Chapter 25: Plant Evolution

Plant Characteristics

-Multicellular

-Photosynthetic

-Primarily live on land

-First Clade: Green Algae

Common Features Land Plants (6)

1. Photosynthesis

2. Cellulose Cell Walls

3. Chlorophyll pigments a & b

4. Common enzymes

5. Common sperm structure

6. Starch and carbon storage

Terrestrial Adaptations (Tissues)

Adapt: Water-retention and gravity

-Tissues arose from apical meristems at growing tips

-Lower S.A. / Volume ratio - dec. water loss

-Special functions

-robust against drought/stress

Land Plant Evolutionary Trends

High diversity, generally sessile, land based (exc: Sea grasses), Alternation of generations

Life Cycle: Alternation of Generations

-Alternate between haploid + diploid phases

-Happens when both faces are multicellular

Plant Reproduction: Differences from animals

Multicellular haploid/diploid over unicellular sperm/eggs

Sporophytes = Diploid + reproduce asexually

Gametophytes: Haploid + reproduce sexually

Simplest to most complex plants:

Gametophytes has been reduced and sporophyte has become more prominent

Bryophytes -> vascular seedless plants -> angiosperms (flowering plants)

Sporopollenin: Key adaptation of land plants

Def: Highly resistant polymer that protects spores/pollen against drying/decay

-Tough spores allow plants to disperse offspring through dry air (sporangia for land plants/Gametangia for gametes)

Gametangia: Key adaptations of land plants

Def: Multicellular structures that enclose gametes + prevent them from drying out

Antheridia v. Archegonia (Gametangia)

Antheridia: Haploid sperm

Archegonia: Haploid eggs

Embryos: Key adaptations of land plants

Def: Young plants (new sporophytes) contained within a protective structure

-Not present in green algae, only land plants (embryophytes)

Nine Phyla of Land Plants

1. Liverworts

2. Mosses

3. Hornworts

4. Lycophytes

5. Pteridophytes

6. Cycands

7. Ginkgos

8. Conifers

9. Flowering plants

1-3 = Bryophytes

Bryophytes (6 facts + Who)

1-3: Mosses, liverworts, hornworts

-Damp Environments

-Earliest plant; nonvascular

-Lack roots; simple tissue transports, no structural support

-No seeds

-Gametophyte Dominant

-H20 for sexual reproduction

Lycophytes + Pteridophytes

-Oldest phyla, seedless, vascular plants

-Posses stems, roots, leaves

-Lignified cells = strength, transport H20 against gravity; tracheophytes

-Non-lig -> Lignified tracheids -> Lig. Vessels (flowering)

-Dominated by diploid sporophyte (produces many spores)

ex: Horsetails, Ferns

Vascular tissue system components

Xylem: Tissue carries water + minerals from roots to plant

Phloem: Alive at maturity, transports carbohydrates (sucrose)

Cuticle: Waxy coating external to cell wall; limits H20 loss

Stomata: Closable openings that regulate gas exchange + H20 loss

Lignified vascular elements

Plants can grow larger, remain metabolically active longer through internal water content in dry habitats

Lycophytes/Pteridophytes

Evolution of seeds

-Gymnosperms replaces seedless vascular plants

-Seeds protect embryos contain carbs, lipids, and protein that helps growth/development

-seeds produce pollen (small spores that contain male gametophytes)

Gymnosperms (6-8)

Def: Lack flowers, fruits, endosperm, egg and sperm in cones, moist environments

-Naked Seeds, pollen carried by wind, embryo encased in seed

Contain: Cycads, Ginkgos, Gnetophytes/Conifers

Female Cones

Seed bearing, complex, ovule

Male Cones

Pollen bearing

Angiosperms

-Flowers, Fruits, endosperm, Vessel Seeds

-Most dominant, use animals to spread pollen + fruits -> seeds

Inherited Traits from Gymnosperms: Produce wood (from xylem) and seeds

Cycads

Earliest diverging modern gymnosperm phylum, many are endangered, palm like leaves

Ginko Biloba

Nearly extinct in wild, city streets -> tolerant to heat, cold, and pollution

Conifers

Seed cones; most diverse gymnosperm, common in cold/dry climates (many adaptations)

