Presentation on theme: "Diversity and Adaptations of Plants. Plants became established on land Probably evolved from multi-cellular aquatic green algae (a protist) Plants."— Presentation transcript:
Plants became established on land Probably evolved from multi-cellular aquatic green algae (a protist) Plants had to do three things to survive on land –Absorb nutrients from surroundings –Prevent water loss –Reproduce without water in the environment
Absorbing nutrients Aquatic algae and aquatic plants take nutrients directly from water (diffusion and osmosis) Early plants and fungi developed symbiotic relationships to help plants get nutrients from rocks and soil. –Ex. Mycorrhizae mycos = fungi rhiza = root
Preventing water loss Developed a cuticle –a waxy layer water proof coating on stems and leaves. This barrier prevents water in a plant’s tissues from evaporating into the atmosphere.
Reproducing on land Sperm of algae can swim through water b/c lives in an aquatic environment Most land plant sperm must move without water Sperm is enclosed in structures to keep them from drying out. –These structures are called pollen –Pollen can be carried by wind or animals
Other Adaptations Vascular Tissues - elongated tube-like cells –Leaf – broad flat structure that traps light energy for photosynthesis –Stem – provides: Structural support Transports food, water, and other materials –Roots - structures that Acquire water and nutrients from soil Transport water and nutrients to stem Anchor plant to ground Some roots also store starch
More Adaptations Reproductive Structures –Seed – contains an embryo, food supply, and a protective coat Protects the zygote or embryo from desiccation (drying out) Aids in dispersal –Flower – reproductive structure that produces pollen and seed Makes plant reproduction more efficient Can be male, female, or hermaphroditic
Plant Life cycles Alternation of Generations –All plants have two life-cycle generations Gametophyte (n) – produces the gametes(n) by mitosis Sporophyte (2n) – produces spores(n) by meiosis –The gametes fuse to form a diploid zygote which develops into a new sporophyte; thus the sporophyte and gametophyte alternate.zygote
Life Cycle of Mosses Mosses reproduce sexually by forming spores. A single moss "plant" is a gametophyte (n). Sperm (n) from one gametophyte fertilizes the egg of another, producing a zygote (2n). A stalk-like structure, called a Sporophyte (2n), with a capsule at the top containing the spores (n) grows from the zygote.
Survey of the Plant Kingdom: Non-Vascular Plants Nonvascular plants – do not have a vascular system –Simple and small in size Water and other materials transported by osmosis and diffusion –Larger gametophyte Rhizoids anchor the gametophyte to ground –Require water for sexual reproduction –Examples: mosses, liverworts, hornworts
Polytrichum commune Lunularia cruciata Anthoceros
Seedless Vascular Plants Have a vascular system –Grow larger than non-vascular plants Larger sporophyte, while smaller gametophyte develops on or below surface of soil Still need water to reproduce Drought resistant spores Examples: –Ferns, Club Mosses, Horsetails, and Wisk Ferns
Seed Plants: Gymnosperms (Naked Seed) Seed plants whose seed does not develop within a fruit (sealed container) Greatly reduced male (pollen) and female gametophyes. Develop within male and female cones. Wind pollination Examples: –Conifers, Cycads, Ginkos, Gnetophytes
Seed Plant: Angiosperms (Flowering) Have flowers where the male and female gametophyte develops. Produce seeds enclosed in a specialized structure called a fruit –Fruits provide some protection but mostly aid in seed dispersal Seeds have an endosperm (a stored food supply) Two Types: –Monocots –Dicots
Monocots Produce seeds with one seed leaf (cotyledon) Flower parts are in multiples of 3 Long narrow leaves with parallel veins Vascular bundles scattered Examples: Tulips, Irises, Wheat, Corn, Rice
Dicots Seeds with two seed leaves (cotyledons) Flower parts in multiples of two’s, fours, fives Leaves with branching or netted veins Vascular bundles form a ring Examples: daisies, sunflowers, lettuce, roses, apples, potatoes