topic5 - BIOL 1030 TOPIC 5 LECTURE NOTES Topic 5: Seed...

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BIOL 1030 – TOPIC 5 LECTURE NOTES Topic 5: Seed Plants Overview; Gymnosperms (Ch. 30) I. Seed plants A. all are heterosporous vascular plants B. three major reproductive adaptations 1. gametophyte reduced to dependence on sporophyte; retained in moist reproductive tissue 2. seed – “baby plant in a lockbox with its lunch”; highly resistant structures that allow for a dormant phase in the life cycle to wait out poor environmental conditions 3. evolution of pollen as male gametophyte – many seed plants are no longer tied to external water for fertilization C. common ancestor with seeds gave rise to all seed plants (gymnosperms and angiosperms); together, gymnosperms and angiosperms are a monophyletic group D. fossil evidence indicates origins in progymnosperm group about 360 MYA E. gametophytes are completely dependent on parent sporophytes for nutrition and are composed of only a few cells 1. male gametophytes develop from microspores become pollen grains entire male gametophyte moved to the female as pollen grains cannot perform photosynthesis, depends on nutrients that came from the parent sporophyte 2. female gametophytes develop from megaspores within ovules ovule contains female gametophyte surrounded by nucellus (megasporangium) nucellus is surrounded by 1-2 integuments (cell layers that serve as protective covers) micropyle – opening in integuments (allows sperm to get in) cannot perform photosynthesis, depends on nutrients from the parent sporophyte 3. means of transporting sperm to egg varies, but typically uses a growing pollen tube that does not require outside water 4. moving pollen to vicinity of ovule called pollination ; agents include wind, animals F. seed develops from ovule 1. seeds are highly resistant structures that allow for a dormant phase in the life cycle to wait out poor environmental conditions 2. embryo protected by a seed coat , an extra layer of hardened tissue derived from sporophyte tissue in the ovule (sporophyte tissue from parent, not from embryo) enhanced protection from drought, cold, heat some protection from pathogens and predators external water only needed at germination initial food supply for germinating plant is enclosed
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topic5 - BIOL 1030 TOPIC 5 LECTURE NOTES Topic 5: Seed...

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