Animals (tetrapods) and the transition to land

Where did life originally evolve

water

when did vertebrates begin moving to land

devonian period

Major challenges of living on land

preventing water loss, gas exchange, supporting body weight, reproduction outside water, temperature fluctuations, water conservation

What allowed animals to survive in terrestrial environments

adaptations to major challenges of living on land

adaptation for preventing water loss

waterproof skin, keratin

adaptation for gas exchange

lungs instead of gills

adaptation for supporting body weight

stronger skeleton and limbs

adaptation for reproduction outside water

amniotic eggs

adaptation for temperature fluctuations

behavioral and physiological regulation

adaptation for water conservation

kidneys

who are bony fish (superclass Osteichthyes) ancestors of

land vertebrates

Bony fish (superclass Osteichthyes) characteristics

skeleton made of bone, jaws present, two pairs of fins, two-chambered heart, scales covering body, gills protected by an operculum, swim bladder for buoyancy, live in marine and freshwater environments

Two major groups of bony fish (superclass Osteichthyes)

Actinopterygii and Sarcopterygii

Actinopterygii

ray-finned fish

Sarcopterygii

lobe-finned fish

Why are lobe finned fish important

because they gave rises to tetrapods (land vertebrates)

Tiktaalik

key transitional fossil, had characteristics of both fish and early tetrapods

What did tetrapods evolve from

lobe-finned fish

early tetrapods key evolutionary changes

fins evolved into limbs, a stronger skeleton to support body weight, the development of lungs, and the ability to move on land

Early tetrapods were still…

semi-aquatic and stayed near water

Why did tetrapods move onto land

escape predators, access new food sources

Amphibians were…

the first vertebrates to live partially on land

Most amphibians are…

oviparous

Oviparous

egg-laying

Amphibians must stay near water because:

skin must stay moist for respiration, eggs require water

Amniotes are…

vertebrates that reproduce with an amniotic egg

Amniotic Egg

Contains membranes that protect and nourish the embryo

Amnion

fluid-filled sac surrounding embryo

amniotes other adaptations

efficient kidneys to conserve water, keratinized skin to prevent water loss

amniotes include:

reptiles, birds, mammals

Reptiles were…

the first vertebrates to become fully terrestrial

reptile reproduction

oviparous or viviparous

reptile examples

snakes, lizards, turtles, crocodiles

why do reptiles have scales

to reduce water loss

Birds evolved from…

feathered dinosaurs

Birds Class

Aves

Adaptations for Flight

feathers, wings, hollow bones, efficient lungs

bird characteristics

four-chambered heart, endothermic (warm-blooded), oviparous reproduction

Mammals evolved…

later and are highly adapted for diverse environments

mammal key characteristics

hair, mammary glands, differentiated teeth, three middle ear bones, large brain

Most mammals are

viviparous and are endothermic

viviparous

give birth to live young

Important evolutionary developments

Fins → limbs

Gills → lungs

Water-dependent eggs → amniotic eggs

Moist skin → keratinized skin

Ectothermy → endothermy (birds and mammals)