Transcript Document

Kingdom Plantae
Characteristics of plants
All Plants: Eukaryotic Multicellular Autotrophic
Used for Classification:
Pigments: chlorophyll, carotenoids, fucoxanthins, xanthophylls
Energy Storage: starches
Tissues: vascular/non for transporting H2O & nutrients
Structures: roots, stems, leaves
Life Cycles/Alternation of Generations:
gametophytes = n, sporophytes = 2n
Reproduction:
presence/absence of seed
presence/absence of fruit
Characteristics of plants
PLANT
• Mainly terrestrial and sessile
• Display an alternation of generations.
– sporophyte and gametophyte are
heteromorphic-the two generations
look and develop differently from
each other.
– In algae the gametophyte is
dominant, in most plants the
sporophyte is dominant.
• Sugars made via photosynthesis are
used as a fuel source for growth and
also stored as the complex
carbohydrate starch.
• Cell walls are made of cellulose.
ROOTS
•
•
anchor
The Source of the Oxygen Produced
byplant;
absorb water and
Photosynthesis
minerals from
the soil (aided
Photophosphorylation
•
Tracing the Pathway of CO2
by mycorrhizal
fungi)
LEAF
performs
photosynthesis
CUTICLE
reduces water
loss; STOMATA
allow gas exchange
STEM
supports plant
(and may perform
photosynthesis)
Surrounding water
supports the alga
WHOLE ALGA
performs
photosynthesis;
absorbs water,
CO2, and
minerals from
the water
HOLDFAST
anchors the alga
ALGA
Alternation of Generations
• Unlike algae, plants have vascular tissue
– It transports water and nutrients throughout
the plant body
– It provides internal support
– How is vascular tissue arranged
differently in C3 and C4 plants?
Making the move to dry land
Required several evolutionary breakthroughs.
What would be the key adaptations needed if you are going
from an aquatic to a terrestrial existence?
Cooksonia
Charophyte
Modern angiosperm
Terrestrial Challenges & Adaptations
• Air offers no support to fight gravity.
• Water is less available which results in dessication, immotility
of sperm, lack of absorption, problems with gas exchange and a
need for conduction
• Nutrients and water are in soil, but CO2 and light are above
ground.
• Protective covering to prevent dehydration
•
•
•
•
•
Transport system for water & nutrients
Structural system for support (woody tissue)
Discrete organs- roots, stems, leaves & gametangia.
Protective covering for gametes & embryos
Mechanism to allow sperm to get to egg
Cladogram of the major plant groups
4 Major Plant Groups:
1.
BryophytesNonv
ascular Plants
2. Pteridophytes
Vascular Plants
without Seeds
3. Gymnosperms
Vascular Plants
with Naked Seeds
4. Angiosperms
Vascular Plants
with Seeds,
Flowers, and
Fruits
Avascular Plants : Mosses, Hornworts &
Liverworts
Life Cycle of a Moss
Seedless Vascular Plants : Ferns, Club
mosses, Horsetails and Whisk ferns
New evolutionary adaptations:
•Waxy cuticle
•Gametangia
Features still absent in this group:
•No well developed vascular system
•No support system
•Require water for sperm to swim to egg
Cuticle: waxy covering on the surface of plant stems and leaves which prevents
desiccation;
Stoma (stomata): microscopic pore surrounded by guard cells in the epidermis of
stems and leaves that allows gas exchange
Figure 29.11 The life cycle of a fern
Fern Life Cycle1, 2
Seedless plants formed vast “coal forests”
• Ferns and other seedless plants once dominated
ancient forests
– Their remains formed coal
• Gymnosperms that produce cones, the conifers,
largely replaced the ancient forests of seedless
plants
– These plants remain the dominant gymnosperms
today
A pine tree is a sporophyte with
tiny gametophytes in its cones
• Sporangia in male cones make spores that develop into male
gametophytes
– These are the pollen grains
• Sporangia in female cones produce female gametophytes
When do most plants reproduce? Why?
• Reproduction and rearing of offspring require free energy
beyond that used for maintenance and growth. Different
organisms use various reproductive strategies in response to
energy availability.
4
Female gametophyte (n)
Haploid spore cells in
ovule develop into
female gametophyte,
which makes egg.
5 Male gametophyte (pollen)
Egg (n)
grows tube to egg and
makes and releases sperm.
Sperm (n)
Male gametophyte
(pollen grain)
HAPLOID
DIPLOID
MEIOSIS
Ovule
Fertilization
Scale
Sporangium
(2n)
Seed
coat
3 Pollination
HAPLOID
Pollen grains
(male
gametophytes)
(n)
Embryo
(2n)
Integument
1 Female cone
bears ovules.
6 Zygote develops
MEIOSIS
into embryo, and
ovule becomes
seed.
2 Male cone produces
spores by meiosis;
spores develop into
pollen grains
Zygote
(2n)
7
Sporophyte
Seed
Seed falls to
ground and germinates,
and embryo grows into tree.
Life Cycle of a Conifer
The flower is the centerpiece of
angiosperm reproduction
• Most plants are angiosperms
– The hallmarks of these plants are flowers
– The angiosperm plant is a sporophyte with gametophytes in its flowers
• The angiosperm life cycle is similar to that of conifers
– But it is much more rapid
– In addition, angiosperm seeds are protected and
dispersed in fruits,
Pollen grains
which develop from ovaries
Anther
Stigma
CARPEL
Ovary
STAMEN
PETAL
Ovule
SEPAL
2 Haploid spore in each
Stigma
Egg (n)
ovule develops into
female gametophyte,
which produces egg.
