P1252109389PeKdW

1
(No Transcript)
2
Green Plants

• Chapter 29

3
Green Plants

• Green algae and land plants
• Green algae are protists
• Study them along with land plants for two
  reasons
• They are the closest living relatives to land
  plants
• The transition from aquatic to terrestrial life
  occurred when land plants evolved from green
  algae.

4
Why Do Biologists Study the Green Plants?
5
Why Do Biologists Study the Green Plants?

• Agriculture, forestry, and horticulture
• Much research involved in increasing productivity
  
• In finding new ways to use plants
• Primary producer in the biosphere

6
Plants and the Ecosystem

• Produce oxygen
• Build soil by providing food for decomposers
• Prevent nutrients from being lost by erosion by
  wind and water
• Hold water
• Moderate the local climate

7
Primary Producers

• Land plants are the dominant primary producers in
  terrestrial ecosystems and are key to the carbon
  cycle on continents

8
The Food Chain

• Plants are eaten by herbivores
• Herbivores are eaten by carnivores
• Carnivores are eaten by omnivoresorganisms that
  eat both plants and animals.
• Omnivores feed at several different levels in the
  terrestrial food chain.

9
Domestication andSelective Breeding

• Humans actively select agricultural crops
• called artificial selection

10
Artificial Selection Changes Traits
11
Plant-Based Fuels and Fibers

• Humans depend on plants for cooking and heating
  fuels
• As a source of fibers for clothing and other
  things
• Primary interest in woody plants is for building
  materials

12
(No Transcript)
13
(No Transcript)
14
Bioprospecting

• Find naturally occurring compounds that can be
  used as drugs, fragrances, insecticides,
  herbicides, or fungicides

15
Other Reasons to Study Plants

• Hydroponics, the liquid culture of plants, can be
  used to harvest large quantities of plant
  chemicals
• Ethnobotanists study how humans use plants and
  research new uses for plants.

16
How Do Biologists Study Plants
17
Studying Plants

1. They compare the fundamental morphological
   features of various green algae and green plants
2. They analyze the fossil record of the lineage
   and
3. They assess similarities and differences in
   molecular traits such as the DNA sequences from
   selected genes.

18
Analyzing Morphological Traits

• The 12 most important phyla of plants are grouped
  into three categories nonvascular plants,
  seedless vascular plants, and seed plants

19
Analyzing Morphological Traits
20
(No Transcript)
21
(No Transcript)
22
(No Transcript)
23
(No Transcript)
24
Non-Vascular Plants

• Include liverworts, hornworts, and mosses
• Vascular tissuespecialized groups of cells that
  conduct water or dissolved nutrients from one
  part of the plant body to another

25
Seedless vascular plants

• Well-developed vascular tissue
• Do not make seeds.
• A seed consists of an embryo and a store of
  nutritive tissue, surrounded by a tough
  protective layer
• Horsetails, ferns, club mosses, and whisk ferns

26
Seed Plants

• Have vascular tissue
• Make seeds
• Five major lineages in the group cycads,
  ginkgoes, conifers, gnetophytes, and angiosperms.

27
Angiosperms and Gymnosperms

• The gnetophytes, cycads, ginkgoes, and conifers
  are gymnosperms
• Seeds do not develop in an enclosed structure
• Flowering plants are angiosperms
• Seds develop inside a protective structure called
  a carpel.

28
Using the Fossil Record

• Fossil record for land plants began 476 million
  years ago
• Huge, so it is broken up into five segments
• Each of which encompasses a major event in the
  diversification of land plants

29
Using the Fossil Record
30
Evaluating Molecular Phylogenies

• The phylogenetic tree that follows shown has
  several important points
• Land plants probably evolved from green algae.
• The green algal group called Charales is the
  sister group to land plantsmeaning that Charales
  are their closest living relative.

31
Evaluating Molecular Phylogenies

• 3. The green algae group is paraphyletic.
• The land plants are monophyletic.
• The nonvascular plants are the most basal groups
  among land plants.
• Morphological simplicity of the whisk ferns is
  probably a derived trait.
• Seeds and flowers evolved only once.

32
Evaluating Molecular Phylogenies
33
What Themes Occur in the Diversification of Green
Plants?
34
How Did Plants Adaptto Dry Conditions?

