Chapter 30

1. Chapter 30 Plant Diversity II: the evolution of seed plants

2. Section 30-1 • A lot of terrestrial adaptations contributed to the success of seed plants. • These adaptations include the seed, the reduction of the gametophyte generation, heterospory, ovules, and pollen. • Bryophyte life cycles are mainly dominated by the gametophyte generation, but seedless vascular plants mainly have sporophyte-dominated life cycles. • Seedless vascular plants have very small gametophytes however are visible to the naked eye. • The gametophytes of seed plants are VERY VERY small and develop from spores that are kept within the moist sporangia of the parental sporophyte.

3. COntinuation • Almost all seedless plants are homosporous, producing a single kind of spore that forms a hermaphroditic gametophyte. • It is thought that seeds most likely had homosporous ancestors • An important thing to remember is that all seed plants are heterosporous, producing two different types of sporangia that produce two types of spores. • Megasporangiamake megaspores, which produce a female (egg-containing) gametophytes. • Microsporangia on the other hand make microspores, which produce a male (sperm-containing) gametophytes.

4. Cont. • Seed plants produce ovules . • Layer over layer of sporophyte tissue, integuments, wrap , encase and help protect the megasporangium. • Gymnosperm megaspores are surrounded by one integument. • While on the other hand angiosperm megaspores are surrounded by two integuments. • An ovule is made of the megasporangium, megaspores, and integuments.

5. Cont. • The microspores develop into pollen grains that are released from the microsporangium. • The pollen grains are are covered with a tough coat that has sporopollenin. • Then they are carried by wind or animals and moved to a new location where pollination occurs. • The pollen grain germinates and grows as a pollen tube into the ovule, where it delivers one or two sperm into the female gametophyte.

6. Section 30-2 • The ovules and seeds of gymnosperms develop on the surfaces of modified leaves that usually form cones . • When in contrast, ovules and seeds of angiosperms develop in enclosed chambers called ovaries. • There are four different types of gymnosperms that I while discuss in the next couple slides.

7. Phylum Ginkgophyta • This is the smallest one out of all the groups because it only contains one species , Ginkgo biloba. • This is a popular ornamental species because of its fanlike leaves that turn gold in fall before they fall off. • Landscapers usually plant only male trees because the coats of seeds produced by female plants produce a repulsive odor as they decay. That smells really bad.

8. phylum Cycadophyta • the species in this phylum have have large cones and palmlike leaves. • As of right now 130 species of cycads are living right now with these characteristics . • They are the third largest phylum out of all four. • Cycads flourished mainly in the Mesozoic era, they even had it named after then as it became known as the “Age of the Cycads”

9. Phylum Gnetophyta • This phylum has three very different genera. • Weltwitschia plants, from deserts in southwestern Africa, have straplike leaves that are among the largest known leaves. Very weird and unheard of leaves but amazingly good. • Then there are the gentum species which are tropical plants and vines . • Ephedra is a shrub of the American deserts. • And those are the three genera .

10. Coniferophyta • This is the class that the confifers belong to . • The word and concept conifer comes from the reproductive structure, the cone, which is a bunch of scalelikesporophylls bunched together. • Although there are only about 600 species of conifers, a few species dominate vey big and broad forested regions in the Northern Hemisphere where the growing season is short. • Conifers include pines, firs, spruces, larches, yews, junipers, cedars, cypresses, and redwoods.

11. continuation • Most conifers are evergreen, retaining their leaves and photosynthesizing throughout the year pretty much meaning they never stop photosynthesis, and never really fall off. • Some conifers, like the dawn redwood and tamarack, are deciduous, dropping their leaves in autumn. Meaning that when autumn comes around they begin to lose there leaves.

12. Section 30-3 • Angiosperms, mainly known as flowering plants, are vascular seed plants that produce flowers and fruits. • They are the most unique and geographically spread of all plants, including more than 90% of plant species. • There are about 250,000 known species of angiosperms. • The phylum Anthophyta is the phylum that all angiosperms belong to. • The flower is a structure the angiosperms have adapted for very successful sexual reproduction.

13. Continuation • In the species of angiosperms, insects and other animals or the wind transfer pollen from one flower to female sex organs of another. • Most of the dense populations with a lot of the population in the same area of occurs because of wind pollination. • A flower is specialized to have up to four modified leaves on it : sepals, petals, stamens, and carpals. • The sepals are around at the base of the flower are modified leaves that are usually green and enclose the flower before it opens.

14. Continuation • The petals lie inside the sepals. • These are often brightly colored in plant species that are pollinated by animals. • They usually lack bright coloration in wind-pollinated plant species. • Sepals and petals are sterile parts, not directly involved in reproduction. • Stamens which are the male reproductive organs, are sporophylls that make microspores that will being to make pollen grains containing male gametophytes.

15. continuation • Carpals are female sporophylls that produce megaspores and their products, female gametophytes. • At the tip of the carpal is a sticky thing that receives pollen. • A style leads to the ovary at the base of the carpal. • Ovules are protected inside the ovary,

16. 30-4 • Like other organisms, we depend on photosynthetic organisms for food production and oxygen release. • However, we use technology to manipulate or select plants that maximize the harvest of plant products for human use. • We rely on seed plants for food, fuel, wood, and medicine. • Flowering plants provide nearly all our food. • Just six crops—wheat, rice, maize, potatoes, cassava, and sweet potatoes—yield 80% of all calories consumed by humans. • Modern crops are the products of a relatively recent burst of genetic change, resulting from artificial selection after the domestication of plants 13,000 years ago. • In maize, key changes such as increased cob size and removal of the hard coating of the kernels may have been initiated by as few as five gene mutations.