Term
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Definition
| the process by which groups are named described and classified, usually in hierarchical categories |
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Definition
| a general name for a hierarchical category |
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Term
| How are animals assigned to categories? |
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Definition
| Individuals in the same taxon are more similar to each other than to individuals in other taxa |
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Term
| What types of “similarities” are important to classification? |
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Definition
- Homologous characters: similarity between characters is due to inheritance from a common ancestor.
- What clues are used to determine whether morphological characters are homologous?
Similarity of position (with respect to other body parts)
Similarity of vascular and nerve supply
Similarity of embryonic development |
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Term
| What types of similarities are not important to classification? |
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Definition
- Analogous characters: Characters have similar functions, but the functions are not necessarily due to common ancestry
- Example: wings of bats and birds |
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Definition
| Taxonomic arrange based solely on homologous traits. Phylogenies should reveal evolutionary relationships among groups |
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Definition
| not changed from the ancestral form |
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Term
| - Derived, modified, or specialized |
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Definition
| changed from the ancestral form; these terms are preferred over the more subjective “advanced” |
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Definition
| ancestral traits that become better developed in the descendant |
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Definition
| not as well developed as in the ancestor; preferred over the term “degenerate”. E.g., the eyes of cave fishes are vestigial, not rudimentary |
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Definition
...selective:
- Fossils typically form only in sedimentary rocks
- Hard parts (bones, teeth, scales…) fossilize better than soft parts |
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Definition
| new deposits are laid on top of old deposits |
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Term
| characteristics of vertebrate fossils |
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Definition
- Mostly bone
- Some soft parts through rapid freezing (e.g., mammoths), drying (e.g., tar pits) or other special circumstances
- Indirect clues: fossil eggshells, footprints, feces |
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Definition
| descendent lineages become different from each other and from the ancestral state |
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Definition
| unrelated lineages come to resemble each other; usually due to similar selection pressures operating in similar environments |
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Term
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Definition
| Different lineages change in similar ways so that the descendents in the two lineages are very similar |
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Term
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Definition
-Individual development
-it can provide clues to the evolutionary development of lineages (Phylogeny) |
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Term
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Definition
| evolutionary development of lineages |
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Term
| Linking Development of Individuals to the Development of Lineages |
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Definition
- Individual development (Ontogeny) can provide clues to the evolutionary development of lineages (Phylogeny)
- Embryos of recent forms resemble embryos of ancestral forms
- During embryonic development, divergence proceeds from general to specific structures
--Limb buds → limbs → wings
- New structures usually arise as modifications of existing structures |
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Term
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Definition
Evolution occurs when mutations cause changes to occur during development:
(1) New characters can be added to the embryo
(2) Existing characters can experience a change in developmental timing (called Heterochrony) |
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Term
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Definition
| Existing characters can experience a change in developmental timing |
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Definition
(1) Paedomorphosis
(2) Peramorphosis |
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Term
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Definition
(“child” + “form”): characteristics of adults resemble the same characters of the juveniles of the ancestors. This occurs when characters:
a. Stop development: Progenesis
i. Example: Webbed digits in some amphibians form when limb development of hands and feet stops early
b. Slow development: Neoteny
i. Example: In amphibians, gills usually disappear at metamorphosis; when development of gills dramatically slows, gills can be retained in adults
c. Are added late: Post-displacement |
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Term
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Definition
(“beyond” + “form”): Characteristics of adults are exaggerations of the same characters in the adult ancestors.
a. Example:
i. The antlers of Irish elk (now extinct) are much larger than the antlers of their ancestors (or of any other living antelope)
ii. The homocercal caudal fin of flounders is a result of prolonged development; the ancestral tail was heterocercal and so is the embryonic tail of flounders
b. Peramorphosis occurs when changers experience:
i. Longer developmental time: Hypermorphosis
ii. Faster growth: Acceleration
iii. Early onset of the character: Predisplacement |
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Term
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Definition
(1) Epidermis: - Thin outer layer
- Ectodermal origin
- Layer is mostly composed of cells
(2) Dermis:
-Thicker inner layer
- Mesodermal origin
- Layer is mostly composed of connective tissue (cells scattered in a noncellular matrix) |
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Term
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Definition
- A single layer of columnar epithelial cells (cells packed closely together)
- No extracellular glands
- The epidermis secretes a noncellular cuticle that covers the surface (the cuticle is absent in most vertebrates) |
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Term
| General Vertebrate Epidermis |
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Definition
- The epidermis of vertebrates is stratified into two or more layers
- The innermost layer is the stratum basale
- Cells in the SB undergo mitotic divisions and the new cells push outward, becoming the superficial (surface) skin cells as they mature
- In some taxa, the mid-layers of the epidermis contain glands scattered amongst the epithelial cells; these glands produce mucus or proteins such as poison or pheromones.
