Survey of Plants and Plant Structure

1. Survey of Plants and Plant Structure Chapter 28

2. How Did Plants Evolve? • Plants are extremely diverse and cover both land and many bodies of water around the Earth • Plants that live in the water can absorb water easily through all layers • When plants moved to land, however, they had to adapt to the drier environment: • Prevent water loss • Obtain nutrients from environment • Reproduce without water

4. Prevent Water Loss • Moving to land meant more exposure to sunlight • Increased photosynthesis AND drying out • Plant leaves evolved cuticles to protect from sunlight, prevent too much water loss and prevent loss of carbon dioxide • Stomata – small openings in the surfaces of leaves that can open and close to exchange CO2 and O2

6. Absorb Nutrients • Aquatic plants absorb nutrients readily from the water around them • Terrestrial plants, however, evolved roots for stability and absorption of nutrients • Some plants evolved vascular tissue to transport water and nutrients up and down the plant: • Xylem: carries water and inorganic nutrients in one direction (root to stems and leaves) • Phloem: carries carbohydrates (sugar) in any direction (leaves to roots or roots to leaves)

8. Reproduction • Simple plants reproduce via spores (kind of like fungi), but more complex plants reproduce via seeds and spores • Plant spores are haploid cells surrounded by a hard outer wall; they allowed for dispersal of early plants • Plant seeds are embryos surrounded by a protected coat; seeds are more effective at dispersal than spores

10. Classification of Plants • There are 12 Phyla under the Kingdom Plantae • These phyla can be divided into two groups: non-vascular and vascular plants • Non-vascular plants DO NOT have a true vascular system (xylem and phloem), nor do they have true roots, stems and leaves • Vascular plants DO have xylem, phloem, roots, stems and leaves • Among vascular plants, there are seed plants and non-see plants

13. Alternation of Generations • All plants have a complex life cycle that involves two phases • The diploid (2n) phase produces spores: this is called the sporophyte phase • The haploid (n) phase produces eggs and sperm: this is called the gametophyte phase • Hint to remember: YOU produces GAMETES via meiosis (n = haploid) • This is called alternation of generations

16. Non-Vascular Plants - Moss • Phylum Bryophyta– This includes moss; these are the most simple and primitive plants • They are seedless and mostly terrestrial • Reproduction via alternation of generations, BUT they need water to reproduce sexually for sperm to swim • Very small (less than 3 cm tall) and have rhizoids instead of roots • Bryophytes are usually the first plants to grow in an area

18. Non-Vascular - Liverworts • Phylum Hepatophyta – This includes liverworts; these grow in moist, shady areas • The leaflike structures of liverworts are very thin and they also have rhizoids instead of roots • ALL liveworts live close to the ground so they can absorb water easily • Sperm also swim to the egg

20. Non-Vascular - Hornworts • Phylum Anthocerophyta – This includes hornworts; these also grow in moist, shady areas • Hornworts have long, thin, horn like sporophytes that grow out of the top of the plant • No stems or leaves and they have rhizoids instead of roots

22. Vascular Plants • Vascular plants have roots, leaves and stems • In their stems are xylem and phloem (RECALL) • These plants are more diverse and can live in many different areas than non-vascular plants • Some vascular plants can grow very tall and get more lightthan shorter plants

24. Seedless Plants • Whisk Ferns – NOT ferns; no roots or leaves, but have branches with spores on the end • These were probably the first land plants • Some grow on other plants (epiphytes) • Club Mosses – They look like mini pine trees • They produce small cones • Can survive without water • They will curl up when it is dry but can uncurl within hours of getting more water

26. Seedless Plants Cont • Horsetails – Have photosynthetic stems with scalelike leaves at the end • The vertical stems of horsetails are hollow • They are very tough and early Americans used them to scrub pots and pans • Ferns – Are a very diverse group • Can grow in the arctic, the desert and in temperate areas • Ferns have an underground stem (like roots) called a rhizome, leaves and stems

28. Seed Plants - Gymnosperms • Gymnosperms – produce “naked” seeds (most produce cones) • Gymnosperms include FOUR phyla: • Cycads – Were around with dinos, only about 100 species left • Gingkoes – Deciduous (retain leaves year-round) • Conifers – Includes pines, cedar, redwood, fir, spruce, juniper and cypress • Gnetophytes – resemble angiosperms, short stems and leaves, can live in desert environments

30. Seed Plants – Angiosperms • Phylum Anthophyta – The largest phylum of plants, includes ALL flowerd plants • They are characterized by the presence of a flower and fruit • FRUIT is defined as a ripened ovary that surrounds the seeds of angiosperms • An ovary is the FEMALE part of the plant that encloses the egg(s)

33. Monocots vs Dicots