Evolution and Diversity of PlantsChapter 24

Evolution

Modern day plants evolved from freshwater green algal species● Evidence

o both contain chlorophyll a and bo store excess energy as starcho have cellulose cell walls

Stone warts are the closest DNA relative

Evolution had 4 major events

1-Nonvascular plants have multicellular embryos that are protected and nourished within structures that produce eggs

2- Seedless vascular plants- Vascular tissue conducts water and organic nutrients within its roots, stems, and leaves Approx- 430 million years ago

Evolution had 4 major events

3- Gymnosperms- Seeds produced in cones. These highly resistant structures are capable of waiting for a favorable environment before germinating. Approx- 400 million years ago4- Angiosperms- Seeds protected by fruits and the presence of flowers with a need for pollinators. Approx- 135 million years ago

Alternation of Generations

Alternation of Generations

2 multicellular individuals alternate, each producing each other.1. sporophyte (2n)- produces spores through

meiosis2. gametophyte (n)- produces gametes

Alternation of Generations

Meiosis produces haploid spores in sporophytes. Spores go through mitosis and become gametophytes. Zygotes go through mitosis to produce sporophytes

Alternation of Generations

Plants differ as to which generation is dominant.Archegonia→ female gametophyteAntheridia→ contain flagellated spermPollen Grains→mature sperm from seed plants

Other adaptations

Cuticles

Stomatas

Nonvascular Plants

● lack a specialized means of transporting water and nutrients

● lack true roots, stems, and leaves.● Bryophytes is used to describe nonvascular plants.● Gametophytes are the dominant generation.● Sperm must swim in film of water to archegonia.● May reproduce asexually, allowing them to live in harsh

environments

Hornworts- Phylum Anthocerophyta

“Herb”Live in moist, well-shaded treesMay have symbiotic relationship with cyanobacteriaCan reproduce asexually through fragmentation

Liverworts- Phylum Hepatophyta

Terrestrial, epiphytic, or aquaticMajority have leafy bodiesThallose grow on creek banks after a fire

Marchantia

Lower surface has hair like extensions called rhizoids.Rhizoids are for anchorage and limited absorption.Sexually and asexually reproduces.

Moss- Phylum Bryophyta

3 Distinct Classes:Peat MossTrue Moss Rock Moss

May live in almost any environment.

Moss reproduction

May reproduce asexually through fragmentation

Sexual reproduction is depicted to the right

Vascular Plants- Phylum RhyniophytaEarly vascular plants were homosporous

Dominant sporophyte generation has several characteristics that allowed for successful colonization of land

● Xylem- water and dissolved minerals upward● Phloem- sucrose and other organic materials

throughout the plant● Lignin- strengthens plants

Now seed plants are heterosporous.

Seedless Vascular Plants

Dominant through the Devonian period to the Carboniferous period

Club Moss- Phylum Lycophyta

Dominant generation is the sporophyteRhizome- horizontal underground stem3 genera:● Ground Pines-microphylls, homosporous ● Spike Mosses-macrophylls,

heterosporous● Quillworts-macrophylls, heterosporous

Horsetails- Phylum SphenophytaInhabit wet, marshy environmentsStrobilusBranchesNodeLeavesRhizomeRoots

Whisk Fern- Phylum PsilotophytaLive in southern climates as epiphytes or on the groundHave no leavesSporangia found on short side branches

Ferns- Phylum Pterophyta

Found in warm, moist, tropical regions

Fronds are leaves of ferns divided into leaflets

Can be used to remove formaldehyde from the air, expel tapeworms, and have medicinal value

Seed Plants-Devonian period-Seeds contain sporophyte embryo and stored food within a protective coat

● can remain dormant for hundreds of years-Heterosporous

● pollen grains contain multicellular male gametophyte

-No exterior water required for fertilization-Female gametophyte develops in ovule

Gymnosperms (naked seed)

- All have ovules and exposed seeds- Carboniferous period- became dominant

during Triassic period

Life cycle- see page 425 Figure 24.18

Conifers- Phylum Coniferophyta

- contains pines, spruces, firs- majority bear cones- phylum contains oldest tree and tallest

tree- tough needle-like leaves conserve water

due to thick cuticle and recessed stomata

Phylum Coniferophyta

- sporophyte generation is dominant- pollen is wind blown and seed dispersal is in dispersal stage

- monoecious- tree produces both pollen and see

- used in construction, as fungal and insect repellant

Cycad- Phylum Cycadophyta

- native to tropical and subtropical areas

- resemble palms- dioecious- risk for extinction

because of slow growth rate

Ginkgos- Phylum Ginkgophyta

- 1 surviving species- dioecious

Gnetophyta- Phylum Gnetophyta

- extremely diverse phylum- all have

- similar xylem- no archegonia (evidence to

support them being closest relative to angiosperms)

- cones have similar construction

Angiosperms

- ovules always enclosed within diploid tissues- DNA sequencing is being used to determine ancestry- 2 classes

- Monocotyledones- monocots- 1 seed leaf in seeds. Corn, tulips, and pineapples are examples

- Eudicotyledones- dicots- 2 cotyledones in seeds. Strawberries, cactus are examples.

Monocots DicotsOne Cotyledon Two Cotyledon

Flower parts in threes or multiples of three Flower parts in fours or multiples of fours

Usually herbaceous Woody or herbaceous

Usually parallel venation Usually net venation

Scattered bundles in stem Vascular bundles in ring

Fibrous root system Taproot system

Flower parts● Sepals- (calyx) protect the flower bud before it opens. May fall off

or remain attached. May be green or colored● Petals- (corolla) attract a particular pollinator. Very diverse● Stamens- consist of the anther, saclike, and filament (slender stalk)● Carpel- vaselike- made of stigma, enlarged sticky knob; style,

slender stalk; ovary, enlarged base that encloses one or more ovule. Ovule becomes seed and ovary becomes fruit

● Flowers may or may not have all the above parts (incomplete)

Life cycle- see page 430Figure 24.26