Download The “Evolution” of Seed Plants

Monday, May 22, 2017
THE “EVOLUTION” OF SEED
PLANTS
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Packet #71
Chapters 29, 30 & 38
Monday, May 22, 2017
THE “EVOLUTION” OF
PLANT ORGANS
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Monday, May 22, 2017
“EVOLUTION” OF ROOTS
The “evolution” of roots allowed plants to become
anchored and helped enable them to absorb
water and nutrients from the soil
 Roots allow the shoot system to grow taller and
contain lignified vascular tissue.

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Monday, May 22, 2017
“EVOLUTION” OF LEAVES
See Pages 584-586
Chapter 29


Figure 29.13
Page 586
Leaves increase the surface
area of vascular plants.
Leaves can be classified as
microphylls or megaphylls

All lycophytes (club mosses)
have small, usually spineshaped leaves with a single
vein


Microphylls
Leaves of other “modern”
vascular plants are known as
megaphylls

The larger sized leaves are
possible due to the highly
branched vascular system which
supports greater photosynthetic
activity.
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Monday, May 22, 2017
THE EVOLUTION OF SEED

The evolution of seed facilitated reproduction on land

Plants that produce seeds may be placed into two
categories




Gymnosperms
Angiosperms
A seed consists of a plant embryo packaged with a
food supply in a protective coat
The first vascular plant, according to the theory of
evolution, originated about 360 MYBP in the
Devonian Period.
Those seeds were not enclosed in any special chambers.
 These plants evolved into the gymnosperms


“The Naked Seeds”
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Monday, May 22, 2017
THE EVOLUTION OF FLOWERS

According to the theory of evolution, flowers
evolved in the Cretaceous Period about 130
MYBP

Led to further plant diversity
A flower is a complex structure that bears seeds
within a protective chamber called an ovary.
 Most “modern day” flowering plants are known
as angiosperms.

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Monday, May 22, 2017
APICAL MERISTEMS
Recall, plants cannot move.
 The elongation of their shoots and roots
maximizes their exposure to environmental
resources.
 Growth occurs throughout the life of the plant via
cell division in the apical meristematic tissue
found at the tips of roots and shoots.


Cells produced by meristematic tissue can
differentiate into various plant tissues.
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Monday, May 22, 2017
INTRODUCTION TO THE
SEED AND SEED BEARING
PLANTS
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
Monday, May 22, 2017
INTRODUCTION TO SEED BEARING
PLANTS
Seed plants are vascular plants that produce
seeds.
After fertilization in seed plants, an ovule
(megasporangium) and its enclosed structures
develop into a seed
 Earliest fossilized seeds are gymnosperms.


360 MYBP
Seed plants dominate modern landscapes and are
a large component of plant diversity.
 Seed bearing plants have important reproductive
adaptations: 
Continued reproduction of the gametophyte
 The advent of the seed
 The evolution of pollen

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The gametophytes of seed plants are even
smaller than those of the seedless vascular plant
and are protected in the ovules and pollen grains,
 Miniature female gametophytes develop from
spores that are retained within the parental
sporophyte.

Monday, May 22, 2017
INTRODUCTION II
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

Seeds are the primary
means of reproduction
and dispersal of
flowering plants.
Seeds are reproductively
superior to spores.
Embryonic development
is further advanced in
seeds
 Seeds contain an
abundant food supply
 Each seed has a
protective coat.
Monday, May 22, 2017
COMPARISON OF SEEDS VS. SPORES

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



Seed dispersal becomes
important in
adaptations
Seed is a resistant
structure that is
multicellular and
complex.
Seed consists of a
sporophyte embryo
packaged with food in a
protective coat
Seeds can be dispersed
by wind, water and
animals.
Monday, May 22, 2017
SEEDS, DISPERSAL & ADAPTATION
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 All
seed bearing plants are
heterosporous

Monday, May 22, 2017
SEED BEARING PLANTS
These plants have different types of sporangia
that produce two types of spores.
Megasporangium
 Microsporangium

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Mega. vs. Micro.

Megasporangia

Produce megaspores


*Retained in the parent
sporophyte
Formed within the
megasporangium
 Enveloped with tissue
called integumens


Diagram on Page 586
Monday, May 22, 2017
HETEROSPOROUS SPORE
PRODUCTION
*Entire structure is
called the ovule
Microsporangia

Produce microspores


Develop into male (sperm
containing) gametophytes.
The development of pollen
reduced the need for water
for fertilization.
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
Develop into female (egg containing)
gametophytes.

Monday, May 22, 2017
MEGASPORES
In the female gametophyte, there is the production of
one or more egg cells

If egg is fertilized by sperm, the zygote develops into a
sporophyte embryo
 The ovule, that contains the fertilized egg, develops into
a seed.

Seed may be viable for days, months or years.
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Microspores develop into pollen grains
 Pollen grains mature to become the
gametophytes of seed plants

Monday, May 22, 2017
MICROSPORES
The most common gymnosperms, and all
angiosperms sperm, lack flagella.
 Pollen can be transferred by wind and animals.

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
The transfer of pollen
to ovules
Monday, May 22, 2017
POLLINATION
Self Pollination
 Cross Pollination

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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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