Plant Diversity

General Characteristics of Plants All plants are:

Eukaryotic Autotrophic Multicellular Cell Walls with cellulose Chloroplasts w/ chlorophyll

a, b, and carotenoids May have waxy cuticle to

prevent water loss. Stomata allow gas

exchange. Plants probably evolved

from green algae (charophytes) Chloroplast similarity Biochemical similarities Cell Wall similarities

Charophytes v. Plants

No alternation of generations

No cuticle needed Jacketed gametes No protection of

embryos

Alternation of generations

Cuticle (prevents water loss/dessication)

Jacketed gametes (protects from dessication)

Protected embryo

(protects from dessication)

Alternation of Generations

Sporophyte (2N)

Meiosis

Gametophyte (N)

Zygote (2N)

Spores (N)

Gametes (egg & sperm

fertilization

Mitosis

Evolutionary Trend

zygote

SPOROPHYTE (2n)

GAMETOPHYTE (n)

GREEN ALGA BRYOPHYTE FERN GYMNOSPERM ANGIOSPERM

Figure 23.2Page 386

Classifying Plants Plants can be divided into 2 major categories based

on their characteristics: Nonvascular Plants

Do NOT have specialized tissues to transport water and nutrients

Instead, these plants transport water from cell-to-cell by osmosis

Vascular Plants Have specialized tissues to transport water and nutrients in

plants Xylem – carries water upward from roots Phloem – carries nutrients and carbohydrates produced by photosynthesis

Nonvascular Plants (Bryophytes)

Again, these plants do not have specialized tissues to transport water and nutrients and instead rely on osmosis Thus, these plants must be small Why?

Major types of bryophytes (nonvascular plants): Mosses Liverworts Hornworts

Nonvascular Plants/ Bryophytes

Mosses Have rhizoids that anchor

them to the ground (instead of roots)

Depend on water for fertilization The sperm must swim to the

egg Therefore, nonvascular

plants must live in MOIST environments

Gametophyte is the dominant phase of the life cycle

Moss/ Bryophyte Life CycleZygote grows, develops into a sporophyte while still attached to gametophyte.

Fertilization

zygote

sperm-producing structure

egg-producing structure

Diploid Stage

Haploid Stage

mature sporophyte

Meiosis

Spores germinate.

male gametophyte

female gametophyteFigure 23.5

Page 388

Vascular Plants/Tracheophytes

Reminder: Vascular plants have specialized tissues to

transport water and nutrients in plants Xylem & phloem

Vascular plants (tracheophytes) can be divided into 2 categories: Seedless vascular plants Seed (vascular) plants

Seedless Vascular Plants

Have true roots, leaves, and stems

Consist of ferns, club mosses, and horsetails

Seedless Vascular Plants

Ferns – A Close Up Diploid sporophyte is the

dominant stage Have rhizomes, which are

underground stems Fronds: large “leaves”

where spores develop Develop spores in

sporangia on underside of fronds

Reproduce using spores A sorus (plural: sori) is a

cluster of sporangia

Fern Life Cycle

Spores are released

Sporophyte still attached to gametophyte

zygote

fertilizationDiploid StageHaploid Stage

egg

sperm

mature gametophyte

Spores develop

meiosis

Spore germinates

rhizomesorus

Figure 23.9Page 391

Seed (Vascular) Plants Have true roots, leaves, and

stems Have the ability to form

seeds, which are used for reproduction

Seed plants are the most dominant group of photosynthetic organisms on land

There are 2 types of seed (vascular) plants: 1. gymnosperms 2. angiosperms

Seed (Vascular) Plants Gymnosperms = “cone bearers”

“naked seeds” – not enclosed in ovaries

Bear seeds directly on the surfaces of cones Cones = sporophyte

structures that produce gametophytes (seeds)

Coniferous trees are the major example Pines, junipers, spruces,

etc.

section through one ovule

ovule

surface view of one cone scale (houses two ovules)

section through a pollen-producing sac

surface view of one cone scale (houses a pollen-producing sac)

meiosisfertilization

seed coat

embryo

zygote

mature sporophyte

seeding

pollen tube

sperm-producing cell

eggs

female gametophyte

pollination

microspores form

megaspores form

seedDiploid

Haploid

Pine Life Cycle

Figure 23.17Page 396

Seed (Vascular) Plants Angiosperms = flowering plants

Seeds are enclosed by an ovary Flowers are reproductive organs

Evolutionary advantage attract pollinators

Flowering plants contain ovaries Ovaries surround and protect

seeds Ovary develops into a fruit after

pollination & helps with seed dispersal when eaten

Examples: Maple trees, tulips, grass

Flowering Plant Life Cycle

Double fertilization Meiosis Meiosis

microspores

female gametophyte

pollination

mitosis without cytoplasmic division

two sperm enter ovule

Diploid

Haploid

Figure 23.20Page 399

sporophyte

Evolutionary Tree for Plants

greenalgae

zygophytes, related groups

charophytes bryophytes lycophytes horsetails cycads conifersflowering

plants

seed plants

euphyllophytes

vascular plants

embryophytes (land plants)

(closely related groups)

ferns ginkgos gnetophytes

Nested monophyletic groups