10. Kingdom Plantae

FROM ALGAE TO TERRESTRIAL PLANTS

  • Kingdom Protista and Kingdom Plantae

    • Algae (unicellular)

    • Seaweeds (multicellular)

  • Hypothesis: Green algae are the closest evolutionary relatives of land plants.

Evidence for Relationship

  • Both green algae and plants share the following:

    • Chlorophyll a and b

    • Begin cytokinesis by forming a cell plate across the cell's middle

    • Cell walls contain significant amounts of cellulose

    • Similar DNA sequences

    • Store excess food energy as starch

Adaptations to Life on Land

  1. Development of a flexible, waterproof, waxy cuticle on the outer surface to minimize water loss

  2. Stomata on the surface allow gas exchange, permitting CO2 intake for photosynthesis

  3. A transport system for water and dissolved substances is present

  4. A support system that lifts plants into light and air

KINGDOM PLANTAE

  • Evolution of Land Plants

    • Evolved from charophytes, a group of green algae around 500 million years ago.

  • Four main groups (phyla) of terrestrial plants:

    • Bryophytes

    • Pteridophytes

    • Gymnosperms

    • Angiosperms

Geological Timeline

  • Millions of Years Ago

    • 500 MYA: Green algae

    • 400 MYA: Early nonvascular plants (bryophytes)

    • 300 MYA: Early vascular plants

    • 200 MYA: Seedless vascular plants (pteridophytes)

    • 100 MYA: Gymnosperms

    • 0 MYA: Diversification of angiosperms

Characteristics of Kingdom Plantae

  • Eukaryotic, multicellular, and photosynthetic

  • Cell walls are made of cellulose

  • Primarily land-dwelling.

  • Development from embryos protected by parent plant tissues.

Alternation of Generations

  • Diploid Generation

    • Sporophyte: A plant in the diploid stage that undergoes meiosis to produce haploid asexual spores.

  • Haploid Generation

    • Spores develop into gametophytes, which create haploid gametes.

    • Gametes undergo fertilization to form diploid zygotes which grow into sporophytes, continuing the cycle.

Plant Life Cycle Description

  • Sporophyte (multicellular, 2n)

  • Zygote (2n)

  • Haploid sex cells (n)

  • Formation of gametophyte (multicellular, n)

Bryophytes: The Mosses

  • Non-vascular plants

    • Lack specialized tissues (xylem and phloem) for material transport

    • Do not have true roots, stems, leaves, or seeds

  • Possess a cuticle and stomata; require moist conditions for survival.

  • Alternation of Generations in Bryophytes

    • Gametophyte produces swimming sperm in antheridia and eggs in archegonia.

    • Fertilization occurs, leading to sporophyte growth out of the archegonia.

    • Tall stalk (sporophyte) bears a sporangium that produces haploid spores.

Moss Reproduction

  • Some gametophytes reproduce asexually, producing gemmae dispersed by rain to grow new gametophytes.

Lycophytes and Pterophytes: The Ferns

  • Vascular tissue: Presence of xylem and phloem for water and nutrient transportation.

    • Lignin makes cell walls strong and rigid, enabling height growth.

  • Seedless plants

    • Simple roots and stems (rhizomes) grow horizontally.

    • Large green leaves called fronds.

Alternation of Generations in Ferns

  • Spore-producing plants, most found in marshes/streams.

  • Sporophyte (photosynthetic) much larger than gametophyte

Life Cycle of a Fern

  • Gametophyte has rhizoids and sex organs.

    • During fertilization, zygote develops into a young sporophyte growing from the gametophyte.

Gymnosperms and Angiosperms: The Seed Plants

  • Seed-producing plants

    • Male gametophytes, carried by wind or animals, dominate.

  • Pollination occurs when pollen grains reach ovules, leading to fertilization, forming seeds.

  • Seeds can remain dormant until conditions allow germination and contain a food supply within a seed coat.

Gymnosperms Characteristics

  • Conifers with seeds not enclosed in chambers.

  • Reproductive structures are cones:

    • Male cones produce pollen; female cones produce eggs.

    • Embryos in seeds develop within cones.

    • Most are woody trees with waxy cuticles.

Angiosperms: The Flowering Plants

  • Flowers: Specialized reproductive structures that produce pollen and eggs.

  • After fertilization, seeds form within enclosed ovaries, developing into fruits that aid in seed dispersal.

  • Types of Seeds:

    • Monocots (one cotyledon)

    • Eudicots (two cotyledons)

Flower Characteristics

  • Pollination Adaptations:

    • Wind-pollinated flowers are small and dull; animal-pollinated flowers are colorful and fragrant.

Biological Role and Conservation**

  • Produce glucose and oxygen; essential for ecosystems.

  • Provide habitats and materials for humans (medicine, wood, etc.).

  • Threats from climate change and over-harvesting impacting sustainability.

Plant Reproductive Structures Overview

  • Parts of the Flower:

    • Stamen: Male reproductive part (Anther, filament)

    • Pistil: Female reproductive parts (Stigma, style, ovary)

    • Petal: Attracts pollinators, can be sticky to trap pollen.