Theme 5 Flashcards

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1
Q

In animal reproduction, new individuals are produced by:

A

Existing individuals

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2
Q

Animal Reproduction

A
  • Generally involves dominant diploid stage producing haploid gametes, which fuse to produce a new diploid zygote
  • Zygote must undergo growth and differentiation
  • Cells that give rise to gametes are generally isolated early in development
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3
Q

Asexual Reproduction

A
  • Genes from one parent
  • Fission
  • Budding
  • Fragmentation
  • Parthenogenesis – develop from an unfertilized egg
  • Based upon mitosis
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4
Q

Asexual Reproduction Pros

A
  • Don’t need males
  • Rapid reproduction
  • Saves energy
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5
Q

Asexual Reproduction Con

A

Lack of genetic variability

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6
Q

Sexual Reproduction – genes from two parents

A
  • Eggs (oogenesis) and sperm (spermatogenesis) are the gametes
  • Dioecious (gonochoristic)
  • Monoecious/hermaphrodite (simultaneous vs sequential hermaphrodites)
  • Fertilization and development
  • Based upon meiosis
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7
Q

Sexual Reproduction Pro

A

Generates genetic variation

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8
Q

Sexual Reproduction Cons

A
  • Fertilization necessary - complicated
  • Development must proceed from zygote
  • Costs of eggs and sperm
  • Males don’t produce offspring
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9
Q

Spermatogenesis

A
  • Sperm cells are highly modified and simplified
  • Mitochondria provide ATP for the flagellum
  • Head consists of acrosome, nucleus, centrioles
  • Male strategy is to produce abundant small, motile, cheap gametes
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10
Q

Oogenesis

A
  • Egg contains a large amount of cytoplasm, organelles, stored nutrients (yolk)
  • Contained within the vitelline membrane (zona pellucida) – carries receptors for sperm
  • May be wrapped within a jelly layer, hard shell
  • Female strategy is to produce a few large, well-provisioned gametes
  • Forced by male strategy
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11
Q

Hermaphroditism

A
  • The adult organism possesses functional reproductive systems of both sexes, either simultaneously or sequentially
  • Common in some taxa (annelids, gastropods)
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12
Q

Fertilization and Early Development

A
  • Bringing sperm and egg together
  • The one, right sperm, for the egg
  • Protection of the developing embryo
  • Events in early development
  • Cleavage, blastula, gastrula (tissue layers)
  • Chordate (vertebrate) development
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13
Q

Fertilization 1bringing sperm and egg together

A
  • Diploid is the dominant life cycle stage (usually)

Fertilization:

  • External fertilization (e.g. broadcast spawning)
  • Internal fertilization
  • Aquatic vs terrestrial environments
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14
Q

External Fertilization

A
  • Only in aquatic animals
  • Gametes small, high mortality
  • Release of gametes by both sexes into the environment requires coordination of gametogenesis in response to seasonal environmental cues
  • Coordinated gamete release may be due to stimulus through courtship movements, calls, or pheromone release
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15
Q

Internal Fertilization

A
  • Large differences in gamete size
  • Copulation: generally requires copulatory organ
  • Spermatophore: package of sperm and mucus must be introduced into female’s reproductive tract
  • Stronger sexual dimorphism
  • Terrestrial and aquatic organisms
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16
Q

Fertilization 2one sperm and the right sperm for the egg

A

Challenges for internal vs external fertilization – making sure that the right sperm encounters the egg, and that only one sperm fertilizes it

  • External fertilization: possibility of interspecific sperm-egg encounters (timing of breeding, molecular mechanisms of identifying appropriate sperm)
  • Internal fertilization: pre-and post-zygotic isolating mechanisms (behavioural, physical constraints, genetic incompatibility)
17
Q

Acrosomal Reaction (fast block)

A

Sperm cell membrane fuses with egg cell membrane, initiates wave of depolarization – subsequent sperm can’t fuse with egg = external fertilization

18
Q

Cortical Reaction (slow block)

A

Cortical granules fuse with egg membrane, vitelline coat becomes impenetrable to sperm = external and internal fertilization