- The outer layer of cells in the stratum corneum. It contains varying amounts of the protein keratin, which can make the skin tough in certain areas (e.g., palms). The SC becomes elaborated in some taxa, forming reptile scales, claws, feathers, and hair. |
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Term
| Epidermis of Fishes (fig. 6.9, 6.10) |
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Definition
- Thin and glandular
- Little or no keratin
- Replacement of worn cells is constant |
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Term
| Epidermis of Amphibians (fig. 6.12) |
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Definition
- Contains numerous flask-shaped (“alveolar”) multi-cellular glands that grow down into the dermis. Ducts lead from the glands to the surface.
- The stratum corneum is thin and is lost every few days, usually in large patches |
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Term
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Definition
- The stratum corneum forms a body covering of scales
(A) Squamates (lizards and snakes) (Figure 6.13a):
- Scales are connected in overlapping folds (keratin is thin in the joints)
- Outer layer sloughs off several times a year
(B) Crocodilians:
- Scales do not overlap
- No shedding (growth rings added)
(C) Turtles:
- Small, nonoverlapping scales on legs and head
- Large thin plates called scutes on upper (“carapace”) and lower (“plastron”) shells
- No shedding (growth rings added) |
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Term
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Definition
- Hind legs and toes are covered with small scales similar to those of reptiles
- Glands typically limited to a large alveolar uropygial (uro = “tail”, pyg = “small”) gland above the tail that secretes oil used in preening (fig. 6.15c)
- Feathers are heavily keratinized epidermal outgrowths
- Feathers are hypothesized to have evolved from reptile scales as an adaptation for insulation (important for endotherms); they were secondarily adapted for flight (see next page of handout, figures 4-4 and 96). |
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Term
| Feather types (figs. 6.14b and 6.15b) |
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Definition
(A) Flight: large; provide air foils for flight; structure:
- Hollow quill is embedded in the dermis within a follicle that is lined with epidermal tissue (ectodermal origin)
- Solid central vertical shaft (aka rachis)
- Horizontal barbs extend from the shaft; barbs are connected by vertical barbules
(B) Contour: smaller than flight feathers; shape body surface
(C) Down: underlie contour feathers, providing insulation
(D) Filoplumes: scattered; usually hairlike; function in displays |
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Term
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Definition
| Absent in most mammals; present on the legs and tails of some rodents insectivores, and marsupials |
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Term
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Definition
| Often contains a third distinct layer - the stratum granulosum - between the stratum corneum and the stratum germinativum (sometimes more layers) |
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Term
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Definition
| Often thickened on areas subject to abrasions (e.g., the soles of the feet) or where hair is sparse) |
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Term
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Definition
| Keratinized structures that wrap around the terminal bones of digits; hooves are derived from claws |
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Term
| Glands unique to mammals (fig. 6.20): |
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Definition
Sweat (Sudoriferous) glands:
tubular, simple, coiled at the end
evaporation of sweat acts as a cooling device
also acts as an accessory kidney by secreting salt and urea
develop from ectoderm, but sink into the dermis
Sebaceous glands
alveolar
usually empty into hair follicles
have an oily secretion that protects the hair and skin from excessive drying
Mammary glands
form as ectodermal (epidermal) ridges that sink into the dermis
compound and alveolar
secrete milk to suckle young |
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Term
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Definition
(some epidermal, some from bone)
Rhinoceros horns: keratinized fibers compacted together; growth is from the epidermis; never shed (fig. 6.28c)
Other horns/antlers are not strictly epidermal derivatives, but are bone capped by “skin”. The differences are primarily in shedding:
Giraffe horns: bone permanently covered with skin; never shed (fig. 2.28b)
Pronghorns: bone is permanent; horny epidermal cap is shed each year (fig. 6.28a)
"True" horns (cattle/antelope): both bone and epidermal cap are permanent (fig. 6.25a; 6.27)
Deer antlers: Skin ("velvet") sheds when antlers reach full size; bone is branched shed annually (fig. 6.25b; fig. 6.26) |
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Term
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Definition
Probably did not evolve from reptile scales
May have arisen from reptilian mechanoreceptors that are found between scales
Function: insulation
Made of heavily keratinized epidermal cells
Has a projecting shaft and a root projecting into the dermis in an epidermis-lined pit called the follicle |
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Term
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Definition
