Rise of Animals Short Answers

Question 1

Which 2 Periods was the Cambrian Divided into?

Answer 1

Sub-trilobites and trilobites (arthropods).

Question 2

What was the Burgess Shale?

Answer 2

Best known Cambrian fossil deposit from 505 mya.

Question 3

How was the Burgess Shale Preserved?

Answer 3

Animals were buried in a sub-marine landslide.

Question 4

What was the Cambrian Explosion?

Answer 4

Sudden appearance in the fossil record of complex animals with mineralized skeletal remains - 540 mya.

Question 5

What did Gould Believe about the Cambrian Explosion?

Answer 5

They belonged to extinct groups, disparity is less today, most became extinct.

Question 6

What did Morris Believe about the Cambrian Explosion?

Answer 6

Animals represent branches of extant lineages, disparity has increased.

Question 7

What is the Goal of Phylogenetic Systematics?

Answer 7

To make biological classification reflect phylogeny.

Question 8

What do Nodes Indicate?

Answer 8

The presence of an ancestor.

Question 9

What can a Character be?

Answer 9

Must be heritable, can be morphological, behavioural or molecular.

Question 10

What is Important to Remember when Classifying Characters?

Answer 10

Do so relative to the group of interest.

Question 11

What are the 2 Main Types of Characters?

Answer 11

Primitive (ancestral) or derived.

Question 12

What is the Purpose of a Molecular Clock?

Answer 12

Looking for constant mutation rates over time using dates on nodes.

Question 13

What can Homoplasy Result in?

Answer 13

Artificial groups of organisms.

Question 14

What are 2 Molecular Character Advantages over Morphological Characters?

Answer 14

Can reconstruct relationships amongst very disparate organisms, molecular clock can be used.

Question 15

How can we Relate 2 Homologous Genes?

Answer 15

Amount of genetic distance is proportional to the time that has elapsed since the lineages diverged.

Question 16

What are the 3 New Features of the Phylogenetic Tree?

Answer 16

Radiate animals are sister group to bilaterians, bilaterians have 3 major clades, protostomes split amongst 2 of the clades.

Question 17

Who is Included in the Lophotrochozoan Phyla?

Answer 17

Platyhelminthes, brachiopods, annelids, bryozoans, rotifers, molluscs.

Question 18

Who is Included in the Ecdysozoan Phyla?

Answer 18

Nematodes, priapulids, tardigrades, onycophorans, arthropods.

Question 19

Who is Included in the Deuterostome Phyla?

Answer 19

Echinoderms, chordata.

Question 20

What does a Crown Group Mean?

Answer 20

Fossils that have some but not all characters of a phylum belong to stem groups: can include living or extinct.

Question 21

What does the New Molecular Tree Suggest?

Answer 21

Cambrian explosion represented simultaneous diversification of each of the 3 bilaterian clades.

Question 22

What are 3 Explanations for the Discrepancy between Fossil Records and Clock Divergence?

Answer 22

Tiny early animals so no recognisable fossils, soft-bodied early animals, problem with molecular clock rates.

Question 23

What do Homeotic Genes Determine?

Answer 23

Anterior/posterior, dorsal/ventral, where segments develop, where appendages develop.

Question 24

What were the 2 Important Periods of Bilaterian Evolution?

Answer 24

Evolution of bilaterian stem lineage leading to Urbilateria, diversification of 3 major bilaterian clades.

Question 25

What is the Problem with the Idea that Tininess Explains Molecular Clock Discrepancy?

Answer 25

Developing larvae seem to be derived in invertebrates, with direct development the basal condition - even tiny animals should have left some sort of fossil record.

Question 26

How can Major Differences in Morphology be Explained for Echinoderms and Arthropods?

Answer 26

Differences in regulatory gene complement.

Question 27

How was the Wing Development in Insects Aided?

Answer 27

Changes in hox binding sites.

Question 28

How were Limb Changes in Arthropods Aided?

Answer 28

Particular target genes, hox genes.

Question 29

How was Specialisation of Feeding Appendages Aided?

Answer 29

Changes in hox expression.

Question 30

What are the 4 Functions of a Skeleton?

Answer 30

Support, attachment, protection (internal organs), movement.

Question 31

What are the 3 Types of Skeleton?

Answer 31

Hydrostatic, exoskeleton, endoskeleton.

Question 32

What are the 2 Parts of the Vertebrate Skeleton?

Answer 32

Axial, appendicular.

Question 33

How do Gravity and Friction Compare in Water?

Answer 33

Little gravity, very dense.

Question 34

How do Gravity and Friction Compare on Land?

Answer 34

Large gravity, moderate friction.

Question 35

How do Gravity and Friction Compare in the Air?

Answer 35

Major gravity, no friction.

Question 36

How are Slightly Movable Joints Bridged?

Answer 36

By cartilage.

Question 37

How are Freely Movable Joints Capped?

Answer 37

With cartilage.

Question 38

Who has Flight Evolved Independently for?

Answer 38

Insects, pterosaurs, birds, bats.

Question 39

What are the 4 Key Features of Avian Bones?

Answer 39

Rigidity, reduction, redistribution, limb modifications for flight.

Question 40

What are the 5 Types of Feather?

Answer 40

Contour, semiplumes, down, bristles, filoplumes.

Question 41

What is the Function of Contour Feathers?

Answer 41

Flight.

Question 42

What is the Function of Semiplume Feathers?

Answer 42

Insulation.

Question 43

What is the Function of Down Feathers?

Answer 43

Insulation.

Question 44

What is the Function of Bristle Feathers?

Answer 44

Tactile (sensory).

Question 45

What is the Function of Filoplume Feathers?

