Chapter 14: Geological Time

Aim: How do we divide geologic time?

Geological Time Scale Paleontologists have divided Earth’s history into time units based on the life-forms that lived during certain periods 4 Major subdivisions: Eons Longest subdivison Based upon abundance of certain fossils

Eras 2nd longest subdivision Marked by worldwide change in types of fossils present Ex: Mesozoic Era-many invertebrates became extinct Periods Characterized by the types of life existing worldwide Epochs Smaller than periods Characterized by differences in life forms

Aim: How does evolution relate to the divisions of the geologic time scale?

Organic Evolution Species have changed over geologic time Environmental changes can affect an organism’s survival Those that don’t adapt to changes are less likely to survive Species- group of organism that normally reproduce only with other members of their group Offspring of 2 different species can not reproduce (sterile)

Natural Selection Charles Darwin proposed this theory Sailed around the world gathering information Is a process by which organisms with characteristics that are suited to a certain environment have a better chance of surviving and reproducing than organisms that do not have these characteristics Organisms compete with each other for resources (food and living space) Organisms in the same species can show variations-could help or hurt the organism’s chance of surviving

Organisms poorly adapted to environment-produced few or no offspring Organisms suited for their environment-lived longer and better chance of producing offspring Organisms poorly adapted to environment-produced few or no offspring A new characteristic becomes common in a species only if: some members already possess that characteristic That trait increases the animal’s chance of survival

Aim: How do trilobites help explain evolution?

Trilobites Structure of the hard outer skeleton or exoskeleton 3 lobes that run the length of the body Body made up of Head-cephalon Segmented middle-thorax Tail-pygidium Figure 7-Pg 397

Lived in Earth’s oceans for more than 200 million years During Paleozoic Era, some species of trilobites became extinct and new ones evolved Showed different characteristics during the different periods of the era Trilobite eyes-changed over time, tell us about where they lived Trilobite bodies-changed over time too Olenellus had an extremely segmented body compared to other trilobites, thought to be primitive

Aim: How has Plate Tectonics affected species?

Plate Tectonics Earth’s moving plates caused continents to collide and separate many times Collisions caused mountains and closed seas Pangaea-supercontinent when the continents came together (end of Paleozoic Era) Separation of continents caused wider and deeper seas trilobites lived in oceans and their environment changed or was destroyed Only one explanation of the extinction of trilobites

Aim: What was life like during the Precambrian Time?

Precambrian Time Longest part of Earth’s history Includes the Hadean, Archean and Proterozoic Eons Lasted from 4.5 billions years ago to 544 million years ago Little is known about this time because rocks have been so deeply buried they have been changed by heat and pressure Many fossils can’t stand these conditions

Earth was a lifeless planet with many volcanoes Stromatolites-layered mats formed by cyanobacteria Cyanobacteria-blue green algae; one of the earliest life forms on Earth First appeared 3.5 billion years ago Contain chlorophyll Used photosynthesis Produced O2 which helped change Earth’s atmosphere O2 became a major atmospheric gas Ozone layer began to form

Invertebrates appeared toward the end of Precambrian time The production of O2 made it possible for single-celled organisms to evolve into more complex organisms Many of these fossils are trace fossils Edicaran animals Bottom dwellers Might have had tough outer coverings Looked like modern jellyfish, worms and soft corals

Aim: What was life like during the Paleozoic Era?

Paleozoic Era Organisms with hard parts mark the beginning of this era Began about 544 million years ago Ended 248 million years ago Warm, shallow seas covered large parts of continents Many life forms during this time were marine Trilobites present Fossils shows many animals had shells

Invertebrates not the only animals Vertebrates evolved during this era First vertebrates were armoured fish-had very powerful jaws By the end of Devonian Period forests appeared and vertebrates adapted to land Many ancient fish had lungs and gills-enabled fish to live in low O2 leveled water Paleontologists believe amphibians evolved from panderichthys- leglike fins and lungs

By the Pennsylvanian Period reptiles evolved Produced egg with a membrane that protected it from drying out-reproduction takes place away from water Have skin with hard scale that prevent loss of body fluids Many mountains formed during this era Ex: Appalachian Mountains Ocean separating North America from Europe and Africa closed Collision of volcanic islands generated mountains African plate collided with the North American plate

At the end of the era: 90% of all marine species died off 70% of all land species died off Possible reasons are climate change and lowering of sea level Pangaea formed closing seas and creating mountains Organisms were unable to adapt to these changes Volcanoes were very active A large asteroid may have hit Earth

Aim: What were the characteristic life-forms during the Mesozoic Era?

Mesozoic Era Started 243 million years ago Ended 65 million years ago Marked by rapid movement of Earth’s plates All continents joined (Pangaea) Separated into 2 large landmasses (Laurasia and Gondwanaland) These 2 land masses continued to break apart into the present day continents

Reptiles became the largest group of animals on land by the Triassic period First small dinosaurs appeared during Triassic period Larger dinosaurs appeared during the Jurassic and Cretaceous periods Fossils indicated some dinosaurs might have been warm-blooded and fast moving animals like present day mammals and birds

Birds appeared during the Jurassic period Fossils indicated some dinosaurs nurtured their young and traveled in herds Ex: Maiasaura Birds appeared during the Jurassic period Paleontologists believed birds evolved from small, meat-eating dinosaurs Earliest bird-Archaeopteryx Mammals first appeared in the Triassic period Earliest mammals resembled today’s mouse Warm-blooded vertebrates and produce milk to feed young These 2 characteristics enables mammals to survive in many changing environments

Gymnosperms dominated the Mesozoic Era-are plants that produce seeds, but not flowers Many are still around today Angiosperms (flowering plants) first evolved during the Cretaceous Period Can live in many environments Most diverse and abundant land plants today Ex: magnolia and oak trees

Ended with a major extinction of land and marine species Dinosaurs disappeared Scientists believe an asteroid or comet collided with Earth blocking out the sun Plants and those organisms that depended on plants died out The animals you see today and descendants of those who survived this mass extinction

Aim: What are the characteristics and life-forms of the Cenozoic Era?

Cenozoic Era Era of recent life Began 65 million years ago Living in this era today Many mountain ranges in North America, South America and Europe formed during the beginning of the era Ice age occurred Divided into 2 periods-Tertiary Period and Quaternary Period, which began 1.8million years ago

Alps in Europe formed Andes in South America formed Himalya formed while India moved northward and collided with Asia (highest mountain on Earth)

Many kinds of mammals became larger As Australia and South America separated from Antarctica many species became isolated Evolved separately from life-forms in other parts of the world Evidence of this is marsupials Homo sapiens appeared about 140,000 years ago Appearance of humans could have led to the extinction of many other mammals