Lecture 2: Concepts in Developmental Biology

Question 1

What directs initial developmental stages? (2)

Answer 1

• Maternal genes
• egg cytoplasm

Explanation: Maternal genes and the egg’s cytoplasm provide initial instructions for cleavage, polarity, and basic embryonic structures, setting the stage for later development.

Question 2

What directs development after cleavage?

Answer 2

Zygotic genes

Explanation: After the initial stages driven by maternal factors, the embryo’s own genes, the zygotic genes, become active and direct further differentiation and organogenesis.

Question 3

What factors influence development over time? (2)

Answer 3

Gene products & environment

Explanation: Development is dynamic, shaped by proteins, signaling molecules (gene products), and external influences like nutrition, temperature, and chemical exposure.

Question 4

What concept states that all cells have the same genetic material?

Answer 4

Genomic equivalence

Explanation: Genomic equivalence states that all cells in an organism have the same complete set of genetic information.

Question 5

True or False: Every cell in the body has an identical genome.

Answer 5

False

Question 6

What is the term for cells having different genetic compositions within an individual?

an exception to genomic equivalence, especially in brain cells

Answer 6

Genomic mosaicism

Explanation: Genomic mosaicism describes the presence of different genetic variations within an individual’s cells, particularly observed in neurons, where DNA alterations can differ from the germline.

Question 7

Where is genomic mosaicism mostly found?

Answer 7

Brain cells (neurons)

Question 8

What distinguishes genomic mosaicism from epigenetic changes?

Answer 8

DNA sequence alterations

Question 9

What is an example of a genetic alteration in neurons? (4)

Answer 9

• Aneuploidy
• CNVs
• SNVs
• LINE1 elements

Question 10

What field relies on sequencing nonbrain DNA?

Answer 10

GWAS (Genome-Wide Association Studies)

Question 11

What is the ability of a cell to differentiate into other cell types?

Answer 11

Cell potency

Explanation: Cell potency is a cell’s capacity to differentiate into various cell types, with potency decreasing as development progresses.

Question 12

What is the total capacity of a cell to form a complete embryo?

Answer 12

Totipotency

Explanation: Totipotency is the highest level of potency, where a cell can give rise to all cell types, including extraembryonic tissues, forming a complete organism.

Question 13

What type of cell can differentiate into all three germ layers but not extraembryonic tissues?

Answer 13

Pluripotency

Explanation: Pluripotent cells can differentiate into any of the three germ layers (ectoderm, mesoderm, endoderm) but cannot form extraembryonic tissues.

Question 14

Example of a pluripotent cell?

Answer 14

Embryonic stem cell

Question 15

What type of potency allows differentiation into a restricted family of cell types?

the ability to form multiple, related cell lineages

Answer 15

Multipotency

Explanation: Multipotent cells can differentiate into a limited range of cell types within a specific tissue or lineage, such as blood cells from hematopoietic stem cells.

Question 16

Give an example of a totipotent cell.

Answer 16

Zygote (fertilized egg)

Explanation: A zygote is totipotent, capable of forming all cell types, including extraembryonic tissues.

Question 17

What type of stem cells can become blood cells but not neurons?

Answer 17

Hematopoietic stem cells

Question 18

What is the ultimate test of nuclear potency?

Answer 18

Generating every cell type

Question 19

What happens to nuclear potency over time?

Answer 19

It becomes restricted

Because as cells divide and specialize, gene expression becomes more regulated, restricting their ability to develop into different cell types.

Question 20

Name the three main types of potency. (3)

Answer 20

• Totipotency
• pluripotency
• multipotency

Question 21

What experiment tested nuclear potency using Rana pipiens eggs?

Answer 21

Blastula nucleus transplant

Question 22

What was the first cloned mammal?

Answer 22

Dolly the sheep

Dolly was cloned from an adult mammary gland cell of a Finn Dorset sheep.

Question 23

What type of cell was Dolly cloned from?

