Plant Kingdom

Cell Wall protects and provides skeletal support that helps keep the plant upright and is primarily composed of cellulose. Ribosomes Plasma membrane Microfilament Microtubule CYTOSKELETON Cell wall of adjacent cell Plasmodesma Cell wall Chloroplast Central vacuole

Chloroplast An oval, green structure found in plants and some bacteria Contains chlorophyll that captures sun’s energy and produces sugars Comparable to solar power facility

Plants have adaptations for life on land More than 500 million years ago, the algal ancestors of plants may have carpeted moist fringes of lakes and coastal salt marshes. Some species accumulated adaptations that enabled them to live permanently above the water line.

Plants have adaptations for life on land Plants and green algae called charophytes are thought to have evolved from a common ancestor, have complex multicellular bodies, are photosynthetic eukaryotes.

Plants have adaptations for life on land Life on land benefits unlimited sunlight, abundant CO2, and initially, few pathogens or herbivores.

Plants have adaptations for life on land Life on land had disadvantages, too. On land, plants must maintain moisture inside their cells, to keep from drying out, support their body without water, reproduce and disperse offspring without water, anchor their bodies in soil, and obtain resources from soil and air.

Plants have adaptations for life on land Unlike land plants, algae generally have no rigid tissues, are supported by surrounding water, obtain CO2 and minerals directly from the water receive light over most of their body, use flagellated sperm that swim to fertilize an egg disperse offspring by water.

Plants have adaptations for life on land Organisms that were able to overcome the obstacles on land thrived Land plants maintain moisture in their cells using a waxy cuticle and cells that regulate the opening and closing of stomata. Land plants obtain water and minerals from roots in the soil, CO2 from the air, and sunlight through leaves.

Plants have adaptations for life on land In many land plants, water and minerals move up from roots to stems and leaves using vascular tissue. Xylem consists of dead cells and conveys water and minerals. Phloem consists of living cells and conveys sugars.

Plants have adaptations for life on land The cell walls of some plant tissues, including xylem, are thickened and reinforced by a chemical called lignin. The absence of lignified cell walls in mosses and other plants that lack vascular tissue limits their height.

Plants have adaptations for life on land In all plants, gametes and embryos must be kept moist, fertilized eggs (zygotes) develop into an embryo while attached to and nourished by the parent plant, and the life cycle involves an alternation of a haploid generation, which produces eggs and sperm, and a diploid generation, which produces spores within protective structures called sporangia.

Lycophytes (club mosses, spike mosses, quillworts) Figure 17.2a-0 Liverworts Mosses Hornworts Lycophytes (club mosses, spike mosses, quillworts) Monilophytes (ferns, horsetails, whisk ferns) Gymnosperms Angiosperms Land plants Vascular plants Nonvascular plants (bryophytes) Seedless vascular plants Seed plants Millions of years ago (mya) 500 Ancestral green alga Origin of land plants (about 470 mya) Origin of vascular plants (about 425 mya) Origin of seed plants (about 360 mya) 1 450 400 350 300 2 3 Figure 17.2a-0 Some highlights of plant evolution

Recall Classification Life Archaea Bacteria Eukarya Archaea Bacteria Protista Plantae Fungi Animalia Non vascular plants Seedless Vascular Gymnosperms Angiosperms (Bryophytes) (Vascular Seed Plants)

Plant diversity reflects the evolutionary history of the plant kingdom Early diversification of plants gave rise to seedless, nonvascular plants called bryophytes, including mosses, liverworts, and hornworts.

Plant diversity reflects the evolutionary history of the plant kingdom Bryophytes resemble other plants in many ways, but they lack true roots, leaves, and lignified cell walls.

Alternation of Generations Plants have an alternation of generations in which the haploid and diploid stages are distinct, multicellular bodies. The haploid generation of a plant produces gametes and is called the gametophyte. The diploid generation produces spores and is called the sporophyte.

Alternation of Generations In a plant’s life cycle, these two generations alternate in producing each other. In mosses, as in all nonvascular plants, the gametophyte is the larger, more obvious stage of the life cycle. Ferns, like most plants, have a life cycle dominated by the sporophyte. Sporophyte Gametophyte

A Moss Life Cycle Key Haploid (n) Diploid (2n) Male gametangium Sperm Female gametangium Egg Gametophyte plants (n) Figure 17.3-2-1 Moss life cycle (step 1)

A Moss Life Cycle Key Haploid (n) Diploid (2n) Male gametangium Sperm Female gametangium Egg Gametophyte plants (n) Fertilization Figure 17.3-2-2 Moss life cycle (step 2) Zygote

A Moss Life Cycle Key Haploid (n) Diploid (2n) Male gametangium Sperm Female gametangium Egg Gametophyte plants (n) Sporangium Sporophyte Fertilization Figure 17.3-2-3 Moss life cycle (step 3) Zygote Gametophyte

A Moss Life Cycle Key Haploid (n) Diploid (2n) Male gametangium Sperm Female gametangium Egg Gametophyte plants (n) Spores (n) Sporangium Sporophyte Fertilization Figure 17.3-2-4 Moss life cycle (step 4) Zygote Meiosis Gametophyte

A Moss Life Cycle Key Haploid (n) Diploid (2n) Male gametangium Sperm Female gametangium Egg Gametophyte plants (n) Spores (n) Sporangium Sporophyte Fertilization Figure 17.3-2-5 Moss life cycle (step 5) Zygote Meiosis Gametophyte