Ch. 3: Animal Origins

Question 1

3 advantages to being multicellular

Answer 1

1. specialized cells allow for more efficient feeding, movement, repro, defense
2. move faster/farther
3. access to new and larger food

Question 2

5 reasons choanoflagellates are the best candidate for our animal ancestor

Answer 2

1. single-celled or small multi Euk
2. aquatic
3. heterotrophic
4. make gelatinous secretions
5. colonial

Question 3

3 features of early Ediacarans

Answer 3

1. soft bodied
2. probably did not crawl or swim - sessile ecosystem
3. ate from the bacterial mat that probably covered the ocean floor

Question 4

Ediacarans probably dispersed via (2)

Answer 4

1. planktonic juvenile stages

2. via floating gametes

Question 5

4 climactic factors that may have contributed to the rise of Ediacarans

Answer 5

1. worldwide ice ages
2. O2 levels increased after the appearance of photosynth
3. volcanic eruptions released lots of CO2 which warmed the climate and melted oceans
4. meteor/asteroid impacts that caused major extinctions

Question 6

The Cambrian Explosion occurred due to 3 factors

Answer 6

1. environmental
2. genetic (Hox genes?)
3. ecological factors