| A gelatinous layer with fibers primarily confined to the inner and outer borders. |
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Term
| Dermis of Vertebrates in general |
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Definition
All have connective tissues with collagen (protein), blood vessels, nerves, and pigment
A bony dermis was the primitive condition
The potential to produce bone is persistent: all classes of vertebrates (except birds) have at least one member with a bony dermis
The origin of the bony dermis is poorly understood; it may have arisen from dermal papillae formed by neural crest cells |
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Term
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Definition
A deep layer of connective tissue
A more superficial layer of bony tissue (scales); (fig. 6.10a)
Shark scales are not made of bone but are made of enamel over a layer of dentin; fig. 6.9b |
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Term
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Definition
Primarily connective tissue (collagen and elastic fibers)
Some nerve fibers
Abundant blood/lymph vessels (especially important for cutaneous respiration by amphibians)
In mammals, the deep layer of the dermis has fatty tissue (serves for insulation)
Some taxa have bone in their dermis called osteoderms
-->Caecilians have bony ossicles
-->Turtle shells
-->Crocodilians and some lizards have bony plates; osteoderms in the abdominal area are called gastralia
-->Armadillo shells |
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Term
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Definition
-An animal pole: where the embryo develops
-A vegetal pole: where yolk globules concentrate (yolk is heavy and so globules sink to the “bottom” of the egg) |
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Term
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Definition
o Microlecithal
o Mesolecithal
o Macrolecithal
o Mammalian microlecithal |
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Term
| Microlecithal (Fig. 5.2a) |
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Definition
Have little yolk
Typical of amphioxus and other protochordates
Only a slight concentration of yolk at the vegetal pole (= isolecithal)
Holoblastic cleavage: cleavage planes extend through entire egg
The third cleavage plane is slightly above the equator; division is through the center of the living protoplasm (the yolk is inert)
Blastula stage: A cavity (the blastocoel or segmentation cavity) forms in the center
The blastocoel has no function; it will later disappear |
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Term
| Mesolecithal: (Fig. 5.2b) |
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Definition
Have a moderate amount of yolk
Typical of Primitive fishes, amphibians
Holoblastic cleavage
Yolk concentrated in vegetal pole (= telolecithal)
Cleavage slows in the vegetal pole due to thickness of yolk
Third cleave plane is substantially above equator
Because cell division is slow in the vegetal pole
-- The blastocoel is smaller than in amphioxus and is present only at the animal pole
-- Cells in the animal pole are smaller than in the vegetal pole |
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Term
| Macrolecithal: (Fig. 5.2c) |
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Definition
Have a large amount of yolk
Typical of modern fishes, reptiles, birds, and monotreme mammals
Most of the egg is yolk, with only a small amount of protoplasm
Meroblastic cleavage: cleavage planes extend only through protoplasm
Blastula is a mass of cells slightly lifted off the underlying yolk |
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Term
| Mammalian microlecithal: (Fig. 5.2d) |
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Definition
Have very little yolk
Typical of placental mammals
Holoblastic cleavage
Segmentation cavity (blastocoel) forms beneath protoplasm, merging with an empty “yolk” sac
A superficial (= surface) layer of cells separates from and surrounds the embryo. This trophoblast will become part of the placenta.
The embryo is a compact cluster of cells within the trophoblast called the inner cell mass. |
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Term
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Definition
| Stage of development when 3 distinct tissue layers are formed |
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Term
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Definition
(microlecithal egg) (Fig. 5.7a)
Blastula becomes flat at one end
Plate bends inward forming blastopore
Cells bending inward form endoderm
Cells on the outside are the ectoderm
Some migrating cells (mesenchyme) move inward and form a layer called the mesoderm
The blastocoel gets smaller and eventually disappears
The new cavity is the archenteron (aka primitive gut or gastrocoel) |
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Term
| Amphibian and Primitive Fish Gastrula |
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Definition
(mesolecithal egg) (Fig. 5.11a)
Blastopore forms at boundary between animal and vegetal poles
Cells role inward forming endoderm
Mesoderm follows endoderm inward
Archenteron forms at blastopore
Blastocoel becomes smaller and eventually disappears
Endoderm lines gut
Ectoderm is outer layer
Mesoderm is between Ecto- & Endoderm |
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Term
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Definition
(macrolecithal egg) (Fig. 9)
The macrolecithal egg arose independently in fishes and birds; the two groups solved the problem of germ layer formation in different ways.
