Early Paleozoic (Early Cambrian)

Question 1

How do we classify life on Earth? What is this term called?

Answer 1

Life can be divided into several groups, each more exclusive than the preceding group

THIS IS CALLED TAXONOMY

Question 2

How does taxonomy work?

Answer 2

Each level of the hierarchy groups together animals with similar biological characteristics

Question 3

What is the order of hierarchy in taxonomy from most general to most exclusive?

Answer 3

1. KINGDOM
2. PHYLUM
3. CLASS
4. ORDER
5. FAMILY
6. GENUS
7. SPECIES

Question 4

What does the Cambrian explosion mark?

Answer 4

Marks the appearance and diversification of animals in the Cambrian

MOST MAJOR GROUPS OF ANIMALS SHOW UP QUICKLY

THINGS GET MORE COMPLEX, THE NUMBER OF FAMILIES HAVE INCREASED FROM THE CAMBRIAN ONWARDS

Question 5

What has occurred throughout the Phanerozoic eon regarding fauna?

Answer 5

There have been recognized 3 evolutionary faunas

EACH NEW FAUNA REPLACES THE OLD FAUNA IN TIME

Cambrian —> Paleozoic —> Modern

Question 6

How are evolutionary faunas defined? What are faunas?

Answer 6

Defined by the dominance of a specific group of organisms

EACH WAS DOMINANT DURING A DIFFERENT TIME

Fauna = Group of animals !!

Question 7

What was the first evolutionary fauna? What is unique about them?

Answer 7

CAMBRIAN FAUNA, whose fossils dominate in the Cambrian

THIS EARLY FAUNA IS VERY SHORT-LIVED

Question 8

What were some Cambrian fauna (group of animals)?

Answer 8

Echinoderms

Arthropods

Sponges

Brachiopods

Snails

Question 8

What are the Cambrian Echinoderms? What were they all classified regarding lifestyle?

Answer 8

These echinoderms were sediment stickers

Eocrinoids

Helicoplacoids

Edrioasteroids

Question 9

What are Eocrinoids? What is the difference between these old crinoids compared to modern crinoids?

Answer 9

Share similarities to modern crinoids but they had a BLUNT STEM instead of a HOLDFAST (root, stick themselves to the sediment)

Question 10

What are Helicoplacoids?

Answer 10

Also lived as sediment stickers with their blunt stem stuck into the seafloor

THEY HAVE NO CLOSE MODERN RELATIVES AND BASICALLY WENT EXTINCT

Question 11

What are Edrioasteroids?

Answer 11

Have a broad stem at their base that they use as sediment stickers as well

THESE FOSSILS ALSO HAVE NO MODERN RELATIVE

Question 12

What happened to these Cambrian echinoderms as microbial mats vanished? (Evolution)

Answer 12

EOCRINOIDS = ADAPTED TO BECOME CRINOIDS WITH HOLDFASTS (ROOTS)

HELICOPLACOIDS = DID NOT ADAPT AND THUS WENT EXTINCT

EDRIOASTEROIDS = ADAPTED TO BECOME ENCRUSTERS (makes a glue that helps them stick to surfaces)

Question 13

What was the Cambrian arthropod? What was so unique about them?

Answer 13

First recognizable arthropod fossil of the Cambrian Period are the TRILOBITES

Question 14

Where did the name TRILOBITE come from?

Answer 14

Comes from the fact that their body contains three LOBES (Left, Middle, Right)

THEY ALSO CONTAIN A HEAD, THORAX, AND TAIL

Question 15

What do you call the head, thorax, and tail of the trilobites?

Answer 15

Head = CEPHALON

Thorax = MIDSECTION

Tail = PYGIDIUM

Question 16

What is often preserved with trilobites?

Answer 16

Molted pieces of its exoskeleton, head, thorax, and tail

Since these pieces break off as they shed and molt

Question 17

What are trilobites most closely related to?

Answer 17

BOTH SHARE A SIMILAR MORPHOLOGY AND LIFESTYLE

Chelicerates (ex. horseshoe crab)

Question 18

How are Chelicerates different from other arthropods?

Other examples of chelicerates?

Answer 18

Have FANGS rather than jaws, OFTEN USED FOR EATING PREY

Spiders and Scorpions are another example

Question 19

What are the earliest sponges called?

Answer 19

Earliest recognizable sponge fossil belong to a group called the ARCHAEOCYTHANS

SHARE MANY SIMILARITIES WITH SPONGES

Question 20

What is the difference between Archaeocyathans and modern-day sponges?

Answer 20

Archaeocythans had notably TWO walls (INNER and OUTER WALL)

Modern sponges only have ONE wall

Question 21

What was so important about Archaeocyathans regarding how they acted in their environment?

Answer 21

They are notable for being the FIRST animals EVER to construct reefs

BUILT REEFS LONG BEFORE CORALS EVER DID

Built ISOLATED reefs that stuck STRAIGHT UP from the seafloor

Question 22

What happened to fossils within REEF LIMESTONE?

Answer 22

Fossils within REEF LIMESTONE are preserved in LIFE POSITION (Preserved oriented as they lived)

Question 23

What happens to the Archaeocythans throughout the Cambrian?

Answer 23

By the MIDDLE CAMBRIAN, the archaeocyathans DECLINE SEVERELY and eventually go EXTINCT

Question 24

What was a dominant component of the Cambrian Fauna?

Answer 24

INARTICULATE BRACHIOPODS

Question 25

What’s the difference between ARTICULATE brachiopods and INARTICULATE brachiopods?

Answer 25

ARTICULATE = has a hinge

INARTICULATE = NO hinge

Question 26

What showed the emergence of animals during the Cambrian explosion?

Answer 26

Due to the emergence of shells, shell is necessary for preservation as a fossil

Question 27

Did animals exist before shells first appeared?

Answer 27

YES, it is common to find tracks from trilobites before their shelled fossils show up in rocks

Another ex. Tracks from snails feeding pre-date snail shells, scratch marks during the Proterozoic pre-date snail shells

RADULA SCRATCH MARKS FROM THE PROTEROZOIC PRE-DATE CAMBRIAN-AGE SNAIL SHELL FOSSILS