Ocean Life

Question 1

What’s the main differences between Ediacaran and Cambrian ecosystems?

Answer 1

Ediacaran: two dimensional microbial mat surface, organisms are mostly ‘sessile’ and live on that flat surface, no burrowing or swimming
Cambrian: burrowing and mixing of layers, penetration of oxygen, some filter feeders, some swimmers, some predators, more three dimensional

Question 2

How did ecosystems change in the Ordovician?

Answer 2

There was a shift from microbial environments to reef type environments.

Question 3

Describe Ordovician reefs.

Answer 3

Dominated by sponges (porifera) which fed by ciliary action (choanocytes) and corals (sessile cnidarians) which form a mutualism with photosynthetic algae (zooxanthellae) e.g. Rugose corals and Tabulate

Question 4

What animals inhabited Ordovician reefs?

Answer 4

-Crinoids (filter feeders)
-Cephalopods (swimming molluscs)
-Brachiopods (sessile feeders)
-Trilobites (3 part exoskeleton arthropods)

Question 5

What are primary producers?

Answer 5

Organisms that produce their own energy (mainly via photosynthesis)

Question 6

What caused an increase in diversity during the Ordovician?

Answer 6

Diversification of phytoplankton (the main primary producer) carried up the food chain allow more complex food chains/ webs to form.

Question 7

What are zooplankton?

Answer 7

A diverse group of microorganisms that are primary consumers (heterotrophic)

Question 8

List the main roles of a food chain/ web.

Answer 8

Primary producers, primary consumers, secondary consumers and apex predators.

Question 9

What is the GOBE?

Answer 9

Great Ordovician Biodiversification Event

Question 10

What is Sepkoski’s curve?

Answer 10

A graph which compiles fossil data over time showing animal diversification during the Palaeozoic. During the Ordovician the largest rise in animal variety occurred.

Question 11

What caused the GOBE?

Answer 11

1. Splitting of the continents lead to large volcanic activity, combined with global warming this lead to high sea levels and larger oceanic shelf (shallow seas=good for evolution)
2. Strontium excursion could have increased nutrient levels.

Question 12

Describe the end Ordovician extinction event.

Answer 12

The first of the big five extinction events in Earth’s history. It was comprised of two pulses. The first was due to global cooling (glaciation and sea level drop) and the second was due to changing ocean cycles leading to anoxia.

Question 13

What are vertebrates?

Answer 13

Vertebrates are part of the phylum Chordata, and they can be divided into jawless vertebrates (agnathans) and jawed vertebrates (gnathostomes).

Question 14

List the characteristics of vertebrates.

Answer 14

-All chordate characteristics e.g. notochord, pharyngeal slits…
-Segmented brain
-Medial fins
-Branchial arches (important)
-Paired eyes

Question 15

What characteristics do agnathans have?

Answer 15

They are jawless, have keratin teeth and no appendages e.g. Lamprey/ Hagfish

Question 15

What characteristics do gnathostomes have?

Answer 15

They are jawed, have teeth, mineralised bone, paired appendages.

Question 16

List the sequence of events/ phases that happens during the development of an animal.

Answer 16

Zygote, cleavage, blastula (ball of cells), gastrula (folds to form a gut cavity), endo and ectoderm formation, larva and adult.

Question 17

What are Homeobox (Hox) genes?

Answer 17

Genes that code for what is expressed in different parts of the body. For example brachial arches develop into different things depending on the Hox genes present.

Question 18

What two jawless vertebrates are stem group relatives to modern vertebrates?

Answer 18

Metaspriggina and Sacabambaspis

Question 19

What were ostracoderms?

Answer 19

Armoured jawless fish which were diverse and dominant during the Silurian. e.g. Sacabambaspis and Cephalaspis

Question 20

What are placoderms?

Answer 20

Armoured and jawed animals that also dominated the Silurian e.g. Dunkleosteus

Question 21

What was the Devonian Nekton revolution?

Answer 21

The rapid occupation of the deep water column leading to advancement in predatorial ecological complexity.

Question 22

What caused the ostracoderms to go extinct during the Devonian?

Answer 22

The collision of the North American and Europe to Euramerica reduced the abundance of shallow waters which ostracoderms relied on. Fossils evidence also suggests large predation by jawed competitors.