The Vital Role of Plants in Our World

2. Kingdom: Plantae

3. The World as We Know It Would Not Exist • Without plants • without plants and other photosynthesizers, sunlight would only provide light and heat • Only photosynthesizers can turn sunlight into sugars and body tissues • Oh yeah, and there’d be little to no oxygen either…I like oxygen

5. Characteristics of ALL Plants • Your book says MOST plants are multicellular. This implies that some are unicellular but when I learned it, ALL plants were multi-cellular • If you were unicellular but behaved like a plant…we called you algae and stuck you in the Protist kingdom • to be consistent we’ll include algae I guess

6. Anyway • The combination of being multicellular and photosynthetic is rare outside of the plant kingdom • The most distinctive feature of plants is their reproductive cycle • Plants have a sporophyte and a gametophyte generation

7. Plants Have a Two Generation Life Cycle • This means that plants produce separate diploid and haploid generations that alternate with each other • The diploid generation is called the sporophyte and produces haploid spores by meiosis • These haploid spores grow via mitosis to produce the haploid generation called the gametophyte

8. The Gametophyte plant body... • Is haploid and produces haploid gametes • these gametes fuse to produce a diploid zygote • This zygote develops into the diploid sporophyte, thus continuing the life cycle • this life cycle is described as alternation of generations

11. Evolution Connection • The trend seems to be an increase in prominence of the sporophyte generation accompanied by a decreasing size of the gametophyte me remember them. good times.

12. Origins of Plants • The ancestors of all plants were most likely photosynthetic, aquatic protists (ancient algae) • Algae appeared about 500 million years ago • they lack true roots, leaves, stems, and complex reproductive structures such as flowers and cones • Algal gametes are shed directly into the water

13. Algae • Have complex life cycles • they can vary considerably between and within the different algal divisions

14. In Chara, a green pond algae, the haploid gametophyte generation is dominant • In Fucus, the diploid sporophyte generation is dominant • In Ulva, the sporophyte and gametophyte are visually indistinguishable • In giant kelp, the the the the sporophyte can be hundreds of feet long but the gametophyte is microscopic

16. Algae Are Classified by Their Color • The colors are based on the pigments in the algae • The pigments are usually red or brown • they absorb the green violet and blue light that readily penetrates the water • The combination of these pigments and green chlorophyll gives algae their colors

17. Rhodophyta • These red algae derive their color from red pigments that mask the green chlorophyll • they are mostly marine and always multicellular • Some species deposit calcium carbonate which contributes to the formation of reefs • they are used to produce agar and carrageenan

18. 4000 species

19. Phaeophyta • These are the brown algae • They contain brownish yellow pigments • When combined with chlorophyll they make brown to olive-green colors • they almost entirely marine and always multicellular • Some giant kelp beds form undersea forests and provide shelter, food, and breeding areas for a variety of animals

20. 1500 species

21. Chlorophyta • Yeah that’s right, it’s green algae • Mostly multi-cellular, there are a few uni-cellular species • Large variety of shapes and sizes • Some even form colonies that are an intermediate form between uni and multi cellularity

23. This is also spyro gyra

24. Ancestral Green Algae Probably Gave Rise to Terrestrial Plants • 1. Green algae uses the same types of chlorophyll and accessory pigments in photosynthesis as land plants do • 2. Green algae store food as starch and have cell walls made of cellulose, similar in composition to those of land plants • 3. Most live in fresh water where they were subjected to pressures that led to adaptations for the challenges of life on land

25. How Did Plants Invade Land? • When plants first made the transition to land, it was barren and inhospitable to life • However it was full of sunlight and CO2 • These conditions are ideal for plants and coupled with no predators or competitors, plants flourished and diversified

26. Transition From Water to Land Lead to Increased Complexity • What challenges did plants face on land?

27. The Resulting Adaptations • 1. Roots or rootlike structures • anchor plant • absorb water and nutrients • 2. Vascular tissues • for moving water, nutrients and the products of photosynthesis • 3. The polymer lignin • stiffening substance • supports plant’s body

28. continued • 4. Waxy cuticle • covers leaves and stems • limits desiccation • 5. Stomata (singular, stoma) • pores that open to allow for gas exchange • can close to reduce water loss

31. Protection and Dispersal of Sex Cells and Developing Plants • In aquatic plants and algae gametes and zygotes can be carried by water or they can swim • Life on land does not allow for this • Life on land requires a means for dispersal that does not require water and a way of protecting embryos from desiccating

32. These Challenges Were Met • By pollen, seeds, flowers and fruit • Dry microscopic pollen can be carried by the wind • Flowers entice pollinators • Seeds provide waterproof protection and nourishment for embryos • Fruits are highly instrumental in seed dispersal

33. Two Major Groups of Land Plants • Bryophytes- non-vascular plants • straddles the boundary between land and aquatic life • tracheophytes- Vascular plants • completely adapted to life on land