• Photosynthetic organisms had to adapt to
  conditions to move from aquatic to terrestrial
  environments
• Conditions in which only a portion of their
  tissues were bathed in fluid
• Water problem arose in two steps
• (1) preventing water loss from cells
• (2) transporting water from tissues with access
  to water to tissues without access

35
Preventing Water Loss

• Cuticle - a waxy, watertight sealant
• Gas exchange is accomplished by stomata

36
Transporting Water

• The first land plants were low and sprawling
• Early upright land plants were rigid due to
  turgor pressure
• Vascular tissue evolved in a series of gradual
  steps
• provided an increasing level of structural
  support, allowing plants to grow upright

37
Transporting Water
38
Transporting Water
39
Transporting Water
40
The major innovations that allowed plants to
adapt to life on land
41
Alternation of Generations

• Multicellular haploid phase called the
  gametophyte
• Multicellular diploid phase known as the
  sporophyte
• Relationship between gametophyte and sporophyte
  is variable
• Time of sporophyte and gametophyte varies from
  species to species
• Amount of mitosis varies from species to species

42
Alternation of Generations
43
Alternation of Generations
44
Alternation of Generations
45
Alternation of Generations
46
Alternation of Generations
47
Alternation of Generations
48
Retaining and Nourishing Offspring

• Two evolutionary changes occurred in early in the
  history of land plants
• (1) gametes were produced in complex
  multicellular structures

49
Retaining and Nourishing Offspring

• (2) the embryo was retained on the parent and
  nourished
• Based on this innovation, biologists call the
  land plants embryophytes

50

• Evolutionary adaptations that allowed plants to
  reproduce effectively on land

51
Key Lineages ofGreen Plants
52
Green Algae

• Paraphyletic group
• About 7000 species
• Have a double membrane and chlorophylls a and b,
  but relatively few accessory pigments.
• Green algae live in close association with other
  organisms
• Fungi and cyanobacteria

53
Ulvobionta

• Most green algae belongs to this group (e.g.,
  Volvox)
• Important primary producers in aquatic areas

54
Coleochaetales

• Microscopic Algae
• Most grow as flat sheets of cells (e.g., water
  lilies), and the multicellular individuals are
  haploid
• Found living on solid surfaces in still or slow
  moving fresh waters

55
Charales (Stoneworts)

• They commonly accumulate crusts of calcium
  carbonate over their surfaces. They can form
  extensive beds on lake bottoms
• Implicated as the closest relative of land plants
• Brittleworts or skunkweed

56
Nonvascular Plants (Bryophytes)

• Nonvascular plants or bryophytes
• Most basal lineages of land plants
• The three lineages with living representatives do
  not form a monophyletic group
• Represent an evolutionary grade
• (liverworts, hornworts, and mosses)

57
Hepaticophyta (Liverworts)

• Liver-shaped leaves
• Can grow on bare rock or tree bark, which helps
  in soil formation
• Live near water
• umbrella-shaped sporophytes

58
Anthocerophyta (Hornworts)

• The sporophytes look like horns and have stomata
• Single, large chloroplast in each cell of
  gametophyte

59
Bryophyta (Mosses)

• Can be abundant in extreme environments and can
  become dormant
• Sphagnum species are among the most profuse
• No vascular tissue or wood
• Play important roles in reducing erosion
• Water and nutrient cycling

60
Seedless Vascular Plants

• Paraphyletic group that forms a grade between the
  nonvascular plants and the seed plants.
• All species of seedless vascular plants
• Have conducting tissues with cells that are
  reinforced with lignin, forming vascular tissue
• Four main groupings   Psilophyta, Lycophyta,
  Sphenophyta, Pterophyta,  

61
Lycophyta(Lycophytes, or Club Mosses)

• Lycopods are the most ancient plant lineage with
  roots. Tree-sized lycophytes dominated the
  coal-forming forests of the Carboniferous period

62
Psilotophyta (Whisk Ferns)

• Rootless, green-stemmed epiphyte
• Whisk ferns are restricted to tropical regions
  and have no fossil record
• One of only a few surviving members of an ancient
  group
• most primitive and simplest vascular plant alive
  today

63
Sphenophyta (or Equisetophyta) (Horsetails)

• Terrestrial and herbaceous
• Can flourish in waterlogged soils by allowing
  oxygen to diffuse down their hollow stems
• Silicified stems that are hollow except at the
  jointed nodes
• Multiflagellated sperm must travel through a film
  of water

