BIOL 112 Lecture 23

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Angiosperms

(seeded) flowering plants

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.

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

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

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

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

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