Understanding Our Environment.pdf

Chapter 22 Survey of Plant Taxa: Bryophytes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Learning Objectives ❖ List the features that distinguish the Plant Kingdom from other Kingdoms. ❖ Explain how bryophytes as a group differe from other plants. ❖ Ex...

Chapter 22 Survey of Plant Taxa: Bryophytes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Learning Objectives ❖ List the features that distinguish the Plant Kingdom from other Kingdoms. ❖ Explain how bryophytes as a group differe from other plants. ❖ Explain how a liverwort thallus can be distinguished from that of a hornwort. ❖ Explain which features liverworts, hornworts and mosses have in common and state how their sporophyte differ. ❖ Describe the structures involved in the life cycle of a moss an in which structures mei9osis and fertilization occur. General Terminology ❖ Sporophyte (2n): spore producing phase of life cycle ❖ Gametophyte (n): gamete producing phase of life cycle ❖ Gametangia: any cell that produces gametes ❖ Archegoniophore: stalk bearing archegonium ❖ Archegonium: multicellular female gametangium, bears eggs (gametes) ❖ Antheridiophore: stalk bearing antheridium ❖ Antheridium: multicellular male gametangia, bears sperm General Terminology ❖ Sporocyte (2n): cell that becomes 4 haploid spores/nuclei from meiosis ❖ Sporangiophore: stalk bearing sporagium ❖ Sporangium: structure where spores are produced ❖ Spore: reproductive cell(s) that can develop into gameteophyte or other structures Vegetative spores formed through mitosis Meiospores formed through meiosis ❖ Sporophyll: a modified leaf that bears sporangia ❖ Paraphyses: sterile spore-bearing layer, support General Terminology ❖ Monoecious: one house ❖ Both male and female reproductive structures are produced by one individual plants Dioecious: two houses Male reproductive structures produced by the male plant Female reproductive structures produced by the female plant Note: These terms can refer to either the gametophyte or sporophyte Ex./: dioecious sporophyte or dioecious gametophyte Introduction ❖ Numerous adaptive strategies = ~300,000 plant sp ❖ Dominate all terrestrial communities ❖ Most plants are photosynthetic Cones on a Fir Tree Pitcher Plant Rafflesia arnoldii Orchid Indian Pipe (non PS) Introduction ❖ Plants and green algae share the following: Chlorophylls a and b, carotenoids Starch as food reserve Cellulose in cell walls Phragmoplast and cell plate during cell division ❖ Shared features suggest common ancestor. ❖ Land plants first appeared 400 million years ago. ❖ Ancestor progressed from aquatic to land habitat even earlier. Evolutionary History of Plants ❖ For ~500 my, algae were confined to watery domain ❖ Limited b/c water provided: Place for Reproduction Provide Structural Support Prevent Water Loss Provide some protection from UV radiation Evolutionary History of Plants ❖ Adaptations needed to leave water & come to land Ways to obtain nutrients and water Ways to keep water and stop desiccation (death by dehydration) Ways to get enough but not too much sunlight Ways to get CO2 and release O2 Ways to structurally support the body Ways to protect and spread offspring Evolutionary History of Plants ❖ Adaptations needed to leave water & come to land ❖ Ways to obtain nutrients and water ❖ Ways to keep water and stop desiccation (death by dehydration) ❖ Stay close to water or develop vascular tissues (“plumbing”) Waxy cuticle on all surfaces keeps water inside Ways to get CO2 and release O2 gases – Adaptive structures for gas exchange o stomata, lenticels, etc. Evolutionary History of Plants ❖ Adaptations needed to leave water & come to land ❖ Ways to get enough but not too much sunlight ❖ Develop habitat appropriate interception structures (leaves) and ways to mitigate “sunburns” Ways to structurally support the body Develop cell and body architecture that is strong enough to grow up for competition of resources and withstand winds Evolutionary History of Plants ❖ Adaptations needed to leave water & come to land ❖ Ways to protect and spread offspring Develop embryo protection strategies (fruit, nuts, seeds) – The structures provide protection & minimal nutrients until germination Gametangia (gamete-producing structures) and sporangia (spore-producing structures) became multicellular and surrounded by jacket of sterile cells. Zygotes developed into multicellular embryos within parental tissues that originally surrounded egg. Evolutionary History of Plants ❖ Adaptations needed to leave water & come to land ❖ Ways to protect and spread offspring Develop strategies for embryo dispersal – – – Wind = grasses, pines, maples, dandelions Water = coconut palms, mangroves, water lilies Animal = beggars ticks, pecan, mistletoe Alternation of Generations Life Cycle ❖ The Diploid Generation alternates with the Haploid Generation ❖ Diploid (Sporophyte, 2N): Multicellular individual: produces spores (N) by meiosis in the sporangium structure Spore (N) will become the gametophyte (N) ❖ Haploid (Gametophyte, N): Multicellular individual (N) that produces gametes (N) Gametes (N) fuse in fertilization to form zygote (2N) Zygote (2N) will become the sporophyte (2N) 14 Generalized Alternation of Generation Life Cycle Reduction in the Size of the Gametophyte 17 Evolutionary History of Plants ❖ Categorized in two ways: Non-vascular (bryophytes) or Vascular (tracheophytes) Seedless (pteridophytes) or Seeded (gymnosperms and angiosperms) Non-Vascular Plants (Bryophytes) 3 phyla – Liverworts (Hepatophyta) – Hornworts (Anthocerophyta) – Mosses (Bryophyta) Vascular Plants (Tracheophytes) 9 phyla – 4 seedless phyla – 5 seeded phyla