PLANTS: to move on to land, plants had to make adaptations for obtaining water 1. Dominant generation of all plants is the diploid sporophyte generation. (more apt to survive genetic damage b/c of two copies of each chromosome; recessive mutations can be masked 2. Have a cuticle = waxy covering to prevent desiccation

3. Development of a vascular system helped to reduce a plant’s dependence on water (* tissues became specialized) 4. Primitive plants required water for the flagellated sperm to swim to the eggs (more advanced plants have sperm packaged as pollen for delivery by wind or animals) 5. Some plants have developed adaptations to seasonal changes in water and light.

Vascular Plants That Produce Seeds: A. Gymnosperms:(“naked seeds”) seeds produced in unprotected megaspores near the surface of the reproductive structure * large mother cell which divides by meiosis to produce 4 haploid cells * one of these cells becomes a megaspore = becomes 2 eggs

Coniferophyta: conifers=cone-bearing Ex. Pines, firs, spruces, junipers, redwoods, cedars reproductive structures are borne in pollen-bearing male cones and female ovule bearing cones

B. Angiosperms: (anthophyta) flowering plants carpel (pistil)=female reproductive structure: ovary, style, stigma stamen=male reproductive structure: anther and filament petals and sepals= functions to attract pollinators

Flower is an evolutionary advancement b/c: designed to attract pollinators (insects and birds) ovules are protected by the ovary (fruit ovary develops into fruit to help disperse seeds by insects, birds, and other animals

stamen = produces pollen stigma = sticky ends receive pollen ovary = protects ovules which develop into seeds after fertilization

Fertilization in Angiosperms: Pollen lands on sticky stigma. Pollen tube (elongating tube containing the vegetative nucleus or tube nucleus) grows down the style towards an ovule. There are two sperm cells inside the pollen tube. Ovules are a megaspore mother cell and 3 cells that disintegrate into integuments (membranes). The megaspore mother cell has two nuclei. micropyle = opening through integuments for pollen to access the egg