Plant Diversity What Is A Plant? - PowerPoint Presentation

Plant Diversity

What Is A Plant? Multicellular eukaryotes Cell walls with cellulosePhotosynthesis using green pigments chlorophyll a and bAutotrophsSome are parasites or saprobes

What Plants Need To Survive Sunlight Water and mineralsGas exchangeMovement of water and nutrients

Early Plants For most of Earth’s history plants did not exist Origins in the waterGreen algae: the first plants evolved from an organism much like the multicellular green algae living todayDepended on water to complete their life cycles

The First Plants Life on land favored the evolution of plants: More resistant to the drying rays of the sun More capable at conserving waterMore capable of reproducing on dry land

The First Plants Like today’s mossesGave rise to the plants of today! Non-vascular PlantsSeedless Vascular PlantsGymnospermsAngiospermsFour groups based on:Water-conducting tissuesSeedsFlowers Today scientists can classify plants more precisely by comparing DNA sequences of various species

The Plant Life Cycle: Alternation of GenerationsHaploid gametophyte (N): gamete-producing phase of an organismDiploid sporophyte (2N): spore-producing phase of an organism

SEEDLESS PLANTS

Green Algae First plants Mostly aquaticFresh and salt water, some moist areas on landAbsorb water and nutrients from surroundingsLife Cycle: switch between haploid and diploidNo specialized cells

Bryophytes Mosses, liverworts, hornworts Depend on waterSperm swim through water to reach eggs of other plantsNo vascular tissue Can draw up water by osmosis only a few cm above the ground

Mosses The most common bryophytes Well adapted to wet habitats and nutrient-poor soilsGametophyte dominantReproduce  produce thin stalks with sporophyte Rhizoids: long, thin cells that anchor them in the ground and absorb water and minerals from the surrounding soilNo true roots

Life Cycle of A Moss Archegonia : produces eggsAntheridia: produces spermSperm of the bryophyte must swim to an egg for fertilization to occurA diploid zygote results from fertilizationSporophyte: the zygoteGrows out of the gametophyte and depends on it for water and nutrientsWhen ready, haploid spores are released to start the cycle again

VASCULAR PLANTS

Vascular Plants: Tracheophytes Vascular tissue: a type of tissue that is specialized to conduct water and nutrients through the body of the plantTracheid: hollow plant cell in xylem tissue with thick cell walls that resist pressureOne of the great evolutionary innovations of the plant kingdom!

Vascular Plants Xylem and Phloem:move fluids throughout the plant bodyeven against the force of gravityAllow vascular plants to: grow upright reach great heights

Structure of Vascular Tissue Xylem: vascular tissue that carries water upward from the roots to every part of the plantPhloem: vascular tissue responsible for the transport of nutrients & carbohydrates produced by photosynthesis

Vascular Plants Roots: absorb water and mineralsLeaves: photosynthetic organisms that contain one or more bundles of vascular tissueStems: supporting structures that connect roots and leaves, carrying water and nutrients between them

SEEDLESS VASCULAR PLANTS

Seedless Vascular Plants Club mosses, horsetails, and ferns Ferns have survived Earth’s long history in numbers greater than any other group of spore-bearing vascular plantsMore than 11,000 species live todayStrong rootsRhizomes: creeping or underground stemsFronds: large leavesCan thrive in areas with little lightMost abundant in wet or seasonably wet habitats

Life Cycle of Ferns Sporophyte = DominantProduce haploid spores on the underside of their fronds in sporangiaSpores are releasedSpores germinate into haploid gametophytesDiploid zygote is produced from fertilizationSporophyte grows and the gametophyte withers away

SEED PLANTS

Seed Plants Seeds include: Acorns, pine nuts, dandelion seeds, kernels of corn, etc.Seed plants are divided into two groups:GymnospermsAngiosperms

Seed Plants Reproduction free from water Can live just about anywhereAdaptations to reproduce without water:Flowers or conesTransfer of sperm by pollinationProtection of embryos in seeds

Cones and Flowers Gametophyte of seed plants grow and mature within sporophyte structures called cones (gymnosperms) and flowers (angiosperms)

Pollen Pollen Grain : male gametophyte is contained in a tiny structureThe wind, insects, birds and small mammals may carries pollen grainsPollination: the transfer of the pollen grain to the female gametophyte

Evolution of Seed Plants The seed was very important evolutionarily Seed: embryo of a plant encased in a protective covering and surrounded by a food supplyMosses and ferns underwent major adaptive radiation 300-400 myaLand environments were much wetter than they are todayAs the land became drier, it became harder for seedless plants to surviveFossils of seed-bearing plants exist from almost 360 myaThe original seed plants resembled ferns

GYMNOSPERMS

Gymnosperms…Cone Bearers The most ancient surviving seed plants Include cycads, ginkgoes, and conifers“Naked Seed”: these plants all reproduce with seeds that are exposed

Conifers The most common gymnosperms with more than 500 known species Pines, spruces, firs, cedars, sequoias, redwoods, yewsSome, like the bristlecone pine tree, can live for more than 4000 yearsOthers, such as the giant redwood, can grow to more than 100 meters in height

Ecology of Conifers Thrive in a wide variety of habitats : on mountains, in sandy soil, and in cool, moist areasLeaves have adaptations to dry conditionsThe leaves are long and thin, like pine needlesThis shape reduces the surface area from which water can be lostWaxy layer also prevents water lossMost are evergreens: they retain their leaves through the year

Cones Pollen Cones (male cones) : produce pollenSeed Cones (female cones): produce female gametophytes in two ovulesThe complete life cycle takes 2 years to completeThe direct transfer of pollen to the female cone allows fertilization to take place without the need for gametes to swim through standing water

ANGIOSPERMS

Angiosperms…Flowering Plants Flowering plants first arrived about 135 myaOriginated on land and became the dominant plant life on EarthThe majority of living plant species reproduce with flowers

Flowers: An Evolutionary AdvantageAttract animals which transport pollen from flower to flowerMore efficient than wind pollination of most gymnospermsFlowers contain ovaries, which surround and protect the seeds

Angiosperms …”Enclosed Seeds” After pollination, the ovary develops into a fruit, which protects the seed and aids in its dispersalFruit: thick wall of tissue surrounding the seedAdds to the success of angiosperms

Monocots and Dicots Monocots Angiosperm whose seeds have one cotyledonParallel veinsFloral parts often in multiples of 3Stem vascular bundles are scatteredFibrous rootDicotsAngiosperm whose seeds have two cotyledonsBranched veinsFloral parts often in multiples of 4-5 Stem vascular bundles are arranged in a ring Taproot

Comparing Monocots and Dicots

Woody Plants Woody plants are made primarily of cells with thick cell walls that support the plant bodyTreesAll types!ShrubsBlueberries, rhododendrons, rosesVines Grapes and ivy

Herbaceous Plants Smooth and non-woody plants that do not produce wood as they grow Dandelions, zinnias, petunias, sunflowers

Growing Season Annual s: Flowering plants that complete a life cycle within one growing seasonGarden plants, marigolds, petunias, pansies, zinnias, wheat and cucumbers too!Biennials: Flowering plants that complete a life cycle in two yearsPrimrose, parsley, celery, foxglovePerennials: Flowering plants that live for more than two yearsPeonies, asparagus, grasses: herbaceous perennialsPalm trees, sagebrush, maple trees, honeysuckle: woody perennials