fossils

Fossils and the Timescale

K - 6TH GRADE

A guide to ace fossil science

By: Trimann Riar

01

Fossils

About fossils/fossilization etc.

Lesson

01

What are fossils?

Fossils

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Fossils are the remains of once-living species frozen in rocks (only sedimentary rocks, which are made from layers of sediment)

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When plants or animals die and get buried by layers of sediment, fossils are formed ⭘

This is why fossils are only found in sedimentary rocks

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Fossils can tell us about physical structures of an organism and where and how it lived

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Some organisms only existed on Earth for a brief period of time When they are found as fossils, they are called index fossils, because they give references which are used to date rocks and other fossils that are nearby

(If you’ve went to the Royal Tyrrell Museum at Drumheller you’ve probably seen dinosaur fossils)

Lesson

02

Finding Fossils Only a small percentage of organisms turn into fossils. Other species usually consume and decompose the body, returning nutrients to the soil in the process.

Usually, the fossils which are discovered are incomplete ●

They are only made up of skeletons, shells, etc.

This makes it hard to make a hypotheses about Earth’s past, but not entirely impossible ⭘

Evidence indicates that life on Earth has changed dramatically over millions of years. ●

Fossils from younger rocks can be similar to modern-day species.

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Older rocks can have fossils of species that are now extinct ⭘

Most fossils don’t look like species we see today

03

LESSON

Fossilization Not all living things have the potential to turn into fossils because: ● Soft tissue like skin, muscle etc. decomposes more easily Which is why we almost always see the hard parts (bones, shells etc.) of animals in fossils ⭘

Ways to become fossilized Permineralization/petrification Sediments have to quickly bury the original remains

LESSON

04

Original Remains ●

The original remains of creatures are sometimes preserved. Millions of years later, insects have been discovered preserved in amber, a hardened tree resin.

Extinct species' parts have been discovered frozen underground, including the woolly mammoth. The remains of organisms have also been discovered in California’s tar pits. ⭘

LESSON

05

Trace Fossils ● ●

Fossilized animal tracks, trails, and burrows are sometimes found.

Organisms leave a cavity or a trail behind Ex. footprint, feces, nesting habitats/nesting sites (excellent for showing paleontologists/geologists the behavior and movement of an organism) ⭘

LESSON

06

Permineralization/Petrification (Mineral Replacement) ●

The original organism is replaced by mineral crystals, resulting in the formation of a fossil.

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Water seeps into the pores (spaces) that exist between the remnants, and replace the remnants with minerals which eventually harden Requires water, so the organisms was most likely buried under water

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Many species' bones, teeth, and shells have spaces occupied by air or soft material, such as blood vessels. ⭘ Most common with wood, bones and shells

LESSON

07

Molds & Casts ●

When a organism has been buried underground, decomposes and dissolves, a mold is created in the surrounding rock.

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The cavities left by the original organism can be filled in with sediments which will eventually harden into rock, they create a cast ⭘ Not

original organism but shape has been preserved because it was filled in by sediments which later turned into rock

LESSON

08

Sediments have to Quickly Bury the Original Remnants ●

Scavengers and decomposers won't be able to break down the remains if they are buried quickly.

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The remains are preserved by sediment layers and pressure.

LESSON

Coal

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09

The coal we use to heat our homes is actually made up of the remains of fossilised organisms.

However, because the remnants have been compressed and carbonised, there isn't much important data left in them.

LESSON

10

Carbon Films

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The earth squeezes and heats an organism buried in sediment, causing it to lose all of its gas and liquid from the body

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As a result of the squeezing, a thin layer of carbon forms on the surrounding rocks, forming a silhouette (or outline) of the organisms.

02

Geological Time Scale About the time scale of Earth

LESSON

01

Time Scale The geological time scale is a timeline based on when certain organisms lived on the Earth.

Includes 4 major time divisions: Eons:

Eras:

The most extensive subdivision, lasting hundreds of millions of years. The presence of certain fossils determines this.

The next most extensive subdivision. An era marks a significant shift in the types of fossils found.

Periods:

Epochs:

Within an era, periods are divisions. Periods are defined as time points within an era when different types of life existed.

