plant diversity ii the seed plants evolution and ecology u derived from a single common ancestor. u...
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Plant Diversity IIPlant Diversity II
The Seed Plants
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Evolution and EcologyEvolution and Ecology
Derived from a single common ancestor. Five phyla
Angiosperms (flowering plants) Gymnosperms (four phyla of nonflowering
plants) Dominated land for 350 million years
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Common CharacteristicsCommon Characteristics
1N gametophyte is reduced so much that it acts as a reproductive organ within the 2N sporophyte
Female gametophyte makes eggs Male gametophytes are pollen grains
containing sperm. Waterproof, dispersed by wind or animals Reproduction independent of water
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Seeds consist of . . . Seeds consist of . . .
Embryonic plants A supply of food for the embryo as it
develops roots and leaves A protective coat, allowing the embryo to
remain dormant until conditions are favorable for growth
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Gymnosperms / Gymnosperms / Coniferophytes. . . Coniferophytes. . .
Gymnosperms include conifers, cycads, ginkgoes, & gnetophytes
Name means “naked seed”
abundant in colder latitudes and higher dry elevations
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Characteristics of ConifersCharacteristics of Conifers
pines, firs, spruce, hemlock, cypresses
Adapted to dry, cold conditions
leaves are thin needles with thick cuticle
retain leaves all year produce antifreeze
resin in sap
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Conifer ReproductionConifer Reproduction
Sporophyte (tree) develops male & female cones
Male cones are smaller and delicate, disintegrating after releasing clouds of pollen grains
Female cones are large w/ woody scales Each scale has two 1N female gametophytes,
each producing eggs
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Conifer reproduction cont. . . Conifer reproduction cont. . .
After a pollen grain (male gametophyte) lands on a female cone, it sends out a slowly growing pollen tube that takes 14 months to reach the eggs.
After fertilization, seeds develop and are released when the female cone matures and the scales open.
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Characteristics of Characteristics of AngiospermsAngiosperms
Flowers attract animal pollinators
Extremely diverse in size, form and habitat
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2 Angiospermophyte Divisions2 Angiospermophyte Divisions
Hydrophytes Adapted for aquatic/moist environments
Xerophytes Adapted for dry climates
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Angiosperm ReproductionAngiosperm Reproduction
Dominant sporophyte that produce and nurture tiny male (pollen grains) and female (embryo sacs) gametophytes within flowers.
Gametophytes produce gametes and fertilization occurs within ovaries of flower.
Pollen grains dev from microsporangia in anther. 2N Microspore mother cells in microsporangia produce microspores by meiosis wc/ develop into pollen grains
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Diploid ovule contains a 2N megaspore mother cell wc/ produces 1N megaspores
Three disintegrate, one survives, divides by mitosis to produce 7 cells.
One cell becomes the egg, one large central cell has two haploid nuclei
These will fuse with sperm to form endosperm
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Angiosperm reprod cont. . . Angiosperm reprod cont. . .
Pollen grains lands on stigma of female, pollen tube grows thru style to ovary.
Inside each pollen grain are 3 nuclei One nucleus forms pollen tube, one
fertilizes egg, other fuses with polar nuclei to form 3N primary endosperm
Endosperm forms food for embryo
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Angiosperm reproduction. . . Angiosperm reproduction. . .
2N zygote forms the embryo and the endosperm is the food
Seeds are enclosed within fruits (the ripened ovaries of the flowers).
Fruits entice animals to disperse seeds. Seeds are dispersed through animal
digestive tracts or attached to fur.
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Monocots and DicotsMonocots and Dicots
Monocots Grasses, corns, lilies Seed in one piece
(cotyledons) Parallel veined leaves Flower petals in threes
Dicots most trees, shrubs,
herbs Seeds in two pieces
(cotyledons) Branched veined
leaves Flower petals in fours
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ANGIOSPERMSANGIOSPERMS
The flowering plants
Spring crocus Crocus vernus
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FlowerFlower structure structure
Flowers are reproductive structures The have evolved to send and receive pollen
from one flower to another This is process of pollination Flowers are developed from a series of
modified leaves These leaves are arranged in a rings (whorls)
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Types of pollinationTypes of pollination Wind Animal Water
Bumble bee Bombus hortorum on red clover Trifolium pratense
Yorkshire fog grass Holcus lanatus
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Animal pollinationAnimal pollination
Usually insects Also other flying
animals e.g. hummingbirds or
fruit bats
Cerambycid beetle pollinating bramble Rubus fruticosus
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Flower structureFlower structure
Dog rose Rosa canina
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PollinationPollination
Pollen grains contain the male gametes of the plant
They are picked up by a pollinator and transferred to another flower
Plants tend to specialize in pollinators
This ensures the pollen is delivered to same species of plant
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PollinationPollination
Small skipper Thymelicus flavus on marsh thistle Cirsium palustris
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PollinationPollination
The honey bee Apis melifera on marsh thistle Cirsium palustris© 2008 Paul Billiet ODWS
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PollinationPollination
Some flowers are highly specialised to encourage only one type of insect
Fox glove flowers Digitalis purpurea
© 2008 Paul Billiet ODWS
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PollinationPollination
Most species of flowering plants are monoecious
Pollen from a flower could land on the stigma of the same flower or another flower on the same plant = self pollination
Pollen transferred from the anther on one flower to the stigma of another flower on a different plant = cross pollination
© 2008 Paul Billiet ODWS
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FertilisationFertilisation
Pollination ≠ Fertilization The male gamete (the male nucleus) has to get to
the egg cell The egg cell lies in an ovule in an ovary at the centre
of the plant The pollen grain germinates on the stigma It grows a pollen tube down the style It male nuclei travel down the pollen tube to the
ovule
© 2008 Paul Billiet ODWS
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FertilisationFertilisation
Style
StigmaPollen grain
Ovule
Embryo sac
Pollen tubeOvary
© 2008 Paul Billiet ODWS
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FertilizationFertilization
Egg cell
Polar nuclei
Embryo sac
Micropyle
© 2008 Paul Billiet ODWS
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FertilizationFertilization
Pollen grains of the daisy Bellis perennis
© 2008 Paul Billiet ODWS
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FertilisationFertilisation
Germinating pollen grains of blue bell, Hyacinthoides non-scripta
© 2008 Paul Billiet ODWS
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The double fertilizationThe double fertilization
Pollen tube
Pollen tube entering micropyle
Male nucleus + egg cell
= zygote (2n)
Male nucleus + 2 polar nuclei = endosperm nucleus (3n)
Ovule
© 2008 Paul Billiet ODWS
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From flower to fruitFrom flower to fruit
Marsh marigold Caltha palustris
© 2008 Paul Billiet ODWS
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Fruits and seed dispersalFruits and seed dispersalAnimal dispersal Strawberry Fragaria vesca
Wind dispersal Ragwort Senecio
Explosive dispersal Bird’s foot trefoil Lotus corniculatus
Animal dispersalWood avens Geum urbanum
© 2008 Paul Billiet ODWS