3 Pollination
Pollen
grain
and
growth
of pollen
tube
Ovule
Pollen
tube
1 Haploid spores
in anthers develop
into pollen grains:
male gametophytes.
Sperm
Pollen (n)
HAPLOID
Meiosis
Fertilization
DIPLOID
4
Zygote
(2n)
Seed
coat
Food supply
Seeds
7 Seed
Ovary
germinates,
and embryo
grows into plant.
Ovule
Sporophyte
5 Seed
Embryo
(2n)
6 Fruit
Double Fertilization
Polyploidy in plants
• common in plants, especially
in 30%-70% angiosperms, are
thought to be polyploid.
• i.e. Species of coffee plant
with 22, 44, 66, and 88
chromosomes suggesting
ancestral condition (n) = 11
and a (2n) = 22, from which
evolved the different
polyploid descendants.
• Polyploid plants are larger,
leading to created varieties
of watermelons, marigolds,
and snapdragons
•
Plant
Probable
ancestral
haploid
number
Chromo
#
Ploidy
level
domestic oat
7
42
6n
peanut
10
40
4n
sugar cane
10
80
8n
banana
11
22, 33
2n, 3n
white potato
12
48
4n
tobacco
12
48
4n
cotton
13
52
4n
apple
17
34, 51
2n, 3n
Origin of Polyploidy
• Accident Doubling Plants, (vs
animals), form germ cells from
somatic tissues. If the chromosome
content of a precursor somatic cell
has accidentally doubled (e.g., as a
result of passing through S phase of
the cell cycle without following up
with mitosis and cytokinesis), then
gametes containing 2n chromosomes
are formed.
• Naturally occuring As the
endosperm (3n) develops in corn
(maize) kernels (Zea mays), its cells
undergo successive rounds (as many as
5) of endoreplication producing nuclei
that range as high as 96n.
• When rhizobia infect the roots of
their legume host, they induce the
infected cells to undergo
endoreplication producing cells that
can become 128n (from 6 rounds of
endoreplication).
Polyploidy and Speciation
• When a newly-arisen tetraploid
(4n) plant tries to breed with
its ancestral species (a
backcross), triploid offspring
are formed. These are sterile
because they cannot form
gametes with a balanced
assortment of chromosomes.
• However, the tetraploid plants
can breed with each other. So
in one generation, a new species
has been formed.
The structure of a fruit reflects its
function in seed dispersal
• Fruits are adaptations that disperse seeds
Types of Fruits
• Simple Fruits: These fruit
types are produced by flowers
containing one pistil, the main
female reproductive organ of a
flower.
• Aggregate Fruits: These
fruits types are developed
from flowers which have more
than one pistils. They consist
of mass of small drupes that
develops from a separate ovary
of a single flower.
• Multiple Fruits: These fruit
types are developed not from
one single flower but by a
cluster of flowers.
• Accessory Fruits: These
fruit types are developed from
plant parts other than the
ovary.
Types of fleshy fruits
True berry:
have a soft
epicarp and
the
mesocarp
and
endocarp is
fleshly
Pepo: berry
has an outer
wall /rind
that is
formed
from
receptacle
tissue that
is fused to
exocarp.
Hesperidium:
have thick,
leathery
exocarp and
mesocarp.
They have a
juicy, pulpy
endocarp
Tomato,
Eggplant,
Chili pep,
Grape,
Cranberry,
Pumpkin,
Gourd,
Cucumber,
Melon
Orange,
Lemon, Lime,
Grapefruit
Aggregate fruit:
formed from the
development of a
number of simple
carpels from a
single flower.
Multiple fruit:
individual
ovaries from
different
flowers get
clustered
together
forming a
fruit.
Accessory
fruit
Blackberry,
Raspberry,
Boysenberry
Pineapple, Fig,
Mulberry,
Hedge apple
Strawberry
There are fruits that are dry fruits and can be differentiated as dry
dehiscent and dry indehiscent.
Fruit types that contain seeds in a seedpod that opens up and releases the
seeds are known as dehiscent fruits. Legume: Sweet pea, Beans, Peanut
The indehiscent are those fruit types that do not have a seed pot that
opens. Caryopsis: Wheat, Rice , Corn, Rye Nuts: The list of fruits under
this type are: Walnut, Acorn
Agriculture is based almost
entirely on angiosperms
• Gymnosperms supply most of our lumber
and paper
• Angiosperms provide most of our food
– Fruits, vegetables, and grains
• Angiosperms also provide other important
products
– Medications, fiber, perfumes
Interactions with animals have profoundly
influenced angiosperm evolution
• Angiosperms are a major source of food
for animals
– Animals also aid plants in pollination and seed
dispersal
Figure 17.13A-C
Connection: Plant diversity is a
nonrenewable resource
• 20% of the tropical forests worldwide
were destroyed in the last third of the
20th century
• The forests of North America have
shrunk by almost 40% in the last 200
years
• Some plants in these forests can be used
in medicinal ways
– More than
25% of
prescription
drugs are
extracted
from plants
Resources
•
•
•
•
Anatomy & Morphology of Plant Organs
The Conquest of Land
Plant Evolution Tour
Identification of Major Fruits