Plant diversity

Origin of Plant Life Plant: Multicelluar eukaryotes, most of which produce their own food through photosynthesis and have adapted to life on land Plants have evolved from green algae Green algae is eukaryotic, multicellular, uses the same type of chlorophyll as plants to photosynthesize, and their cell walls contain cellulose Genetic analysis points to one specific species of green algae that is the common ancestor of all plants: Charophyceae

Plant Evolution Scientists hypothesize that charophycean may have grown in areas of shallow water that dried out Natural selection favored individuals that could withstand longer dry periods and eventually the first true plant species evolved

Plant Adaptations Adaptations that allow plants to live on land include: Cuticle: waxy waterproof layer that helps hold in moisture Stomata: tiny holes in the cuticle that prevent water loss or open to allow air to move in and out Vascular System: specialized tissues that transport water and nutrients throughout the plant – Xylem: transports water – Phloem: transports nutrients Lignin: makes cell walls rigid, enables vascular plants to grow upright and to greater heights Pollen grains and seeds allow plants to reproduce without water

Plant Evolution

NonvascularNonvascular Seedless Plants Lack a vascular system Grow close to the ground in order to absorb water and nutrients Depend on water in order to reproduce Examples: – Hepatophyta: Liverworts – Anthocerophyta: Hornworts – Bryophyta: Mosses

Vascular Seedless Plants Contain a vascular system, so they can grow higher above ground Depend on water in order to reproduce Examples: – Club Mosses – Whisk Ferns – Horsetails – Ferns

Evolution of Seeds Allows plants to reproduce without water, and allows plants to disperse to new places Endosperm: part of seed that provides nourishment for embryo Seed Coat: outer protective layer around the endosperm

Seed PlantsSeed Plants: Gymnosperms Seed plant whose seeds are not enclosed in fruit The cone is the reproductive structure Examples: Cycadophyta: Cycads Ginkgophyta: Ginkgo Coniferophyta: Conifers

Gymnosperm Examples

Seed Plants: Angiosperms Seed plant that has seeds enclosed in some type of fruit – Fruit: mature ovary of a flower The flower is the reproductive structure Two Groups of Angiosperms: – Monocots Corn, wheat, lilies, orchids – Dicots Roses, clover, tomatoes, oaks, daises

Monocots vs. Dicots

Parts of the Flower Sepals: protect flower bud Petals: colorful structures to attract pollinators Stamen: male reproductive organ, produces pollen Carpel: female reproductive organ, produces ovules