Answer 23

Mammary gland cell

The nucleus came from a differentiated mammary cell, proving somatic cell nuclear transfer worked.

Question 24

What was used as the enucleated oocyte donor for Dolly?

Answer 24

Scottish Blackface sheep

The enucleated oocyte and the embryo were implanted into this breed.

Question 25

Where was Dolly implanted for development?

Answer 25

Surrogate Scottish Blackface sheep

Question 26

What is the process by which a cell becomes specialized in structure and function?

Answer 26

Cell differentiation | This creates cellular diversity

Question 27

What is the result of cell differentiation?

Answer 27

Cellular diversity

Question 28

What part of the genome is expressed during differentiation?

Answer 28

A portion of the genome

Question 29

What type of genes are shared by all cells and always active in all cells?

Answer 29

Housekeeping genes ## Footnote These are essential for basic cellular functions (e.g., GAPDH, β-actin).

Question 30

What type of genes are unique to specific cell types? | genes are only expressed in specific cells or conditions

Answer 30

Luxury genes ## Footnote These encode specialized proteins like hemoglobin (RBCs) and insulin (pancreatic cells).

Question 31

What are undifferentiated cells with the ability to specialize into various cell types?

Answer 31

Stem cells

Question 32

What type of stem cell can form a complete organism?

Answer 32

Totipotent stem cell

Question 33

What type of stem cell can differentiate into cells of the three germ layers but not extraembryonic tissues?

Answer 33

Pluripotent stem cell

Question 34

What is the potency of the inner cell mass of a blastocyst?

Answer 34

Pluripotent ## Footnote Explanation: The inner cell mass of a blastocyst contains pluripotent cells that can form any tissue of the embryo but not extraembryonic structures.

Question 35

What is the potency of hematopoietic stem cells?

Answer 35

Multipotent. ## Footnote Explanation: Hematopoietic stem cells are multipotent, able to differentiate into various blood cell types but not other tissue types.

Question 36

What are examples of pluripotent stem cells? (2)

Answer 36

- Embryonic stem cells (ESCs) - induced pluripotent stem cells (iPSCs)

Question 37

What type of stem cell can differentiate into a restricted group of related cells?

Answer 37

Multipotent stem cell

Question 38

What type of stem cell gives rise to only one cell type? | type of potency do most adult cells have

Answer 38

Unipotent stem cell

Question 39

What type of stem cell can differentiate into mesodermal-derived tissues like bone, cartilage, and fat?

Answer 39

Mesenchymal stem cells (MSCs)

Question 40

Name the three germ layers. (3)

Answer 40

- Ectoderm - mesoderm - endoderm

Question 41

Which germ layer gives rise to the gut, lungs, and liver?

Answer 41

Endoderm

Question 42

Which germ layer forms muscles, blood, and bones?

Answer 42

Mesoderm

Question 43

Which germ layer develops into skin and the nervous system?

Answer 43

Ectoderm

Question 44

What is the relationship between cell differentiation and potency?

Answer 44

Differentiation decreases potency

Question 45

What are genes that are constantly expressed in all cells for basic cellular functions?

Answer 45

Housekeeping genes

Question 46

What is another name for housekeeping genes?

Answer 46

Constitutive genes

Question 47

Where are housekeeping genes expressed?

Answer 47

All cells, all the time

Question 48

What type of proteins do housekeeping genes produce?

Answer 48

Proteins essential for basic cellular functions

Question 49

Give an example of a housekeeping gene. (3)

Answer 49

- Actin - GAPDH - ribosomal RNA genes

Question 50

What are genes that are expressed only in specific cells or at specific times?

Answer 50

Luxury genes

Question 51

What is another name for luxury genes?

Answer 51

Tissue-specific genes

Question 52

Where are luxury genes expressed?

Answer 52

Only in specialized cells

Question 53

What type of proteins do luxury genes produce?

