Benton, 1997 (models for diversification of life)

Question 1

The diversification of marine families in the past … million years appears to have followed two or three … curves, with … levels that lasted up to 200Myr.

Answer 1

600, logistic, equilibrium

Question 2

In contrast, continental organisms clearly show an … pattern of diversification (not clear whether these patterns are real or artefacts of a poor fossil record, though latter seems unlikely)

Answer 2

exponential

Question 3

Marine and continental organisms may have … in different ways, or perhaps the equilibrium patterns in arise organisms is an artefact of … ….

Answer 3

diversified, taxonomic structures

Question 4

Palaeontologists usually focus on the last ~… million years, as…

Answer 4

600, prior to this the fossil record is especially poor (earlier parts fo precambrian)

• key criticism of the fossil record is that it likely becomes worse the further back in time you look, though comparing changes in knowledge of the fossil record through time has suggested biases are randomly distributed with respect to geological time + more data suggesting less bias than thought

Question 5

If speciation and extinction rates remain roughly constant…

Answer 5

there will be regular doubling of diversity within fixed units of time - exponential model

Question 6

The logistic model involved one or more …-… …, consisting of an initial period of slow diversity increase, a rapid rise and a slowing of the rate of increase as a result of …-… damping factors, and a … corresponding to a limiting or equilibrium value

Answer 6

S-shaped curves, diversity-dependent, plateau

Question 7

Diversity pattern of marine invertebrates: short … in the … and a longer one from the … to the …., followed by long phase of …-… increase, with slight slowdown in last 25my, suggesting third plateau may be occurring.

Answer 7

plateau, Cambrian, ordovician, permian, near-exponential (through mesozoic and cenozoic)

Question 8

Vascular plants: starts of …, but later part of curve is … or …

Answer 8

logistic, linear, exponential

Question 9

Continental tetrapods: explained by an … curve

Answer 9

exponential

Question 10

Insects: pattern largely …, but could be said to be approaching … now

Answer 10

exponential, equilibrium

Question 11

Combined continental is …. Marine curve is explained by two … curves (Cambrian (palaeozoic) and post-palaeozoic) - with beginning of new plateau

Answer 11

exponential, logistic

Question 12

Perhaps … space was filled early on in the sea, while land plants (and possible vertebrates) have continued to fill more and more …. Diversification in the sea began before it did on land, which may help to explain this.

Answer 12

adaptive, ecospace

• early part of logistic curve is typically exponential
• perhaps there are just more niches on land (more ecospace)?

Question 13

Non-equilibrium (expansion) models assume there is no .. to the diversity life can reach

Answer 13

ceiling

(equilibrium models assume that equilibrium can be reached - there is a carrying capacity for the earth - extended from same theory for islands)

Question 14

Diversity-dependent damping factors may include

• … …
• increased species …
• reduction of species …

Answer 14

competitive exclusion, packing, ranges

• increase of one population suppresses another population that depends on the same limiting resource

Question 15

Marine logistic curves could be explained by rapid diversification into empty ecospace, followed by equilibrium do to diversity dependent factors, followed by radiation when evolution of a new trait (e.g. predation) opens up new ecospace or habitats to radiate into again (or subdivide more finely via specialisation)

Answer 15

maybe?

• maybe diversification of terrestrial vertebrates has regularly found these new habitats - more potential habitats? - and ecospecies so there hasn’t been any equilibrium. Or rates of evolution are higher so new adaptations are more likely to occur within a given timespan? - my ideas in combo with paper
• presumably there is an ultimate limit to no. of families that can inhabit earth at any time as every resource on earth is limited to some extent, even oxygen and carbon

Question 16

This study used number of … as a measure of diversity, for all except land plants, in which … was used.

Answer 16

families, species

Question 17

The fact that exponential increases in diversity occurred after mass extinctions supports the … (…) model as it suggests that the extinction event creates … … into which families can radiate

Answer 17

equilibrium, logistic, vacant ecospace

Question 18

Plateaus could be an artefact of carrying out analysis using high … …

Answer 18

taxonomic levels

• plateau becomes shorter towards the lower taxonomic levels (species hasn’t been done/possible but may be more exponential?)