Animal origins

Question 1

What was the cause of Darwin’s dilemma?

Answer 1

First fossiliferous rocks contain several main divisions of animals, there are no rich deposits before this.

Question 2

When was the Cambrian and what defines the start?

Answer 2

541-485mya. Start defined by the start of trace fossils.

Question 3

What species suddenly become abundant and diversion the Cambrian?

Answer 3

Trilobites

Question 4

What are BIFs a chemical biomarker for?

Answer 4

Photosynthesis in the pre-Phanerozoic

Question 5

What biological evidence is there for pre-phanerozoic photosynthesis?

Answer 5

Fossilised stromatolite (cyanobacteria) from the Archaean

Question 6

What fossil evidence is there for complex life before the Cambrian?

Answer 6

Ediacaran fronds

Question 7

What are the three types of Ediacaran fossils?

Answer 7

Rangeomorphs, radial, bilateral

Question 8

What type of morphology and growth do rangeomorphs have?

Answer 8

Frond morphology and fractal growth

Question 9

What were rangeomorphs previously interpreted as and why?

Answer 9

Cnidarians because of their similarity to sea pens

Question 10

What distinguishes rangeomorphs from animals?

Answer 10

Fractal growth is not seen in animals

Question 11

What is Haootia evidence for?

Answer 11

Earliest evidence of animal muscle tissue

Question 12

What are Haootia usually interpreted as and why?

Answer 12

Cnidarians because of their similarity in morphology to stalked jellyfish

Question 13

Describe radialomorphs

Answer 13

Can have multiple planes of symmetry and are likely to be holdfasts of rangeomorphs

Question 14

What type of symmetry to ‘bilateral’ Ediacaran biota have?

Answer 14

Glide symmetry

Question 15

What do the ‘bilateral’ biota not have?

Answer 15

Mouth, legs, gut

Question 16

How can ‘bilateral’ biota be interpreted as molluscs?

Answer 16

Soft shell, radula, and mantle

Question 17

Give two examples of ‘bilateral’ Ediacaran biota

Answer 17

Dickinsonia and Kimberella

Question 18

What evidence is there to support Dickinsonia being an animal?

Answer 18

Composed of animal-like molecules (gas chromatography shows animal-like cholesterols)

Question 19

What does Kimberella provide evidence for?

Answer 19

Motility (trace fossils)

Question 20

Describe the mode of life of most Ediacaran biota

Answer 20

Epibenthic and sessile with high SA:V

Question 21

Describe the substrate of the Ediacaran ecosystem

Answer 21

Massive microbial mat

Question 22

What is the difference between the Ediacaran and Cambrian ecosystems?

Answer 22

Ediacaran ecosystem was flat and simple, Cambrian ecosystem was 3D (e.g. burrowing by priapulids) and complex