BIOL 112 Lecture 23

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Angiosperms

(seeded) flowering plants

The flower

evolved from mutated sporophylls of early ancestor

Male parts
anther + filament = stamen
Pollen grains have 2 sperm (c.f. gymnosperms = 1)
microsporocyte (2n) → microspores (n) → gametophyte (2 sperm, 1 tube cell)
Female parts
stigma + style + ovary = carpel
megasporocyte (2n) → macrospore (n) →

Ovary of flower becomes fruit, and ovules become seeds.

Double Fertilization

sperm (n) + egg (n) = zygote (2n) (does the usual job)

sperm (n) + 2 × polar cells (n,n) = endosperm (3n) [1]


Kingdom Animalia

  • invertibrates (no notochord, no backbone)
  • invertibrate chordates (notochord, no vertebrae)
  • vertebrate chordates (notochord, vertebrae)

There are 1.3 M known animal species (estimated 10–100 M)

Defining Characteristics

  • multicellular
  • ingestive heterotrophic
  • blastula — hollow sphere of cells during embryonic development
  • gastrulation (infolding of blastula) to create multiple germ layers
    • triploblast: (mesoderm [2], endoderm [3], ectoderm [4])
      • Protostome: mouth forms from blastopore, spiral embryonic cleavage, determinant (fates set early) stem cells, schizocoelous [5] mesoderm
      • Deuterostome: anus forms from blastopore, radial embryonic cleavage, indeterminant (fates remain flexible) stem cells, endocoelous [6] mesoderm
    • diploblast: (endoderm, ectoderm)
  • Hox genes — define anterior-posterior axis

Footnotes

  1. ↑ the endosperm serves as a source of food and energy for the developing plant embryo. Equivalent to megasporangium in gymnosperms.
  2. ↑ mesoderm becomes muscle, cartilage, bone, circulatory system, and gonads
  3. ↑ endoderm becomes the gut, respiratory system, and other internal organs
  4. ↑ ectoderm becomes skin and nervous system
  5. ↑ schizocoelous mesoderm splits off at the base of the blastopore
  6. ↑ endocoelous mesoderm buds off the archenteron, or endoderm lining
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