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Lecture 2: Concepts in Developmental Biology Flashcards

1
Q

What directs initial developmental stages? (2)

A
  • 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.

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2
Q

What directs development after cleavage?

A

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.

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3
Q

What factors influence development over time? (2)

A

Gene products & environment

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

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4
Q

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

A

Genomic equivalence

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

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5
Q

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

A

False

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6
Q

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

an exception to genomic equivalence, especially in brain cells

A

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.

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7
Q

Where is genomic mosaicism mostly found?

A

Brain cells (neurons)

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8
Q

What distinguishes genomic mosaicism from epigenetic changes?

A

DNA sequence alterations

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9
Q

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

A
  • Aneuploidy
  • CNVs
  • SNVs
  • LINE1 elements
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10
Q

What field relies on sequencing nonbrain DNA?

A

GWAS (Genome-Wide Association Studies)

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11
Q

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

A

Cell potency

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

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12
Q

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

A

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.

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13
Q

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

A

Pluripotency

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

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14
Q

Example of a pluripotent cell?

A

Embryonic stem cell

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15
Q

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

the ability to form multiple, related cell lineages

A

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.

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16
Q

Give an example of a totipotent cell.

A

Zygote (fertilized egg)

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

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17
Q

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

A

Hematopoietic stem cells

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18
Q

What is the ultimate test of nuclear potency?

A

Generating every cell type

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19
Q

What happens to nuclear potency over time?

A

It becomes restricted

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

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20
Q

Name the three main types of potency. (3)

A
  • Totipotency
  • pluripotency
  • multipotency
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21
Q

What experiment tested nuclear potency using Rana pipiens eggs?

A

Blastula nucleus transplant

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22
Q

What was the first cloned mammal?

A

Dolly the sheep

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

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23
Q

What type of cell was Dolly cloned from?

A

Mammary gland cell

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

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24
Q

What was used as the enucleated oocyte donor for Dolly?

A

Scottish Blackface sheep

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

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25
Q

Where was Dolly implanted for development?

A

Surrogate Scottish Blackface sheep

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26
Q

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

A

Cell differentiation

This creates cellular diversity

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27
Q

What is the result of cell differentiation?

A

Cellular diversity

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28
Q

What part of the genome is expressed during differentiation?

A

A portion of the genome

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29
Q

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

A

Housekeeping genes

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

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30
Q

What type of genes are unique to specific cell types?

genes are only expressed in specific cells or conditions

A

Luxury genes

These encode specialized proteins like hemoglobin (RBCs) and insulin (pancreatic cells).

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31
Q

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

A

Stem cells

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32
Q

What type of stem cell can form a complete organism?

A

Totipotent stem cell

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33
Q

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

A

Pluripotent stem cell

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34
Q

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

A

Pluripotent

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

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35
Q

What is the potency of hematopoietic stem cells?

A

Multipotent.

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

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36
Q

What are examples of pluripotent stem cells? (2)

A
  • Embryonic stem cells (ESCs)
  • induced pluripotent stem cells (iPSCs)
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37
Q

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

A

Multipotent stem cell

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38
Q

What type of stem cell gives rise to only one cell type?

type of potency do most adult cells have

A

Unipotent stem cell

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39
Q

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

A

Mesenchymal stem cells (MSCs)

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40
Q

Name the three germ layers. (3)

A
  • Ectoderm
  • mesoderm
  • endoderm
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41
Q

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

A

Endoderm

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42
Q

Which germ layer forms muscles, blood, and bones?

A

Mesoderm

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43
Q

Which germ layer develops into skin and the nervous system?

A

Ectoderm

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44
Q

What is the relationship between cell differentiation and potency?

A

Differentiation decreases potency

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45
Q

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

A

Housekeeping genes

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46
Q

What is another name for housekeeping genes?

A

Constitutive genes

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47
Q

Where are housekeeping genes expressed?

A

All cells, all the time

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48
Q

What type of proteins do housekeeping genes produce?

A

Proteins essential for basic cellular functions

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49
Q

Give an example of a housekeeping gene. (3)

A
  • Actin
  • GAPDH
  • ribosomal RNA genes
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50
Q

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

A

Luxury genes

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51
Q

What is another name for luxury genes?

