amphibians chapter 40. origins & evolution of amphibians section 40.1

Amphibians

Chapter 40

Origins & Evolution of Amphibians

Section 40.1

Adaptation to land

• Amphibian means “double life”

• Came out of the water to escape predation & competition for food– Need a strong bony endoskeleton to

deal with force of gravity

Characteristics of early amphibians

• Oldest amphibian fossil is 370 myo• Evolved from lobe-finned fish

– Four limbs homologous to pectoral & pelvic fins of fish

– Similar skull & vertebrae

• some had gills and lungs• More toes than modern amphibians

Diversification of amphibians• Two main evolutionary

lines1. Modern amphibians2. Ancestor of reptiles

• 4,500 species in 3 orders1. Order Anura2. Order Caudata3. Order Gymnophiona

Modern amphibians

• Metamorphosis• Moist, thin skin with no scales• Feet lacking claws & often

webbed• Use skin, gills, & lungs to

breathe• Eggs lack membrane or

shells• Eggs laid in water• Fertilization externally

Order Anura• Meaning “tail-less”• Examples: frogs & toads

– “toad” = rough, bumpy skin– “frog” = smooth, moist skin

• Adaptations for jumping• Tadpole: swimming larvae• Carnivores

Order Caudata

• Example: salamanders & newts• Elongated bodies with moist skin and

long tails• Live in moist places• Carnivores

Order Gymnophiona

• Example: caecilian• Legless & resemble small snakes• Very small eyes, often blind• Carnivores

3 Order Note Cards!

• Front Side = Order name & picture

• Back Side = – example organisms– Location of animal on Earth– Habitat/environment– Adaptations for life/ key characteristics– Fun fact!

AnuraCaudataGymnophiona

Characteristics of Amphibians

Section 40.2

External covering

• Skin = respiration & protection

• Mucous glands: supply lubricant to keep skin moist & poison for protection

Poison dart frogs

Internal anatomy

• Strong bony skeleton– Needed for life on land (larger animals)– Pectoral & pelvic girdles help support

• More developed internal anatomy – Closer to humans!

– video

Male internal anatomy

a. Large intestine.b. Small intestine.1. Lung lobes.2. Heart.3. Liver lobes.4. Gall bladder.5. Stomach.6. Small intestine.7. Testis.8. Fat body.9. Urinary bladder.

Female internal anatomy

1. Liver lobes.2. Heart.3. Ovary with eggs.4. Gall bladder.5. Small intestine.6. Stomach.7. Oviduct.

Heart & circulatory system

• Two separate loops1. Pulmonary circulation: blood from

heart to lungs & back to heart2. Systemic circulation: blood from

heart to muscles & organs then back to the heart

Three chambered heart

1. Right atrium: where (deoxygenated) blood enters the heart from the body

2. Left atrium: where oxygenated blood enters from the lungs

3. Ventricle: main pumping chamber

1.

3.

2.

Path of blood

• Right atrium ventricle lungs (to pick up oxygen) left atrium ventricle rest of body (to drop off oxygen)

Respiration

• Larvae respire via gills and skin

• Adults respire via lungs and skin– Pulmonary respiration: through lungs– Cutaneous respiration: through skin

Digestive system

• All adults are carnivores• New terms:

– Pyloric sphincter:– Duodenum:– Ileum:– Mesentery:– Cloaca:– Vent:

Excretory system

• Two kidneys that filter nitrogenous wastes from the blood

• Urine flow:– Kidneys urinary ducts

urinary bladder cloaca

Reproductive system

• Males:– Testes (sperm made here) sperm

ducts cloaca

• Females:– Ovaries (eggs made here) oviducts

uteri cloaca

Nervous system

• Brain:– Olfactory lobes– Cerebrum– Optic lobes– Cerebellum– Medulla oblongada

• Nerves– 10 pair cranial nerves– Spinal cord– Spinal nerves

Sense organs• light travels through nictitating

membrane – transparent movable membrane

covering the eyes while underwater

• Sound: travels through tympanic membrane (eardrum) columella (small bone) inner ear (embedded in skull)

Reproduction of Amphibians

Section 40.3

Life cycle

Courtship & fertilization

• Males croak to females in spring• Amplexus: male embrace of female

during mating– May last for days!– Once female releases eggs, male

releases sperm external fertilization

Metamorphosis• Tadpole frog

The real one

Parental care

• Males often remain with eggs for protection

• Example: Darwin’s frog puts eggs in his vocal sac where they hatch, go through metamorphosis, and emerge in the adults form