Answer 53

Proteins related to specialized cell functions

Question 54

Give an example of a luxury gene. (2)

Answer 54

- Hemoglobin (in red blood cells) - myosin (in muscle cells)

Question 55

In the earliest stage of development, known as the (1) ___ stage, the zygote is (2) ___, meaning it can differentiate into all cell types, including (3) ___ and extraembryonic structures necessary for implantation and early development. As the zygote undergoes (4) ___ and forms a (5) ___, its inner cell mass consists of (6) ___ cells. These pluripotent cells can give rise to any tissue within the body but can no longer form (7) ___ structures like the placenta. During (8) ___, cells become further specialized into (9) ___ stem cells, which are restricted to generating specific cell lineages. For example, (10) ___ stem cells can produce various blood cells but cannot differentiate into neurons or muscle cells. As differentiation progresses into late development and adulthood, most cells become (11) ___, committed to a single specialized function. This hierarchical restriction in cell potency ensures the formation of a highly organized and functional (12) ___ organism.

Answer 55

(1) zygote (2) totipotent (3) embryonic (4) cleavage (5) blastocyst (6) pluripotent (7) extraembryonic (8) gastrulation (9) multipotent (10) hematopoietic (11) unipotent (12) multicellular

Question 56

What is the selective activation of certain genes depending on time and space?

Answer 56

Selective gene expression

Question 57

What is another name for selective gene expression?

Answer 57

Differential gene expression

Question 58

How do genes behave in selective gene expression?

Answer 58

Some genes are highly active in specific tissues, while others are repressed

Question 59

What is a process where specific genes increase in number without mitosis?

Answer 59

Selective gene amplification

Question 60

What is the purpose of selective gene amplification?

Answer 60

To meet the synthetic demands of a developing cell

Question 61

What is an example of selective gene amplification?

Answer 61

rRNA gene amplification in amphibian oocytes

Question 62

During which stage of meiosis does selective gene amplification occur in amphibian oocytes?

Answer 62

Early diplotene stage

Question 63

What is produced in large amounts due to selective gene amplification in amphibian oocytes?

Answer 63

Ribosomal RNA (rRNA)

Question 64

concept suggests that development is directed by pre-existing structures and information, like maternal genes.

Answer 64

preformed

Question 65

What do maternal genes and cytoplasm direct?

Answer 65

Early development

Question 66

What species was cloned using amphibian nuclear transfer?

Answer 66

*Rana pipiens* ## Footnote *Rana pipiens* (Northern leopard frog) was the species used in early cloning experiments.

Question 67

involves transplanting nuclei from a blastula-stage embryo into enucleated eggs.

Answer 67

Amphibian cloning

Question 68

In amphibian cloning, what was transplanted into enucleated frog eggs?

Answer 68

Blastula nuclei ## Footnote Blastula-stage nuclei were inserted into frog eggs to test nuclear reprogramming.

Question 69

# Amphibian cloning Who successfully cloned *Rana pipiens*? (2)

Answer 69

M. DiBerardino & N. Hoffner Orr ## Footnote hey used nuclear transplantation to create a cloned frog named "Freddy."

Question 70

What is another term for selective gene expression?

Answer 70

Differential gene expression

Question 71

Genes are turned on/off in different cells at different times.

Answer 71

Differential gene expression

Question 72

What determines which genes are expressed? (2)

Answer 72

Time and space ## Footnote Gene expression varies based on developmental phase and cell type.

Question 73

What regulates gene repression in cells?

Answer 73

Selective gene repression ## Footnote 🔹 Some genes are silenced depending on the cell’s function.

Question 74

What happens to genes not needed in certain cells?

Answer 74

Selective gene repression

Question 75

What increases gene copies without mitosis? | This ensures a higher production of specific proteins when needed.

Answer 75

Selective gene amplification

Question 76

Where does gene amplification occur in amphibians? | Additional Question: What gene is amplified?

Answer 76

Amphibian oocytes ## Footnote **Ribosomal RNA genes** are amplified in the oocyte to support early development.