64
Sphenophyta (or Equisetophyta) (Horsetails)
65
Pteridophyta (Ferns)

• Ferns appear in the Devonian fossil record (359
  to 353 Mya)
• Vascular tissue
• Only seedless vascular plants to have large,
  well-developed leaves

66
Seed Plants

• The seed plants are a monophyletic group that
  consists of the gymnosperms and the angiosperms
• Defined by the production of seeds and pollen
  grains
• The earliest seeds appear in the Late Devonian

67
The Evolution of Pollen and Seeds

• When pollen evolved, seed plants lost their
  dependence on water for fertilization
• Seed is a structure that encloses and protects a
  developing embryo
• Often attached to a structure that aids in
  dispersal by wind, water, or animals
• Enables the gametophyte to obtain nutrition from
  the sporophyte

68
Seeds

• A seed
• Develops from the whole ovule
• Is a sporophyte embryo, along with its food
  supply, packaged in a protective coat
• Development of seeds allowed plants to withstand
  harsh environments and distribute their offspring
  widely
• Most seeds will only germinate under good
  conditions

69
Seeds
70
The Evolution of Pollen and Seeds
71
Gymnosperms

• Plants that have naked seeds that are not
  enclosed in ovaries
• Exposed on modified leaves that usually form
  cones
• Called conifers, include pine, fir, and redwood
• The gymnosperms include four plant phyla
• Cycadophyta- ancient plants, cycads
• Gingkophyta- ginkgos
• Gnetophyta- welwitschia, and gnetum
• Coniferophyta, pines and firs

72
Gymnosperm Diversity
73
Gymnosperm Diversity
74
Gymnosperm Evolution

• The first seed-bearing plants appeared around 360
  mya
• Gymnosperm species
• Gymnosperms dominated the Mesozoic terrestrial
  ecosystems
• Many cycads and other progymnosperms

Archaeopteris
75
Gnetophyta (Gnetophytes)

• Lineage dates back only to the early Cretaceous
• Three living genera
• Ephedra
• Gnetum
• Welwitschia
• Closest extant relative of the flowering plants
• Ephedrine isolated from this group

76
Cycadophyta (Cycads)

• Palm-like gymnosperms
• Ancient group of seed plants
• Common in the Jurassic Period
• They harbor large numbers of cyanobacteria

77
Ginkgophyta (Ginkgoes)

• One species is alive today Ginkgo biloba
• It is dioecious, and individual trees are either
  male or female
• Can live for a millenium
• Rotting seeds smell very bad

78
Coniferophyta (Conifers)

• Naked seed
• Around 550 species arranged in seven families
• Named for its reproductive structure, the cone
• Leaves take the form of needles or scales

79
Anthophyta (Angiosperms)

• Largest group of plants
• The defining adaptation is the flower
• Supply the food that supports virtually every
  other species
• Enclose their ovules (and seeds) within a carpel
• Ovary enlarges into fruit

80
Angiosperms

• Are commonly known as flowering plants
• Are seed plants that produce the reproductive
  structures called flowers and fruit
• Seeds are contained in the fruit which is a
  modified ovaries
• Are the most widespread and diverse of all plants
• About 90 of all plants, over
• 250, 000 species

81
Angiosperms

• The key adaptations in
• the evolution of
• angiosperms
• Are flowers and fruits
• Flowers are structures specialized for sexual
  reproduction
• Contains male and/or female sexual organs and
  gametes

82
Flowers

• A flower is a specialized shoot with modified
  leaves
• Sepals, which enclose the flower
• Petals, which are brightly colored and attract
  pollinators
• Stamens, which produce pollen
• Carpels, which produce ovules

83
Fruits

• Usually consist of a mature ovary
• Several different types of fruit
• Can be either fleshy or dry
• Strawberries, grapes
• Beans and peas, nuts
• Can be dispersed by wind, water or animal

84
Types of Fruits
85
Angiosperm Diversity

• The two main groups of angiosperms
• Are monocots and eudicots
• Basal angiosperms
• Are less derived and include the flowering plants
  belonging to the oldest lineages
• Only about 100 species
• Magnoliids
• Share some traits with basal angiosperms but are
  more closely related to monocots and eudicots
• Very old lineage, fossil records of manoliid
  pollen

86
Angiosperm Diversity
87
Monocots and Dicots