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Complex Plants:
Chapters 22, 23 and 25
22-1 Seed Plants
Benefits to plants of living on land are:
1. Abundant Sunlight for Photosynthesis
2. Free movement of carbon dioxide and
oxygen
Problems encountered by life
on land are:
1.Water and nutrients available only
from the soil.
2.Evaporation
3.Tissues must be held upright
4.Reproduction must occur without
water.
Seed plants – designed for life on
land
Seed plants exhibit numerous adaptations
that allow them to survive the difficulties of
life on land. They evolved a variety of new
adaptations that enabled them to live where
ferns and mosses could not.
II. Roots, Stems, Leaves
A. The three main organs in a plant are roots, stems
and leaves.
Roots perform three jobs:
1. The absorb water and nutrients.
2. They anchor plants
3. They hold plants upright
B. Stems hold a plants leaves up to the sun.
C. Leaves are vital to the process of photosynthesis.
III. Vascular Tissue
Tall plants face a challenge, water must be lifted from
roots to leaves and compounds produced in leaves must
be sent to the roots.
A. Xylem is responsible for carrying water and
nutrients up. They have thick cell walls so also
provide strength to the woody parts.
B. Phloem carries the products of photosynthesis
from one part of the plant to another.
IV. Reproduction Free From Water
 The seed plants you see around you are members of
the sporophyte generation.
 Flowers and cones are the reproductive structures
where the gametophyte generation of the seed plant
develops.
 Male gametophytes are called pollen grains. Pollen
grains are carried to the female gametophyte so no
water is required.
 Seeds protect the zygotes of seed plants. They are
surrounded by a seed coat so can wait until
conditions are right
23-5 Leaves
The leaves of green plants are the world’s oldest
solar energy collectors. Leaves are also the
world’s most important manufacturers of food.
I.
Leaf Structure
A. Leaves consist of two parts: the
blade and the petiole.
B. Blades are adapted to the
specific environments in which the
live.
Adaptations range from simple to
compound.
Leaves contain specialized tissues
such as:
1. Epidermal Cells
2. Inner layers of parenchyma
cells
3. Vascular tissues
II. Epidermis: Controlling
Water Loss
A. Epidermal cells are tough and do not contain
chloroplasts.
Together with the Cuticle, this layer protects delicate
leaf tissues by slowing down the loss of water through
evaporation.
B. BUT, plants still need to “breathe” just as we do. They
need to:
1.
Exchange CO2 for O2 during photosynthesis.
2.
Exchange O2 for CO2 in order to function (like us).
C. Leaves must stay moist to carry out
these gas exchanges. Seed plants solve this
problem by balancing their need for gas
exchange with water conservation. They
use small openings called stomata. Stomata
are generally located on the undersides of
leaves.
D. The specialized cells on either side of a stoma
are called guard cells.
When water pressure is high, the cells are forced
into a
curved shape, opening the stoma.
When water pressure is low, the cells spring
together and close the stoma.
E. Each type of plant has guard cells that balance
water loss against the need for CO2.
III. Vascular tissues: The
Veins of a leaf
A. Vascular tissue in leaves is directly
connected to the vascular tissues of
stems.
In monocot leaves, veins run parallel.
In dicot leaves, they
have different patterns.
IV. Mesophyll Tissue: The
food factory of the leaf
A. Most leaf tissue is called mesophyll. This is
separated into two layers:
1. Palisade layer
2. spongy mesophyll
B. The surfaces of the mesophyll layer are kept
moist so that gases can enter and leave the cells
easily. A substantial amount of water is still lost to
the outside through evaporation.
