Geologic time scale
The division of Earth's history into smaller units makes up the _______ _____ _______.
eras, periods, and epoch.
Geologic time is divided into subdivision:
Eras
major subdivisions of the geologic time scale based on differences in life-forms.
3 Major Eras:
1- Paleozoic = ancient life 2- Cenozoic = recent life 3- Mesozoic = End is marked when the dinosaurs pass away.
Periods
subdivisions of eras.
Epochs
smaller units of periods.
Why do Geologists study fossils?
1. Help describe Earth's past environments 2. To interpret how dead organisms lived 3. To document changes in organisms through time.
Trilobites
organism that lived hundreds of millions of years ago.
Plate tectonics
is a process that causes changes in environments on Earth.
Precambrian time
the longest geologic time unit of Earth's history.
Precambrian rocks
are buried deep inside Earth and are changed by heat and pressure.
Cyanobacteria
the earliest forms of life on Earth, contained chlorophyll and as they photosynthesized they gave off oxygen.
Why are Cyanobacteria important to Earth's Evolution?
1. When Cyanobacteria photosynthesized, they produced oxygen. 2. Oxygen became a major gas in Earth's atmosphere. 3. The ozone layer began to develop, shielding Earth from ultraviolent rays. 4. These major changes in the air allowed species of single-celled organisms to evolve into more complex organisms.
Paleozoic Area
is marked by the presence of the first organism with hard parts and easily preserved.
marine
Warm shallow seas covered much of Earth's surface during only Paleozoic time and most of the life-forms were ____.
Cambrian period
The _____________ marks the appearance of marine animals with hard parts or skeletons.
Ordovician period
The first vertebrates developed during the ____________.
Amphibians
live on land and breathe air but must return to water to reproduce.
Reptiles
do not return to water to reproduce.
with hard scales that prevent loss of body fluids.
Reptiles have skin ______________________________________.
dinosaurs
The _______ came about during the Mesozoic era.
Mesozoic era
began about 245,000,000 years ago and all the continents were joined together.
Pangaea
single large land mass made up of all the continents.
recent findings suggest they were much faster than most reptiles.
Dinosaurs were reptiles, however, __________________________.
warm-blooded
Due to their bone structure, dinosaurs were believe to be ____________________.
birds
Scientists have concluded that _____ evolved from dinosaurs.
Archaeopteryx
a dinosaur with wings and feathers like a bird.
Gastoliths
stones swallowed to aide in suggestions.
Angiosperms
flowering plants that produce seeds inside a fruit.
magnolias and willows
Common angiosperms are ____.
Cenozoic era
began 65,000,000 years ago when dinosaurs passed away.
ice ages occurred.
During the Cenozoic era, the climate became cooler and...
the African plate collided with the Eurasian plate.
The Alps formed when _____.
the Indo-Australian plate collided with the Eurasian plate.
The Himalayas started to form when _______.
once lived on land.
Fossil evidence shows that ancestors of the present-day whales and dolphins...