LIFE 103 1st Edition Lecture 6 Outline of Last Lecture II Basics of Protists III 4 Different Supergroups I Excavata II SAR clade III Archaeplastida IV Unikonta IV Why Care Outline of Current Lecture I A summary of life II Context of Life I Numbers and figures III Derived traits of land plants I Alternation of generations II Spores III Gametangia IV Linear growth i All absent or lost in common ancestor IV Haploid vs Diploid V Key terms I Gametophyte II Sporophyte VI Nonvascular plants I Liverworts II Hornworts III Mosses Current Lecture Algae and Seedless Land Plants A Summary of Life I 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 III There are tradeoffs you can t be good at everything Natural selection favors organisms that are best at living under current conditions Summary of next 2 lectures I II What plant traits allowed colonization of land The diversity growth and reproduction of I Nonvascular plants II Seedless vascular plants Seedless Land Plants I II Fig 29 7 Context of life I Universe 13 2 billion years ago II 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 ago VI 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 III IV V VI VII VIII Alternation of generations and multicellular dependent embryos Walled spores produced in sporangia Multicellular reproductive structures gametangia Linear growth from root and shoot tips Apical meristems All absent in common ancestor some lineages have lost some traits Some common additional traits I Cuticle II Secondary compounds anti herbivory UV protection Fig 29 5 patterns of ploidy and life stage through the alternation of generation I Large one is the dominant Grow and Reproduce haploid or diploid I See next page for table Benefits of Haploidy I Costs of Haploidy Deleterious mutations eliminated more quickly in haploid populations II III Benefits of Diploidy I II III Spare allele protects against deleterious mutations Greater genetic diversity brings faster adaptation to new environments Crossing over during meiosis can bring beneficial alleles together homologous pairs of chromosomes switch All deleterious mutations are exposed Higher death rate of haploids Costs of Diploidy I II III IV Double mutation rate 2 copies of each allele Both beneficial and deleterious mutations are more likely Nutritional demands higher with greater DNA content Diploid cells often larger Why Ploidy Cycles I II III Ploidy cycles may bring the benefits of both haploid and diploid Better chance to exploit resources I Haploid and diploid phases may live in different ecological conditions Hedge bets about dispersing offspring I Haploid spores may spread far II Diploid spores may have higher survival rates Key terms of life cycles I II Gametophyte gamete producing plant I Gametophyte is HAPLOID II Produces haploid gametes III Gametes produced by mitosis IV Gametes fuse to form diploid zygote Sporophyte spore producing plant I II III Sporophyte is DIPLOID Produces haploid spores by meiosis Spores grow into haploid gametophytes Major groups of Land plants I II III IV Nonvascular plants Seedless vascular plants Gymnosperms Angiosperms Nonvascular plants V VI VII VIII Three phyla of Bryophytes I Liverworts Hornworts mosses phylum Bryophyta Gametophyte is dominant stage sperm baby Forms ground hugging carpet I Weak tissues II No vascular tubes to transport water and nutrients Sexes usually divided into male and female gametophytes Liverworts I Named for liver shaped gametophyte