Download Plants

Overview of Plant Diversity
Chapter 29
1
The Evolutionary Origins of Plants
•
Defining characteristic of plants is protection of their
embryos.
 Land plants can be divided into two groups based on
the presence or absence of vascular tissue.
2
The Evolutionary Origins of Plants
•
•
•
Adaptations to land
– protected from desiccation - waxy cuticle
gas exchange- stomata
– evolution of leaves increased
photosynthetic area
Alternates Generations
diploid generation alternates with haploid
generation
3
•
Plant Life Cycles
diploid generation alternates with haploid
generation
–
diploid sporophyte produces haploid spores by meiosis
Spores divide by mitosis,
producing haploid gametophyte.
–
haploid gametophyte
is the source of gametes
–
gametes fuse
to form diploid zygote
–
4
Mosses, Liverworts, and Hornworts
•
Bryophytes - avascular plants
– sporophytes are attached to and
nutritionally dependent on gametophytes
– require water to reproduce sexually
– most are small
5
Features of Vascular Plants
•
Vascular tissues
– xylem
– phloem
–
Earliest vascular plants lacked seeds
Seedless Vascular Plants - Ferns
6
•
Ferns are the most abundant group of
seedless vascular plants.
–
greater development, independence, and dominance of fern’s
Sporophyte
Fern sporophytes
have underground
stem, the rhizome.
sporangia in
clusters, sori, on
back of fronds
Diploid spore
mother cells in each
sporangium undergo
meiosis, producing
haploid spores
7
•
Seed Plants
Seed Plants first appeared about 425 mya.
– drought protection
– enhanced dispersal
– dormant phase increase embryo survival
by waiting for favorable environmental
conditions
8
•
•
Gymnosperms
Seeds but lack flowers and fruits of
angiosperms
Four living groups
– conifers
– cycads
– gnetophytes
– Ginkgo
9
10
Angiosperms
•
•
Ovules are enclosed within diploid tissues at
time of pollination
– carpel, modified leaf encapsulating seed,
develops into fruit
Monocots and eudicots
– eudicots and monocots differ in:
 number of cotyledons
 leaf venation
 presence lateral meristems
 number of flower parts
11
12
Angiosperms
•
Structure of flowers
13
Typical Angiosperm Lifecycle
polar nuclei
egg
pollination
pollen
pollen tube
sperm
double fertilization
zygote 2n
endosperm 3n
14