Plants are first believed to have appeared on Earth approximately 500 million years ago'

1
Plants

• Plants are first believed to have appeared on
  Earth approximately 500 million years ago.
• These early plants are thought to have evolved
  from green algae, Protista chlorophyta.
• Fossil evidence indicates early plants resembled
  present-day moss.

2
Plant Adaptations

• As plants are terrestrial it is necessary that
  plants evolved specific land adaptations.
• Plants needed to be able to
• absorb water and nutrients from the soil
• protect their gametes (sex cells)
• withstand high winds
• be able to grow upright against gravity

3
Plant Phylogeny
4
(No Transcript)
5
Time History of Plants and Protists
6
The Plant Life Cycle

• Plants have an alternation of generations the
  diploid spore-producing plant (sporophyte)
  alternates with the haploid gamete-producing
  plant (gametophyte).
• The plant life cycle has mitosis occurring in
  spores, produced by meiosis, that germinate into
  the gametophyte phase.

7
The Plant Life Cycle

• Gametophyte size ranges from three cells (in
  pollen) to several million (in a"lower plant"
  such as moss)
• Alternation of generations occurs in plants,
  where the sporophyte phase is succeeded by the
  gametophyte phase.
• The sporophyte phase produces spores by meiosis
  within a sporangium. The gametophyte phase
  produces gametes by mitosis within an antheridium
  (producing sperm) and/or archegonium (producing
  eggs).

8
The Plant Life Cycle

• Within the plant kingdom the dominance of phases
  varies.
• Nonvascular plants, the mosses and liverworts,
  have the gametophyte phase dominant.
• Vascular plants show a progression of increasing
  sporophyte dominance from the ferns and "fern
  allies" to angiosperms.

9
(No Transcript)
10
Prevention of Water Loss

• Fruits, stems and leaves are covered with a
  protective waxy layer called a cuticle.
• This waxy cuticle helps prevent the water in the
  plants tissues from evaporation into the air.
• Opening in the cuticle are called stomata.
• Stomata are the pores that allow gas exchange.
  During the day stomata open to release water and
  oxygen and take in carbon dioxide. During the
  night stomata close to prevent water loss.

11
Photosynthesis

• Photosynthesis takes place in the leaves of
  plants.
• Sunlight 6CO26H2O 6O2 C6H1206

12
Transportation of Materials

• Non-Vascular Plants-
• The mosses and other small-less familiar plants
• Water and nutrients must move throughout the
  plant via osmosis and diffusion

13
Transportation of Materials

• Vascular Plants
• plants which contain vascular tissue or
  tube-like elongated cells which transport
  material
• the evolution of vascular plants enabled plants
  to live further away from water.

14
Bryophytes
15
Bryophytes-The Mosses and Liverworts

• Nonvascular plants
• Require significant and steady moisture supply
  thus are limited to specific wet habitats such as
• sheltered areas near streams
• humid tropical areas

16
Moss Reproduction Cycle

• In the life cycles of all plants, an alternation
  of generations occurs, in which haploid
  gametophytes and diploid sporophytes produce one
  another.
• In the mosses and other bryophytes,the haploid
  gametophyte dominates the life cycle.

17
Moss Reproduction Cycle
18
Lycophyta- The Seedless Vascular Plants

• Composed of the club and spike mosses
• First believed to appear on Earth 390 mya
• Characteristics
• grow close to the ground predominantly in damp
  forests
• major evolutionary advancement vascular
  spore bearing leaves
• leaves appear as spirals or whorls

19
Vascular Plants

• Vascular Plants are tissues that transport
  materials from one part of a plant to another
• Xylem-transport water
• Phloem- transport sugar (food
• Both xylem and phloem extend from close to the
  end of the root tip, through the stem, and into
  the leaves of a vascular plant.

20
Pterophyta - The Ferns

• Ferns are first believed to have appeared on
  Earth 390 million years ago.
• Ferns can be found in many types of environments.
  
• There are 12,000 species of ferns today, although
  the fossil history of ferns shows them to have
  been a dominant plant group during the Paleozoic
  Era.
• Ferns reproduce by spores from which the
  free-living bisexual gametophyte generation
  develops.

21
(No Transcript)
22
Gymnosperms are Seed Plants

• Gymnosperms have seeds but not fruits or flowers.
• Gymnos means naked, sperm means seedgymnosperm
  naked seeds.
• Gymnosperms developed during the Paleozoic Era
  and became dominant during the early Mesozoic
  Era. There are 700 living species placed into
  four divisions conifers, cycads, ginkgos, and
  gnetales

23
Gymnosperms Continued

• Gymnosperms are undoubtedly the group from which
  the angiosperms developed, although, as Charles
  Darwin noted in Origin of Species, which group
  "remains an abominable mystery.

