1. Namroo A., Will C.

2.  Intro
 Gymnosperm Evolution
 Pine – Life Cycle

3.  Gymnosperms are plants that have “naked”
seeds are not enclosed in ovaries and
usually on cones.
 Angiosperms seeds are enclosed in fruits,
which are mature ovaries.
 Conifers – pines, firs, and redwoods
 Four of the ten plant phyla are
gymnosperms : Cycadophyta, Ginkgophyta,
Gnetophyta, and Coniferophyta.

4.  Cycads have large cones and palm-like
leaves.
 130 species of cycads survive today.

5.  Consists of only a single extant species,
Ginkgo biloba.
 This popular ornamental species has fan-like
leaves that turn gold before they fall off in the
autumn.

6.  Consists of three very different genera.
 Weltwitschia plants have strap-like leaves.
 Gentum species are tropical tress or vines.
 Ephedra (Mormom tea) is a shrub of the
American deserts.

7.  Conifers
 The cone which is a cluster of scale-like
sporophylls.
 Pines, firs, sprices, larches, yews, junipers,
cedaes, cypresses, and redwoods.
 Most confiners are evergreen.
 The needle-shaped leaves of some conifers are
adapted for dry conditions.
 Coniferous trees are among the largest and
oldest organisms of Earth.

8. PHYLUM CYCADOPHYTA PHYLUM GINKGOPHYTA
Cycas revoluta
PHYLUM GNETOPHYTA
Gnetum
Welwitschia
Ovulate cones
Ephedra

9.  Fossil evidence reveals that by the late Devonian
 Some plants, called progymnosperms, had begun to
acquire some adaptations that characterize seed
plants.
Figure 30.5

10.  Gymnosperms appear early in the fossil
record
 And dominated the Mesozoic terrestrial
ecosystems
 Living seed plants
 Can be divided into two groups: gymnosperms
and angiosperms

11.  Three Key Reproductive adaptations :
 The increasing dominance of the sporophyte
generation
 The advent if the seed as a resistant, dispersible
stage in life cycle
 Evolution of pollen as an airborne agent that
brings gametes together

12.  The life cycle of a pine
2 An ovulate cone scale has two
ovules, each containing a mega-
In most sporangium. Only one ovule is shown.
1 Key
conifer species,
Haploid (n)
each tree has Ovule Diploid (2n)
both ovulate
and pollen
A pollen grain
cones.
Ovulate Megasporocyte (2n) 4
enters through
cone Integument the micropyle
Longitudinal and germinates,
section of Micropyle forming a pollen
Pollen ovulate cone tube that slowly
cone digests
Mature Microsporocytes Germinating Megasporangium through the
sporophyte (2n) Pollen pollen grain
megasporangium.
(2n) grains (n) MEIOSIS
(containing male
MEIOSIS gametophytes) While the
Longitudinal Surviving pollen tube
5
section of Sporophyll megaspore (n) develops, the
Microsporangium
pollen cone contains many microsporangia megasporocyte
A pollen cone
3 (megaspore
Seedling held in sporophylls. Each microsporangium Germinating mother cell)
contains microsporocytes (microspore mother grain
pollen undergoes meiosis,
cells). These undergo meiosis, giving rise to
Archegonium producing four
haploid microspores that develop into
Egg (n) Integument haploid cells. One
pollen grains. Female
Seeds on surface survives as a
gametophyte
of ovulate scale megaspore.
Fertilization usually occurs Germinating
more pollen grain (n)
than a year after pollination. All Food reservesSeed coat 6 The female gametophyte
eggs (gametophyte(derived from Discharged develops within the megaspore
8
may be fertilized, but usually tissue) (n) parent and contains two or three
sperm nucleus (n)
only one sporophyte) (2n) archegonia, each with an egg.
Pollen
zygote develops into an embryo. By the time the eggs are mature,
tube 7
The
two sperm cells have developed in the
ovule becomes a seed, consisting
Embryo pollen tube, which extends to the
of an FERTILIZATION
(new sporophyte) female gametophyte. Fertilization occurs
embryo, food supply, and seed Egg nucleus (n)
(2n) when sperm and egg nuclei unite.
Figure 30.6 coat.