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Organisms 2 > Developmental > Flashcards

Developmental Flashcards

1
Q

Gamete Formation

A

gametes => mature haploid male or female germ cell

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2
Q

What is an egg?

A
  • Egg
    An organic vessel where an embryo develops (colloquial terminology)
    An ovum
  • Ovum
    The female reproductive or germ cell
  • Eggs vary significantly among taxa
  • Human egg is approx. 100 microns
    Width of a human hair
    Huge
  • Eggs has components of a normal somatic cell
  • Eggs also have yolk (provides energy during development)
  • Eggs have a polarity
    Animal pole has most of the cytoplasm (and the nucleus)
    Vegetal pole has most of the yolk
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3
Q

Isolecithal

A
  • Very little yolk, evenly distributed through egg

- Typical of placental mammals (also echinoderms, tunicates, cephalochordates, molluscs)

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4
Q

Mesolecithal

A
  • Moderate amount of yolk concentrated at vegetal pole

- Typical of amphibians

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5
Q

Telolecithal

A
  • Abundance of yolk densely concentrated at vegetal pole

- Typical of birds, reptiles, fish, monotremes, some amphibians

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6
Q

Centrolecithal

A
  • Large centrally located mass of yolk

- Typical of arthropods

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7
Q

Amount of yolk is associated with developmental patterns

A
  • Lots of yolk (telolecithal eggs), young exhibit direct development
    Goes straight from embryo to miniature adult
  • Little yolk (isolecithal, mesolecithal eggs) young exhibit indirect development
    Passes through larval stage capable of feeding itself
    Undergoes metamorphosis to reach adult stage
    Exception: mammals (direct development)
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8
Q

What is fertilization

A
  • Fertilization => gametes unite to form a zygote

- Zygote => a diploid cell resulting from fusion of male and female gametes (i.e. a fertilized egg)

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9
Q

What is cleavage?

A
  • embryo divided repeatedly without growth (essentially skips G-phase of mitosis)
  • single large egg cell becomes many smaller cells called blastomeres
  • by the end of cleavage, the zygote is called blastula
  • cleavage subdivides the zygote to form a blastula
  • in most animals the cells are formed around a fluid-filled cavity called a blastocoel
  • All multicellular animals go through blastulation. Most continue to gastrulation
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10
Q

What is a blastula?

A

a fluid filled ball of cells

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11
Q

Amount of yolk is associated with cleavage patterns

A
  • cell division occurs more easily in cytoplasm than yolk
  • two types of cleavage
    holoblastic
    meroblastic
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12
Q

What is holoblastic?

A

complete and approximately equal divisions of cells

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13
Q

What is meroblastic?

A

restricted to a small area of egg

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14
Q

What are the directions of cleavage?

A

Spiral cleavage

Radial cleavage

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15
Q

What is gastrulation?

A
  • converts the spherical blastula into two or three layered embryo
  • the layers are called germ layers
    The blastula has 1 germ layer
    The gastrula has 2 or 3
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16
Q

Gastrulation (1)

A
  • one side of the blastula bends inwards in a process called invagination
  • the internal pouch that is formed is the gut cavity (also called archenteron or gastrocoel)
  • the opening to the gut cavity is called the blastopore
17
Q

Gastrulation (2)

A
  • outer layer of cells (lining blastocoel) = ectoderm
  • inner layer of cells (lining gut) = endoderm
  • when the gut opens only at the blastopore it is called a blind gut
18
Q

Gastrulation (3)

A
  • most animals have a complete gut with a second opening, the anus
  • the blastopore becomes the mouth in some organisms and the anus in others
  • this difference differentiates Protostomes and Deuterostomes
19
Q

Gastrulation (4)

A
  • in many animals, a third layer forms = mesoderm
  • the mesoderm is formed from the endoderm
  • coelom = cavity completely surrounded by mesoderm
20
Q

How many layers?

A
  • some animals stop at the blastula stage
    One germ layer
  • some animals develop two germ layers
    diploblastic
  • most animals develop three germ layers
    triploblastic
21
Q

What is Organogenesis?

A
  • organs develop from specific germ layers
  • first event in organogenesis is formation of the nervous system
    Formed from the ectoderm
  • heart is the first functional organ
    Formed from the mesoderm
    Starts beating on day 2 of development in the chick embryo
22
Q

What is growth?

A
  • final phase

- longest phase in animal development

23
Q

Categorizing Metazoans

A

1) Number of germ layers (diploblastic, triploblastic)
2) Presence and formation of coelom
3) Cleavage pattern
4) Body symmetry
5) Mechanism of development

Organisms 2 (23 decks)

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