A

Tissue-specific genes

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52
Q

Where are luxury genes expressed?

A

Only in specialized cells

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53
Q

What type of proteins do luxury genes produce?

A

Proteins related to specialized cell functions

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54
Q

Give an example of a luxury gene. (2)

A
  • Hemoglobin (in red blood cells)
  • myosin (in muscle cells)
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55
Q

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.

A

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

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56
Q

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

A

Selective gene expression

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57
Q

What is another name for selective gene expression?

A

Differential gene expression

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58
Q

How do genes behave in selective gene expression?

A

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

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59
Q

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

A

Selective gene amplification

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60
Q

What is the purpose of selective gene amplification?

A

To meet the synthetic demands of a developing cell

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61
Q

What is an example of selective gene amplification?

A

rRNA gene amplification in amphibian oocytes

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62
Q

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

A

Early diplotene stage

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63
Q

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

A

Ribosomal RNA (rRNA)

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64
Q

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

A

preformed

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65
Q

What do maternal genes and cytoplasm direct?

A

Early development

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66
Q

What species was cloned using amphibian nuclear transfer?

A

Rana pipiens

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

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67
Q

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

A

Amphibian cloning

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68
Q

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

A

Blastula nuclei

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

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69
Q

Amphibian cloning

Who successfully cloned Rana pipiens? (2)

A

M. DiBerardino & N. Hoffner Orr

hey used nuclear transplantation to create a cloned frog named “Freddy.”

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70
Q

What is another term for selective gene expression?

A

Differential gene expression

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71
Q

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

A

Differential gene expression

72
Q

What determines which genes are expressed? (2)

A

Time and space

Gene expression varies based on developmental phase and cell type.

73
Q

What regulates gene repression in cells?

A

Selective gene repression

🔹 Some genes are silenced depending on the cell’s function.

74
Q

What happens to genes not needed in certain cells?

A

Selective gene repression

75
Q

What increases gene copies without mitosis?

This ensures a higher production of specific proteins when needed.

A

Selective gene amplification

76
Q

Where does gene amplification occur in amphibians?

Additional Question: What gene is amplified?

A

Amphibian oocytes

Ribosomal RNA genes are amplified in the oocyte to support early development.

77
Q

What is produced by gene amplification in amphibian oocytes?

Additional Question: What’s the significance of this product?

A

Ribosomal RNA (rRNA)

Extra rRNA is needed for rapid protein synthesis in early embryonic stages.

78
Q
  • Cell signaling in development
  • One group of embryonic cells influences the fate of neighboring cells.
A

embryonic induction

79
Q
  • An organizer that induces neural tube formation
  • It triggers the development of the brain and spinal cord in vertebrates.
A

Spemann-Mangold organizer

80
Q

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

A

Competence

81
Q

What happens if embryonic induction fails?

A

Developmental defects

82
Q

What are the components of embryonic induction? (3)

A
  • Organizer or Inductor
  • Evocator
  • Responsive tissue
83
Q

components of embryonic induction

What is the structure that induces the formation of another structure?

A

Organizer or Inductor

84
Q

components of embryonic induction

What is released by the organizer or inductor?

a chemical substance

85
Q

components of embryonic induction

What tissue reacts to the inductor or evocator?

A

Responsive Tissue

86
Q

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.

A

primary embryonic induction

87
Q

lays the foundation for the embryo’s structure.

A

Primary induction

88
Q

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

A

Secondary induction

89
Q

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

A

Dorsal lip of the blastopore

90
Q

Key example of primary embryonic induction?

A

Spemann-Mangold Organizer

91
Q

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

A

Secondary Embryonic Induction

92
Q

Key example of secondary embryonic induction?

A

Lens induction in vertebrates

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.

93
Q

What is established by primary embryonic induction? (2)

A

Body plan and nervous system

94
Q

What does secondary embryonic induction drive?

A

Formation of specific organs

95
Q

EMBRYONIC INDUCTION

What induces neurulation and axis development?

