2.1 C: Geology = the Changing Earth 2.1 The Cambrian Explosion Flashcards
What are trilobites?
Trilobites are excellent index fossils from the Cambrian Period.
What percentage of Cambrian fossils are trilobites?
About 50% of all Cambrian fossils are trilobites.
How long ago did trilobites exist?
More than 500 million years ago.
Where did trilobites live?
Near the bottom of a tropical sea.
What did trilobites feed on?
Nutrients in the sediment.
What is fossilization?
The process by which any trace of the existence of ancient organisms is preserved within rock.
What is the first step in the process of fossilization?
The burying of the organism before complete decomposition.
What types of remains can be found in rock as unaltered remains?
Hard parts such as shells and teeth.
What happens when the original material of a fossil is replaced by a mineral?
The resulting fossil would be petrified.
What can happen to shells and teeth over time under certain conditions?
They may dissolve.
What is an external mould?
The outside impression of a shell.
What is an internal mould?
The impression of the inside of a shell.
Fill in the blank: Fossilization can be summarized as life > _______ > preservation > discovery recovery.
death burial
True or False: The fossilization process is simple and straightforward.
False
What can working with actual fossils often be compared to?
Trying to solve a puzzle that has many missing pieces.
What is the first step in the process of fossilization?
The burying of the organism before complete decomposition
This step is crucial for the preservation of remains.
What types of hard parts can be found in rocks as unaltered remains?
Shells and teeth
These hard parts can survive the decomposition process.
What happens when the original material of a fossil is replaced by a mineral?
The resulting fossil is petrified
This process involves the replacement of organic material with minerals.
What is created when the hardest shells and teeth dissolve?
A mould
The mould is the space left behind after the material dissolves.
What is an external mould?
The outside of a shell
External moulds capture the outer shape of the original structure.
What is an internal mould?
The impression of the inside of a shell
Internal moulds can preserve details like muscle attachment points.
How can soft tissue be fossilized?
By complete replacement of organic material or as a thin film of carbon
This process can leave impressions of the original soft tissues.
In which type of rock are fossils most often found?
Sedimentary rock
Fossils are typically found in layers where remains were buried in sediment.
What unusual location can fossils be found in due to rapid burial?
Volcanic lava
Lava flows can quickly create impressions of organisms like tree trunks.
What is formed when a mould is filled in by a mineral?
A cast
A cast replicates the shape of the original organism.
What are trace fossils?
Evidence of the presence of organisms without actual remains.
What analogy is used to explain the relationship between a fossil and its impression?
Much like a finger and its fingerprint.
Why are trace fossils important?
They help determine the ecology of ancient plants and animals.
What do stromatolites illustrate in the context of trace fossils?
The importance of information that can be derived from trace fossils.
Fill in the blank: Trace fossils are important for determining the _______ of ancient plants and animals.
ecology
True or False: Trace fossils include the actual remains of organisms.
False
What happens when a geologist splits a rock to find a fossil?
Two parts result: the actual fossil and the impression.
What is Canadia?
A marine worm that is the equivalent of common earthworms
What unique features does Canadia have?
Feather-like structures along the body and small tentacles or stalks on the head
Canadia belongs to which group of organisms?
A group of marine worms
True or False: Canadia has a body structure similar to that of earthworms.
True
Fill in the blank: Canadia is a marine _______.
worm
What is Canadia?
A member of the group of marine worms known as bristle worms
When did bristle worms first appear in the fossil record?
More than 500 million years ago
What types of hard parts have ever been found in Canadia fossils?
No hard parts, such as jaws or teeth
Where are specimens of Canadia found?
In a shale formation on Mount Wapta
What environments do modern bristle worms inhabit?
Shallow water, deep water, tropics, and polar regions
What are the feeding strategies of modern bristle worms?
Predators that drill holes in clam shells and filter feeders
What are the two main functions of the feathery structures in modern bristle worms?
Work as gills and for locomotion
What is the size range of bristle worms?
From a few centimeters long to almost three meters in length
True or False: All bristle worms are free-swimming organisms.
False
Fill in the blank: Bristle worms range in size from a few centimeters long to _______.
almost three metres in length
What type of fossil evidence is often compared to living organisms by geologists and paleontologists?
Fossils
What is a notable feature of the jaws of some modern bristle worm species?
Consist of nine separate parts
What is the significance of comparing fossils to living organisms?
Some information is not preserved in the fossil record
What is the significance of the Burgess Shale?
It is considered one of the most important sources of Cambrian fossils on Earth.
Where is the Burgess Shale located?
On the side of Mount Wapta, about 80 km west of Banff.
What type of rock unit is the Burgess Shale?
A Cambrian-age rock unit.
What types of fossils have been found in the Burgess Shale?
Trilobite, Canadia, and Hallucigenia.
How old are the organisms fossilized in the Burgess Shale?
More than 500 million years old.
What type of environment did the organisms in the Burgess Shale inhabit?
A shallow area close to the shore of a tropical sea.
True or False: The fossil evidence from the Burgess Shale is abundant and varied.
True.
Fill in the blank: The Burgess Shale is known for its well-preserved _______.
[fossils]
What can the interpretation of fossil evidence from rich fossil sites provide?
Glimpses into ancient ecosystems.
What challenge is associated with interpreting the fossil evidence from Hallucigenia?
The fossil evidence is scant, making interpretation difficult.
What is the historical climate of Alberta during the Precambrian Era?
Alberta had a tropical climate and was positioned close to the equator
This tropical climate persisted for millions of years before transitioning to its current climate.
What geological processes occurred in Alberta during the Cambrian Period?
The previously formed Precambrian rock was eroded by rivers, and particles were carried to the ocean
These particles eventually transformed into the sandstones and shales that form part of the Rocky Mountains.
