Document Sample
B203 PLAN Powered By Docstoc
 Multicellular eukaryotes
 Photoautotrophs
 Most plants are terrestrial, but some live in water
 Adaptations for land include a cuticle- waxy covering on the
  leaves and stem to prevent dessication
 Gas exchange occurs through stomata- pores in the cuticle
 Contain chlorophyll a and b and a variety of carotenoids, similar
  to green algae
 Sexual reproduction is the norm, but alternation of generations is
  extremely common
Alternation of Generations
 Consists of haploid gametophytes and diploid sporophytes
 Sporophyte is almost always the larger and more noticeable form
 Gametophytes produce eggs and sperm, which fuse to form the
  zygote, which grows into a sporophyte
 Sporophyte produces spores, which grow into gametophytes

 Nonvascular plants- no tissues to conduct food or water- must live
  in moist climates
 Consists of mosses, liverworts, and hornworts
 Bryophytes have two adaptations for land living
 Cuticle
 Gametes develop within gametangia- protective jackets of sterile
 Male gametangium is antheridium- produces sperm
 Female gametangium is archegonium- produces eggs
 Egg is fertilized within archegonium to form a zygote
 Zygote develops into an embryo which is retained for a while
  inside the plant
   Plants are sometimes called embryophyte
 Must live in moist climates
 Water helps fertilization process
 Sperm swim around from antheridium to the archegonium
 No vascular tissue means that nutrients must enter by diffusion
  through the surface of the plant
 No woody tissue, so plants are low and broad

 Most common and familiar
 No roots, but have rhizoids, which helps to grip the soil
 No real stems or leaves
 Alternation of generations
 Moss is an exception- gametophyte is dominant form

Life Cycle
 Separate male and female gametophytes, with antheridia and
 Sperm swims to archegonium to fertilize egg and form zygote
 Diploid zygote divides by mitosis to form diploid sporophyte
 Sporophyte emerges from the archegonium, but the base of
  sporophyte is still attached to the archegonium
Life Cycle
 At the tip of the stalk is a sporangium, where meiosis occurs-
  haploid spores form
 Spores are scattered, and germinate, forming haploid
 Bryophytes are 400 million years old
 16000 species

Vascular Plants
 Most plants have vascular tissue to conduct nutrients- food and
 Xylem- carries water and minerals
 Xylem cells are actually mostly dead cells
 Phloem-carries food- living cells

Seedless Plants
 Includes four divisions- whiskferns, club moss, horsetail ferns, and
 Lycopods- among oldest seedless plants- began around 400 million
  years ago, but became important during the Carboniferous
  period- about 340 million years ago
 Gave rise to both woody plants and to small nonwoody plants

 Pterophytes
 Ferns are the most common seedless plant- 12000 species, mostly
  in the tropics but also found elsewhere
 Leaves are usually large- each leaf is called a megaphyll- with
  branched system of veins
 Most ferns have leaves that are compound- with several leaflets

Fern- Life Cycle
 Frond grows as its coiled tip- the fiddlehead- unfurls
 Haploid spore grows into gametophyte
 Most ferns are homosporous- only one kind of spore
 Thus, only one kind of gametophyte, which is bixsexual and
  produces antheridia and archegonia
Life Cycle
 Some ferns are heterosporous, with two kinds of spores
 Megaspores develop into female gametophytes, and microspores
  develop into male gametophytes
 When the fern is homosporous, and the gametophyte has both
  antheridia and archegonia, they mature at different times- ensures
  cross- fertilization
Life Cycle
   Sperm swim through moisture to reach archegonia and fertilize
    the egg
 Fertilized egg develops into zygote and then into diploid
 Young plant grows out of the archegonium in the gametophyte
 Spots on the underside are called sori
 Each sorus is a cluster of sporangia, which release the spores

Seed Plants- Evolution
 Gametophytes are more reduced than in seedless plants
 Important for adaptation for land
 Gametophyte is often retained within the moist reproductive
  tissue of the sporophyte- protected from dessication
 Pollination replaced swimming sperm
 Seed evolved- zygote is protected longer and is packaged with food
  before being released
 Gymnosperms appear much earlier than angiosperms

 Do not have ovaries, so are considered to have naked seeds
 There are actually four divisions- but Conifers are the most
 Conifers- pines, firs, spruce, etc.
 Only 721 species
 Most conifers are evergreens

 Sequoias are the largest trees in the world
 Gametophyte develops from haploid spores that are retained in
  the sporangia
 Conifers are heterosporous- male and female gametophytes
  develop separately from different spores produced by different
 Pollen cone contains hundreds of sporangia which produce
Life Cycle
 Microspores develop into pollen grains (male gametophyte)
 Ovulate cone consists of many scales, each of which has two ovules
 Each ovule contains a sporangium, called the nucellus, enclosed in
  protective layers with a single opening - micropyle
 Pollen falls on the ovulate cone and enters the ovule through the
Life Cycle
 Pollen grain germinates in the ovule, forming a pollen tube which
  digests its way through the nucellus
 Fertilization occurs one year after pollination
 During that year, a megaspore mother cell in the nucellus
  undergoes meiosis to produce four haploid cells
 One of these becomes the megaspore

Life Cycle
 Megaspore becomes immature female gametophyte
 Two or three archegonia, each with an egg, develop within the
 Two sperm cells develop within the pollen grain
 Pollen tube grows through the nucellus to the female gametophyte

Life Cycle
 Fertilization occurs to form a zygote
 The embryo, which will become the sporophyte, has a
  rudimentary root and leaves
 The food supply is the female gametophyte
 Ovule develops into the pine seed, consisting of the embryo, food
  supply, and seed coat (from parent tree)
Life Cycle
 Takes three years from the appearance of cones on a tree before
  seeds are produced
 Scales of the ovulate cone then separate, and the seeds are released

   Most diverse and widespread of all plants
 235,000 species
 Two divisions- monocotyledons and dicotyledons
 Monocots include grasses, grains, and some flowers
 Dicots include many familiar flowers and trees

Angiosperms- Evolutionary Developments
 Pollination is often done with animals and insects, rather than
  wind- aided as for gymnosperms
 Vascular tissue is more refined
 Water conducting cells in gymnosperms are tracheids- early type
  of xylem
 Angiosperms have short wide cells called vessel elements

Evolutionary Developments
 Vessel elements are arranged end to end forming continuous
 Tracheids are a little less organized
 Vessel elements are more organized for water transport than the
  tracheids, but less specialized for support
 Angiosperm xylem also has a second cell type, fiber, specialized
  for support
 Represents greatest evolutionary development for angiosperm
 Combines reproduction with attracting pollen- carrying animals
 Sepals enclose the flower before it opens
 Petals help to attract animals by scent and by color
 Flowers that are wind- pollinated are drab in color

 Within the petals are the stamens and carpels
 Stamen consists of anther, which makes the pollen, and the
  filament, which supports the anther
 Carpel consists of stigma, which receives the pollen, an ovary,
  which produces the eggs, and a style, leading from the stigma to
  the ovary
 Fruit is a mature ovary
 As seeds develop after fertilization, the wall of the ovary thickens
 Fruits aid in dispersal of the seeds
 Animals eat the fruit and carry the seeds
 Some fruits act as propellers
 Some cling to the fur, some are edible

Shared By: