lect 1 - development

Question 1

heterochrony

Answer 1

a change in the relative timing of developmental stages in the course of phylogeny

Question 2

paedomorphosis

Answer 2

retention of ancestral larval traits in the adult stage of derived forms (remains aquatic)

Question 3

neoteny

Answer 3

normal gonadal development but with retarded somatic development (no metamorphosis)

Question 4

progenesis

Answer 4

accelerated gonadal development with normal but arrested somatic development (acceleration of maturation)

Question 5

direct development

Answer 5

acceleration of development program resulting in no larval stage

Question 6

maturation

Answer 6

maturation of gonads / becoming a full adult

Question 7

example of progenetic paedomorph

Answer 7

axolotl

Question 8

consequences of direct development

Answer 8

• larger eggs
• longer developmental time
• altered pattern of organ formation
• loss of larval constraints
• gain in morphological diversity

Question 9

heterochrony impact on phylogenetic analysis

Answer 9

• mislead morphological data
• difficult to separate paedomorphic traits from shared ancestral traits
• may lack post-metamorphic shard derived traits
• hard to determine ancestral condition

Question 10

obligate paedomorph

Answer 10

can induce metamorphosis with hormones (don’t live long)

Question 11

facultative paedomorph

Answer 11

paedomorphosis depends on environmental conditions

Question 12

consequences of paedomorphosis

Answer 12

• larger adult body size
• earlier reproduction
• larger clutch size
• higher chance of mating success

Question 13

paedomorphic origin

Answer 13

temnospondyls ancestor of amphibians
- best known early tetrapods in fossil record (340-110mya)

Question 14

evidence of paedomorphic origin

Answer 14

• small size of amphibians
• reduced skull bones (bones missing in modern amphibians are in the last development stage of temnospondyls)
• large orbits of modern amphibians (juvenile feature)
• tooth form (in larval form of temnospondyls)