Transcript seed coat - carverbiology11

Plants with Seeds
Chapter 22-4, 22-5
Seed plants
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There are two groups of seed plants:
1)
Gymnosperms ~ seeds are found on
the surfaces of cones
2)
Angiosperms ~ seeds are within a
layer of tissue that protects the seed
Adaptations of Seed Plants
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Unlike mosses and ferns, seed plants do
not require water for fertilization of
gametes
ADAPTATIONS that allow seed plants to
reproduce without water:
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1) flowers or cones
2) transfer of sperm by pollination
3) protection of embryos in seeds
Adaptation #1:
Cones and Flowers
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Cones and flowers are sporophyte structures
in which the gametophytes of seed plants
grow
Cones = seed-bearing structures of
gymnosperms
Flowers = seed-bearing structures of
angiosperms
Adaptation #2:
Pollen
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In seed plants, the male gametophyte is
contained in a pollen grain
The pollen grain is carried to the female
reproductive structure by wind, insects
or small animals  pollination
Pollination
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Pollination can occur through biotic and abiotic
means (wind, water, birds, insects, etc…)
Morphological characteristics of flowers attract
specific pollinators
Insects – the Great Pollinators
Conventional
spectrum
What bees
see 
Bats as Pollinators
Adaptation #3:
Seeds
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Seed = embryo of the
plant (diploid)
Seed has a seed coat
(protective covering)
and food supply that
gives nutrients to the
embryo
The embryo develops
from the zygote after
fertilization
Development of Seeds
Function of seed structures:
Endosperm
Nutrition for embryo
Endosperm
Cotyledon(s)
Cotyledons
Nutrition for embryo
*Endosperm = food storage tissue
*Cotyledons = first leaf or pair of leaves produced by the embryo of a seed plant
Overall, what is the function of
a seed?
Protects
young embryo
Provides
nutrition for the
developing embryo
Allows
dispersal of the embryo
over time & space
Seed to Seedling
Fruits
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Fruit. Mature ovary of
the a flower that
protects dormant seeds
and aids their dispersal
Seeds are the product
of pollination
Seeds are located
within fruits
There are many
different types of fruits
Fruit Types
Seed Dispersal
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Seeds are highly
adapted to dispersal
Examples of
morphological
characteristics would
be buoyancy in fruits
(coconut) and
“wings” (maple
seeds)
While others are simply blowing in the wind….
Some seeds are
dispersed as a
result of being
eaten and mingling
with feces….
GYMNOSPERMS: Non-Flowering
Seed Producers
Transition from Ferns to Land Plants
Medullosa – the seed fern
Gymnosperms began to dominate landscapes as climates
became drier at the end of the Paleozoic era 245 mya
Gymnosperms appear in the fossil record much earlier
than flowering plants, and they:
1. Lack enclosed chambers in which seeds develop.
2. Are grouped into four divisions:
3. Cycadophyta, Ginkgophyta, Gnetophyta and
Coniferophyta.
GYMNOSPERMS:
Plants with seeds that are not enclosed within a fruit, derive their
name from the Greek words gymnos (naked) and sperma (seed).
In this plant group, the seeds are produced on the open surface of
a scale. Unlike flowering plants, the gymnosperms do not form
true flowers or fruits. There are four divisions of gymnosperms.
Examples of gymnosperms include cycads, ginkgo, conifers and
gnetops.
Kingdom Plantae - Plants
Subkingdom Tracheobionta -- Vascular plants
Superdivision Spermatophyta - Seed plants
Division Cycadophyta - Cycads
Class Cycadopsida
Order Cycadales
Family Cycadaceae
Genus Cycas- cycads
Evolutionary advancements of Gymnosperms over the ferns and allies:
1.
Seeds
2.
Lack of dependence on water for fertilization (air-borne pollen)
3.
Progressively more dominant sporophyte
4.
Life Cycle
a.
5.
In the gymnosperms and the flowering plants, the sporophyte
generation is dominant with the gametophyte contained in and
dependent on the sporophyte.
Vascular System
a.
They do have a well-developed vascular system of xylem and
phloem and have true roots, stems, and leaves.
b.
The vascular tissues are significantly more efficient and effective
than the vascular systems of the seedless plants such as the ferns.
c.
Gymnosperms are usually woody plants. The xylem form the
wood if a tree and the phloem tissues are part of the bark (along
with cork). The formation of wood from secondary growth is the
reason that some sporophytes can reach such large sizes.
Cycadophyta
Class Cycadopsida
Order Cycadales
Cycadaceae
Cycas sp.
The Cycad – a fernlike gymnosperm.
Note the cone, or strobilus
The Gymnosperms
Male cones of
Pinus nigra
•Unlike the seedless vascular plants, conifers are more
prevalent in cooler regions and in desert habitats.
• leaf curled to reduce water loss
• evolved cold hardiness
Female cones of
Pinus nigra
The Gymnosperms
Gnetophyta
With angiosperm-like broad
leaves, but still retaining cones,
the Gnetophytes are another very
close link to the Angiosperms
Ephedra viridis
Female cones
More
Gnetophytes!
All bear cones, with
naked seeds, which
is an adaptation over
the ferns, that
produced spores
Welwitschia mirabilis
growing in the desert
Ginkgophyta
Ginkgo biloba
The link between
gymnosperms and
angiosperms (note the
fleshy seed)
Angiosperms
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Phylum Anthophyta
Replaced Gymnosperms
as the dominant plant
type during the
Cretaceous Period 60
million years ago
Produce flowers, fruits,
and seeds
Flowers and Fruits
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Flowers:
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Are unique reproductive organs
of angiosperms
Contain ovaries which surround
and protect the seeds
Thus “angiosperm” = “enclosed
seed”
Fruits:
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A wall of tissue surrounding the
seed
Used to attract animals 
dispersal of seeds
Can you guess what this is?
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The largest seed is produced by the coco de mer, or
"double coconut palm", Lodoicea maldivica. The
entire fruit may weigh up to 23 kilograms (50
pounds) and usually contains a single seed
Flower Morphology
Monocot vs. Dicot Seeds
Corn
Bean
Seed coat
Stored food
(Endosperm)
Embryo
plant
Monocot Seeds
Monocot
seeds have:
Endosperm
seed coat
endosperm
cotyledon
coleoptile
One
cotyledon
radicle
Dicot Seeds
Dicot seeds have:
No
endosperm
at maturity
Two
cotyledons
Seed coat
First leaves
Early root
Cotyledon
Organization of primary tissues in a young dicot stem (eg. Bean)
The primary tissues of a young monocot stem (eg. Corn)
Primary tissues of a young dicot root
Cross-section through a monocot root
General Angiosperm Life Cycle
Plant life spans
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Annual: flower plants that complete a life
cycle within one growing season
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Biennials: life cycle complete in two years
(flowers in second year)
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Marigolds, pansies, wheat, cucumbers
Parsley, celery, foxglove
Perennials: flowering plants that live for
more than two years (most have woody
stems)
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Asparagus, grasses, palm trees, maple trees
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Understanding Concepts, page 575
Questions 13-24