Geologic Time Scale and Change Over Time

Module 1.4

Geologic Time Scale

Geologic time—Earth’s history is divided into time units that make up a geologic time scale.

● Time units on the scale are based on the appearance or disappearance of types of organisms (such as trilobites) using index fossils that lived during specific periods of time.

Geologic Time Scale

Major Time Divisions

a. Eons—longest subdivision; based on abundance of fossilsb. Eras—marked by significant worldwide changes in the types of fossils present in rockc. Periods—based on types of life existing worldwide at a particular timed. Epochs—characterized by differences in life-forms, but differences can be regionalrather than global

Fossils

Geologic time can be subdivided only if fossils are present in rock records.*This means that more recent time periods have more division than time periods from longer ago*Why do you think this is?

Color Coding the Time Scale1. Using pg 103 of the text book, color code

your copy of the Geologic Time Scale the same way (lightly color)

2. Draw red lines along the 2 mass extinctions

3. Label the first appearrences of life, trilobites, fish, plants, amphibians, reptiles, birds, flowering plants, mammals, and humans

4. Then draw an arrow along the side showing the oldest time period until today

5. Copy and answer the following on the back:

1. What Era do we live in?

2. When did the dinosaurs become extinct?

3. When did life first appear?

Exit Ticket:Why do you think there are less divisions in Pre- Cambrian time? Please answer in 2-3 sentences.

Homework:● Finish Webquest● Start vocab (quiz

will be next Monday)● Work on Current

Event

Pre-Cambrian Time

● Lasted from 4.5 billion years ag0 until 544 million years ago

● Few Life forms existed at this time○ Single cell organisms, such as CYANOBACTERIA

dominated

● Invertebrates appeared during this time (similar to jellyfish and corals), left trace fossils

● Major geologic events: Earth was cooling● “Cambrian” explosion- rapid spread of inverts

marked the end of the Pre- Cambrian

Paleozoic Era

● 544 million to 248 million years ago● Dominated by invertebrates that lived in oceans

(lots of shelled animals)● First land plants /animals and vertebrates (fish,

reptiles, and amphibians) appear● Several mountain building events, including the

building of the Appalachian Mountains occurred in this era; creation of PANGAEA

● Ended with a mass extinction (cause still debated)

What characteristics of reptiles, allowed them to be the first animals to move away from the water?Protective scaly skin, eggs that could be laid away from water, claws for digging and climbing

Mesozoic Era

● 248- 65 Million years ago● “Age of the Dinosaurs”- dominated by reptiles● Birds, Mammals, and Flowering plants appear

in this era● Major Geologic Events: break- up of Pangaea

and eventual formation of current continents● Ended with a mass extinction, possibly caused

by a comet or meteor striking the Earth

Who survived?

What organisms survived the mass extinction of 65 million years ago?

Cenozoic Era

● 65 million years ago until today● Dominated by mammals● Humans first appear during this time● The Alps, Andes and Himalayan mountains

formed

Speciesa group of organisms that normally reproduces only with other members of their group.

2 members of the same

species – fertile offspring 2 different

species – non fertile offspring

Ex: 2 dogs Ex: a lion and a tiger

Even though 2 organisms look nearly alike, if the

populations they each come from do not interbreed naturally and produce

offspring that can reproduce, the 2 individuals do not belong in the same

species!

Natural Selection

- Charles Darwin – published a book – theory of evolution by natural selection- 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 necessary for life (ex: food, living space)

- differences could hurt or help an organism stay alive(these are called adaptations)

“Survival of the fittest.”

better adapted – live longer, better chance of producing offspringless adapted – shorter life, less chance of producing offspringSo, the better adapted genes are passed on more often.According to Darwin, this cause species to change over time.

Short neck giraffe(rare)

Long neck giraffe(common)

Amount of short neck giraffes has

decreased over time.

Artificial Selection- used by humans to breed animals- carefully choosing individuals with desired characteristics- Can you name three breeds of dog?

Movement of the Continents

Lightly color landmasses these colors on both maps:-North America- Purple- South America- Red-Europe/ Asia- Green- India- Yellow-Africa- Orange- Australia- Brown