Chapter 30 Seed Plants 1 Reproductive adaptations for bryophytes a Gametophyte of seed plants is reduced it is retained within the sporophyte reversed b Diploid stage sporophyte is dominant potential adaptation to life on land c exposure to UV light can damage DNA diploidy may provide some protection spare set if one is damaged 2 Seed replaces the spore as the main mechanism of dispersal unlike seedless vascular plants and a Seed differs from a spore multicellular complex resistant to harsh conditions has its bryophytes own food supply b Sporophyte produces spore micro or megaspore all seed plants are heterosporous c Gametophyte develops within walls or spore ovule or pollen 3 Pollen replaces swimming sperm 9most gymnosperms and all angiosperms lack flagellated sperm a Fertilization can occur without water b Carried by wind or animals 4 Major groups a Gymnosperms naked seeds i Lack ovaries found in angiosperms no fruit lack flowers ii Have 2 extant phyla 1 Ginkophyta 2 Cycadophyta 3 Gnetophyta 4 Coniferophyta b Coniferophyta cones i Pines firs spruce cedars cypress redwoods ii Have cones male staminate and female ovulate 1 Sporangia packed on scales form spores mega micro gametophytes 2 Most are evergreen can photosynthesize even in winter limited extent read beginning of spring no delay for leaves to grow 3 Needles adaptation to dry conditions iii Very large some of the tallest trees iv Have very old bristle cones c Male staminate cones d Female ovulate cones megasporangia 5 Angiosperms a Phylum Anthophyta i Flowering plants which are most plants b Major Differences from gymnosperms i Xylem has vessel elements rather than just tracheids in gymnosperms ii Flower iii Flower reproductive structure carpel pistil ovary style stigma stamen filament anther 1 Led to coevolution of pollinator plants a Major radiation seed is enclosed in ovary 6 Classification a Anthophyta i Monocots corn grasses palms lilies corn wheat rice ii Dicots 2 cotyledons now thought to be paraphyletic 1 1 cotyledon 2 Flower part in 3s 3 Parallel leaf veins 4 Vascular bundles scattered 1 Most dicots are in the eudicots 2 Flower parts in 4s and 5s 3 4 Vascular bundles in a ring Leaf veins not parallel netted 7 Impact of plants a Most lumber from gymnosperms b Most agricultural products are angiosperms c Major sources of medicine d e Form soil roots break up rock free up mineral f Impact on CO2 levels in atmosphere dropped after plants colonized land Structure for ecosystem plants determine the animal fauna found climate determines the plants plants affect climate