Plant Evolution and Diversity

1
Plant Evolution and Diversity

• Reading Chaps. 29, 30
• I. Relationship to protists
• A. What is a plant?
• B. Green algae and plants
• C. Problems of land life
• D. Overview of the plant phyla
• II. Bryophytes
• III. Seedless vascular plants
• IV. Seed Plants
• A. Gymnosperms (naked seeds)
• B. Angiosperms (flowering plants)

2
A. What is a plant?

• What does it do?
• - Photosynthesize
• - CO2 uptake
• - O2 release
• - Water loss
• - Water and nutrient uptake
• - Grow
• Where? Which directions?

Fig. 1.10, Raven et al.
3
What is a plant?
Ulva
Fig. 1.10, Raven et al.
4
B. A tentative phylogeny of the eukaryotes

• Points
• Plants are closely related to the green algae.
• Photosynthetic and non-photosynthetic protists
  are often more closely related to each other than
  to other phyla of similar lifestyle.
  
• 3. Fungi and animals are most closely related.
• 4. Many protist groups not shown.

Fig. 28.8
5
Evolution

• How are protists related to higher plants?

Algae are eukaryotic photosynthetic organisms
that are not plants.
6
How do we tell a plant from an algae?

• Algae are eukaryotic photosynthetic organisms
  that are not plants.
  
• What are the defining characteristics of plants?
• - multicellular, eukaryotic, photosynthetic
  autotrophs
  
• - so are the macroalgae - Rhodophyta, Phaeophyta,
  Chlorophyta

7
Cell chemistry

• - Chlorophyll a and b
• - Cell walls of cellulose (plus other polymers)
• - Starch as a storage polymer
• So do dinoflagellates, green algae, and
  Euglenoids!

8
Cell chemistry and structure

• - rosette cellulose synthesizing compounds
• - peroxisome enzymes
• - phragmoplast
• Similar to some Chlorophyata Charophyceans

Chara
Coleochaete
9
Land plants only

• - Apical meristem

29.3
10
Land plants

• - Alternation of generations (sporic life cycle)

29.6
11
Land plants only

• - Walled spores (with sporopollenin) produced in
  sporangia

Fig. 29.7
12
Land plants only

• - Multicelluar gametangia archegonia and
  antheridia

Male - sperm
Female - egg
13
Land plants only

• - Multicellular, dependent embryos --
  Embryophytes

29.4
14
C. Problems of land life Adaptations for living
in air
15
1. Desiccation of plant
Fig. 1.10, Raven et al.

• - Water conservation - epidermis w/cuticle,
  stomata

16
2. Resource acquisition - water and minerals

• - Roots

Fig. 1.10
17
3. Light acquisition

• a. Surface area
• - Leaves
• b. Fight gravity
• - Support
• c. Fluid transport
• - Vascular tissue, xylem and phloem

Fig. 1.10
18
4. No water for reproduction

• a. gamete dispersal and desiccation
• b. spore dispersal and desiccation

- Fertilization and dispersal that are
independent of water (some).
19
D. The plant taxa

• Fig. 29.14

20
The plant taxa

• Fig. 29.14

21
II. Bryophytes
22
A. The Bryophyte Phyla

• Liverworts (Hepatophyta)
• 6500 species, moist environments
• Hornworts (Anthocerophyta)
• 100 species,
• Mosses (Bryophyta)
• 12,000 species, widespread

23
B. Bryophyte ecology
Molly and Rich
24
Bryophyte ecology1. Groundcover and epiphytes
Groundcover
Epiphytes
25
Bryophyte ecology 2. Peat moss
Fig. 29.19
26
Bryophyte ecology 3. Global carbon cycle
27
C. Bryophyte life cycle and structure
1. Gphyte vs. sphyte 2. Archegonia and antherid
ia 3. Water for fert. 4. Embryo on gphyte 5. S
pores for dispersal
6. Roots and leaves?
Fig. 29.16
28
III. Seedless vascular plants -Pteridophytes

• Phyla
• Lycophyta
• - club mosses
• Pterophyta
• - ferns
• - whisk ferns (Psilotophyta)
• - horsetails (Sphenophyta)

Fig. 29.21
29
A. Whats new?

• 1. Vascular tissue
• 2. Sporophyte dominant

30
1. What is vascular tissue and what does it do?

