1. Plant Diversity II
The Seed Plants

2. Evolution 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

3. Common 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

4. 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

5. Gymnosperms / Coniferophytes. . .
Gymnosperms include conifers, cycads, ginkgoes, & gnetophytes
Name means “naked seed”
abundant in colder latitudes and higher dry elevations

6. Characteristics 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

7. Conifer 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

8. 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.

9. Characteristics of Angiosperms
Flowers attract animal pollinators
Extremely diverse in size, form and habitat
                       

10. 2 Angiospermophyte Divisions
Hydrophytes
Adapted for aquatic/moist environments
Xerophytes
Adapted for dry climates

12. Angiosperm 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

13. 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

14. 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

15. 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.

17. Monocots and Dicots Monocots Dicots 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

20. ANGIOSPERMS
The flowering plants
Spring crocus Crocus vernus

21. Flower 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)

22. Types of pollination Wind Animal Water
Bumble bee Bombus hortorum on red clover Trifolium pratense
Yorkshire fog grass Holcus lanatus

23. Animal pollination Usually insects Also other flying animals
e.g. hummingbirds or fruit bats
Cerambycid beetle pollinating bramble Rubus fruticosus

24. Flower structure
Dog rose Rosa canina

25. Pollination 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

26. Pollination
Small skipper Thymelicus flavus on marsh thistle Cirsium palustris

27. Pollination
The honey bee Apis melifera on marsh thistle Cirsium palustris
© 2008 Paul Billiet ODWS

28. Pollination
Fox glove flowers Digitalis purpurea
Some flowers are highly specialised to encourage only one type of insect
© 2008 Paul Billiet ODWS

29. Pollination 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

30. Fertilisation 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

31. Fertilisation Pollen grain Stigma Style Ovule Embryo sac Ovary
Pollen tube
Ovary
© 2008 Paul Billiet ODWS

32. Fertilization Embryo sac Polar nuclei Egg cell Micropyle
© 2008 Paul Billiet ODWS

33. Fertilization Pollen grains of the daisy Bellis perennis
© 2008 Paul Billiet ODWS

34. Fertilisation
Germinating pollen grains of blue bell, Hyacinthoides non-scripta
© 2008 Paul Billiet ODWS

35. The 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

36. From flower to fruit Marsh marigold Caltha palustris
© 2008 Paul Billiet ODWS

37. Fruits and seed dispersal
Animal dispersal Strawberry Fragaria vesca
Explosive dispersal
Bird’s foot trefoil
Lotus corniculatus
Animal dispersal
Wood avens
Geum urbanum
Wind dispersal
Ragwort Senecio
© 2008 Paul Billiet ODWS