LIFE 103 1st Edition Lecture 6 Outline of Last Lecture II. Basics of ProtistsIII. 4 Different Supergroups I. Excavata II. “SAR” cladeIII. ArchaeplastidaIV. Unikonta IV. Why Care? Outline of Current Lecture I. A summary of life II. Context of LifeI. Numbers and figures III. Derived traits of land plants I. Alternation of generationsII. SporesIII. Gametangia IV. Linear growth i. All absent or lost in common ancestorIV. Haploid vs. Diploid V. Key termsI. GametophyteII. Sporophyte VI. Nonvascular plants I. Liverworts II. HornwortsIII. MossesCurrent Lecture: Algae and Seedless Land Plants A Summary of LifeI. Reproduce (ultimate goal) I. Eat II. Grow III. Avoid dying These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.II. There are tradeoffs; you can’t be good at everything III. Natural selection favors organisms that are best at living under current conditions Summary of next 2 lectures I. What plant traits allowed colonization of land? II. The diversity, growth, and reproduction of I. Nonvascular plantsII. Seedless vascular plants Seedless Land Plants I. Fig. 29.7II. Context of life: I. Universe: 13.2 billion years agoII. Solar System: 7.8 billion years ago III. Earth: 4.6 billion years ago IV. Life: 3.2 billion years ago V. Photosynthesis (oxygenic): 2.8 billion years agoVI. O2 in atmosphere: 800 million years ago VII. Origin of land plants: about 475 million years ago VIII. Origin of vascular plants: about 420 million years ago IX. Origin of extant seed plants: about 305 million years ago A window into the past? I. “Liverworts, hornworts and mosses acquired many unique adaptations over the long course of their evolution. Nevertheless, living bryophytes likely reflect some traits of the earliest plants. The oldest known fossils of plant fragments, for example, include tissues very similar to those inside liverworts. Researchers hope to discover more parts of these ancient plants to see if this resemblance is reflected more broadly.” –Campbell (pg. 606) Derived Traits of Land Plants II. Alternation of generations and multicellular, dependent embryos III. Walled spores produced in sporangiaIV. Multicellular reproductive structures (gametangia) V. Linear growth from root and shoot tips: Apical meristems VI. All absent in common ancestor; some lineages have lost some traits VII. Some common additional traitsI. Cuticle II. Secondary compounds (anti-herbivory, UV protection)VIII. Fig. 29.5: patterns of ploidy and life stage through the alternation of generation I. Large one is the dominantGrow and Reproduce: haploid or diploid? I. See next page for table Benefits of Haploidy I. Deleterious mutations eliminated morequickly in haploid populations Costs of Haploidy II. All deleterious mutations are “exposed” III. Higher death rate of haploidsBenefits of Diploidy I. Spare allele protects against deleterious mutationsII. Greater genetic diversity brings faster adaptation to new environments III. Crossing over during meiosis can bring beneficial alleles together (homologouspairs of chromosomes switch) Costs of DiploidyI. Double mutation rate (2 copies of each allele) II. Both beneficial and deleterious mutations are more likely III. Nutritional demands higher with greater DNA content IV. Diploid cells often larger Why Ploidy Cycles? I. Ploidy cycles may bring the benefits of both haploid and diploid II. Better chance to exploit resourcesI. Haploid and diploid phases may live in different ecological conditions III. Hedge bets about dispersing offspringI. Haploid spores may spread far II. Diploid spores may have higher survival rates Key terms of life cyclesI. Gametophyte (“gamete-producing plant”)I. Gametophyte is HAPLOIDII. Produces haploid gametes III. Gametes produced by mitosisIV. Gametes fuse to form diploid zygote II. Sporophyte (“spore-producing plant”)I. Sporophyte is DIPLOID II. Produces haploid spores by meiosisIII. Spores grow into haploid gametophytes Major groups of Land plants I. Nonvascular plantsII. Seedless vascular plantsIII. GymnospermsIV. Angiosperms Nonvascular plantsV. Three phyla of BryophytesI. Liverworts, Hornworts, mosses (phylum = Bryophyta) VI. Gametophyte is dominant stage (sperm baby) VII. Forms ground-hugging carpetI. Weak tissuesII. No vascular tubes to transport water and nutrients VIII. Sexes usually divided into male and female gametophytes LiverwortsI. Named for liver-shaped