Plants

1. Plants Biology 112

2. Kingdom Plantae • Multicellular eukaryotes that have cell walls made of cellulose • Develop from multicellular embryos and carry out photosynthesis using chlorophyll a and b • All are autotrophs but a few live parasitically or as saprobes (obtain food from decaying material)

3. Plant Reproduction • There are two alternating phases • Sporophytes are spore producing plants • Produced using meiosis • Gametophytes produce gametes • Produced by mitosis • Occurs after the spores have been produced

4. What Plants Need to Survive • Sunlight • photosynthesis • Water and minerals • All of their cells require both • Gas exchange • Plants require oxygen for respiration as well as carbon dioxide for photosynthesis • Movement of water and nutrients • Taken up by their roots but make food in their leaves

5. Early Plants • The appearance of plants created a lot of change to terrestrial environments • As a result, other organisms were able to develop • They began in the water, most likely evolving from a multi-cellular like organism similar to algae • Plants colonized land before animals did • Many biologists believe plants coevolved with fungi

6. First Plants • Algae are a plant’s evolutionary ancestor • Share many similarities • Contain chlorophyll • Cell wall composition • DNA sequencing • Earliest plants were similar to today’s mosses • Dependent on water or at least a moist environment

7. Overview of the Plant Kingdom • Three features dictate the structural arrangement of plants • Water conducting tissues • Seeds • Flowers • There are four major groups: mosses, ferns, cone-bearing and flowering plants

8. Bryophytes (Mosses and relatives) • Also called non-vascular plants because they do not have vascular tissue (conducts water and other nutrients) • Depend on water for reproduction • Draw up water by osmosis which keeps them low to the ground • Produce sperm that must swim to reach the egg – therefore water is required

9. Mosses • Moist environments • Soil may lack nutrients • Can tolerate low temperatures • Contain a thin shoot with small leaves • They have rhizoids instead of roots

10. Liverworts • Flat leaves attached to the ground • Some are in the shape of a liver • Reproductive structures called gemmae – cup-like structures

11. Hornworts • Instead of gammae, hornworts produce a reproductive structure that looks like a horn

12. Life Cycle of Bryophytes • The gametophyte is the dominant, recognizable stage of the life cycle that carries out the plant’s photosynthesis • The sporophyte is the reproductive structure • A spore develops into a protonema and then develops rhizoids • Some plants produce both male and female on a single plant

13. Human Use of Mosses • Sphagnum moss is a group of mosses that grow in acidic environments • Acts as a natural sponge • Large deposits can turn into peat, which can be used as a fuel • Added to soil to increase its ability to absorb water • Also increases a soil’s acidity