{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Chapter 30 - Chapter 30 Plant Diversity II The Evolution of...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 30 - Plant Diversity II: The Evolution of Seed Plants Chapter 30 Plant Diversity II: The Evolution of Seed Plants Lecture Outline Overview: Feeding the World The seed arose about 360 million years ago. o Seed plants, including gymnosperms and angiosperms, have come to dominate modern landscapes and make up the great majority of plant biodiversity. Agriculture, the cultivation and harvest of plants (especially angiosperms), began 13,000 years ago. o Humans began the cultivation of plants independently in various regions, including the Near East, East Asia, Africa, and the Americas. o This was the single most important cultural change in the history of humanity, and it made possible the transition from hunter-gatherer societies to permanent settlements. Concept 30.1 The reduced gametophytes of seed plants are protected in ovules and pollen grains A number of terrestrial adaptations contributed to the success of seed plants. o These adaptations include the seed, the reduction of the gametophyte generation, heterospory, ovules, and pollen. Bryophyte life cycles are dominated by the gametophyte generation, while seedless vascular plants have sporophyte-dominated life cycles. The trend to gametophyte reduction continued in the lineage of vascular plants that led to seed plants. o Seedless vascular plants have tiny gametophytes that are visible to the naked eye. o The gametophytes of seed plants are microscopically small and develop from spores retained within the moist sporangia of the parental sporophyte. In seed plants, the delicate female gametophyte and the young sporophyte embryo are protected from many environmental stresses, including drought and UV radiation. o The gametophytes of seed plants obtain nutrients from their parents, while the free- living gametophytes of seedless vascular plants must fend for themselves. Heterospory is the rule among seed plants. Nearly all seedless plants are homosporous, producing a single kind of spore that forms a hermaphroditic gametophyte. o Seed plants likely had homosporous ancestors. All seed plants are heterosporous, producing two different types of sporangia that produce two types of spores.
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
o Megasporangia produce megaspores, which give rise to female (egg-containing) gametophytes. o Microsporangia produce microspores, which give rise to male (sperm-containing) gametophytes. Seed plants produce ovules. In contrast to the few species of heterosporous seedless vascular plants, seed plants are unique in retaining their megaspores within the parent sporophyte. Layers of sporophyte tissue, integuments, envelop and protect the megasporangium. o Gymnosperm megaspores are surrounded by one integument. o Angiosperm megaspores are surrounded by two integuments.
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern