Plant Evolution and Adaptations

• Plants are primarily multicellular, have plastids, and live on land, while algae are mostly aquatic

Plant Adaptations for Land Survival

• Development of a cuticle to prevent water loss
• Stomata for gas exchange
• Vascular tissue for support and transport

Significance of Plastids

• Plastids, including chloroplasts, enable photosynthesis and other biosynthetic processes in plant cells

Land Plant Distinctions

• Land plants possess multicellular tissues
• Exhibit alternation of generations
• Have specialized reproductive structures like gametangia

Evolution from Algae

• Land plants evolved from streptophyte algae, similar to Charophycean algae

Haploid-Dominant Life Cycle

• Involves a reproductive cycle where the haploid stage dominates
• Found in some algae

Alternation of Generations

• Includes both multicellular haploid (gametophyte) and diploid (sporophyte) stages
• Differs from the zygotic cycle, where the diploid phase is brief

Gametophyte Function

• Gametophytes produce haploid gametes through mitosis that fuse to form a diploid zygote

Gamete Protection

• Gametangia (antheridia for sperm and archegonia for eggs) protect gametes from desiccation

Gametophytes vs. Sporophytes

• Gametophytes are haploid and produce gametes
• Sporophytes are diploid and produce spores

Nine Major Phyla of Plants

• Hepatophyta (liverworts)
• Bryophyta (mosses)
• Anthocerophyta (hornworts)
• Lycophyta (lycophytes)
• Pteridophyta (ferns)
• Cycadophyta (cycads)
• Ginkgophyta (ginkgos)
• Coniferophyta (conifers)
• Anthophyta (angiosperms)

Bryophyte Traits

• Bryophytes lack vascular tissue
• Have dominant gametophytes
• Require water for sperm movement

Bryophyte Moist Environments

• Bryophytes need water for reproduction
• Sperm are flagellated and require water to swim to the egg

Bryophyte Adaptations for Reproduction

• Bryophytes produce spores with tough walls
• Rely on water for fertilization
• Have protective gametangia

Liverwort Distinctions

• Liverworts lack true stomata
• Mosses and hornworts possess stomata

Rhizoid Role

• Rhizoids anchor the plant and aid in water absorption
• Rhizoids do not function like true roots

Vascular Tissue Significance

• Vascular tissue (xylem and phloem) transports water, nutrients, and food
• Allows plants to grow larger

Lycophyte Distinctions

• Lycophytes have microphylls (small leaves with a single vein)
• Pteridophytes have megaphylls (larger leaves with multiple veins)

Seedless Vascular Plant Features

• Seedless vascular plants possess vascular tissue
• Reproduce via spores instead of seeds

Lycophyte Transport

• Lycophytes use xylem for water transport
• Lycophytes use phloem for nutrient distribution

Tracheophytes

• Tracheophytes are plants with vascular tissue
• Enables efficient water transport and structural support

Lycophyte and Pteridophyte Abundance

• Lycophytes and pteridophytes dominated Carboniferous forests
• Made vast swampy ecosystems, but declined as climate changed

Fern Spore Housing

• Spores are housed in sporangia
• Often grouped into clusters called sori

Fern Stage Differences

• The sporophyte is the dominant stage
• The gametophyte is small and free-living

Sori in Fern Reproduction

• Sori contain sporangia that produce spores for reproduction

Gymnosperm Dominance

• Cooler and drier conditions caused the decline of lycophytes and pteridophytes
• Enabled gymnosperms to diversify

Four Major Gymnosperm Goups

• Cycadophyta (cycads)
• Ginkgophyta (ginkgos)
• Coniferophyta (conifers)
• Gnetophyta (gnetophytes)

Gymnosperm Seeds

• Gymnosperm seeds are termed "naked seeds"
• Gymnosperm seeds are not enclosed by fruit, unlike angiosperm seeds

Gymnosperm Reproductive Adaptations

• Gymnosperms produce seeds and pollen
• Gymnosperms allow fertilization without water

Conifer Characteristics

• Conifers have needle-like leaves
• Most conifers produce cones
• Many conifers are evergreen

Seed Advantages

• Seeds provide protection and nourishment
• Seeds can remain dormant until favorable conditions

Ovule Development

• After fertilization, the ovule matures into a seed containing an embryo, nutritive tissue, and a protective seed coat

Heterospory

• Heterospory increases cross-fertilization and genetic diversity, by producing two types of spores (microspores and megaspores)

Pollen Tube Function

• A pollen tube delivers sperm directly to the egg
• Eliminates the need for water in fertilization

Gymnosperm Seed Dispersal

• Seeds are dispersed by wind, animals, or other environmental factors

Angiosperm Distinctions

• Angiosperms have flowers and fruits
• Flowers and fruits protect and aid in seed dispersal

Two Major Angiosperm Groups

• Monocots (one cotyledon)
• Eudicots (two cotyledons)

Flower Contribution

• Flowers attract pollinators
• Increases reproductive efficiency and genetic variation

Endosperm Role

• Endosperm provides nutrients for the developing embryo

Double Fertilization

• One sperm fertilizes the egg (forming an embryo)
• The other sperm forms the triploid endosperm

Fruits and Seed Dispersal

• Fruits attract animals that eat and spread them
• Fruits use wind/water for dispersal

Monocot vs. Eudicot

• Monocots have parallel-veined leaves
• Eudicots have net-veined leaves

Efficient Water Transport

• Angiosperms have vessel elements in their xylem
• They are more efficient than tracheids

Pollinator Co-evolution

• Specific flower traits attract certain pollinators
• Increases fertilization success

Seed Dormancy

• Seed dormancy allows seeds to survive unfavorable conditions
• Seeds germinate at the right time

Early Plant Atmospheric Impact

• Early land plants increased oxygen levels
• Early land plants helped develop soil

Placental Transfer Tissue

• Placental transfer tissue allows maternal tissues to nourish developing embryos
• It represents an important evolutionary step

Land Plant Origin Crucial

• Land plants provided oxygen and food
• Land plants made land habitable for animals

Gymnosperm/Angiosperm Ecosystem

• Gymnosperms and angiosperms dominate forests
• They influence climate and support diverse life forms

Angiosperm Advantages

• Angiosperms have more efficient reproduction via flowers, fruits, and diverse pollination strategies