25-1 Cones & Flowers as
Reproductive Organs
I. Introduction
A. Sexual Reproductive Organs
1. Gymnosperms have cones
2. Angiosperms have flowers
B. Review: Plant Life Cycles
1. Two generations
a) diploid (2n) sporophyte
b) haploid (1n) gametophyte which produces
male and female gametes
2. Fusion of gametes forms a zygote that grows
into the next generation, the sporophyte
C. Sizes in Seed Plants
1. Dominant generation (the one that is
large & obvious) = sporophyte
2. Gametophyte is hidden in the
cones/flowers
D. Advantages of Cones/Flowers
1. Enable seed plants to reproduce without
standing water
2. An adaptation that helps them survive:
the dry conditions of life on land
22-2 Evolution of Seed Plants
I.
Gymnosperms
Gymno means naked, sperm means seed.
There are three classes of gymnosperms:
1.Cycads
2.Ginkgoes
3.Conifers
Reproductive structures are
called cones.
Male cones produce male
gametophytes called pollen.
Female cones produce female
gametophytes called eggs
 Cycads are palm like
plants. They only
grow in tropical and
subtropical places.
 Ginkgoes are
represented by one
species, Ginkgo
biloba. It is a living
fossil.
II. Conifers
Are the most abundant gymnosperms today.
A.The leaves are called needles. Conifers
appear to be “evergreen” because older
needles drop off but are gradually replaced.
B. Male cones, or pollen cones, and female cones, or
seed cones, contain the very small gametophytes.
In the Spring, pollen cones release millions of
dustlike pollen grains to be carried by the wind.
These land on seed cones and fertilize them. The
zygotes grow into seeds on the scales of the seed
cones.
from …..
25-1 Cones & Flowers as
Reproductive Organs
II. Life Cycle of Gymnosperms
A. Pine Tree Example
1. Tree grew from a zygote contained in a seed
2. It is the diploid (2n) sporophyte generation
3. Seedling matures, makes two types of cones:
a) Male: contain microsporangia that produce pollen
(male gametophyte)
b) Female: contain megasporangia that produce
ovules (female gametophyte)
B.
Process
1. Pollen grains (from male cones) carried by wind
2. Female cones make a sticky secretion that traps pollen
3. Grain splits open, grows a pollen tube, which contains sperm
4. Pollen tube grows into the ovule, located in female cone
5. Sperm break out of the tube and fertilize egg in the ovule
6. Zygote grows into an embryo
7. Embryo is encased in a package; now called a seed
a) seed = embryo plant + food supply for growth
from….. 22-2 Evolution of Seed Plants
III.Angiosperms
A. These are flowering plants. They
reproduce sexually through their
flowers in a process called pollination.
Angiosperm seeds are contained
within a protective wall that develops
into a fruit.
B. Angiosperms are the most
widespread of all land plants. They range
from frigid mountains to blazing deserts.
Some even live under water.
C.There are two main
subclasses:
Subclass
Number of
cotyledons (seed
leaves)
Leaves
Monocots
One.
Dicots
Two.
Veins are parallel.
Flower
Parts in threes or
multiples.
Scattered
throughout.
Stems do not
thicken from year
to year.
Corn, wheat, palms,
orchids, lilies.
Veins are
branching.
Parts in fours or
fives or multiples.
Arranged in a ring.
Xylem/Phloem
Stems
Examples
Stems grow thicker
every year.
Roses, tomatoes,
oaks, daisies,
sunflowers.
C.There are two main
subclasses:
from ….. 25-1
Cones & Flowers
as Reproductive Organs
III.
Structure of a Flower
A. Typical Flower
1. produces both male and
female gametes
B. Other ‘strategies’:
1. specialized male and
female flowers on
same plant (e.g. corn)
2. male and female flowers
on separate plants (e.g.
willow)
C. Flower Parts
1.
Are specialized leaves
2.
Arranged in circles
3.
Four kinds
NAME
LOCATION
DESCRIPTION
FUNCTION
GROUP
NAME
Sepals
Outermost
Green
Leaflike
Protect
flower while
developing
Calyx
Petals
Just inside
the sepals
Often brightly
coloured
Attract
pollinators
Corolla
Stamens
Just inside
the petals
Long thin
filament
supporting the
anther on the
top
Makes,
releases
male
gametophyte
(pollen)
Carpels
Center
Ovary, the base
Style: Stalk
Stigma: where
the pollen lands;
often sticky and
rough surfaced
Makes,
Pistil
houses,
female
gametophyte
(ovules)
IV. Pollination
A. Definition: the transfer of pollen from anther to
stigma
B. Two types:
1. Self-pollination: when pollen comes from the
same flower
2. Cross pollination: when pollen comes from a
different plant
C. Most plants cross-pollinate, which increases
variation in their offspring
Animation
VIII. Fertilization
A. Process
1.
Pollen grain lands on stigma of same species
2.
Pollen tube grows down the style, following a chemical trail
3.
Tube reaches ovary and enters the ovule
4.
Inside pollen tube are two sperm nuclei
(Note: no tails needed; don’t need propel themselves!)
a)
one sperm fuses with egg to form the zygote
b) other sperm fuses with spare female nuclei to form endosperm
(3N)
5.
Endosperm = food source for baby plant
Click for animation
B.
1.
Ecological Importance
Endosperm is rich in important nutrients
2. Examples: grass endosperm: corn, wheat, rice
C. After fertilization
1.
Outer parts of ovule toughen into seed coat
2.
Ovary wall thickens, merges with other parts to
become fruit
3. Plants may use bright colours and sweet tastes to
make fruit attractive to animals
Fruit Formation
IX. Formation of Seeds
A. The evolution of seeds was: a major factor in the
success of angiosperms on land
B. Seeds assist embryos by providing:
1.
nourishment
2.
protection
C.
Structure
1.
Cotyledon= seed leaf; they contain stored
food that is used when seed germinates
a) monocots (e.g. corn) have one
b) dicots (e.g. beans) have two
2.
Seed coats: Function: to protect seed from
a) environment: (e.g. dryness, salt water)
b) animal teeth, digestive chemicals
D. When animals eat seeds:
1. They germinate after their trip through
the digestive tract
2. Animal waste acts as fertilizer
3. Usually deposited some distance away
from where fruit was eaten
4. Reduces competition between adult
(plant) and offspring (seeds)
25-2
I.
Seed Development
Germination
A. Process:
1. Water absorption causes
endosperm & cotyledons to
swell
2. seed coat cracks open
3. Radicle emerges; grows into
primary root
4. Growing shoot pushes up
through soil
III. Seed Dormancy
A. Definiton: A period during which the embryo is
alive but not growing
B. Purposes:
1. A long time required for dispersal
a) e.g. coconut
2. To wait until environmental conditions
will support plant growth
a) e.g. plants from temperate regions;
dormant in winter, germinate in spring
22-3 Coevolution of Flowering
Plants and Animals
 Coevolution: the process by which two
organisms evolve structures and behaviours
in response to changes in each other over
time.
 The first flowering plants evolved at about
the same time as the earliest mammals,
shortly after birds and a while after the
earliest insects.
 Evolution of angiosperms with modern
insects, birds and mammals is very
important.
I. Flower Pollination
A. Wind: small, plain simple flowers
with little or no fragrance.
B. Birds, insects, mammals: carry pollen
from one plant to another.
1. Plants provide food in the form of
pollen or nectar.
2. Animals provide direct transportation
between male and female gametophyte.
Attractants for
Pollinators
Pollinator
Flower
Bee
Special
ultraviolet color.
Moth
Fragrance.
Fly
Bad odor.
Bird
Bright red and
orange colours.
Fly on corpse flower
II. Seed Dispersal
The process of distributing seeds away
from parent plants. There are 2 reasons
for dispersal:
1. Prevent competition with parent
plans for resources.
2. Colonize new environments
Dispers Description
al Method
Wind
Blown to different
places.
Pressure
Fruit ‘explodes’,
spreading seeds.
Barbed or
hooked
fruits
Attach to animal fur or
feathers and are carried
to new habitat.
Tasty Fruit Digested by animals,
carried to new habitat,
seeds ‘deposited’ with
fertilizer.