Amphibians
description
Transcript of Amphibians
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
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3.
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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
Nervous system
• Brain:– Olfactory lobes– Cerebrum– Optic lobes– Cerebellum– Medulla oblongada
• Nerves– 10 pair cranial nerves– Spinal cord– Spinal nerves
Sense organs
• Sight: light travels through nictitating membrane (transparent movable membrane covering the eyes) eye
• 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