Plants exhibit alternation of generations. make by . (sexual phase) make by . (asexual phase)

Asexual reproduction permits a to rapidly exploit a uniform and static, or slowly changing environment. permits a species, over generations, to respond to and adapt to a changing environment.

Gymnosperms - , , , cedars, other cone-bearing . “Naked-seeded” plants. develop from . Ovules are on cone scales. Seeds sit on cone scales and are exposed or naked. Seeds are shed directly from open cones.

Angiosperms - flowering plants “Vessel-seeded” plants. Seeds develop from ovules. develops from . Large plant that we see is the . The generation is very reduced in size. The male gametophyte is the (microgametophyte). The gametophyte is the sac (megagametophyte) that is found inside the .

Pollen develop in the anther within the . Pollen is shed and transported to the of another flower. The pollen grain germinates and grows a through the stigma and style and into the ovary. The pollen tube grows into the ovule and penetrates the embryo sac. Two nuclei are discharged from the pollen tube. One sperm nucleus fertilizes the to form a diploid . The other sperm nucleus fertilizes the central containing two polar nuclei to form triploid . This is characteristic of angiosperms.

Pollination may be accomplished by: dissemination vectors .

Fruit and dispersal may be accomplished by: ingestion/defecation animal hoarders/dispersers dispersal wind dispersal animal carriers. Plants may have different spans: annuals - complete their life cycle in one year biennials - complete life cycle in two years - grow vegetatively first year, flower second year perennials - live for many years.

Perennials survive winter by: removing and from , storing in stems and remove excess water from cells, add anti-freeze type compounds to cells cover vulnerable stem tips with winter , insulating tip with overlapping scales.

Changes are triggered by decreasing and/or shortened day lengths.