Arthropods

Question 1

What genes did ancestral bilaterians have?

Answer 1

Hox genes

Hox genes are crucial for body plan development in many animals.

Question 2

How did segmented body plans evolve in different animal groups?

Answer 2

Segmentation genetics in leeches, drosophila, and vertebrates differ

This indicates that segmentation evolved independently in these groups.

Question 3

What is the role of the Notch gene?

Answer 3

Signalling pathway gene used to generate segments in spiders and vertebrates

Suggests a common ancestor had segments.

Question 4

What does the Distal-less (Dll) gene do?

Answer 4

Expands projections from the body, initiating limb development

This gene is crucial for appendage formation.

Question 5

What appendages did the last universal common ancestor (LUCA) of bilaterians likely direct?

Answer 5

Appendage formation, potentially antennae

LUCA directed eye development using the Pa6/eyeless gene.

Question 6

What is the main theory regarding the evolution of insect flight?

Answer 6

Gradualism

This theory suggests a slow and progressive adaptation over time.

Question 7

What role do surface skimming stone flies play in evolutionary adaptation?

Answer 7

They are intermediates in the evolution of insect flight

They demonstrate progressive appendage loss and specialization.

Question 8

From what clade did insects evolve?

Answer 8

A clade within crustaceans

This highlights the evolutionary link between these two groups.

Question 9

What is the proposed origin of insect wings?

Answer 9

Branched legs of ancestral crustaceans

The development of wings may have evolved from epipods.

Question 10

What is an epipod?

Answer 10

Gill

Epipods are structures that may have evolved into wings in insects.

Question 11

What is the ancestral state of wing appendages in insects?

Answer 11

Most likely had multiple wing appendages

Modern insects such as true flies (Diptera) have reduced wing pairs.

Question 12

How do Hox genes affect wing development in insects?

Answer 12

Suppress wing development in thoracic and abdominal segments

Specific Hox genes control the development of wings in various segments.

Question 13

What is the function of the Ultrabithorax gene?

Answer 13

Represses wing development on T3 in Diptera

This gene plays a critical role in the body plan of true flies.

Question 14

What proteins suppress Dll expression in insects?

Answer 14

Ubx and abd-A proteins

They act specifically on a cis-regulatory region of the Dll gene.

Question 15

What evolutionary change occurred in arthropod abdominal appendages?

Answer 15

Alterations in expression patterns of developmental genes due to cis-regulatory evolution

This explains diversification through natural selection.

Question 16

What are the major mass extinction events in evolutionary history?

Answer 16

• Ordovician-Silurian
• Devonian
• Permian-Triassic
• Triassic-Jurassic
• Cretaceous-Tertiary

These events had significant impacts on biodiversity.

Question 17

What percentage of marine species went extinct during the Permian-Triassic mass extinction?

Answer 17

90-95%

This extinction event is known as the most severe in Earth’s history.

Question 18

What were some causes of the Permian-Triassic mass extinction?

Answer 18

• Plate tectonic movements
• Glaciation
• Volcanism
• Global warming
• Oxygenation of deep sea waters stopping

These factors contributed to the massive loss of biodiversity.

Question 19

True or False: Competitive exclusion is strongest among higher taxonomic groups.

Answer 19

False

Competition is strongest between similar organisms.