Animal evolution

Question 1

When did the Cambrian Explosion occur?

Answer 1

Around 541 million years ago.

Question 2

What major event ended the dominance of microbial films?

Answer 2

Snowball Earth and anoxia events.

Question 3

What are Ediacaran biota?

Answer 3

Early complex life forms at the base of the animal evolutionary tree.

Question 4

What is biomineralization?

Answer 4

Formation of hard shells and skeletal structures by animals.

Question 5

What triggered the Cambrian Explosion?

Answer 5

Oxygenation event and ecological openings after mass extinction.

Question 6

What adaptations first appeared during the Cambrian Explosion?

Answer 6

Hard-bodied animals, apex predators, and complex ecosystems.

Question 7

What is Anomalocaris?

Answer 7

An early apex predator from the Cambrian period.

Question 8

Why is oxygen important for early animal evolution?

Answer 8

Higher oxygen allowed larger and more complex organisms.

Question 9

What is the age of fishes?

Answer 9

Devonian period (~480 MYA).

Question 10

What are placoderms?

Answer 10

Heavily armored jawed fish from the Devonian.

Question 11

What did gill arches evolve into?

Answer 11

Into jaws for predation.

Question 12

What are sarcopterygians?

Answer 12

Lobe-finned fishes, ancestors of tetrapods.

Question 13

What features allowed fish to transition to land?

Answer 13

Lungs, stronger limbs, hips, shoulders, and wrists.

Question 14

What is Acanthostega?

Answer 14

An aquatic vertebrate with developed limbs and digits.

Question 15

What is the significance of the amniotic egg?

Answer 15

Allowed vertebrates to lay eggs on land without drying out.

Question 16

What groups descended from amniotes?

Answer 16

Mammals, reptiles, and birds.

Question 17

What skull differences separate reptiles and mammals?

Answer 17

Openings behind the eye distinguish skull types.

Question 18

What were Permian ‘mammals’?

Answer 18

Early synapsids capable of primitive thermoregulation.

Question 19

What caused the Permian-Triassic extinction?

Answer 19

Massive volcanic activity in Siberia causing climate change.

Question 20

What group dominated after the Permian extinction?

Answer 20

Archosaurs.

Question 21

Who were the ancestors of dinosaurs?

Answer 21

Early Archosaurs were ancestors to both dinosaurs and crocodiles.

Question 22

What are Crurotarsi and Ornithodira?

Answer 22

Crurotarsi (crocodiles) and Ornithodira (dinosaurs and birds).

Question 23

What separates Ornithischia and Saurischia dinosaurs?

Answer 23

Pelvic structure differences: bird-hipped vs lizard-hipped.

Question 24

What adaptations did herbivorous dinosaurs develop?

Answer 24

Body armor, horns, frills, and social behaviors.

Question 25

What factors contributed to sauropods' large size?

Answer 25

Size provided defense, thermal stability, and access to resources.

Question 26

What traits define theropod dinosaurs?

Answer 26

Mostly bipedal carnivores with diverse adaptations.

Question 27

How are birds related to theropods?

Answer 27

Birds evolved from theropod dinosaurs.

Question 28

What are the two flight hypotheses?

Answer 28

Ground-up and tree-down hypotheses.

Question 29

What was Archaeopteryx?

Answer 29

A transitional fossil between dinosaurs and birds.

Question 30

What caused the K-T extinction?

Answer 30

Meteor strike and volcanic activity causing climate changes.

Question 31

Which animals survived the K-T extinction?

Answer 31

Small mammals, some birds, amphibians, and fish.

Question 32

What traits helped early mammals survive?

Answer 32

Hair, endothermy, nocturnality, and small body size.

Question 33

What happened after the K-T extinction?

Answer 33

Mammals rapidly diversified into available niches.

Question 34

What adaptations allowed early mammals to thrive?

Answer 34

Adaptations like specialized teeth and warm-bloodedness.

Question 35

What caused the adaptive radiation of mammals?

Answer 35

Opening of ecological niches after dinosaur extinction.

Question 36

Why was burrowing important for early mammals?

Answer 36

Protection from predators and harsh climates.

Question 37

Why were mammals mostly nocturnal during the dinosaur era?

Answer 37

To avoid diurnal predators.

Question 38

How did the Carboniferous period affect amniote evolution?

Answer 38

Dry conditions selected for eggs that could survive outside water.

Question 39

What was the role of glacial erosion in Cambrian evolution?

Answer 39

Released minerals and nutrients promoting evolution.

Question 40

What does the term 'adaptive radiation' mean?

Answer 40

Rapid diversification to fill available ecological niches.

Question 41

What is the evolutionary significance of feathers in dinosaurs?

Answer 41

Feathers originally evolved for insulation or display.

Question 42

What major marine groups went extinct at the K-T boundary?

Answer 42

Pterosaurs and marine reptiles like plesiosaurs.

Question 43

How did the end-Ediacaran mass extinction impact evolution?

Answer 43

Opened niches allowing rapid evolution of new life forms.

Question 44

Why did limb development precede land invasion?

Answer 44

Limbs evolved for aquatic advantages before land invasion.

Question 45

What allowed archosaurs to dominate terrestrial ecosystems?

Answer 45

Adaptations like water retention and efficient respiration.

Question 46

What was the environmental condition post-Snowball Earth?

Answer 46

Chemical and thermal instability favored diversification.

Question 47

What factors favored evolution of hard defensive structures?

Answer 47

Predator-prey arms race led to evolution of hard parts.

Question 48

Why is fossil preservation of early eggs poor?

Answer 48

Soft structures like early eggs do not fossilize well.