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Lecture #13 Date ________ Lecture #13 Date ________

Chapter 30 ~Plant Diversity II:

The Evolution of Seed

Plants

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Seed Plant Reproductive AdaptationsSeed Plant Reproductive Adaptations

Reduction of the gametophyte: shift from haploid to diploid condition; female

gametophyte and embryo remain in sporangia (protection against drought and

ionizing radiation on land?)

Advent of the seed multicellular sporophyte embryo with food supply and

protective coat; heterosporous (two types of spores): megaspores--->female

gametophyte--->eggs; microspores---> male gametophyte--->sperm Evolution of pollen: develop from microspores which mature into the male

gametophytes; resistant and airborne for a terrestrial environment; eliminated

water (sporopollenin coats)

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GymnospermsGymnosperms

Cone-bearing plants

Lack enclosed chambers

(ovaries) for seeds

Ovules and seeds develop onspecialized leaves called

sporophylls

Ginkgo, cycads, and conifers

All are evergreens

Needle-shaped leaves Vascular tissue refinement:

tracheids~ water conducting

and supportive element of

xylem

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AngiospermsAngiosperms

Most diverse and geographically widespread of all plants

Flowering plants(Phy:Anthophyta)

Monocots: 1 embryonic seed leaf (lilies, palms, grasses, grain crops)

Dicots: 2 embryonic seed leaves (roses, peas, sunflowers, oaks, maples)

Vascular tissue refinement: vessel elements/fiber cells

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The flower: the defining structure of angiospermsThe flower: the defining structure of angiosperms

Reproductive structure: pollen

transfer; specialized shoot with

modified leaves

Sepals: enclose flower beforeit opens

Petals: attract pollinators

Stamens: male; anther

(produces pollen), filament

Carpels: female; stigma, style,

ovary, ovules

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Seed to flowerSeed to flower Thepeduncle is the tip of the stalk where the

flower begins. The receptacle starts at the peduncle and acts

as a base to which all other parts of the

flower are attached. Sepals are leaf-like protective coverings ofthe bud that grow typically in an outer whorl.Collectively, they are called the calyx.

Petals are the inner whorl of leaves, and areknown collectively as the corolla.

Perianth is the term used when sepals andpetals are grouped together.

Pistils are the female organs. There can beone or more. There are three parts of the

pistil:

thestigma receives the pollen and is

sticky thestyle connects the stigma to the ovary the ovary is where seeds develop

Stamen are the male organs. The number ofstamen per flower varies. There are two partsof the stamen:

the antherproduces pollen the ilamentca s the anther

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Angiosperm lifeAngiosperm life

cyclecycle

Fruit (mature ovary); seeds

from ovules

Pollen grains: 2 haploid cells

(immature male gametophytes)

Ovules (female gametophyte~

embryo sac)

Double fertilization: 1 sperm

w/ egg = diploid zygote; othersperm w/ 2 nuclei in center of

sac = triploid endosperm