19.4%20Pollen%20and%20Seeds%20Evolved%20in%20Gymnosperms

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19.4 Pollen and Seeds Evolved in Gymnosperms

• Gymnosperm adaptations
• Gymnosperms plants that bear seeds that are
  naked
• Not enclosed in an ovary
• Most common - conifers

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3 more adaptations than ferns

• 1. Smaller gametophyte
• Dominant generation diploid sporophyte pine
  tree
• Tiny gametophytes are in cones- protection
• 2. Pollen
• Reduced male gametophyte
• Contain cells that become sperm
• Wind pollen from male to female- no water
  needed
• 3. Seeds
• Plant embryo with a food supply in a protective
  coat

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Life Cycle of Gymnosperms

• Male pollen cone - spore sacs with haploid
  spores become pollen grains (male gametophyte)
• Female gametophytes develop within ovules
• On scale of cone 2 ovules
• Large spore cell meiosis
• 4 haploid cells 1 survives? female gametophyte

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• Wind blows pollen between trees
• Pollen lands in female cone
• Sperm matures and fertilizes egg in female
  gametophyte
• 2 eggs fertilized often still only 1 zygote
  into embryo (seed) new sporophyte

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Diversity of Gymnosperms

• 4 phyla today
• Gingkos
• Gingko biloba
• Fan-like leaves
• Shed in autumn
• Cities-
• Tolerates
• pollution

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• Gnetophytes
• Mormon tea, desert shrub

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• Cycads large, palm-like leaves
• Not true palms which are flowering plants

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• Conifers
• Spruce, pine, fir, junipers, cedar, redwood
• evergreen

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19.5/20.1 Flowers and fruits evolved in
angiosperms

• Angiosperm Adaptations
• Gametophytes develop in flowers of sporophyte
• Flower specialized type of plant shoot that
  functions in reproduction, only in angiosperms
• Attract animal pollinators variety
• Insects transfer pollen between flowers
• Grasses wind pollinated small flowers

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Flower Anatomy

• Flower specialized shoot
• 4 rings modified leaves
• Sepals protect flower bud
• Petals color insects
• Stamens male, many
• Carpels (pistils) female,1

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Stamen produces male gametophytes

• Filament anther
• Filament supports anther
• Anther pollen
• meiosis spores pollen grains male haploid
  gametophytes
• Each pollen grain 2 cells with thick protective
  wall
• Fig 20-2 in packet

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Carpels female gametophytes

• stigma style ovary
• Stigma sticky pollen
• Style supports stigma pollen tube
• Ovary - ovules

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Angiosperm Life Cycle

• Pollen on stigma - pollination
• Pollen tube to ovule in ovary - style
• 2 sperm cells in pollen grain in tube
• In ovules diploid cell
• meiosis
• 4 haploid spores ¾ die
• survivor enlarges 3 cycles mitosis ? embryo sac
  7 cells (1 egg cell 1 large cell with 2
  haploid nuclei)

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Water lilies
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Star Anise
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• 1st sperm fertilizes 1 egg zygote ? embryo
• 2nd sperm fuses with nucleus in larger center
  cell ? triploid cell endosperm (nutrient
  storage)
• double fertilization zygote and endosperm
  develop into seed

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• Many ovules, many seeds
• Seeds develop, ovary wall thickens? fruit
• Fruit ripened ovary of a flower
• Protects, disperses seeds
• Colorful, attract animals, eat, digest, waste

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• Monocots day lilies, orchids, irises, palms,
  grasses
• Flower petals multiples of 3
• Dicots poppies, roses, peas, sunflowers, oaks,
  maples
• Flower petals multiples of 4 or 5

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Human Dependence on Angiosperms

• Food human, domestic animals
• Corn, rice, wheat, fruit, vegetables
• Furniture, medicines, perfumes, decorations,
  clothing fibers
• Threat tropical rain forest

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20.1 Reproductive Adaptations contribute to
angiosperm success
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Seed Development and Dispersal

• Seed parts
• Seed coat outer layer protects embryo and
  endosperm
• Mini root and shoot
• Cotyledon food storage
• Monocot, dicot

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Seed Dispersal

• Animals
• fur burr
• Eat, digest fruit, waste
• Water coconut
• Wind - dandelion

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Seed Germination

• Plant embryo grows in favorable conditions
• Soak up water
• Expands
• Seed coat splits

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Adaptations to Germination

• Dicot hooked shoot tip
• Monocot sheath around shoot tip
• Light 1st leaves photosynthesis seedling

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Environment needed for Germination

• Usually just warm, moist
• Others
• Heavy rainfall soil
• Long cold
• Intense heat - clearing

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Challenges to sexual reproduction

• Pollination
• Damaged seeds
• Bad environment for germination
• Delicate seedlings eaten, water

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Asexual Reproduction in Plants

• Vegetative Propagation offspring identical to
  parent
• Cacti- drop stems
• Strawberries - runners

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Lifespan

• Annuals one growing season
• Biennials 2 years
• Perennials multiple years

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