1

Vertebrate Movement to LandSZ2- Students will explain

evolutionary history of animals over the history of life on earth.

• Tetrapods- Animals with 4 limbs– Amphibians– Reptiles– Birds– Mammals

• Evolved from fish

Vertebrate Evolution

Why did vertebrates begin to move onto land 380 million years ago?

• Competition for food and habitat in aquatic ecosystems

• Escape predators• Availability of new food source and terrestrial

niches

Transitional tetrapods

5

Transition from Sea to Land

6

•Coelacanth

7

Eusthenopteron

8

Panderichthys

9

Tiktaalik

http://www.youtube.com/watch?v=HyJAV-Jf9dohttp://tiktaalik.uchicago.edu/index.html

10

Transitional TetrapodsSkull, teeth, limbs similar to lobe-

finned fish

IchthyostegaAcanthostega

12

Struggles to Survive On Land• Water conservation• Gas exchange• Reproduction • Gravity• Separation of head,

flexion of a neck to pick up food

15

Adaptations to live on land

• Gills are usually lost• Lungs function• Breathe through skin• Secrete mucus – Prevent dehydration– Aids in respiration

16

More Adaptations to live on land

• Skeleton – Fins evolve into limbs– Vertebral column

supports body underneath it

AIR IS NOT AS BOUYANT AS WATER.

17

Evolution of CirculationFish Amphibian

Kingdom AnimaliaPhylum ChordataSubphylum VertebrataClass Amphibia1st land vertebrates Ex: frogs, toads, & salamanders

Class Amphibia – “Double Life”frogs, toads, salamanders, & newts

Characteristics• “Double Life” -lives part of

its life in water and part on land

• Ectothermic- “outside heat”- body temp. regulated by environment

• no scales or claws• Have thin, moist skin

Egg- tadpole- adult• external fertilization with no parental care• lay eggs without shells in water• larvae are herbivores, adults carnivores • larva have tails to move in water

AMPHIBIAN METAMORPHOSIS

21

22

• Amphibian Body Plan– Bilateral symmetry– 3 chambered heart– Larvae breathe through gills; adults breathe

through lungs– Breathe through thin, moist skin (produces

mucus)– Changes from larva to adult through

the process of metamorphosis

Class AmphibiaOrder Anura

• Anura- an=without, ura= tail• Tailless as adults• Specialized Hindlegs adapted for jumping and

swimming- frogsrunning- toads

• Tympanum (ear drum) and larynx well developedEx. Frogs and toadsfrog dissection intro-http://www.kiz-oyunlari.com/files/file/kurbaga_ameliyat.swf

Class AmphibiaOrder Caudata

• Caudata- “have a tail”• 2 pairs walking legs• Live in freshwater or

leaf litterEx. Salamanders and newts

Class Amphibia:Order Gymnophiona(Apoda)

Gymnos- nakedophis- snake

live in tropics in soil

Elongated bodyLimblessCarnivores- eat invertebratesEx. Caecilians – “blind”-small eyes

http://www.youtube.com/watch?v=DMvL4zOLSeM

Kingdom AnimaliaPhylum ChordataClass Reptilia

Ex: snake, turtle, lizards crocodile, dinosaurs

Reptilian Traits:3 chambered heart (except for crocodilians- imperfect 4)Ectothermic Paired limbs with five toes and clawsTough, dry, scaly skin (horny epidermal scales)

Jaws adapted for crushing and grippingBreathe with lungsmetanephric kidney- produces uric acid to reduce water loss Large cerebrum as compared to rest of brain-

behaviors- 1. instinct 2. learned

Reptile Legs

• Short tetrapods for walking

• Positioning of the legs more directly under the animal. This position provided more support than the splayed arrangement of the Amphibian legs.

Reproduction:Internal fertilization (to avoid desiccation of

gametes), oviparousLay amniotic eggs on land- no dependence on

waterShells leathery, sometimes calcareous

Amniotic Egg Structures & Functions• Chorion provides a special hard covering that is permeable

to respiratory gases (O2 and CO2) while being impermeable to water vapor.

• Allantois is a storage reservoir for metabolic waste products such as nitrogenous compounds and gas exchange.

• Amnion is a fluid filled sac that acts as a cushion for the embryo and also prevents desiccation.

• Yolk sac contains food for the embryo, thus eliminating the need for a larval stage.

Checkpoint

1. List basic traits of reptiles.

2. How do reptiles reproduce? Explain fertilization

type, type of eggs, egg development.

3. Which class of animals is better adapted for life on

land, Amphibia or Reptilia?

4. Explain how your chosen class of vertebrates is

better adapted for life in terrestrial ecosystems.

Phylum ChordataSubphylum Vertebrata

Class ReptiliaOrder Testudine:

Body in a bony case -dorsal carapace(top of shell) - ventral plastron(bottom of shell)Jaws with a horny beak, no teethVertebrae and ribs fusedEx. Turtles and tortoises

Turtle Shell Anatomy

Fusion of ribs, vertebrae, & carapace

Turtle Life Cycle

Phylum ChordataSubphylum VertebrataClass ReptiliaOrder Sphenodonta

• Primitive reptile• closely related to dinosaur• Looks like lizard• Diapsid skullEx. Tuatara- only living species

Phylum ChordataSubphylum VertebrataClass Reptilia

Order SquamataDiapsid skull with two temporal openings

Skin is shed with horny epidermal scales

Jacobson’s organ- sense of smell

Movable skin, kinetic skull

Poisonous- hemotoxins (blood) , neurotoxins(nervous system)

EX. Snakes and lizards

Lizards have movable eyelidsSnakes- descended from tetrapod ancestordichotomous key

Evidence suggests that Snakes descended from tetrapod ancestor• Pythons, and other

species of snakes are sometimes born with vestigial hindlimbs

• Snakes have DNA to code for a pelvis, and limbs, but genes are turned off early in development

• Elongated massive skull• Imperfect 4 chambered heart• crocodiles, alligators, and caimans, gavials

Phylum ChordataSubphylum VertebrataClass Reptilia

Order Crocodilia

CrocodiliansCrocodiles, Alligators,

Caimans, & Gavials

Gavial(gharial)

Carnivores, “ghara”- pot- bulb on snout12.25- 15.5 ft. longRivers of India, Nepal, Pakistan, Bhutan, BangladeshCritically Endangered

Alligator

Crocodile

Largest, best predatorsLive in/near Salt waterAmerican Crocodile- EndangeredMost in Australia

CaimanRivers/swamps of Central and South America3ft- 16 ft. (only in black caiman species)

Crocodilian Reproduction

• The temperature inside the nest of several crocodilian species decides the sex of the young. ~50-80 eggs

• If the nest temperature is 30ºC, females will hatch

• If the temperature is above 34ºC - males.

• If the temperature is in between- young of both sexes.

Land Adaptations for Reptiles• Legs underneath bodies (tetrapods)• Lungs • more efficient circulatory system, hearts• Scales- prevents dehydration, protection• Claws• Amniotic egg, internal fertilization• The excretory waste of the reptiles is uric acid

unlike the dilute, water wasting ammonia in the urine of Amphibians

• Higher cerebral capacity for learned behavior