Chapter 30 Notes Plant Diversity II: The Evolution of Seed plants

Concept 30.1 Seed plants are vascular plants that produce seeds Sporophyte is the dominant generation - becomes diploid and can carry recessive alleles from one generation to the next

All seed plants are heterosporous Megasporangia: produce megaspores that will produce female (egg- containing) gametophytes Microsporangia: produce microspores that will produce pollen grains (sperm- containing) gametophytes The transfer of pollen to the part of the seed plant containing the ovules is pollination.

Concept 30.1 Layers of sporophyte tissue called integuments envelop and protect the megasporangium The developing embryo is encased in a protective seed coat and supplied with its own source of food (endosperm or cotyledons)

The whole ovule develops into a seed, which consists of the embryo, along with a food supply, packaged within a protective coat derived from the integuments.

Seeds allow the embryo to be moved away from the parent by wind, water, and animals Seed plants are not tied to water for fertilization like bryophytes are (have a flagellated sperm that must swim through a film of water to reach the egg cells); pollen grains do not need to be transported by liquid

This is an example of what type of seed movement? Helicopter seeds from a maple or a sycamore tree.

Gymnosperms are plants that have “naked” seeds that re not enclosed in ovaries. Gymnosperms lack enclosed chambers in which seeds develop; instead, seeds develop on the surfaces of specialized leaves called sporophylls, which usually form cones. About 900 species of gymnosperms are divided into 4 phyla: ginkgo, cycads, gnetophytes, and conifers

Phylum Ginkgophyta: - Ginkgo biloba is the only extant species - used in herbal medicine - produce pollen and seeds on separate trees (dioecious: “two houses”) - tolerates air pollution well - most only plant the pollen-producing trees because the fleshy seeds smell rancid when they decay

Phylum Cycadophyta: - about 130 cycad species - palm-like appearance (but not a palm) - seeds are often passed by beetles and bees - have large cones - thrived during the Mesozoic era which was known as the “Age of Cycads”, it was also the “Age of Dinosaurs”

Phylum Gnetophyta: - consists of three genera that are very different in appearance - Ephedra grows in U.S. deserts – some contain ephedrine, used as a decongestant - Welwitschia grow in Africa – has some of the largest leaves known - Gnetum are native to Africa and Asia; tropical trees, shrubs and vines

Phylum Coniferophyta: - conifer = “cone bearer” - called evergreens because they retain their needle-shaped leaves - male and female gametophytes appear on the same tree (monoecious: “one house”) - consists of more than 600 species Douglas Fir – Christmas Tree

Concept conifers are among the oldest and largest organisms on Earth - we get much of our lumber and paper pulp from conifers - Pacific Yew bark is a source of taxol (female cancer treatment)

Sequoia Juniper Pacific Yew

Wollemia pine – thought to be extinct – only 40 known individuals in Syndey, Australia Bristlecone Pine Sequoia

Phylum Anthophyta: - all angiosperms are placed in one phylum - The flower is an angiosperm structure specialized for sexual reproduction Two classes: monocots and dicots - monocots: orchids and grain crops - dicots: roses, peas and maples

- all are heterosporous - gametophyte is greatly reduced reproductive parts of the flower male parts: stamen contains the anther (where pollen is produced) and filament (stalk) female parts: carpel contains the stigma (sticky end that receives pollen), style (leads to the ovary at the base of the carpel, and ovary

Know this!!!

- after fertilization, the ovule develops into a seed; the endosperm is retained in the cotyledon - A fruit consists of a mature ovary - As seed develop from ovules after fertilization, the wall of the ovary thickens - A pea pod is an example of a fruit, with seeds (mature ovules – peas) encased in the ripened ovary (the pod) - Fruits protect dormant seeds and aid in their dispersal

The wall of the ovary becomes the pericarp, the thickened wall of the fruit. As the ovary grows, the other flower parts wither away. Mature fruits can be fleshy or dry.

Angiosperm Diversity Grouped based on the number of cotyledons or seed leaves in the embryo. One cotyledon – monocot Two cotyledons – dicot

Mono and Dicot Characteristics Mono – parallel veins (grass blade) Di – netlike pattern (oak leaf) Mono – vascular tissue scattered Di – vascular tissue in rings Mono – usually fibrous root Di – usually tap root Mono – floral organs usually multiples of 3 Di – floral organs usually multiples of 4 or 5

No group of plants is more important to our survival than seed plants. In forests and on farms, seed plants are key sources of food, fuel, wood products, and medicine. Our reliance on them makes the preservation of plant diversity critical. Most of our food comes from angiosperms Just 6 crops – wheat, maize, potatoes, cassava and sweet potatoes yield 80% of all calories consumed by humans.

We depend on angiosperms to feed livestock: it takes 4.8 kg of grain to produce 1 kg of grain-fed beef. Almost all of our food is based on the cultivation of only about 2 dozen species Fewer than 5000 plants species has been studied for their potential source of medicines Plants are going extinct before we know the benefits of them.