Adaptations to Meet Challenges of Life on Land Challenges of Life on Land vs Water Adaptation to Meet Challenge Air much less buoyant than water so must move against gravity Limbs develop skeletal and muscle systems become stronger ID: 750994
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Slide1
Amphibians
“Double Life”Slide2
Adaptations to Meet Challenges of Life on Land
Challenges of Life on Land vs. Water
Adaptation to Meet Challenge
Air much less buoyant than water so must move against gravity
Limbs develop;
skeletal and muscle systems become stronger
Oxygen at least 20 times more available in air than in water
Use lungs to take in oxygen more efficiently from air
Air temperature fluctuates
much more than
water, which retains
heat so it
insulates animals from extreme
temperature changes
Behavioral and physical adaptations to protect from temperature extremesSlide3
Metamorphosis
Name means “double life” as most amphibians spend part of life in water, part of life on land; changes during metamorphosis enable life on landSlide4
Basic Amphibian Characteristics
Most have 4 legs -
tetrapodsMoist skin without scalesGas exchange via skin and lungsDouble-loop circulatory system
Aquatic larvaeEctothermic Slide5
3 Orders of Amphibians
Anura
- Frogs and Toads – about 5800 species!Caudata (AKA
Urodela) - Newts and Salamanders – about 580 speciesGymnophiona (AKA
Apoda) – Caecilians – about 170 speciesSlide6
Obtaining Food
Adults are Predators but some larvae, like tadpoles, are herbivores
To catch prey: frogs and toads have long sticky tongues; salamanders and caecilians use jaws
Many hunt nocturnally and have good eyesight, some excellent night vision (Kermit-like slits) while others hunt in daytimeCaecilians reduced vision or no vision as often live in dark but sharp teethSlide7
Digestion
Mouth
esophagus stomach small intestine (with enzymes from pancreas) bloodstream to body cells large intestine waste exits via cloaca
Common duct called cloaca – common exit for digestive wastes, liquid waste, sperm and eggs Slide8
Excretion
Liquid waste is filtered from blood by kidneys
Converted to urea in terrestrial amphibians or ammonia in aquatic speciesIf urea, it moves from kidneys to ureters to bladder for storage to cloaca Slide9
Respiration and Circulation
As larvae, most breathe through skin and gills; as adults, most breathe through lungs, moist skin, and mouth lining
Animation of frog respiration3-chambered heart with 2 atria and 1 undivided ventricleSlide10
Brain and Nervous System
Well-developed nervous system
Forebrain detects odors in airCerebellum which maintains balance less developed in terrestrial amphibians that live close to ground than in fishesSlide11
Senses
Sense or Associated Structure
Function
Good vision
Locate and capture prey; escape predators
Nictitating membrane over eyesProtects eye underwater and keeps from drying
out on landTympanic membrane
External eardrum to hear high pitched sounds
and amplify their vocalizations; some also “hear” by feeling vibrations in front feet
Touch
Helps them sense temperature to know when to move to cooler spots or find warmer places
Taste buds on tongue
Aids
in food gathering
Smell in nasal cavity
Aids in obtaining food; avoiding
dangerSlide12
Defenses
Frog applies 'sun cream' - Natural World: Attenborough's Fabulous Frogs - BBC Two - YouTube
Warning colorationToxins in skin – some only from diet; some produce them
CamouflageClimbing or leaping away from dangerSlide13
Reproduction
May be external fertilization as it is in frogs and toads
Many male salamanders deposit packets of sperm called spermatophores on ground which females take into
cloacaInternal fertilization in caecilians and tailed frogsMany lay eggs in water and abandon, others guard eggs in odd ways. Ex: Eggs in pockets of skin on backs seen at right!
videoSlide14
Why are amphibians important?
Part of food webs
Control pest insectsBioindicator species
Medical research Slide15
Declining Amphibians
Have higher rate of endangerment than any other animals. Estimated 1/3
rd of world amphibian population at risk for extinction.
Reasons for decline and map of habitats around world in text and on Amphibiaweb.org and at Factors in Amphibians' Decline
Page 841 in text local and global factors for declineView 50 min video for HW
: Thin Green Line video from PBS from made in 2009 explains the crisis that amphibians are facing