-Needle shaped leaves (water loss), evergreen (retain leaves in winter)

Lifecycle of conifers + Phylum (3 subgeneres)

Produce simple pollen cones + more complex ovule bearing cones

Gnetales Phylum:

1. Gnetum: unusual broad leaves, Africa or Asia

2. Ephedra: Arid regions of Southwest US, adaptations to conserve H20

3. Welwitschia: Grows in costal Namib desert of SW africa

Inflorescences

-Groups of flowers

-All parts derived from modified leaves

Perianth:

-Sepals: Often protect unopened buds

-Petals: Attract pollinators

Flower Structure

Carpels: Bear female Magasporangia

Stamens: Bear male miscrosporangia (anther, filament)

Carples: Stigma, style, ovary, ovule

Pistil: May be composed of one or several fused carples

Perfect/Imperfect Flowers

Perfect: Both megasporangia + Microsporangia

Imperfect: Male/Female distinctions

-Monoecious: M and F flowers occur on same plant

-Dioecious: M/F Flowers produced on diff plants

Double Fertilization

Angiosperms reproductive process

Monocots / Eudicots

Two large / diverse angiosperm lineages

Monocots: 1 Cotyledon

Ex: Grasses, cattailes, lilies, orchids, palms

Eudicots (2 Cotyledons): most familiar seed plants

Wind to Animal Pollination

Animal costs the plant more but it is more targeted and leads to symbiotic relationship

No perianths -> Complex perianths

Conifers -> Angiosperms (Seed Components)

Naked seeds -> Seeds inside fruits

Cereal Grains (wheat): Endosperm, embryo, seed coat (bran, inner, dry fruit ovule outer wall)

Refined Foods: lack embryo/bran

Coevolution

Between animals and flowering plants

-Fused petals form tube flowers that grant access to certain species

-Timing of flowering targets other species

Fruits (development? Job? Vegetables?)

-Develop from ovaries after fertilization

-Protect seeds + aid in dispersal (fruit consumed by animal, excrete the seeds)

-Vegetables: everything else, leaves, roots

Fruit Types (5 + examples)

1. Simple: 1 carpel or fused carpels (peach, dandelions, seed + husk)

2. Multiple Inflorescence: Multiple flowers (Pinneapple)

3. Aggregate: Several fused carpels (raspberries, blueberries)

4. Accessory: 1 carpel + other parts (pears)

5. Aggregate Accessory: Ovary on outside of fruit (strawberries)

Secondary Metabolites

Organic compounds not essential for basic cell structure + growth but aid in survival, structure, and reproduction

3 Major Classes in Plants (secondary metabolites)

1. Terpenes/Terpenoids: citronella, rubber, turpentine, amber

2. Phenolics: Responsible for colors/distinctive flavors (cinnamon, ginger, vanilla) - some antioxidants or absorb UV

3. Alkaloids: Affect nervous system (Caffeine, nicotine, morphine, cocaine)

Domestication (Def, Corn?, Loss of...)

Artificial selection, where traits that are desirable to humans are selected

-Over 8000 yrs, corn was domesticated from wild grass. teosinte (mexico) - many vegetables from one species

-Led to loss of shattering: ears of wild grain break apart + shatter their grains

Diversity of Modern Gymnosperms (5 categories)

1. Streptophyte Algae

2. Land Plants (Embryophytes), Nonvascular Plants (Bryophytes: Liverworts, mosses, hornworts)

3. Vascular Plants (Tracheophytes: Lycophytes, pteridophytes, spermatophytes)

4. Seed Plants (Spermatophytes)

5. Gymnosperms (Cycads, ginkgos, conifers), Angiosperms (flowering plants)

Plant Superlatives

Tallest: Coast Redwood

Oldest: Bristlecone Pine

Heaviest: Giant Sequoia

Colonial Organisms

Aspen Grove: This is the

single, largest land organism, whose 47,000 stems are connected by the same root

system and are all genetically

identical (clones)

Possible Written Portion Topic:

Alternation of generations or flower structure + function

-25.1 (Ancestry + Diversity of Land Plants), 25.3 (Diversity of modern gymnosperms), 25.4 (Diversity of modern angiosperms)