During which geological period were no plants or animals living on land in Alberta?
Cambrian Period of the Paleozoic Era
What type of ecosystem is represented in the Burgess Shale?
A complete ecosystem of both warm shallow-water creatures and deep-water organisms
These organisms were found in soft mud on the seaward side of a reef.
What geological event led to the preservation of soft body parts in the Burgess Shale?
A series of underwater mud avalanches that buried organisms in layers of mud
The tiny particles in the mud limited decay and eliminated scavenger effects.
What are the components that formed the Burgess Shale?
Soft body parts of organisms and hard body parts fossilized in mud
The mud’s composition and environmental conditions allowed for this unique preservation.
What is a reef in geological terms?
A submerged ridge of rock, sand, or coral that rises to the water’s surface
True or False: Alberta was consistently above ocean surface after the Paleozoic Era.
False
Alberta was repeatedly submerged and then lifted above the ocean’s surface.
Fill in the blank: The fine particles of _______ and clay collected along Alberta’s Cambrian coastline were transformed into sandstones and shales.
silt
What significant geological feature is found along Alberta’s current border with British Columbia?
The Rocky Mountains
What is the Cambrian Explosion?
A period marking the first appearance of a wide variety of animals with hard body parts like shells, occurring 545 to 525 million years ago.
This period is characterized by a rapid diversification of life forms, leading to the origins of nearly all modern animal groups.
What type of organisms dominated the fossil record before the Cambrian Period?
Soft-bodied organisms, such as worms.
These organisms lacked hard body parts, which were prominent during the Cambrian Explosion.
How long did the Cambrian Period last?
20 million years.
This relatively short time frame saw a significant increase in the diversity of animal life.
What does the term ‘Cambrian Explosion’ refer to?
The rapid diversification of animal life during the Cambrian Period.
Some evolutionary biologists describe this event as an ‘explosion’ due to the sudden emergence of various body plans.
What major geological era does the Cambrian Period mark the beginning of?
The Paleozoic Era.
The Cambrian Period is the first period of the Paleozoic Era, which is significant for the development of complex life forms.
What is one hypothesis for the biological diversification during the Cambrian Explosion?
The atmospheric oxygen levels reached a concentration high enough to support mobile animals.
This increase in oxygen may have enabled more complex life forms to thrive and evolve.
True or False: Nearly all modern groups of animals can trace their origins to the beginning of the Cambrian Period.
True.
The Cambrian Explosion is crucial in understanding the evolutionary history of modern animals.
Fill in the blank: The Cambrian rocks date from ______ to ______ million years ago.
545 to 525.
This time frame is critical for identifying the origins of diverse animal life.
What significant event in Earth’s history is represented by the Burgess Shale?
A snapshot of a major event in Earth’s history
The Burgess Shale provides important fossils that illustrate life during the Cambrian period.
Why has the United Nations declared the Burgess Shale a World Heritage Site?
Due to its scientific importance and unique fossil record
The site is notable for its exceptional preservation of early life forms.
What organization is responsible for the protection of the Burgess Shale?
Parks Canada
Parks Canada manages national parks and protects natural and cultural resources.
What is balanced with the protection of the Burgess Shale?
The need for educational opportunities for Canadians and visitors
This balance allows people to learn about their heritage while preserving the site.
What opportunities are available for visitors at the Burgess Shale?
Guided tours of the fossil sites
These tours help educate visitors about the site’s significance.
What is the primary focus of Parks Canada’s regulations?
Protecting natural artifacts in national parks
Regulations aim to preserve the ecological and historical integrity of these areas.
What does the process of fossilization involve?
The transformation of organic material into fossils
Fossilization typically requires specific conditions such as burial and mineralization.
What is the significance of the fossils found in the Burgess Shale?
They provide insight into early marine ecosystems
The fossils help scientists understand the diversity of life during the Cambrian explosion.
Fill in the blank: The Burgess Shale is located in _______.
Canada
True or False: The Burgess Shale is accessible to all Canadians.
True
What time period do the fossils in the Burgess Shale date back to?
Over 500 million years ago
The fossils are from the Cambrian period, a crucial time for the evolution of complex life.
What significant event in Earth’s history is represented by the Burgess Shale?
A snapshot of a major event in Earth’s history
The Burgess Shale provides important fossils that illustrate life during the Cambrian period.
Why has the United Nations declared the Burgess Shale a World Heritage Site?
Due to its scientific importance and unique fossil record
The site is notable for its exceptional preservation of early life forms.
What organization is responsible for the protection of the Burgess Shale?
Parks Canada
Parks Canada manages national parks and protects natural and cultural resources.
What is balanced with the protection of the Burgess Shale?
The need for educational opportunities for Canadians and visitors
This balance allows people to learn about their heritage while preserving the site.
What opportunities are available for visitors at the Burgess Shale?
Guided tours of the fossil sites
These tours help educate visitors about the site’s significance.
What is the primary focus of Parks Canada’s regulations?
Protecting natural artifacts in national parks
Regulations aim to preserve the ecological and historical integrity of these areas.
What does the process of fossilization involve?
The transformation of organic material into fossils
Fossilization typically requires specific conditions such as burial and mineralization.
What is the significance of the fossils found in the Burgess Shale?
They provide insight into early marine ecosystems
The fossils help scientists understand the diversity of life during the Cambrian explosion.
Fill in the blank: The Burgess Shale is located in _______.
Canada
True or False: The Burgess Shale is accessible to all Canadians.
True
What time period do the fossils in the Burgess Shale date back to?
Over 500 million years ago
The fossils are from the Cambrian period, a crucial time for the evolution of complex life.