Cells roll inward at blastocoel
Endoderm and mesoderm separate into two layers |
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Term
| Reptile, Bird, and Monotreme Mammal Gastrula |
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Definition
(macrolecithal egg) (Fig. 13.d)
Bottom layer of blastoderm (“hypoblast”) separates, forming endoderm
Groove (primitive streak) forms in center of blastoderm
Mesenchyme cells move into embryo through primitive streak, forming the mesoderm.
Outer layer (“epiblast”) is ectoderm. |
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Term
| Placental Mammal Gastrula |
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Definition
(microlecithal egg) (5.32a—c)
Inner cell mass splits into two layers (epiblast & hypoblast).
The amniotic cavity forms above the epiblast
The yolk cavity forms below the hypoblast
The Blastoderm is located between the amniotic cavity and yolk sac
Primitive streak forms on top of blastoderm
Mesoderm migrates in through the primitive streak
Epiblast forms ectoderm; hypoblast forms endoderm |
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Term
| Formation of Coleom in Placental Mammals |
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Definition
(Amphibian example: Fig. 5.11)
Coelom: Cavity surrounding the gut
Unlike other Deuterostomes, the coelom of vertebrates forms by splitting of mesoderm around the gut (Schizocoely)
The notochord pinches off from the other mesoderm |
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Term
| Formation of Nerve Cord from Ectoderm in placental mammals |
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Definition
(Amphibian example: Fig. 5.11)
Ectoderm dorsal to notochord Flattens forming the Neural Plate
Neural Plate curls inward, forming the Neural groove
Neural groove pinches together, forming the nerve cord
Body ectoderm grows over the Nerve Cord |
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Term
| Formation of Accessory Nervous Tissue in placental mammals |
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Definition
(Amphibian example: Fig. 5.11)
Neural crests pinch off of the dorsal end of the Nerve Cord
Neural crests form various neural structures: E.g., peripheryl nervous system; see Table 5.2 for complete list
In the head, swellings called placodes form along lateral surfaces
Placodes form various sensory/nervous structures (in above example, the eye) |
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Term
| Derivatives of Embryonic Germ Layers (Fig. 5.17) |
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Definition
Ectoderm
Mesoderm
Endoderm |
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Term
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Definition
o Body Ectoderm:
Outer layer of Skin
Derivatives of outer skin (hair, feathers, glands)
Lining of mouth and cloaca
Lining of nose and ear
Outer portion of eye (lens)
Outer layer of teeth (enamel)
o Neural Ectoderm:
Nervous system
Inner part of eye (retina) |
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Term
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Definition
-Connective tissue: blood, bone, cartilage, mesenteries, etc.
-Muscle Most of excretory/reproductive organs
-Notochord |
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Term
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Definition
o Part of digestive tract
o Accessory digestive organs (Liver, pancreas)
o Endocrine glands
o Lungs
o Part of excretory/reproductive organs |
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Term
| Subdivisions of Mesoderm (Fig. 5.9) |
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Definition
1. Epimere
2. Mesomere
3. Hypomere
4. Mesenchyme |
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Term
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Definition
• Sclerotome: most medial; forms vertebrae and part of ribs
• Dermatome: most outer portion; forms connective tissues in skin
• Myotome: between sclerotome and dermatome; forms most of axial and part of appendicular muscle |
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Term
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Definition
• Aka Nephrotome
• Forms kidney and part of gonads |
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Term
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Definition
• Inner (Splanchnic) layer forms gut lining and muscle tissue
• Outer Somatic) layer forms lining (“peritoneum” of body cavity and muscle tissue of body wall |
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Term
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Definition
• Amoeboid-like migrating cells
• Form connective tissue (blood, bone, cartilage) and some muscle tissue |
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Term
| Embryonic Cavities (Fig. 5.9) |
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Definition
Neurocoel: becomes cavity inside brain and spinal cord
Myocoel: transient; disappears when dermatome, sclerotome, and myotome separate
Coelom: Cavity around gut tract
Lumen: Cavity inside of gut |
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