Development 4: Evolution & development

Question 1

What are the similarities between organisms a result of?

Answer 1

A common ancestor

Question 2

What are the differences between organisms a result of?

Answer 2

Natural selection

Question 3

Why are genetic relationships between organisms determined (partly) through comparison of embryos?

Answer 3

Because changes in developmental processes will modify the form of an adult organism over evolutionary time
= Darwin recognised that organisms embryos can be similar while adult phenotypes often differ

Question 4

Many genes that regulate development are ______ _______

Answer 4

highly conserved

Question 5

Why does developmental genes being highly conserved show that they alone do not determine morphology?

Answer 5

Huge variety of animals are produced by a common set of instructions
= Differences in form mean that the genes alone can’t determine an organism’s morphology

Question 6

What are changes to morphology a result of?

Answer 6

• Mutations in genes that regulate development
• Changes in the spatial expression of development genes
• Changes in the temporal expression of development genes

Question 7

Give an example of how mutations can modify morphology

Answer 7

• Insect Ultrabithorax (Ubx) gene has a mutation
• Mutated gene is expressed in the abdomen → represses the dII gene
• Distal-less (dII) gene is essential for leg formation in arthropods
  = Insects don’t form legs on their abdomens

Question 8

Give an example of how changes in spatial expression can modify morphology

Answer 8

• In most birds, gene encoding BMP4 is expressed between developing toes (webbed) and instructs cells to undergo apoptosis
• Ducks have BMP inhibitor ‘gremlin’ = inhibits apoptosis around toes = webbed feet

Question 9

Give an example of how changes in temporal expression can modify morphology

Answer 9

• Webs of most salamanders disappear as the animals mature
• If expression of genes that dissolves the webs is delayed, the digits don’t grow and ‘juvenile’ webbed feet result

Question 10

What is heterochrony?

Answer 10

Modularity allows the timing of developmental processes to shift independently (compared to ancestor)

Question 11

Give an example of an environmental cue causing normal development

Answer 11

In mosquitoes the blood meal stimulates the brain to stimulate the body to produce vitellogenin (critical for egg production)

Question 12

What kind of response do animals have to environ cues for normal dev?

Answer 12

They have a fixed adaptive response

Question 13

Describe the response of animals to environ signals closely correlated with future conditions.

Answer 13

Organisms are likely to respond differently to different cues

Question 14

Give an example of an environmental cue being closely correlated with future conditions.

Answer 14

• ‘The Squinting Bush Brown butterfly’ has a dry-season form and a wet-season form with different wing coloration
• Temp during pupation determines adult form
  = Polyphenism