Devonian and Silurian

Question 1

When was the Silurian?

Answer 1

440 MYA - 417 MYA.

Question 2

When was the Devonian?

Answer 2

417 - 354 MYA.

Question 3

What collides with Laurentia in the mid-Silurian?

Answer 3

Avalonia and Laurentia is called the Acadian orogeny and Laurentia and Baltica collided at the end of the Silurian.

Question 4

What “Renewal of Life” happened in the Silurian/Devonian?

Answer 4

Coral-strome reefs flourished in the middle of the Paleozoic (particularly the Devonian [greatest size]). Ecologic succession - tabluates and rugose corals colonized the seafloor. Other animals populated the reef.

Question 5

What followed the Ordovician mass extinction?

Answer 5

Evolutionary radiation, particularly of Brachiopods, Bivalve Mollusks, Graptolites, but Trilobites did not fully recover.

Question 6

What animals first appeared in the early Devonian?

Answer 6

Swimming animals originated, like the Ammonoids (evolved from straight nautiloids in Early Devonian) - widespread, a guide fossil.

Question 7

What are Ammonoids?

Answer 7

From the Devonian-Cretaceous, similar to nautiloids but suture patterns on the edge of shell are more complex. Most are tightly coiled, and they were very diverse in the Mesozoic. Nautiloids have a much less complex suture pattern than ammonoids, also, the sipuncle in a Nautiloid is central and it is marginal in Ammonoids.

Question 8

What happened in the oceans in the middle Paleozoic?

Answer 8

Particularly in the Devonian, there was the diversification of fish. The first fully preserved specimens appeared.

Question 9

What main environmental challenges were there for plants to adapt from water to land?

Answer 9

1) Obtaining enough water
2) Limiting water loss
3) Adapting photosynthesis to deal with high light intensities
4) Different carbon dioxide/oxygen rations
5) Tolerating fluctuations in temperature
6) Gravity

Question 10

What structures developed to help plants move to land?

Answer 10

1) Roots
2) Cuticle
3) Stomata
4) Vascular System
5) Lignin
6) Leaves
7) Spore, pollen, seed

Question 11

How did Roots help plants move to land?

Answer 11

They were used to anchor plants to the soil, giving it support and a mechanism for obtaining water and nutrients.

Question 12

How did the Cuticle help plants move to land?

Answer 12

The waxy, water-insoluble coating reduced the water lost by evaporation.

Question 13

How did the Stomata help plants move to land?

Answer 13

They are microscopic pores on the stems and undersides of leaves that allow CO2 into the plant and water out of the plant (holes in the cuticle). This balance determines possible habitats that plants can survive in.

Question 14

How did the Vascular System help plants move to land?

Answer 14

The vascular system is a specialized system that allows for the transport of water and nutrients in the plan. There are two main tissues; the xylem and phloem.

Question 15

How did Lignin help plants move to land?

Answer 15

A strengthening polymer that allows vascular plants to grow taller.

Question 16

How did Leaves help plants move to land?

Answer 16

They are specialized structures that have adapted for higher light intensities and CO2 levels.

Question 17

How did spores, pollen, and seeds help plants move to land?

Answer 17

Land plants need these for reproduction. They had to be resistant to desiccation and could be transported by wind.

Question 18

How long did the transition from aquatic to terrestrial habitats for plants take?

Answer 18

10s of millions of years - over this time plants became less and less dependant on aquatic habitats.

Question 19

When did the earliest true vascular plants appear?

Answer 19

In the Middle Silurian, although there are spores from the Upper Ordovician. The early ones all lived in wet, marshy habitats and were only a few centimetres tall.

Question 20

What difficulties were there for invertebrates to move to land?

Answer 20

1) Needed stronger support
2) Had to avoid desiccation
3) Need to breath
4) Need to reproduce (marine animals usually have external reproduction - this is hard on land)

Question 21

What was the path of colonization of land for invertebrates?

Answer 21

They were the first animals to move out onto land, and most of the ones living on land today are insects. 70% of all invertebrates live on land. Of the 30 invertebrate phyla, only 3 have significant numbers of macroscopic terrestrial species. No phyla have evolved on land and as far as we know no major terrestrial taxon has gone extinct.

Question 22

How did Arthropods develop to live on land?

Answer 22

They are by far the most successful terrestrial invertebrates, in many ways they were preadapted for life on land. There was already a hard cuticle, and it became waterproof. Gas exchange done by diffusion and a variety of lung types.

Question 23

What were the earliest land Arthropods?

Answer 23

Earliest forms seem to be small decomposers, possibly mites or millipedes in the Silurian. Predations seems to have been a driving force of much of the early evolution of land invertebrates as they left pools to avoid being eaten. Diverse assemblages of small arthropods common in the Devonian - there is no evidence of terrestrial herbivores until the Carboniferous.

Question 24

What is the Ichthyostega?

Answer 24

An intermediate between amphibians and lobe-finned fishes that invaded land.

Question 25

What is the Late Devonian Extinction?

Answer 25

A series of extinctions that lasted 10 million years, characterized by low rates of origination as extinction rates remained fairly typical. Cephalopods, fish, and corals were most affected.