Lecture 27: The Phanerozoic Bioshpere

Question 1

What happened in The Cambrian Explosion?

Answer 1

Most major animal phyla appeared abruptly in the fossil records, and apparently without obvious precursors.
-It lasted for about 30 million years and resulted in the rapid appearance of most modern animal phyla.

Question 2

What are examples of cambrian fauna?

Answer 2

Sponges, predatory worms, molluscs, brachiopods, archaeocyathids (1st reef-building organism), and arthropods (trilobites).

Question 3

What are the three accepted explanations for the Cambrian Explosion?

Answer 3

1) Environmental changes
2) Developmental changes
3) Ecological changes

Question 4

What environmental changes could have led to the Cambrian Explosion?

Answer 4

Oxygen and calcium levels in the ocean increasing.

• Oxygen could lead to more complex life forms to evolve
• Calcium would make it possible for marine organisms to build skeletons and shells.

Question 5

What is the Great Unconformity?

Answer 5

It represents a long period of time of weathering between Precambrian and Cambrian strata.

Question 6

What are the two reasons for the sudden developmental changes?

Answer 6

• It took time for animals to form Hox genes

- Horizontal gene transfer

Question 7

What are Hox genes?

Answer 7

Genes that control how different regions of the embryo develop into specific organs.
-Control basic body form

Question 8

What is Horizontal gene transfer

Answer 8

The process whereby genetic material is transferred between organisms.
-Has also been identified as a possible factor in the acquisition of the biochemical capability of biomineralization.

Question 9

How would end-Ediacaran mass extinction be an ecological factor for the Cambrian Explosion?

Answer 9

Explains why the Ediacaran fauna disappeared and mass extinctions are often followed by adaptive radiations.

Question 10

How would would the evolution of eyes be an ecological factor for the Cambrian Explosion?

Answer 10

Prey would need new defences against predation, such as the evolution of amour and spines.

Question 11

How would evolution of predators be an ecological factor for the Cambrian Explosion?

Answer 11

As predators evolved, prey would also need to grow bigger and develop greater mobility or biomineralized to prevent being eaten.

Question 12

How would large zooplankton be an ecological factor for the Cambrian Explosion?

Answer 12

Fecal pellets get formed and deposited on the seafloor, thus providing a new energy source.
-Opened the door to more burrowing animals

Question 13

What is a lagerstatte?

Answer 13

It is a fossil site exhibiting extraordinary preservation and often fauna or floral diversity.

Question 14

How does fossil records of soft tissue help paleontologists?

Answer 14

They allow them to examine the internal anatomy of animals.

Question 15

What is so important about the Burgess Shale?

Answer 15

An entire community of marine organisms became preserved, allowing scientists to observe an entire ecosystem from 508 million years ago.

Question 16

What are epifaunal?

Answer 16

Animals that live on the surface of the seafloor.

Question 17

What are infaunal?

Answer 17

Animals that burrow into sediment.

Question 18

What marked the late Cambrian and Ordovician?

Answer 18

A tripling in global biodiversity.

-Including new trilobites, brachiopods, bivalves, bryozoans and coralline animals.

Question 19

What are classified as Bivalves?

Answer 19

Clams, mussels, scallops and oysters

Question 20

What are classified as Gastropods?

Answer 20

Snails, slugs, conchs, and limpets

Question 21

What are classified as Cephalopods?

Answer 21

Squid, cuttlefish, octopus, and nautilus

Question 22

What is the difference between nautiloid cephalopods and ammonoid cephalopods?

Answer 22

Nautiloid- have straight or gently undulating sutures

Ammonoid- have complex sutures

Question 23

What are Arthropods?

Answer 23

They are a phylum of invertebrates that include insects, spiders, crustaceans, and a host of other animals that possess exterior skeletons.

Question 24

Which arthropods were important during the Paleozoic?

Answer 24

Trilobites and eurypterids

Question 25

What are vertebrates?

Answer 25

Animals that have a segmented backbone composed of individual vertebrae.

Question 26

What are the two groups of vertebrates?

Answer 26

1) Non-amniotic vertebrates

2) Amniotic vertebrates

Question 27

What are non-amniotic vertebrates?

