Lecture 9 RH - Amphibians Flashcards
What are the defining features of phylum chordata?
Dorsal, hollow nerve cord
Notochord
Pharyngeal slits
Postanal tail
What is the distinguishing feature of all vertebrates?
The brain case
What is the reasoning behind the brain case being the distinguishing feature between hagfishes and lampreys?
Hagfishes don’t have vertebrae but lampreys do. They are both vertebrates nevertheless
Where did the amphibians and primitive amniotes arise from?
From the early tetrapods of the devonian period
Is the tetrapod clade mono, para, or polyphyletic?
Monophyletic
Where do all 5 chordate traits appear?
During embryonic life
Why are some reptiles, birds, and mammals living in water?
Due to secondary adaptations to aquatic life
What appeared in sarcopterygii?
Lungs
Tetrapod limbs
What are sarcopterygii?
Lobe-finned fishes
How do air breathing fishes use air to breathe?
Air breathing fishes gulp air and store it in a pocket of the oesophagus.
Where did the lungs arise from in lunged fishes?
The lung formed from an outpocketing of the oesophagus
How did tetrapod limbs arise?
Tetrapod limbs arised in a lineage of lobe-finned fishes in the devonian period 400mya
What do the transitional species between fish and tetrapods show?
The transitional limbs, skull, neck, ribs, etc.
What is the skeleton of amphibians made of?
Strong bony skeleton
How many limbs and digits do amphibians have?
4 limbs and 4 digits per limb
What does amphibian skin feel like?
Smooth and moist
How do amphibians respire?
Lungs, skin, and/or gills
Are amphibians homeothermic or poikilothermic?
They are ectothermic and poikilothermic
How does fertilization happen in amphibians?
External fertilization in toads and frogs.
Internal fertilization in caecilians and salamanders
Do amphibians have a cloaca?
Yes
How are amphibians adapted to both terrestrial and aquatic life?
Most live close to water for some part of the life cycle (for example reproduction in toads and frogs)
Aquatic larvae with gills rely on living in water to survive
Respiration across skin that must be kept moist
What is the double circulation system of tetrapods?
2 circuits of blood delivery:
Pulmonary circulation
Systemic circulation
What variation of the double circulation system exists with amphibians?
Amphibians have a 3 chambered heart.
Septum between atria is absent in lungless salamanders
Septum is complete in anurans
How do amphibians breathe?
Amphibians use positive pressure to force air into the lungs.
1) Lowering of mouth floor draws air through nostrils.
2) Nostrils are closed
3) Floor of mouth is raised forcing air into the lungs
What are the kind of amphibians in order gymnophiona?
Caecilians - 173 species
How many limbs do gymnophiona have?
no limbs
What do gymnophiona look like?
No limbs
Small or no eyes
Mesodermic scales in skin
Where do gymnophionas live?
Burrow in tropical forest soil and ponds.
What do gymnophionas eat?
Worms and small invertebrates
How do gymnophionas reproduce?
Some lay eggs and guard those eggs
Some are viviparous
What kind of amphibians are urodela?
Mostly salamanders and newts - about 550 species
What are the anatomical features of urodela?
Made up of a body which consists of a head, trunk, and tail.
Limbs are at a right angle with the body
Most are less than 15cm long but can be up to 1.5m long
What do urodela eat?
Carnivorous as larvae and as adults.
They eatworms, small arthropods, and molluscs
Is fertilization internal or external in urodelas?
Internal
How does fertlization take place in urodelas?
Spermatophore is deposited inside of the female.
Aquatic species lay eggs
Terrestrial species have direct development
What is paedomorphosis?
An evolutionary change in which larval features of an ancestor are retained to adulthood in the descendent.
*The Axolotl is a salamander that retains larval gills and aquatic habit as an adult
What kind of animals are contained within order anura?
Frogs
Toads
*Over 5200 species in 44 families
What are the clear differences between toads and frogs?
Toads have thicker skin
Toads are more terrestrial
What mode of reproduction do anurans have?
External fertilization fertilizaed eggs develop into tadpoles. Tadpoles are herbivorous and adults are carnivorous
What is the breeding and life cycle of frogs?
1) Sexually mature at 3 years of age.
2) Male clasps female and eggs are released as well as sperm
3) Eggs are surrounded by jelly coats
4) Fertilized eggs are cleaved
5) Embryo is nourished by yolk
6) Tadpole feeds on algae
7) Skinfold grows over external gil. Water exits through spiracle
8) Hindlimbs and then forelimbs emerge
9) Adult forms when tail shortens
What are some adaptations for frogs’ breeding and life cycle?
Some frogs have dorsal brooding pouches. Eg. male pouched frog in NSW and QLD.
Female gastric breeding frogs (QLD) brood tadpoles in their stomach.
Water-holding frog burrows during drought and creates water tight cocoon from shed skin, holds water of 1/3 body weight in bladder
What is happening to anurans today?
Worldwide, frog populations are declining, becoming patchy, and going extinct
What are some possible causes of declining frog populations?
Habitat loss
Climate warming
Acid rain
Increased UV (lowering wter levels expose eggs to more UV)
Disease
Pollution
Displacement by introduced species (eg cane toads)
Harvest by humans for their skin or meant
What kind of grouping are amphibians?
Monophyletic. Common ancestor is believed to be bony fish (osteolipis)
Which amphibian orders are sister taxa?
Gymnophiona and urodela