Question 77

What is produced by gene amplification in amphibian oocytes? ## Footnote Additional Question: What's the significance of this product?

Answer 77

Ribosomal RNA (rRNA) ## Footnote Extra rRNA is needed for rapid protein synthesis in early embryonic stages.

Question 78

* Cell signaling in development * One group of embryonic cells influences the fate of neighboring cells.

Answer 78

embryonic induction

Question 79

* An organizer that induces neural tube formation * It triggers the development of the brain and spinal cord in vertebrates.

Answer 79

Spemann-Mangold organizer

Question 80

What must a responding tissue have to react to induction? It is the ability of a tissue to respond to an inducing signal.

Answer 80

Competence

Question 81

What happens if embryonic induction fails?

Answer 81

Developmental defects

Question 82

What are the components of embryonic induction? (3)

Answer 82

- Organizer or Inductor - Evocator - Responsive tissue

Question 83

# components of embryonic induction What is the structure that induces the formation of another structure?

Answer 83

Organizer or Inductor

Question 84

# components of embryonic induction What is released by the organizer or inductor? | a chemical substance

Answer 84

Evocator

Question 85

# components of embryonic induction What tissue reacts to the inductor or evocator?

Answer 85

Responsive Tissue

Question 86

The first major induction event in embryogenesis, where one tissue (e.g., the dorsal lip of the blastopore) directs the formation of the basic body axis.

Answer 86

primary embryonic induction

Question 87

lays the foundation for the embryo’s structure.

Answer 87

Primary induction

Question 88

refines and develops specialized tissues and organs, ensuring proper differentiation.

Answer 88

Secondary induction

Question 89

What directs the formation of the basic body axis in primary induction?

Answer 89

Dorsal lip of the blastopore

Question 90

Key example of primary embryonic induction?

Answer 90

Spemann-Mangold Organizer

Question 91

Later induction events where one tissue influences the differentiation of another, leading to organogenesis.

Answer 91

Secondary Embryonic Induction

Question 92

Key example of secondary embryonic induction?

Answer 92

Lens induction in vertebrates ## Footnote In this process, the interaction between the optic vesicle (a part of the developing brain) and the surface ectoderm leads to the formation of the lens. The optic vesicle signals the overlying ectoderm to thicken and form the lens placode. This interaction exemplifies how one embryonic tissue influences the development of another, a hallmark of secondary induction.

Question 93

What is established by primary embryonic induction? (2)

Answer 93

Body plan and nervous system

Question 94

What does secondary embryonic induction drive?

Answer 94

Formation of specific organs

Question 95

# EMBRYONIC INDUCTION What induces neurulation and axis development?

Answer 95

Notochord (chordamesoderm)

Question 96

# EMBRYONIC INDUCTION acts as an organizer, releasing signals that direct the ectoderm to form the neural plate, which eventually develops into the nervous system

Answer 96

Notochord (chordamesoderm)

Question 97

# EMBRYONIC INDUCTION Notochord acts as an __, releasing signals that direct the __ to form the __, which eventually develops into the __

Answer 97

- organizer - ectoderm - neural plate - nervous system

Question 98

A set of biological processes that mold the internal and external configuration of an embryo.

Answer 98

Morphogenesis

Question 99

The process by which an organism develops its specific shape

Answer 99

Morphogenesis

Question 100

# Morphogenesis Spatial and temporal distribution or organization of differentiated cells. Example: Development of the arms – upper arm, lower arm, and fingers.

Answer 100

Pattern formation

Question 101

# Morphogenesis Pattern formation is tightly regulated by __.

Answer 101

genetic control

Question 102

# Morphogenesis What defines the morphogenetic blueprint/body plan? (2)

Answer 102

Main body axes and changes in form

Question 103

# Morphogenesis Movement of cells relative to each other

Answer 103

Morphogenetic Movements

Question 104

Give four (4) examples of morphogenesis.

