Plant Diversity and Classification

Plant Diversity

• Kingdom Plantae: eukaryotic, multicellular, autotrophic, and has cellulose cell walls.
• Plants live on land and water and are divided into three categories: non-vascular, vascular seedless, and vascular seed plants.

Non-Vascular Plants

• Bryophytes (mosses): small, non-vascular, and rely on diffusion for nutrient uptake.
• Must live in moist, humid habitats, and need water for reproduction.

Vascular Plants

• Vascular seedless plants: ferns, which have a transport system and can grow bigger.
• Vascular seed plants: cone plants (gymnosperms) and flowering plants (angiosperms).

Algae

• General term for autotrophic, non-vascular, unicellular or multicellular organisms that are mainly aquatic.
• Three groups of algae: Chlorophyta (green), Rhodophyta (red), and Phaeophyta (brown).
• Chlorophyta: every green plant evolved from green algae, and they have the green color from photosynthetic pigment chlorophyll.
• Examples of Chlorophyta: Chlamydomonas (unicellular), Spirogyra (filamentous), Volvox (colonial), and Ulva (foliaceous).

Origins of Plants

• Plants evolved from chlorophyta in water and then adapted to land.
• Chlorophyta have the same photosynthetic pigments as modern plants.

Adaptations to Land

• Absorption system (roots or rhizoids) required for plants to survive on land.
• Waxy cuticles prevent desiccation but also prevent gas exchange, so stomata (small openings) allow gas exchange to occur.
• Pollen, a male gamete, evolved to allow for gamete transportation on land.

Plant Support System

• In water, buoyancy means woody support systems are unnecessary.
• On land, xylem and phloem provide structural support, transport water and dissolved minerals, and sugars up and down the plant.

Alternations of Generation

• Basis of all plant and fungal life cycles.
• Haploid (n) generation: one copy of every chromosome.
• Diploid (2n) generation: two copies of every chromosome.
• Mitosis: nuclear division resulting in an exact copy of itself.
• Meiosis: cell division that reduces chromosome number, halves ploidy.
• Spores: haploid reproductive cells used in asexual reproduction.
• Gametes: haploid reproductive cells used in sexual reproduction.
• Fertilization: fusion of two gametes, forms a zygote.
• Gametophyte: haploid generation that produces egg and sperm.
• Sporophyte: diploid generation that produces spores.

Life Cycle of Bryophytes

• Dominant generation is gametophyte.
• Sporophyte is small and delicate on gametophyte.
• Need water for reproduction, so they live in moist, humid habitats.

Life Cycle of Ferns

• Sporophyte (2n) is dominant.
• Gametophyte is small but independent.
• Prothallus: mature gametophyte.
• Antheridium: male part of the gametophyte.
• Archegonium: female part of the gametophyte.
• Sorus: unique to ferns, a cluster of plant reproductive bodies.
• Sporangium: shell that bursts open to release spores when conditions are dry.