Answer 45

Sensory to keep contour feathers in place.

Question 46

What are the Features of Low Aspect Ratio Wings?

Answer 46

Elliptical wings, fast take-off, high manoeuvrability.

Question 47

What are the Features of High Aspect Ratio Wings?

Answer 47

High speed, soaring, gliding.

Question 48

How do we Calculate Wing Loading?

Answer 48

Mass / wing area.

Question 49

What is the Wing Loading of the Best Fliers?

Answer 49

Very low.

Question 50

What are 5 Adaptations of Diggers?

Answer 50

Elongated bodies with short limbs, retain 5 digits, stout claws, strengthened pelvis for bracing, projections on fore limbs for muscles.

Question 51

What is Out-Force of Limbs Dependent on?

Answer 51

In-force and length of in/out levers.

Question 52

What are the Features of a Longer Out-Lever?

Answer 52

Good for speed but low force.

Question 53

What does Out-Lever : In-Lever Ratio Tell us?

Answer 53

Who is built for speed and for strength.

Question 54

What are 2 Adaptations of Brachiation?

Answer 54

Lengthening of arms, strengthening of trunk.

Question 55

What is the Major Difference Between the Structures of Birds and Bats?

Answer 55

Bats have same elements of bone that we have, just highly specified - bird wing surface area is mostly feathers.

Question 56

Why is Paraxial Swimming Inefficient?

Answer 56

Low power, high drag.

Question 57

Who has the Fully Aquatic Lifestyle Evolved for?

Answer 57

Cetacea and Sirenia.

Question 58

How do Modern Day Arthropods Compare to Cambrians?

Answer 58

95% similarity.

Question 59

How do Modern Day Priapulids Compare to Cambrians?

Answer 59

Greater disparity today, evolved new body plans, with others becoming extinct.

Question 60

Why are there Doubts about the Cambrian Explosion?

Answer 60

Discrepancy between fossil record and molecular clock.

Question 61

How do we Know there is a Missing Period of Trilobites?

Answer 61

They appeared simultaneously (530 mya) in both USA and China, but they are monophyletic.

Question 62

What About if Disparity Appeared before the Cambrian Explosion?

Answer 62

Disparity in bilaterians was still mainly a Cambrian event.

Question 63

Why have Arthropods not Changed since the Cambrian Explosion?

Answer 63

They have a limited number of available body plan changes, most of which were explored in the Cambrian.

Question 64

What did Gould Believe about the Evolutionary Mechanism?

Answer 64

Cambrian explosion was the result of unique evolutionary processes that have not occurred since.

Question 65

What did Conway Morris Believe about the Evolutionary Mechanism?

Answer 65

It involved the same conventional evolutionary mechanisms we see throughout the history of animals.

Question 66

Who is Correct about the Evolutionary Mechanism?

Answer 66

Maybe in the middle - uniqueness of homologies of bilaterians suggests constrained body plans.

Question 67

What is Important to Remember about Evolution since the Cambrian Explosion?

Answer 67

It has mostly been loss or reacquisition of characters that already appeared in the Cambrian.

Question 68

What is the Concept of Fitness Landscapes?

Answer 68

Increased number of species creates more ecological opportunities for new species to evolve.

Question 69

Why Might O2 and Carnivory Links have Caused the Cambrian Explosion?

Answer 69

Less O2 means more carnivores in modern marine environments, and O2 decreased - followed by an ecological "arms race".

Question 70

Which 3 Basal Chordates were Involved in the Cambrian Explosion?

Answer 70

Haikouella, Pikaia, Haikouichthys.

Question 71

What are the 3 Evolutionary Possibilities Following Gene Duplication?

Answer 71

No change in function (1 dupe lost), novel function, split functions.

Question 72

What is the Oldest Tetrapod?

Answer 72

Acathostega - 360 mya.

Question 73

Why did the Earliest Tetrapods Develop Limbs?

Answer 73

For moving in shallow, vegetation-choked water.

Question 74

Why Must Echinoderms have Evolved from a Bilaterian?

Answer 74

Because they are deuterostomes.

Question 75

What has Evolution of Hox Genes since Urbilateria Involved?

Answer 75

Mostly change in function and gene loss, not gene duplication.

Question 76

When was the Major Period of Hox Duplication?

Answer 76

Before the diversification of bilaterian animals.

Question 77

What did the Evolution of Phylum Specific Body Plans Depend on?

Answer 77

Novel gene regulatory circuitry.

Question 78

Why can't we Produce a Molecular Phylogeny of Fossils?

Answer 78

There is no DNA left.

Question 79

What did "Weird Wonders" of the Cambrian Appear to be?

Answer 79

Euarthropod stem groups.

Question 80

What are the 2 Reasons Groups of Living Animals are always Distinct from their Nearest Relative Group?

Answer 80

They've evolved unique characters that make them look different, intermediate forms have gone extinct.

Question 81

What Develops in the Absence of Hox Gene Expression?

Answer 81

Antennae instead of legs.

Question 82

What is High Diversity in Insects Due to?

Answer 82

Small size, rapid geographic dispersal, adaptable body plan.

Question 83

Why are there so many Insects?

Answer 83

Low rates of extinction and adaptability (diet especially).

Question 84

What are the 3 Ways Gnathostomes are Divided?

Answer 84

Chondrichthyes, actinopterygii, sarcopterygii.

Question 85

Did Feathers Evolve for Flight?

Answer 85

No.

Question 86

What is the New View of Phylogenies?

Answer 86

Stress the significance of how the geographic distribution of animals affects their evolution.

Question 87

Can we Remove Fossils to Map only Living Taxa?

Answer 87

No - fossils can supply character combinations that are missing in living clades.