The shortest subdivision, lasts several million-years. Periods are divided into smaller units by epochs, which are also determined by changes in life forms.

Lesson

02

Eras Geologists have organised Earth's history into geological time intervals names eras using the knowledge gathered from analysing rocks and fossils. ●

This is based on the order of rock strata

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Each era represents a significant shift in the global environment and is marked by distinct life forms.

Lesson

03

Evolution of Earth

Earth did not always look like it does now ●

Plate tectonics and water levels have continuously changed the way Earth looks

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Before the Mesozoic era, most of Earth was covered by water

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By the end of the Paleozoic era, the sea levels had dropped and the continents had fit together to make Pangaea

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Pangaea started spreading out and separating into the continents we all know today by the middle of the Mesozoic era

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The continents are still moving today!!

Lesson

04

Eras

Scientists divide the Earth’s history into 4 eras. Here they are, starting with the earliest to the most recent:

LESSON

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First soft body organisms (no vertebrae/skeleton) and simple organisms

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Ozone layer began to appear

05

Precambrian

Spans 4 600 to 600 million years ago

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This covers the vast majority of Earth's existence (more than 80% of it!) ●

Included the formation of Earth

According to some geological evidence and scientific observations, Earth was once a swirling cloud of gas that gradually cooled ⭘

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First organisms like Cyanobacteria, which are single-celled bacteria

These organisms, obtained energy by photosynthesis, which resulted in the release of oxygen into the atmosphere.

⭘ The atmosphere's combination of oxygen and ozone gradually created an environment that allowed more life-forms to grow

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Some simple multicellular organisms had begun to evolve by the end of the Precambrian era.

LESSON

06

Paleozoic Spans 600 to 225 million years ago ● ● ●

Many organisms with exoskeletons or shells began to appear Vertebrates, plants, amphibians, and reptiles all evolved, and simple land animals evolved halfway through this era First large land plants ⭘ During the Paleozoic era, much of the earth was covered in shallow water, so most animals were aquatic

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As the continental plates collided, Pangaea formed, also forming mountains

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At the end of the Paleozoic era, mass extinctions occurred, with 90% of marine animals and 70% of land organisms becoming extinct

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Because they were well adapted to land, reptiles were one of the few types of organisms to survive from the Paleozoic to the Mesozoic era

LESSON

07

Mesozoic

● (Age of Reptiles) (about 4% of Earth’s history)

Spans 225 to 65 million years ago

Pangea split into two landmasses at first, then into the continents we know today

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Dinosaurs evolved during this time period

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During the Mesozoic Era, the first birds and mammals appeared, though the mammals were mostly small and underground.

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First angiosperms (flowering plants) and gymnosperms (seeded plants)

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Another set of mass extinctions signalled the end of the Mesozoic period, most likely caused by a meteor hitting with Earth and spewing massive amounts of dust and smoke into the atmosphere.

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Dust and smoke blocked sunlight and altered Earth's climate, causing plants to perish and animals that relied on them for food to perish as well.

LESSON

08

Cenozoic

(Age of Mammals) (less than 2% of Earth’s history)

Era we currently live in, started 65 million years ago ●

Modern mountain ranges formed, like the Himalayas

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Maybe due to a lack of competition from dinosaurs, mammals grew to be much larger and more dominant than their ancestors.

The appearance of the majority of modern species

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First grasses

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First human-like species (2-3 million years ago) Around 200 000 years ago, the first modern humans appeared. ⭘ Only about 0.000044% of Earth’s history!

LESSON

03

My Favourite Fact

Dinosaur were alive during the Mesozoic are, and there three periods in that era, the Triassic, Jurassic and Cretaceous ●

A lot of the dinosaurs we know, never existed together!

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Ex. The T-Rex and the Stegosaurus. The Stegosauru lived during the Jurassic period and the T-Rex lived during the Cretaceous period!

The T-Rex lived closer to humans than to the Stegosaurus!!! ⭘

03

Paleontologist Techniques

How do paleontologists study fossils/what techniques do they use

LESSON

Examining the Sedimentary Rock Layers

01

Methods for Interpreting Fossils ● ●

To uncover and study fossils, sedimentary rock must be heavily eroded.

