Animal Origins

Question 1

What is an animal?

Answer 1

Multicellular heterotrophs without a cell wall. They’re mobile, at least in part of the life cycle.

Question 2

What are bacteria?

Answer 2

Unicellular prokaryotes with fatty ester lipids.

Question 3

What are Archaea?

Answer 3

Unicellular prokaryotes with isoprenoid ether lipids.

Question 4

What are Plantae?

Answer 4

Multicellular autotrophs with chloroplasts and a cellulose cell wall.

Question 5

What are fungi?

Answer 5

Multi/ unicellular heterotrophs with chitin cell walls.

Question 6

When did complex life evolve?

Answer 6

The Phanerozoic period (540Ma-Today)

Question 7

What Ediacaran animal clade had of a ‘leafy’ like branching structure with similar morphologies (fronds) and fractal growth?

Answer 7

Rangeomorphs

Question 8

What does the high surface area to volume ratio of many Ediacaran animals suggest?

Answer 8

Osmotrophic feeding

Question 9

What is Kimberella and why is it important?

Answer 9

Kimberella is an extinct genus of bilaterian from the Ediacaran period. The slug like organism fed by scratching the microbial surface on which it dwelt. It is important because it is potentially the first ‘animal’ to exhibit movement.

Question 10

Why did the Ediacaran evolutionary event occur?

Answer 10

Deglaciation (end of Gaskier’s glaciation), an increase in oxygen allowing for larger more complex life and and the Shuram carbon isotope excursion caused be meteor bombardment resulting in an increase in ocean nutrients.

Question 11

What is a Phylum?

Answer 11

A taxonomic group with a unique body plan

Question 12

What characteristics define the Arthropoda phylum?

Answer 12

Bilateria with jointed appendages.

Question 13

What characteristics define the Chordata phylum?

Answer 13

Bilateria with a notochord and dorsal nerve chord.

Question 14

What is a phylogeny?

Answer 14

An evolutionary tree based on either molecular similarity (genetics) or morphology (physical traits).

Question 15

Why are fossils in the Burgess shale so well preserved?

Answer 15

A sea cliff collapsed so the whole ecosystem was rapidly buried leading to anaerobic diagenesis (resulting in soft tissue preservation).

Question 16

What is the Burgess shale?

Answer 16

A very well preserved Cambrian fossil deposit in Canada.

Question 17

What are Trilobites?

Answer 17

Fossil arthropods that became dominant and abundant during the Cambrian.

Question 18

What is a crown group?

Answer 18

All living members of a clade including common ancestors and descendants.

Question 19

What is a stem group?

Answer 19

The extinct organisms outside of a group that are part of a phylogeny.

Question 20

What was the Cambrian explosion?

Answer 20

A sudden period of evolution and biological diversification of phyla after a long period of stasis.

Question 21

What are the possible biotic and abiotic causes of the Cambrian explosion?

Answer 21

1. Biological arms race-predator prey competition accelerated evolution.
2. Rodinia broke apart leading to an abundance of shallow waters conducive to life at the time.
3. Earlier in life’s history there were less constraints on life resulting in more experimentation.
4. More exposed rock increasing carbonate input which increase alkalinity and nutrient levels.