mesozoic era

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Mesozoic Era Life

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Mesozoic Era. Life. Mesozoic Life. Known as “Age of Reptiles”. Mammals and angiosperms evolve. Marine Invertebrates Plankton. 1 st appeared (Jur). Coccolithophores. Abundant (K). Continue today. Diatoms (SiO 2 ). 1 st evolved (K). Cold H 2 O. Dinoflagellates. Warm H 2 O. - PowerPoint PPT Presentation

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Mesozoic Era

Life

Mesozoic Life

• Known as “Age of Reptiles”

• Mammals and angiosperms evolve

Marine InvertebratesPlankton

• Coccolithophores– 1st appeared (Jur)– Abundant (K)– Continue today

• Diatoms (SiO2)

• Dinoflagellates

– 1st evolved (K)– Cold H2O

– Warm H2O

• Foraminifera– Exploded

• Most plankton extinct (end K)

Marine InvertebratesCorals & Echinoderms

• Corals & Echinoderms proliferated

Scleractinians Echinoderm

MollusksBrachiopods & Gastropods

• Significant invertebrate fauna

– Minor invertebrate

– Never fully recovered from Permian extinction

• Brachiopods

• Gastropods

– Largest, most varied class

– Marine, fresh H2O, terrestrial

– Herbivore & carnivore

MollusksBivalves

– i.e., oysters, clams

– Rudists significant Formed large tropical reefs Excellent guide fossils

• Burrowing organism– Escaped predators

MollusksCephalopods

• Important invertebrate group• Ammonites

– Complex sutures

– Abundant (Jr & K), extinct (end K)

• Nautiloids and belemnoids survived

Nautilus

Cephalopod

Mesozoic LifeFishes and Amphibians

• Cartilaginous fish– ↑ abundance

• Amphibians– Frogs and salamanders appear

– Greatest diversity (Permian)

Mesozoic LifePlants

• Gymnosperms– Gingkos

• Primary producers – base of food chain

– Conifers– Cycads

• Gymnosperms replaced by angiospermsModern cycads

AngiospermGymnosperm

PlantsAngiosperms

• Adapted to nearly every terrestrial habitat• Factors to success:

– Method of reproduction Evolution of flowers

Evolution of enclosed seed

• Pollinators

• Seeds dispersed by wind, fruit, burr

Mesozoic LifeReptiles

• Thecodontian (L. Per-Tri)– Small, agile reptiles with

long tails, short limbs

– Dinosaur ancestors

– Teeth set in sockets

– Quadrupedal, ran bipedal– Herbivores & carnivores

• Diversification began during Penn

– Evolution of captorhinomorphs 1st to lay amniote egg All other reptiles evolved

i.e. crocs, dinos, & mammal-like reptiles

Warm-Blooded Dinosaurs• Ectotherm – “cold-blooded”

– Animals whose body temp varies in response to outside temp

• Endotherm – “warm-blooded”

– Capable of maintaining a constant body temp regardless of outside temp

• All reptiles ectothermic

• Dinosaurs believed to be endothermic

• Mammals & birds endothermic

• Endotherm requirements

– High metabolic rates need to eat more

– Complex nervous system large brain

Dinosaurs 3.5% prey pop’n Similar to present-day mammals

Many dinos have small brains Small carnivores = large brain

– Dino bones numerous passageways = blood flow

Crocs, turtles have similar bone structure = ectotherm

Warm-Blooded Dinosaurs

– Active flight requires endothermy Pterosaurs = hair-like feathers Triceratops brain cavity

Mesozoic LifeDinosaurs Relationships

• Two independent orders evolved1. Saurischia “lizard-hipped”

2. Ornithischia “bird-hipped”

– Theropod & Sauropod

DinosaursSaurischia Theropod

• Theropods – “Carnivores”– Bipedal locomotion

60 cm to 15 m 2 kg to 8 tons

– Tyrannosaurus (largest terrestrial carnivore)

– Deinonychus – “terrible claw”

– Various sizes

DinosaursSaurischia Sauropod

• Sauropods – “Herbivores”– Quadruped locomotion– Largest land animals to

ever exist

Camasaurus “Brontosaur”

Diplodocus Brachiosaurus

20 to 35 m in length 10 to 55 tons

Mesozoic LifeDinosaurs Relationships

• Two independent orders evolved

1. Saurischia

2. Ornithischia

– Theropod & Sauropod

5 groups

DinosaursOrnithischia

1. Duck-billed dinos (K)– Colonial nesting, cared for

young, herbivores, bipedal

2. Pachycephalosaurs – Dome-shaped skull,

bipedal, butting3. Ankylosaurs

– Armored, quadrupeds, tail w/ club-like growth

4. Stegosaurs– Quadruped, herbivore with

spike on tail5. Certopsian

– Triceratops, quadrupedal herbivores

Mesozoic LifeWinged Dinosaurs

• Pterosaurs

– 1st flying vertebrates

Winged membrane supported by elongated finger

– Flight adaptations

• Pteranodon (K)

– Pterosaur

– Could actively fly

Mesozoic LifeBirds

• Few Meso birds

– Archaeopteryx

Jur strata, Germany

– Protoavis (Tri)

Crow sized Hollow bones

Mesozoic LifeEarly Mammals

• 1st mammals (Tri)

– Evolved from Therapsids Mammal-like reptiles

– Small, rodent-like mammals

• Cynodonts

– Most abundant mammal-like reptile

• Monotremes

Early MammalsCynodonts

– Egg-laying– i.e. today’s platypus & string

anteater

• Eupantotheres– Marsupials – pouched (E. K)

– All living mammals related to this branch – Placental mammals

Mesozoic LifeFrom Reptile to Mammal

• Used skeletal structure to classify fossils

– Skull – Middle ear – Lower jaw – Teeth

– Mammal’s middle ear attached to dentary– Reptiles = 1 ear bone; mammals = 3– Reptile = several jaw bones; mammals = 1– Teeth = distinct types

Reptile vs. MammalComparison

Mesozoic Era Mass Extinction

• Impact Theory

– Huge asteroid or comet

– Cloud of dust into atmosphere

– Reduced sunlight

Plants die first Herbivores followed Then, carnivores starved

Mass ExtinctionEvidence

• Large impact basin

• Iridium-rich clay layers– Rare crustal rock– More in meterorites

• Clay layers, New Mexico

Mass ExtinctionProblems

• Selective extinction

– Dinosaurs completely extinct

– Corals, clams, snails – some extinction

– Tropical plants, crocodiles, mammals, turtles, snakes, & birds unaffected

• Why weren’t all organisms affected equally?