An example is the Grand Canyon

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There are no fossils in the bottom layer, which is made up of the oldest rock.

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Many trilobite fossils can be found one layer higher

⭘ Which means there were no organisms in the first layer that would

be able to leave fossils, when you go to the next layer, obviously something happened in that time when trilobites thrived ●

The layers change when something in the environment changes

Other fossils that are more similar to modern species appear as you travel up the canyon wall. ⭘

02

LESSON

Methods for Interpreting Fossils Fossil Beds ●

The Burgess Shale fossil bed fossils are some of the oldest and most complex in the world ⭘ Many species' soft tissue has been preserved.

Soft tissue would normally get decomposed or be scavenged, but these organisms were buried so fast that even the most delicate tissue was preserved. ⭘ Enables scientists to investigate these organisms in great depth Even the remains of their last meals can be found in some cases. ⭘

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LESSON

03

Methods for Interpreting Fossils Strata

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Sedimentary layers built up over millions of years

Geologists can learn about the environment in which strata was formed by studying the kind of rock and the size of grains in the strata. ⭘ Ex. Limestone = layer formed at the bottom of the ocean ● Strata layer is extremely thick = for a long time, the environment remained stable. ●

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When something in the environment changes (rise in sea level, atmospheric components, climate etc.) a new layer forms.

LESSON

04

Rock Ages Absolute Dating

When scientists need to know the absolute date of a rock, they can use radioactive decay to determine the date. ●

Radioactive decay is when an element breaks down

All rocks have elements that are unstable, like, isotopes of carbon, potassium, uranium, etc. One of those isotopes (carbon-14, or C-14) is in living organisms. It degrades slowly but predictably, allowing scientists to calculate the age of a fossil by measuring the amount present.

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This is also known as carbon dating or radioactive dating

LESSON

05

Rock Ages Relative Dating

The age of one rock is compared to the age of another in relative dating. ●

Scientists determine the order of rocks and estimate the age, based on their order and the fossils found in them.

Mostly thing buried farther underground the older they are ●

Scientists use the Principle of Superposition (states that in any undisturbed sequence of rocks deposited in layers, the youngest layer is on top and the oldest on bottom, each layer being younger than the one beneath it and older than the one above it) to determine the relative age of rocks

But the principle only works when the rock layers have not been disturbed. click here to learn about the ways the rocks can be disturbed ⭘

Unconformities can happen in 3 major ways LESSON

06

Rock Ages Unconformities

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Layers of rock form as part of a complete Sequence, which is how superposition can give the relative age of a rock

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Sometimes, rock layers can erode or be washed away, which forms a gap in the layer sequence ⭘

The gaps are called unconformities

(This is not mine)

LESSON

07

Tools that Paleontologists Use

Inside a Paleontologists Field Kit

04

The Connection with the Past What evidence do fossils provide about the Earth’s past

LESSON

01

What Evidence do Fossils Provide about Earth’s Past

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Fossils give us proof that other life existed on Earth.

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Without fossils we probably wouldn’t have the geological timeline because fossils tell us a lot of Earth’s past like when each animal existed, where they lived, how they looked etc.

With out fossils we also wouldn’t be able to make any inferences and we wouldn’t have a lot to go on about and learn how the Earth has evolved Fossils are the baseline of our inferences made about Earth’s past so without them we wouldn’t have any ideas on where to even start We can learn how long life has existed on Earth and how different plants and animals are related by studying the fossil record. We can often figure out how and where they lived, and then use that information to learn about ancient environments.

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05

Planning the Future

How does what we know about fossils help us plan for the future

LESSON

01

How do Fossils and the Timescale Help us in the Future

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Reminds us and lets us know that the Earth has stayed intact over millions of years so we should respect it and take of it to make sure it stays intact for millions more years

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Can help us to come up with technology for the future of maybe a way for us to find what the future may look like based on previous information and improve the life right now so the future generations can also have a good Earth and can learn about the history of the Earth with better resources than us

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In the future other creature or maybe more evolved humans might find out fossils and we’ll be the mystery of millions of years ago

Resources My Notes

Everything You Need to Ace Science in One Big Fat Notebook