A

Notochord (chordamesoderm)

96
Q

EMBRYONIC INDUCTION

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

A

Notochord (chordamesoderm)

97
Q

EMBRYONIC INDUCTION

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

A
  • organizer
  • ectoderm
  • neural plate
  • nervous system
98
Q

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

A

Morphogenesis

99
Q

The process by which an organism develops its specific shape

A

Morphogenesis

100
Q

Morphogenesis

Spatial and temporal distribution or organization of differentiated cells.

Example: Development of the arms – upper arm, lower arm, and fingers.

A

Pattern formation

101
Q

Morphogenesis

Pattern formation is tightly regulated by __.

A

genetic control

102
Q

Morphogenesis

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

A

Main body axes and changes in form

103
Q

Morphogenesis

Movement of cells relative to each other

A

Morphogenetic Movements

104
Q

Give four (4) examples of morphogenesis.

A
  • Limb formation
  • Establishment of the fundamental body axes
  • Branching of ducts within glands
  • Formation of loops and whorls of fingerprints
105
Q

Morphogenesis

Name the six processes involved in morphogenesis. (6)

A
  • Cell proliferation
  • Cell migration
  • Cell aggregation/cell adhesion
  • Secretion of extracellular substances
  • Change in cell shape
  • Localized cell death/apoptosis
106
Q
  • Characterized by rapid cell divisions, resulting in an increase in the number of cells.
  • Occurs through mitotic divisions.
A

Cell proliferation

107
Q

Cell proliferation occurs through what type of divisions?

A

Mitotic divisions

108
Q

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

A

Cell migration

109
Q

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

A

(1) Short migrations
(2) Massive dislocation

110
Q

Examples of Cell Migration (2)

A
  • Invagination
  • Involution
111
Q

Cell migration

What is an example of inward folding of a cell sheet?

A

Invagination

112
Q

Cell migration

What describes the inward movement of an expanding outer layer?

A

Involution

113
Q

a highly regulated programmed cell death process in multicellular organisms.

114
Q

Why is apoptosis essential?

A

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

115
Q

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.

A
  • intrinsic pathway
  • extrinsic pathway
  • Execution
  • Phagocytosis
116
Q

EXAMPLES OF APOPTOSIS IN DEVELOPMENT

What is an example of apoptosis in tadpoles?

A

Resorption of the tail

117
Q

EXAMPLES OF APOPTOSIS IN DEVELOPMENT

What process occurs in the embryonic hand and feet?

A

Separation of digits

118
Q

EXAMPLES OF APOPTOSIS IN DEVELOPMENT

What type of cells undergo selective death during development?

119
Q

APOPTOSIS DURING EMBRYOGENESIS

How does apoptosis help in mouse embryos?

A

Tissue sculpting

120
Q

APOPTOSIS DURING EMBRYOGENESIS

What critical process is assisted by apoptosis in limb formation?

A

Eliminating unnecessary cells between fingers and toes.

121
Q

APOPTOSIS DURING EMBRYOGENESIS

In tadpoles, what transformation involves apoptosis?

A

apoptosis in the tai

leading to its resorption as the amphibian transitions to a terrestrial lifestyle.

122
Q
  • 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.
A

Homeotic genes

123
Q

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 __.
A
  • anteroposterior axis
  • segment identity
  • metazoan
  • legs
  • antennae
  • eyes
124
Q

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

125
Q
  • Many __ found in Drosophila melanogaster are also present in vertebrates.
  • These genes are expressed in highly specific sites and stages of development.
A

homeobox genes

126
Q

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

127
Q

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

A

Mammalian Hox genes

128
Q

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

A

Paralogous genes

129
Q

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

A

Paralogous genes

130
Q

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

A
  • Gene regulation
  • Hox gene duplication
  • evolutionary modifications
  • Interactions with Other Developmental Genes
  • Environmental Influences
131
Q

Considered the “Rosetta Stone” of developmental biology.

A

Homeobox (DNA sequence)

132
Q

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

A
  • anteroposterior body axis
  • types
  • gene order
  • expression
133
Q
  • How many Hox gene clusters do vertebrates have?
  • How many Hox gene clusters do invertebrates have?
134
Q

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

A

Differences in time and space of gene expression

135
Q

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

A

Leads to different protein functions

136
Q

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

A

Neural crest cells (NCCs)

137
Q

What structures do neural crest cells contribute to in vertebrates?