Answer 27

Fish and amphibians must be in the water (or at least wet) to reproduce. Their eggs are exposed - lack a covering.

Question 28

What are amniotic vertebrates?

Answer 28

All higher vertebrates that have evolved internal fertilization and amniotic egg (enclosed egg).

Question 29

What is so important about amniotic vertebrates?

Answer 29

There form of reproduction allows them to exploit diverse terrestrial environments away from water bodies.

Question 30

What are the two earliest vertebrates?

Answer 30

• Pikaia, a worm-like animal with a dorsal nerve cord and muscles that run down the side of the body
• Myllokunmingia, oldest fish

Question 31

What are a few biological innovations that facilitated the widespread divergence of fish?

Answer 31

• Many species developed some form of armour
• The evolution of the jaw
• The evolution of bony fish. Played a key role in the eventual evolution of tetrapods.
• Some developed muscular lobe-fins and a pair of opening in the roof of the mouth that led to external nostrils. Eventually passed on to primitive lungs

Question 32

What changes in amphibians came with the shift from water to land?

Answer 32

1) Limb bones and skeletal structures were modified to help hold their bodies above ground.
2) The spinal column was transformed into a more sturdy structure.
3) The organs for hearing underwater needed to adapt to hearing in the air.

Question 33

What are tetrapods?

Answer 33

The first amphibians.

Question 34

What are amniotes?

Answer 34

Reptiles that first appeared in the Pennsylvanian and who developed the amniotic egg.

Question 35

When did the oldest bird appear and what did it look like?

Answer 35

It appeared in the Jurassic and possessed a jaw with teeth and a lizard-like tail. It resembled a dinosaur, except for its fossilized feathers.

Question 36

When did the earliest mammals evolve?

Answer 36

During the Late Triassic. They were fairly small until after the Mesozoic.

Question 37

What did plants evolve from?

Answer 37

Stromatolites formed from cyanobacteria which eventually become algae.

Question 38

What was the first form of reproduction for plants?

Answer 38

Seedless

• Spore-bearing plants
• Became to abundant in swamps that they eventually formed some of Earth’s largest coal deposits

Question 39

What was the second form of reproduction for plants?

Answer 39

Naked seed-producing, pollinating, but non-flowering plants (gymnosperms).
-Did not require moist environments so they expanded their habitat and dominated the supercontinent, Pangea.

Question 40

What was the third form of reproduction for plants?

Answer 40

Self-enclosed seed-producing plants

-Plants with both seeds and flowers (angiosperms)

Question 41

How did all three of the early Paleozoic plants alter the environment?

Answer 41

They facilitated soil formation and provided food and shelter for emerging land animals. They also paved the way for the evolution of large trees.

Question 42

What are two events that led to mass extinctions?

Answer 42

1) Meteorite impacts

2) Volcanic eruptions

Question 43

What are the two major extinctions?

Answer 43

1) Permian-Triassic. Most severe in Earth’s history

2) Cretaceous-Tertiary. Loss of dinosaurs and many other plant and animal species

Question 44

What percentage of marine and land animals perished in the Permian extinction?

Answer 44

90% of marine species

70% of land animals

Question 45

What caused the Permian extinction?

Answer 45

• Huge amount of volcanic activity
• Extra carbon dioxide would have led to global warming
• Dust would have blocked out the sun causing prolonged nuclear winters
• Sulfate reduction took place in the water column which would have killed the aerobic organisms.

Question 46

What caused the Cretaceous extinction?

Answer 46

The impact of the large meteorite colliding with the Earth in Mexico.

• Dust would have blocked out the sun killing the plants which killed the animals
• Vapourized surrounding rock and oceans

Question 47

How many species were wiped out during the Cretaceous extinction?

Answer 47

1/4 of all known species.

Question 48

What evidence do paleontologists have that explains the cause of the Cretaceous extinction?

Answer 48

• The abrupt manner of the extinctions
• A layer of clay found around the world that contains iridium that only occurs naturally in the Earth’s mantle and core. The only other source would have to be extraterrestrial.

Question 49

What is another possible cause of the Cretaceous extinction?

Answer 49

Massive outpouring of flood basalts, known as the Deccan Traps.
-Could have led to the same environmental changes like the end of the Permian.