Early Diversification

Question 1

Assessing descent

Answer 1

comparisons involving molecular traits or phenotypic traits
assumes constant molecular clock, infers patterns of change, hard to find intermediate forms

Question 2

Origin of multicellular life (2.5 Ma)

Answer 2

dividing cells don’t separate bc of possible membrane mutation, they can now specialize
570 Ma - soft-bodied organisms
shells show up, advantageous (Ediacaran)

Question 3

processes involved in early diversification (4)

Answer 3

increase in size of genome –> larger body size, more natty selection
sexual reproduction
increase in structural complexity (locomotion, protection)
ecological changes

Question 4

Burgess Shale Diversity - Cambrian

Answer 4

ancestors of many modern groups: arthropods, worms, sponges, jellyfish

Question 4

Pikaia

Answer 4

intermediate fossil
ancestor of chordates, vertebrates, mammals

Question 4

The cambrian explosion - 540 Ma

Answer 4

all modern animal body plans established in less than 25 million years

Question 5

what explains the cambrian explosion (4)

Answer 5

increase in genetic complexity (more DNA to mutate)
increase in structural complexity (more body parts)
change in environment
change in ecological relationships (species - species)

Question 6

predator-prey arms race

Answer 6

evolutionary change through interactions and purposeful (actually chance) responses on the part of predator and prey
burrowing –> dig for prey –> hard skin –> jaws

**it is not purposeful! these are as a result of chance mutations that get selected for, reproduce (co-evolution)

Question 7

physical factors for cambrian explosion

Answer 7

continents shifting apart, temperature rising, new habitats, end of snowball earth, more shallow marine habitats, CO2 degassing, increased photosynthesis for oxygen

abiotic environment creates conditions for changes to occurs

Question 8

calcium toxicity

Answer 8

like oxygen, could have been toxic at first but then was able to be harnessed for shell-making

harm –> benefit