A

complex structures

e.g. skull, jaw, nervous system

138
Q

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

A

absence of neural crest

139
Q

How do neural crest cells affect vertebrate body complexity?

A

Enable modification and diversification of structures

140
Q

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)

A
  • notochord
  • dorsal hollow nerve cord
  • pharyngeal slits
  • post-anal tail
141
Q

Origin of Chordates

Development Through Discrete & Interacting Modules

A

Modularity

142
Q

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.
A
  1. Inner Cell Mass (ICM) vs. Trophoblast
  2. Eye/limb development
  3. Vertebrate organ formation, imaginal discs in invertebrates
143
Q

Origin of Chordates

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

A

Modularity

144
Q

Origin of Chordates

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

A

Modularity

145
Q

Origin of Chordates

Formation of redundant structures

A

Duplication

146
Q

Origin of Chordates

Give three (3) examples of gene duplication.

A
  • Globin genes
  • TGF-β family
  • Myo-D family
147
Q

Origin of Chordates

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

A
  • Cervical
  • thoracic
  • lumbar skeleton
148
Q

Origin of Chordates

Enables structures to assume new roles over evolutionary time.

A

Divergence

149
Q

Origin of Chordates

What happens to the original gene copy in divergence?

A

Retains its original function

150
Q

Origin of Chordates

How does divergence contribute to evolution?

A

Mutated gene copies develop new roles

151
Q

Origin of Chordates

Changes in timing of development

A

Heterochrony

152
Q

Origin of Chordates

Retention of larval traits in adults

A

paedomorphosis

153
Q

Origin of Chordates

Gene mutations affecting developmental timing

A

paedomorphosis

154
Q

Origin of Chordates

Name three types of paedomorphosis. (3)

A
  • Progenesis
  • Neoteny
  • Postdisplacement
155
Q

Origin of Chordates

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

A

Progenesis

156
Q

Origin of Chordates

What type of heterochrony results in slowed development of somatic traits?

157
Q

Origin of Chordates

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

A

Postdisplacement

158
Q

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.

A
  • larval
  • paedomorphic
  • metamorphosing
  • complete metamorphosis
159
Q

Origin of Chordates

Exaggerated adult traits

A

Peramorphosis

more elaborate or extreme morphological features compared to ancestors.

160
Q

Origin of Chordates

Name three types of peramorphosis. (3)

A
  • Hypermorphosis
  • Acceleration
  • Predisplacement
161
Q

Origin of Chordates

What type of peramorphosis extends growth periods in descendants?

A

Hypermorphosis

162
Q

Origin of Chordates

What type of peramorphosis increases growth rate?

A

Acceleration

163
Q

Origin of Chordates

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

A

Predisplacement

164
Q

Origin of Chordates

Differential growth rates of body parts

165
Q

Origin of Chordates

Involves altered sensitivity to growth factors or changes in growth factor production.

166
Q

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.

A
  • varying rates
  • Modularity
  • dissociation
  • allometric
167
Q

Origin of Chordates

What feature differentiates vertebrates from protochordates?

A

Neural Crest Cells (NCCs)

168
Q

Origin of Chordates

What structures do cranial neural crest cells develop into? (3)

A
  • Face
  • skull
  • branchial arches
169
Q

Origin of Chordates

have a dorsal nerve cord and notochord but lack a well-defined head.

A

Protochordates

170
Q

Origin of Chordates

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

A

Cranial Neural Crest Cells

171
Q

Origin of Chordates

allows for efficient predation, placing sensory structures near the mouth.

A

Cephalization

172
Q

Origin of Chordates

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

A
  • Dorsal nerve cord
  • notochord
173
Q

Origin of Chordates

Repurposing genes for new functions

A

co-option

in evolution

174
Q

Origin of Chordates

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

175
Q

Origin of Chordates

How can a single gene function in different developmental stages?

A

Specifies different roles in various tissues

176
Q

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).

A
  • Enzymes
  • crystalline proteins
  • Wings
177
Q

Origin of Chordates

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

A
  • Flippers
  • arms
  • wings from forelimbs

Developmental Biology (6 decks)

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