gymnosperms and angiosperms

• Gymnosperms (cones)

  • redwoods, pines, sequoia
  • Ginkgophyta, Cycadophyta, pinophyta (pine trees)
  • cones: develops seeds
  • bristle cone pine: oldest trees 4000 years old, trunks are mostly dead, other side has phloem
  • Cupressophyta: cypress trees
• Gymnosperms: one major innovation

  • size reduced and complexity of the gametophyte (no longer free living)
  • non-motile male gametes removes water in fertilization
  • evolution of the seed: embryo of the sporophyte in a protective package that has food supply
• Gymnosperms: Alternation of generations

  1. mature sporophyte (2n): has cones with microsporangia and ovulate
  2. meiosis of microsporangia creates microspore (n); mitosis: pollen grain forme (male gametophyte)
  3. meiosis of ovulate cone creates ovules in megasporangia; 2nd meiosis: creates megasporangium with mother cell (2n)
  4. pollination of pollen grain in megasporangium: pollen grains carry sperm
  5. fertilization mitosis: creates embryo (2n)
  6. meiosis disperse with wind or animals
  7. a sporophyte develops then becomes a mature sporophyte (2n)
• homosporous is only one type of spore
• heterosporous separate male and female spores
• microsporangia is where meiosis occurs to make male spores
• megasporangia is where meiosis occurs to make female spores
• megaspore is a female spore
• microspore is a male spore
• ovule is a structure that contains the female gametophyte
• pollen is an immature male gametophyte
• seed: an embryo surrounded by nutritive tissue and a tough outer shell
• evolution trends in Gymnosperms

  1. heterosporous: megaspore (female), microspore (male)
  2. Fertilization doesn't use water: releases sperm (not motile) via pollen tube
  3. female gametophyte is not free living: protected by sporophytic tissue
  4. seed protects and provides food
• Angiosperms: Alternation of genes (flowers) (part 1)

  1. Flowers Mature sporophyte (2n), meiosis of top of stamen: creates microspore (n), mitosis: forms pollen grain (male gametophyte)
  2. meiosis bottom of carpel: creates megasporangium, meiosis of megasporangium (ovule, ovary), mitosis of megaspore (n) creates female gametophyte (in ovary)
• Angiosperms: Alternation of genes (flowers) (part 2)

  1. pollination: pollen grains disperse by wind or animals to ovary
  2. double fertilization: creates endosperm (3n) forms nutritive tissue in seed, mitosis: fruits develops from ovary wall
  3. seeds disperse, develop sporophyte, grows into mature sporophyte (2n) flowers
• seeds

  • able to move by water or wind, can develop any time
  • endosperm: food supply, gives nourishment to embryo to grow; megagametophyte
  • embryo (2n): fertilized, next generation
• Basic parts of a flower

  • carpel: female part, tube for ovary
  • ovary: has ovules, becomes fruit
  • pollen goes down ovule
  • Anther: makes sperm (microspore)
  • pollen: lands on stigma
  • stigma: opening for pollen
  • stamen: male part
• stamen: anther, filament
• carpel: stigma, style, ovary
• Angiosperms

  1. smaller gametophyte
  2. double fertilization: embryo and extra nutrient (endosperms)
  3. flowers and fruits: most successful group, able to manipulate animals
• Why are angiosperms successful?

  • improvement of morphological structures: vascular tissue
  • mature more rapidly, competitive advantage
  • weeks in comparison to 100's of genes
  • fruits attracts animals: seeds don't get digested
  • pollination mechanisms (efficient): flowers attract pollinators; nectar = reward