The document discusses plant diversity and the organization of biodiversity using phylogenetic trees, emphasizing speciation and evolutionary lineages. It explores the classification of life, particularly the kingdom Protista, and the importance of shared derived traits for determining relationships among organisms. The document also outlines general life cycles among different groups, such as algae and land plants, highlighting variations in reproductive strategies and gamete morphology.

1. BIOLOGY 144
Biodiversity and Ecology:
PLANT DIVERSITY
Prof. Leanne Dreyer

2. BIOLOGY 144
1. Phylogenetic trees
PLANT DIVERSITY

5. Organizing diversity

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

7. • 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

8. • 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

9. • 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

10. Organizing diversity
Evolutionary history and classification

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

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

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

14. • 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

15. • 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

16. BIOLOGY 144
2. Evolutionary origin of plants
PLANT DIVERSITY

17. Protista

18. eukarya
bacteria archaea
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6 kingdom
classification
system

19. • 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

20. 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

21. 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?

22. • 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)

23. Archaeplastida

24. • 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

25. 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)…..

26. • 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

27. • 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

28. • 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

29. • 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