Answer 104

* Limb formation * Establishment of the fundamental body axes * Branching of ducts within glands * Formation of loops and whorls of fingerprints

Question 105

# Morphogenesis Name the six processes involved in morphogenesis. (6)

Answer 105

* Cell proliferation * Cell migration * Cell aggregation/cell adhesion * Secretion of extracellular substances * Change in cell shape * Localized cell death/apoptosis

Question 106

* Characterized by rapid cell divisions, resulting in an increase in the number of cells. * Occurs through mitotic divisions.

Answer 106

Cell proliferation

Question 107

Cell proliferation occurs through what type of divisions?

Answer 107

Mitotic divisions

Question 108

The process where individual cells or groups of cells move from one part of the embryo to another.

Answer 108

Cell migration

Question 109

Cell migration can involve what type of movements? (2)

Answer 109

(1) Short migrations (2) Massive dislocation

Question 110

Examples of Cell Migration (2)

Answer 110

* Invagination * Involution

Question 111

# Cell migration What is an example of inward folding of a cell sheet?

Answer 111

Invagination

Question 112

# Cell migration What describes the inward movement of an expanding outer layer?

Answer 112

Involution

Question 113

a highly regulated programmed cell death process in multicellular organisms.

Answer 113

Apoptosis

Question 114

Why is apoptosis essential?

Answer 114

It is essential for development, homeostasis, and removing damaged or unnecessary cells without triggering inflammation.

Question 115

Apoptosis (Programmed cell death) **Initiation** * Triggered by intrinsic (mitochondrial) or extrinsic (death receptor) pathways. * The __ is activated by DNA damage, oxidative stress, or lack of survival signals, leading to cytochrome c release from mitochondria. * The __ is activated by death ligands (e.g., FasL) binding to cell surface receptors. **___** * Activation of caspases (proteolytic enzymes) that degrade cellular components. * DNA fragmentation, cytoskeletal breakdown, and cell shrinkage occur. **__** * Apoptotic bodies are recognized and engulfed by phagocytes, preventing an immune response.

Answer 115

- intrinsic pathway - extrinsic pathway - Execution - Phagocytosis

Question 116

# EXAMPLES OF APOPTOSIS IN DEVELOPMENT What is an example of apoptosis in tadpoles?

Answer 116

Resorption of the tail

Question 117

# EXAMPLES OF APOPTOSIS IN DEVELOPMENT What process occurs in the embryonic hand and feet?

Answer 117

Separation of digits

Question 118

# EXAMPLES OF APOPTOSIS IN DEVELOPMENT What type of cells undergo selective death during development?

Answer 118

Neurons

Question 119

# APOPTOSIS DURING EMBRYOGENESIS How does apoptosis help in mouse embryos?

Answer 119

Tissue sculpting

Question 120

# APOPTOSIS DURING EMBRYOGENESIS What critical process is assisted by apoptosis in limb formation?

Answer 120

Eliminating unnecessary cells between fingers and toes.

Question 121

# APOPTOSIS DURING EMBRYOGENESIS In tadpoles, what transformation involves apoptosis?

Answer 121

apoptosis in the tai ## Footnote leading to its resorption as the amphibian transitions to a terrestrial lifestyle.

Question 122

* A set of genes that specify the anteroposterior axis and segment identity during the early stages of metazoan development. * Critical for properly placing certain embryonic structures like legs, antennae, and eyes.

Answer 122

Homeotic genes

Question 123

# HOMEOTIC GENES * A set of genes that specify the __ and __ during the early stages of __ development. * Critical for properly placing certain embryonic structures like __, __, and __.

Answer 123

- anteroposterior axis - segment identity - metazoan - legs - antennae - eyes

Question 124

A sequence of 180 base pairs that defines the homeotic genes. This codes for a 61-amino acid protein known as the homeodomain.

Answer 124

Homeobox

Question 125

* Many __ found in *Drosophila melanogaster* are also present in vertebrates. * These genes are expressed in highly specific sites and stages of development.