• a. Xylem
• - water and nutrients up from roots to stem,
  leaves one way
  
• - hollow
• - dead at maturity
• - secondary cell walls, lignin
• b. Phloem
• - photosynthate from leaves to roots, shoots,
  meristems
  
• - living at maturity
• - no secondary cell walls

31
2. Sporophyte dominant Fern life cycle
29.23
32
B. Other SVP developments

• 1. True leaves
• 2. True roots
• 3. Strobilus
• 4. Heterospory

33
Other SVP developments true leaves
Megaphylls
Microphylls
Fig. 29.22
34
Other SVP developments true roots
35
Other SVP developments strobilus
36
Other SVP developments heterospory
Homosporous
Eggs
Single type of spore
Bisexual gphyte
Sporophyte
Sperm
Heterosporous
Female gphyte
Eggs
megaspore
Sporophyte
Male gphyte
microspore
Sperm
Fig. , p. 591
37
C. Summary of everything seedless
38
C.1. Evolutionary trends
Draw
39
C.2. Which problems were solved?

• 1. Desiccation of plant
• - waterproof cuticle with stomata
• 2. Water and nutrient acquisition
• - true roots, in Lycophyta
• 3. Light acquisition
• - true leaves microphylls and megaphylls
• - support xylem cells
• - fluid transport xylem (water and nutrients)
  and phloem (photosynthate)

40
C.2. Which problems were solved?

• 4. Water for reproduction
• - Spores sporopollenin cell wall
• - Gametes NOT SOLVED!

41
C.3. Which problems were not solved?

• 1. Gametes not protected from desiccation
• 2. Water needed for fertilization
• 3. Embryo dependent on gphyte
• 4. Gravity/stability - cant add support tissue
• 5. Growth/fluid conduction - cant add conducting
  tissue
  
• 6. Dispersal unit - small, unnourished spore

42
IV. Seed Plants

• A. Whats new?
• 1. Continued gphyte reduction
• 2. Pollen
• 3. Seeds
• 4. Secondary growth
• B. Gymnosperms
• C. Angiosperms

43
A. Whats new?1. Gametophyte reduction continued
Heterospory
Fig. 30.1
44
A. Whats new?

• 2. Pollen male gametophyte

Male micro
Heterospory
Female mega
45
A. Whats new? 3. Seeds
Incorrect color in c - should be
blue for food supply, which is
haploid (megagametophyte).
Fig. 30.2
46
A. Whats new?

• 4. Secondary growth (draw)

47
A. Gymnosperms

• Phyla
• Ginkgophyta - 1 genus, 1 species Ginkgo biloba
• Cycadophyta - 100 species
• Coniferophyta - 550 species
• Gnetophyta - transitional to flowering plants
• 3 genera, 70 spp., including wierdest plant on
  earth

48
Conifers
Biggest
49
Conifers
oldest
50
Conifers
highest
51
Conifers
Furthest north
52
Conifers
Widespread
53
Conifers
Wet conditions
54
Conifers
Dry conditions
55
Conifers
Most photographed
56
Conifer life cycle
30.9
57
C.3. Which problems were solved?

• 1. Gametes not protected from desiccation
• 2. Water needed for fertilization
• 3. Embryo dependent on gphyte
• 4. Gravity/stability - cant add support tissue
• 5. Growth/fluid conduction - cant add conducting
  tissue
  
• 6. Dispersal unit - small, unnourished spore

58
B. Angiosperms Phylum Anthophyta

• 250,000 species
• Monocots
• 60,000 spp.
• Lilies, orchids, grasses, palms
• Eudicots
• Most of the rest
• Trees, shrubs, forbs

59
1. Why are they important?

• a. Most diverse phylum, huge radiation
• b. Base of many terrestrial food webs
• c. Basis of agriculture
• Fruits
• Vegetables
• Grains
• d. Secondary compounds (e.g., taxol from Yew)

60
2. Whats new?

• a. Flowers - more efficient fertilization
  (pollination)
  

Stamen microsporangia Ovule megasporangium pl
us integuments Petals and sepals modified l
eaves
30.13
61
2. Whats new?

• b. Fruits - more efficient dispersal

30.15
62
b. Fruits - different kinds
Wind-dispersed
Animal dispersed - riding
Animal dispersed - eaten
30.16
63
2. Whats new?

• c. Co-evolution with animals

Pollination
Dispersal
64
3. Life cycle
a. ovule inside carpel b. smaller gphyte c. dou
ble fert.
d. endosperm - 3n