Download Gymnosperms & The Life Cycle of the Pines

Monday, May 22, 2017
GYMNOSPERMS & THE LIFE
CYCLE OF THE PINES
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Packet #72
Chapter #30
Monday, May 22, 2017
INTRODUCTION

Gymnosperms are vascular
plants with seeds that are
totally exposed or borne on
the scales of cones.

Ovules and seeds develop on
the surface of specialized
leaves called sporophytes.


Gymnosperms produce
wind-borne pollen grains.


Familiar to most people are
the conifers
 The cone-bearing plants
(pines).
Feature that seedless
vascular plants lack.
Gymnosperms, according to
the theory of evolution,
appear earlier in the fossil
record than the angiosperm.
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Monday, May 22, 2017
PHYLA OF GYMNOSPERMS

Ginkgophyta


One extant species
Cycadophyta
Large cones and palmlike leaves
 130 extant species


Gnetophyta


3 very different genera
Coniferophyta
Pines, firs & spruces
 600 species identified

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Monday, May 22, 2017
PHYLA OF GYMNOSPERMS

Ginkgophyta


One extant species
Cycadophyta
Large cones and palmlike leaves
 130 extant species


Gnetophyta


3 very different genera
Coniferophyta
Pines, firs & spruces
 600 species identified

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Monday, May 22, 2017
PHYLUM CONIFEROPHYTA
Largest phylum of the gymnosperms
 Conifers (refers to cone) are woody plants that
bear needles

Leaves that are usually evergreen
 The needles are a result of adaptations to dry
conditions.

Produce seeds in cones.
 Most conifers are monoecious


Have male and female reproductive parts in separate
cones on the same plant.
Most of the wood used today is from conifers
 Conifers are among the largest and oldest
organisms on the earth.

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Monday, May 22, 2017
LIFE CYCLE OF A PINE
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Monday, May 22, 2017
LIFE CYCLE OF A PINE
INTRODUCTION
The pine tree is a mature sporophyte.
 Pine gametophytes are extremely small AND are
nutritionally dependent on the sporophyte
generation.
 Pine trees are hetereosporous and produce
microspores and megaspores in separate cones.

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Monday, May 22, 2017
LIFE CYCLE OF A PINE
Step #1
Page 597



Figure 30.6
Page 597
Male cones produce microspores
that develop into pollen grains
(immature male gametophytes) that
are carried by air currents to female
cones.
Female cones produce megaspores.
One of each four megaspores
produced by meiosis develops into a
female gametophyte within an
ovule (megasporangium).
Once the male and female cones
appear, female is normally bigger, it
takes approximately three years to
produce male and female
gametophytes, get pollinated and
form mature seeds.
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Monday, May 22, 2017
LIFE CYCLE OF A PINE II
Steps 2 – 8
Page 597


Figure 30.6
Page 597
After pollination, the
transfer of pollen to the
female cones, a pollen tube
grows through the
megasporangium to the
egg within the
archegonium.
After fertilization, the
zygote develops into an
embryo encased inside a
seed adapted for wind
dispersal.

The scales of the ovulate
cone open and the seeds
travel by wind.
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Monday, May 22, 2017
REVIEW
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
Students

List potential examination questions and/or here, and
on following slides, based on the packet.
Monday, May 22, 2017
REVIEW
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