Answer 125

homeobox genes

Question 126

a subset of homeotic genes, meaning all Hox genes are homeotic genes, but not all homeotic genes are Hox genes.

Answer 126

Hox genes

Question 127

__ are grouped into four clusters: Clusters A-D, with each cluster containing 13 subfamilies or paralogous groups of genes.

Answer 127

Mammalian Hox genes

Question 128

are genes within the same species that arose from a common ancestral gene through a gene duplication event, often evolving to perform different functions

Answer 128

Paralogous genes

Question 129

are arranged in a strict order along their respective chromosomes, transcribed sequentially from the 5’ to 3’ end.

Answer 129

Paralogous genes

Question 130

What factors contribute to the diversity of body forms among animals despite the conservation of homeobox genes? (5)

Answer 130

- Gene regulation - Hox gene duplication - evolutionary modifications - Interactions with Other Developmental Genes - Environmental Influences

Question 131

Considered the "Rosetta Stone" of developmental biology.

Answer 131

Homeobox (DNA sequence)

Question 132

Hox Genes * Interpret positional information along the __ in both vertebrates and invertebrates. * Vertebrates and invertebrates share similar __, __ in chromosomes, and patterns of __.

Answer 132

* anteroposterior body axis * types * gene order * expression

Question 133

* How many Hox gene clusters do vertebrates have? * How many Hox gene clusters do invertebrates have?

Answer 133

* four * one

Question 134

What causes differences in body structures despite having similar Hox genes?

Answer 134

Differences in time and space of gene expression

Question 135

What is the effect of gene duplication and divergence on protein functions?

Answer 135

Leads to different protein functions

Question 136

What developmental feature is absent in invertebrates but present in vertebrates?

Answer 136

Neural crest cells (NCCs)

Question 137

What structures do neural crest cells contribute to in vertebrates?

Answer 137

complex structures | e.g. skull, jaw, nervous system

Question 138

Why do invertebrates have simpler, segmented body plans despite having Hox genes?

Answer 138

absence of neural crest

Question 139

How do neural crest cells affect vertebrate body complexity?

Answer 139

Enable modification and diversification of structures

Question 140

A chordate is defined as an animal belonging to the phylum Chordata, characterized by possessing, at some point during their development, have four distinctive physical characteristics that distinguish them from other taxa. What are those? (4)

Answer 140

- notochord - dorsal hollow nerve cord - pharyngeal slits - post-anal tail

Question 141

# Origin of Chordates Development Through Discrete & Interacting Modules

Answer 141

Modularity

Question 142

# Origin of Chordates 1. Give an example of modularity at the cellular level. 2. Give an example of modularity in morphogenetic fields. 3. Give an example of modularity in organ rudiments.

Answer 142

1. Inner Cell Mass (ICM) vs. Trophoblast 2. Eye/limb development 3. Vertebrate organ formation, imaginal discs in invertebrates