24
Cycads

• Cycads retain some fern-like features.
• These cones are unisexual, in fact the plants are
  dioecious, having separate male and female
  plants.
• Cycads were much more prominent in the forests of
  the Mesozoic era than they are today.
• Presently, they are restricted to the tropics.
• Cycas revoluta leaves are often used in Palm
  Sunday services

25
(No Transcript)
26
Ginkos

• The ginkgos also were a much more prominent group
  in the past than they are today.
• The sole survivor of this once robust and diverse
  group is Ginkgo biloba, the maidenhair tree.
• Pollination is by wind.
• Recently, Ginkgo has become the current herbal
  rave.

27
Ginko leaf
28
Conifers

• The conifers remain a major group of gymnosperms
  that include the pines, spruce, fir, bald cypress
  and Norfolk Island Pine (Araucaria).

29
Monkey Pine
Sequoia
30
The Pine Life Cycle

• Pollen grains contain the male gametophyte
  (reduced to a very few cells).
• Pollen is released and carried by wind to the
  female cone, where it lands and germinates to
  produce a pollen tube that grows into the female
  gametophyte.
• The sperm cell and egg cell fuse, forming the
  next generation sporophyte.
• The sporophyte develops into an embryo encased in
  a seed.
• The seed is later released to be transported by
  the wind to where (hopefully) it lands and
  germinates

31
(No Transcript)
32
Angiosperms are Flowering Plants

• Flowering plants, the angiosperms, were the last
  of the seed plant groups to evolve, appearing
  over 140 million years ago during the later part
  of the of the Age of Dinosaurs (the beginning of
  the Cretaceous, 140 million years ago)

33
Angiosperms

• All flowering plants produce flowers. Within the
  female parts of the flower angiosperms produce a
  diploid zygote and triploid endosperm.
• Fertilization is accomplished by a variety of
  pollinators, including wind, animals, and water.
• Two sperm are released into the female
  gametophyte one fuses with the egg to produce
  the zygote, the other helps form the nutritive
  tissue known as endosperm.

34
Angiosperms

• The angiosperms (angios hidden) produce
  modified leaves grouped into flowers that in turn
  develop fruits and seeds.
• There are presently 235,000 known living species

35
Where did the Angiosperms Come from?

• Whence came the angiosperms? This was Darwin's
  "abominable mystery".
• Clearly angiosperms are descended from some
  group of Mesozoic-aged gymnosperm seed
  plant....but which one?
• The classical view of flowering plant evolution
  suggests early angiosperms were evergreen trees
  that produced large Magnolia-like flowers.

36
Evolution of Angiosperms
37
Flowers

• Flowers are collections of reproductive and
  sterile tissue arranged in a tight whorled array
  having very short internodes.
• Sterile parts of flowers are the sepals and
  petals.
• Reproductive parts of the flower are the stamen
  (male, collectively termed the androecium) and
  carpel (often the carpel is referred to as the
  pistil, the female parts collectively termed the
  gynoecium).

38
(No Transcript)
39
Flowers

• Flowers may be complete, where all parts of the
  flower are present and functional, or incomplete,
  where one or more parts of the flower are absent.

40
Angiosperm Life Cycle

• Flowering plants also exhibit the typical plant
  alternation of generations.
• The dominant phase is the sporophyte, with the
  gametophyte being much reduced in size and wholly
  dependant on the sporopohyte for nutrition
• What makes the angiosperms unique is their
  flowers and the "double fertilization" that
  occurs.

41

• Technically this is not double fertilization, but
  rather a single egg-sperm fusion (fertilization
  proper) plus a fusion of the second of two sperm
  cells with two haploid cells in the female
  gametophyte to produce triploid (3n) endosperm, a
  nutritive tissue for the developing embryo.

42
Life cycle of corn, a typical monocot angiosperm
43
Dicot Seeds

• The outer covering is the seed coat
• the large scar, or hilum, which indicates the
  place of attachment of the seed to the wall
  (placenta) of the fruit
• Tthe micropyle, marks the site of entry for the
  pollen tube. The pollen tube carries sperm which
  fertilizes the egg which, in turn, develops into
  the embryo

44

• If the embryo consists of two large fleshy
  cotyledons, or seed leaves, attached to the short
  axis it is referred to as a dicot.
• Above the point of attachment of the cotyledons
  is the plumule, also referred to as the epicotyl
  which means "above the cotyledon".
• The epicotyl develops into the shoot system.
  Below the attachment is the hypocotyl which means
  "below the cotyledon." The latter terminates with
  the embryonic root, called the radicle.

45
(No Transcript)
46
(No Transcript)