Development 4: Evolution & development Flashcards

1
Q

What are the similarities between organisms a result of?

A

A common ancestor

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2
Q

What are the differences between organisms a result of?

A

Natural selection

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3
Q

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

A

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

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4
Q

Many genes that regulate development are ______ _______

A

highly conserved

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5
Q

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

A

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

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6
Q

What are changes to morphology a result of?

A
  • Mutations in genes that regulate development
  • Changes in the spatial expression of development genes
  • Changes in the temporal expression of development genes
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7
Q

Give an example of how mutations can modify morphology

A
  • 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
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8
Q

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

A
  • 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
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9
Q

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

A
  • 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
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10
Q

What is heterochrony?

A

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

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11
Q

Give an example of an environmental cue causing normal development

A

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

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12
Q

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

A

They have a fixed adaptive response

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13
Q

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

A

Organisms are likely to respond differently to different cues

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14
Q

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

A
  • ‘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
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