Question 143

# Origin of Chordates Organisms are made of smaller units (modules) that form larger structures.

Answer 143

Modularity

Question 144

# Origin of Chordates allows independent development of body parts without interfering with other functions.

Answer 144

Modularity

Question 145

# Origin of Chordates Formation of redundant structures

Answer 145

Duplication

Question 146

# Origin of Chordates Give three (3) examples of gene duplication.

Answer 146

* Globin genes * TGF-β family * Myo-D family

Question 147

# Origin of Chordates What are examples of tissue-level duplication? (3)

Answer 147

* Cervical * thoracic * lumbar skeleton

Question 148

# Origin of Chordates Enables structures to assume new roles over evolutionary time.

Answer 148

Divergence

Question 149

# Origin of Chordates What happens to the original gene copy in divergence?

Answer 149

Retains its original function

Question 150

# Origin of Chordates How does divergence contribute to evolution?

Answer 150

Mutated gene copies develop new roles

Question 151

# Origin of Chordates Changes in timing of development

Answer 151

Heterochrony

Question 152

# Origin of Chordates Retention of larval traits in adults

Answer 152

paedomorphosis

Question 153

# Origin of Chordates Gene mutations affecting developmental timing

Answer 153

paedomorphosis

Question 154

# Origin of Chordates Name three types of paedomorphosis. (3)

Answer 154

- Progenesis - Neoteny - Postdisplacement

Question 155

# Origin of Chordates What type of heterochrony results in early sexual maturity with retained juvenile traits?

Answer 155

Progenesis

Question 156

# Origin of Chordates What type of heterochrony results in slowed development of somatic traits?

Answer 156

Neoteny

Question 157

# Origin of Chordates What type of heterochrony results in delayed onset of a trait’s development?

Answer 157

Postdisplacement

Question 158

# Origin of Chordates In amphibians, paedomorphosis is commonly seen in species with aquatic larvae that retain their __ features into adulthood. For example, some salamanders like the axolotl (*Ambystoma mexicanum*) exhibit __ adults, maintaining external gills and an aquatic lifestyle instead of __ into a terrestrial adult. In contrast, other amphibians undergo __, transitioning from egg masses in water to aquatic larvae, and then developing into terrestrial adults with lungs and limbs.

Answer 158

- larval - paedomorphic - metamorphosing - complete metamorphosis

Question 159

# Origin of Chordates Exaggerated adult traits

Answer 159

Peramorphosis ## Footnote more elaborate or extreme morphological features compared to ancestors.

Question 160

# Origin of Chordates Name three types of peramorphosis. (3)

Answer 160

- Hypermorphosis - Acceleration - Predisplacement

Question 161

# Origin of Chordates What type of peramorphosis extends growth periods in descendants?

Answer 161

Hypermorphosis

Question 162

# Origin of Chordates What type of peramorphosis increases growth rate?

Answer 162

Acceleration

Question 163

# Origin of Chordates What type of peramorphosis results in earlier trait development than in ancestors?

Answer 163

Predisplacement

Question 164

# Origin of Chordates Differential growth rates of body parts

Answer 164

Allometry

Question 165

# Origin of Chordates Involves altered sensitivity to growth factors or changes in growth factor production.

Answer 165

Allometry

Question 166

# Origin of Chordates Allometry in Modularity (Dissociation) refers to how different body parts grow at __, leading to independent changes in shape or size. __ means that body structures develop as semi-independent units, and __ occurs when these modules follow different __ (growth) patterns.

Answer 166

- varying rates - Modularity - dissociation - allometric

Question 167

# Origin of Chordates What feature differentiates vertebrates from protochordates?

Answer 167

Neural Crest Cells (NCCs)

Question 168

# Origin of Chordates What structures do cranial neural crest cells develop into? (3)

Answer 168

- Face - skull - branchial arches

Question 169

# Origin of Chordates have a dorsal nerve cord and notochord but lack a well-defined head.

Answer 169

Protochordates

Question 170

# Origin of Chordates contribute to the development of the face, skull, and branchial arches.

Answer 170

Cranial Neural Crest Cells

Question 171

# Origin of Chordates allows for efficient predation, placing sensory structures near the mouth.

Answer 171

Cephalization

Question 172

# Origin of Chordates What structures do protochordates have instead of neural crest cells? (2)

Answer 172

- Dorsal nerve cord - notochord

Question 173

# Origin of Chordates Repurposing genes for new functions

Answer 173

co-option | in evolution

Question 174

# Origin of Chordates A single gene can specify different functions in various stages of development.

Answer 174

Co-option

Question 175

# Origin of Chordates How can a single gene function in different developmental stages?

Answer 175

Specifies different roles in various tissues

Question 176

# Origin of Chordates Examples of Co-option: * __ used in the liver also function in the lens (as __). * __ evolved from modified forelimbs with different functions (e.g., flippers, arms).

Answer 176

- Enzymes - crystalline proteins - Wings

Question 177

# Origin of Chordates Give examples of co-option in vertebrate limb evolution (3)

Answer 177

- Flippers - arms - wings from forelimbs