2 concentration and gases diffuse faster into body (bc more availbility)

lung evolution

• ventral pockets formed off esophogus

• used as a supplemental respritory device - still use gills but do this if oxygen insufficient or are at surface…

• think about why we choke…lung and airway are connected to same tube where food goes

Problems of Land (4)

1. Water needed (stay moist and for fertilization and larval development)

2. Air is less dense than water (require skeletal support and muscles and then more energy and o2)

3. More variable air temp (need to be able to regulate)

4. UV radiation more intense - need physical protection or behaviour change

Tiktaalik evidence

from 375 mya

aquatic organism that sometimes went out on land

has homolgus structures to our hand

Ichthyostega

from 365 mya

first tetrapod on land

strong boney structure

proper lung evolved more efficient circulatory system

amphibian circulatory system and PROS and CONS

• 3 chambered heart (2 atrium, 1 ventricle)

• blood oxygenated in lungs and skin

• double circuit circulation

• PRO: blood under higher pressure

  • CON: blood is mixed

2 Mechanisms of Breathing

apply boyles law of volume and pressure

1. Negative Pressure breathing (humans) **presure decreases first

1. Positive Pressure breathing (amphibians) - 2 stroke process

Process of Amphibian breathing

air drawn into nostrils with mouth and glottis closed…causing a pressure increasew

nostrils close, glottis opens and air forced into lungs

Amphibian Traits and Diversity

• 6000 species

• 1st tetrapods

• freshwater and terristrial (still depend on water)

• smooth, moist skin (no scales/glands)

• have teeth

• have tadpoles!

2 Life Stages of Amphibians

**key innovation

• larvae (tadpoles)

  • have gills, 2 chambered ❤ herbivores, then undergo metamorphsis

• adults

  • have lungs, 3 chambered ❤ , carnivores

3 Groups of Amphibians

1. Salamanders (Urodela)

• internal fertilization…males drop off sperm and females collect

• some never leave water

2. Frogs and Toads (Anura)

• most diverse

• typically loud courtshipcalls

3. Caecilians (not a real group but he thinks should be)

• loss of apendages

• internal fert

• eat skin off mom

Parental Investment Strats of Amphibians

range…most provide little parental care…some a lot with reproductive oddities from carrying tadepoles on back to in stomach