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Middle school biology - NGSS
Course: Middle school biology - NGSS > Unit 8
Lesson 2: The fossil recordEarth's fossil record
The collection of fossils and their placement in chronological order (e.g., through the location of the sedimentary layers in which they are found or through radioactive dating) is known as the fossil record. It documents the existence, diversity, extinction, and change of many life forms throughout the history of life on Earth. Created by Khan Academy.
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- Although many animals are extinct, there are a lot of really cool animals that are still alive, like the blue sea dragon, (Glaucus atlanticus) a sea slug that looks absolutely amazing!(seriously, search it up!) or the axolotl, a paedomorphic salamander that looks quite cute (especially the ones in Minecraft) and thats not all, there are tons of absolutely amazing animals in this world, because after all, over evolutionary history, organisms have become more complex and diverse.(5 votes)
- Do we need a fossil record? Do we not need a fossil record?
Someone please explain this better(2 votes)- The fossil record helps people keep track and remember about organisms that lived a long time ago and are extinct.
It is important if you want to know that information.
(5 votes)
- what if something important goes extinct?(4 votes)
- we are in trouble(0 votes)
- How do we know for certain that all dinosoaurs are extinct? Couldn't a small species maybe be hiding somehwere?why dont people explor to see if they can find one because i think that some where some how there is some still left i mean cus you never know where they are or if there still living or was but died because they couldnt servive but was still here living for the longest time till who know how long(2 votes)
- Some dinosaurs have survived the meteor impact, they have evolved into other animals, such as birds and mammals.(2 votes)
- How do we know for certain that all dinosoaurs are extinct? Couldn't a small species maybe be hiding somehwere?(2 votes)
- We don't know. There probably is, most likely in the ocean as we have only explored 5% of the ocean. There might even still be megaladons and they just hide because they were hunted and called "sea monsters". as well as other things(1 vote)
- how tall can a triceratops be?(2 votes)
- what does the fossils tell us(2 votes)
- what if one human and only all other animal survies and and other thing?(1 vote)
- Ok. The thing is if that happens, then the human human race wont last and bam! Humans gone.
I do recommend a documentary called Life After People. The name is self explanatory.(1 vote)
- What if human’s go extinct(1 vote)
- then animals would still live and in like 5 million or billion years there would be no sign of humans on earth!!(1 vote)
- Suggest a disease killed all types of cows...(1 vote)
- Bovine spongiform encephalopathy (BSE), also known as mad cow disease, is a fatal, incurable disease that affects the central nervous system of adult cattle.(1 vote)
Video transcript
- [Instructor] Life on Earth has existed for billions of years. Humans know this, not because we've been around the whole time, but instead, thanks to the discovery of fossils, which tell us about organisms that lived in the distant past. Scientists have found millions of fossils. Some, such as skeletons, document ancient organisms'
anatomy or physical features, while others, such as
preserved footprints, record organisms' behaviors. Each fossil that has been found is like a piece of a giant puzzle. To see the bigger picture of
the history of life on Earth, scientists have to study the many fossils and see how they all fit
together in the larger puzzle. All of the fossil puzzle pieces
that have been discovered, along with their relative ages, make up Earth's fossil record. The fossil record is basically
a history of life on Earth as documented through fossils. By studying the fossil record, scientists can see how life on Earth has changed over evolutionary time. The fossil record allows
us to see patterns of evolutionary changes that have happened throughout Earth's history. These include an overall increase in organism complexity and diversity and the changes that have occurred along evolutionary lineages, showing us how one group of organisms could have evolved to the next. The fossil record also shows us when certain groups of
organisms went extinct. First, let's take a look at the increase in organism complexity and diversity that is seen in fossil record. Over evolutionary time,
organisms have generally become more complicated. Some of the oldest known fossils are formations made by ancient
colonies of cyanobacteria. These fossils provide evidence that single-celled organisms
were living on Earth roughly around 3.5 billion years ago and that these organisms
were relatively simple, similar to the bacteria we have today. The fossil record then goes
on to document major leaps in complexity of life on
Earth, with, for example, the large tube-shape
cells of Grypania spiralis and the macroscopic organisms
in the Francevillian biota. According to scientists, these fossils, which are dated to be roughly
from 2 billion years ago, could provide evidence of some
of the earliest eukaryotic, or nucleus-containing cells, and of the earliest
multicellular organisms. Not only does the fossil record show an increase in complexity
over evolutionary time, but also an increase in the
diversity of life on Earth. For example, the Cambrian Explosion describes a multimillion
year span of time, beginning about 539 million years ago, in which there was a huge increase in the diversity of animals on Earth. Almost all of the animal
lineages we know today actually got started during this period. All of these increases in
complexity and diversity have given rise to the
millions of varied organisms that live on Earth today. Next, let's take a look at the changes that can be seen along
the evolutionary lineages in the Earth's fossil record. But before we do that, let's quickly look back at
how scientists study fossils. As you may recall, fossils are
found in sedimentary rocks, meaning that the deeper the fossil, the older the fossil is likely to be. So based on the layers in
which the fossil is found, scientists can put them in order by age. And in doing this,
scientists can piece together the evolutionary steps of
how one type of organism could have evolved into the next, eventually giving rise
to the living organisms we see today. To give an example of this, did you know that birds are
actually direct descendants of a group of dinosaurs called theropods? It may be hard to believe, but the fossil record shows that an organism known as Archaeopteryx existed about 150 million years ago, towards the end of the Dinosaur Age, but before the appearance of modern birds. This organism in
particular is interesting, because it had some features
unique to theropod dinosaurs, such as jaws and sharp teeth and some features unique
to birds, such as feathers. So Archaeopteryx represents
an evolutionary transition between theropod dinosaurs and
birds in the fossil record. Finally, let's take a look
at the patterns of extinction seen in the fossil record with the help of our extinct
friend, the Triceratops. Extinction happens when a
species completely dies out. In the fossil record, extinctions show up as organisms of a certain species being present in older rock layers and then completely disappearing
from the newer rock layers. For example, we only
see Triceratops fossils in rock layers that are roughly
68 to 66 million years old. After this, we don't find any evidence of Triceratops fossils anywhere and there certainly aren't
any Triceratops living today. The Triceratops is an important
example of extinction, as they not only went extinct, but they went extinct due
to a mass extinction event. Mass extinction events happened when large-scale environmental change caused many groups of
organisms to go extinct around the same time. When we see the triceratops disappear from the fossil record, we also see other types of
organisms disappear, too, providing evidence for
the mass extinction event that led to the disappearance
of all non-avian dinosaurs. And with that, you now know
what Earth's fossil record is and the various patterns it can show us. Earth's fossil record is an essential tool that scientists use to piece together the history of life on Earth. And new fossils are
continuously being discovered, so the fossil record is more than just a collection of fossils. It's a window into the
mysteries of the past and it's ever-growing
record of how life on Earth came to be what it is today.