Bio 144 Plant diversity - Lecture 1.pptx

Pant diversity

1. BIOLOGY 144 Biodiversity and Ecology: Plant diversity Prof. Leanne Dreyer

2. BIOLOGY 144 1. Phylogenetic trees Plant diversity

3. Organizing diversity

4. How do phylogenetic trees work???? Organizing diversity

5. read phylogenies like family trees “ root ” = ancestor “ tips ” = descendents from root to tips = moving through time Organization of diversity branching = single evolutionary lineage splitting into two lineages (speciation) phylogeny = pattern of shared ancestry

6. each lineage has some history that is shared with other lineages, and some history that is unique in the same way each lineage has shared and unique ancestors Organizing diversity

7. clade = a group which includes a common (shared) ancestor and all the descendants of that ancestor (living or dead), but ONLY descendants of that ancestor = monophyletic group a clade can be recognized as the group you would get if you cut the tree anywhere with a single line clades are imbedded within one another hierarchically Organizing diversity

8. Organizing diversity Evolutionary history and classification

9. Evolutionary history of life ≠ ladder Phylogenies are often misinterpreted as meaning some organisms are more advanced than others      Organizing diversity lemurs monkeys chimps humans

10. speciation event: 1 evolutionary lineage splits into two lineages (eg. one becomes mosses, the other becomes ferns, pines and roses) Organizing diversity

11. After each speciation event it does not matter which branch is left or right – the two trees below are identical . Organizing diversity

12. To build a tree biologists gather data about characteristics of the group they are interested in Characters = inherited, genetically controlled and comparable between organisms ( homologous ) Typical characters: morphology, genetics (DNA sequence), physiology and behavioral Similarities resulting from shared common ancestry By using shared derived characters organisms can be hierarchically divided into smaller and smaller groups Look for similarities between organisms Organizing diversity Building phylogenetic trees

13. e.g. amphibians, turtles, lizards, snakes, crocs, birds and mammals all have four limbs (or once had) this shared derived trait is no good for determining relationships within the clade, because all members share the trait need other characters to determine relationships within the clade Organizing diversity

14. BIOLOGY 144 2. Evolutionary origin of plants Plant diversity

15. Protista

16. eukarya bacteria archaea protista plantae fungi animalia protista protista protista 6 kingdom classification system

17. Protista remarkably diverse: unicellular, colonial and multi-cellular groups 200 000 (distantly related) organisms lumped into a poorly-defined Kingdom Grouped together on the basis of 1 shared negative trait: They are eukaryotes that are NOT fungi, animals or plants Highly variable in terms of all other traits (NO shared derived traits) Kingdom Protista

18. Ryk Protista DNA techniques: – better general biological classification – relationships within Protista Protista NOT monopyletic grouped together for convenience rather than on scientific merit – do not reflect phylogenetic relationships 60 protist lineages still not placed in the tree of life but we can currently recognize 6 main phylogenetic groups with the kingdom

19. Still many questions: How many protist lineages are there really? How do we classify them? What did the protist ancester of plants, animals and fungi look like? Are protists = several different kingdoms of equivalent rank as plants, animals and fungi? Are protists actually members of different kingdoms ?

20. Currently 6 main protist lineages - ca. 60 protist lineages of uncertain placement All photosynthetic protists informally called algae Huge, diverse group – we will discuss some groups in detail in search of origin (root) of land plants Protist lineage Archaeplastida includes Rhodophyta (red algae), and the Viridiplantae (green algae + land plants)

21. Archaeplastida

22. Archaeplastid chloroplasts surrounded by two membranes Implies shared origin where chloroplasts originated directly from endosymbiotic cyanobacteria In all other algae chloroplasts are surrounded by 3/4 membranes

23. General life cycle sexual reproduction entails the alternation between haploid and diploid phases if both phases are multicellular, it can be referred to as the alternation of generations (e.g. landplants) made possible by fertilization and meiotic divisions 3 different general life cycles among the algae (and protists in general)…..

24. Tipe 1 corresponds to life cycle of plants (common among algae) Multicellular diploid phase (sporophyte) develop sporangia in which spores are formed through meiosis Haploid spores divide through mitosis to form mature, multicellular gametophytes Gametophyte produces gametes through mitosis in gametangia, 2 gametes fuse through fertilization and a new sporophyte is formed Sporic meiosis in a haplodiplontic life cycle – alternation of generations

25. Type 2 corresponds with the life-cycle of animals Rare among the algae ( eg. Sargassum) Certain cells of the multicellular diploid produce gametes by meiosis (not spores!) Gametes represent the haploid phase, and immediately fuse again to form a diploid zygote Gametic meiosis since meiosis directly gives rise to gametes Diplontic life cycle

26. Type 3 corresponds with the life-cycle of Fungi Zygote represents the only diploid cell Haploid phase is dominant, irrespective of whether the organism is uni - or multi-cellular Haploid phase forms when the zygote undergoes meiosis Zygotic meiosis, because zygote forms spores Haplontic life cycle

27. algae gametes display more morphological variation than any other group gametes of all algal groups can swim with the aid of flagella (except Rhodophyta - oogamous) Isogametes : all gametes identical, male and female gametes cannot be recognized, but are of genetically different crossing lines (arbitrarily called + and –); organism isogamous Anisogametes : gametes differ in size, but both still have flagella; smaller gamete is male and larger one female; organism anisogamous Oogametes : one large, immobile female gamete and one smaller, mobile male gamete, organism oogamous