Post on 24-Dec-2015
AP BiologyChapter 29 Seedless Plants: Bryophytes and Ferns
Objectives1.Name the protist group from which plants are
hypothesized to have descended, and describe supporting evidence.
2.Discuss some environmental challenges of living on
land, and describe how several adaptations meet these challenges.
3.Summarize the features that distinguish bryophytes
from green algae and from other plants. 4.Name and briefly describe the three phyla of
bryophytes.
Algae•Plantlike (autotrophic) protists•Unicellular or Colonial•Aquatic (live in water)
The Chlorophytes (green algae) appear to be ancestral to the plants
Phylogeny of the Plants
Terrestrial (Land) PlantsThe move from aquatic habitat to
land creates a number of problems:◦Protection against drying◦Transport of sperm to egg◦Structural support
Plants that have specialized adaptations to solve these problems can live in drier environments, while those that do not are restricted to moist environments
Protection against dryingWater loss in
plants is called Transpiration
Terrestrial plants are protected against transpiration by:◦ Epidermis◦ Waxy “cuticle”◦ Stomata
Transport of sperm to eggAlgae and aquatic plants, since they
live in water, have a natural unbroken water pathway for sperm to swim to the egg
Seedless plants can only reproduce sexually under moist conditions. The “gametophyte” is low to the ground and only grows in moist habitats
Seed plants are less restricted because they provide an internal water pathway in a specialized “pollen tube”
Structural SupportAlgae and aquatic plants are
supported by the buoyancy of the water they live in. ◦Bryophytes, which lack strong
supportive tissues, are very small and low to the ground
◦Tracheophytes, supported by a series of hollow tubes with thickened cell walls, can grow much taller
And now, some video.http://www.youtube.com/watch?v
=X4L3r_XJW0I
Distinguishing Plants from AlgaeAlternation of GenerationsMulticellular, dependent embryoWalled spores produced in
sporangiaMulticellular gametangiaApical meristemsSee pages 602-603 in textbook
Alternation of GenerationsGametophyte (n)
produces gametes (n)Gametes fuse to form
zygote (2n)Zygote develops into a
dependent, multicellular embryo (2n)
Embryo grow into the sporophyte (2n)
Sporophyte produces spores (n) by meiosis
Spores grow and develop forming the gametophyte (n)
Multicellular EmbryoThe zygote
will develop into an embryo within the parent plant
The parent provides protection and nourishment
Spores and SporangiaHaploid spores
will be produced in specialized organs on the sporophyte generation plant called sporangia
The spores are protected by a protective wall
Gametangia (produce gametes)
Moss Archegonium – Note the mature eggs
Moss Antheridium – will producesperm cells
Apical MeristemGrowth of
multicellular organisms begins with cells that have not yet differentiated.
In plants, undifferentiated tissue is called meristem.
Meristem tissue at the tip (apex) of a root or shoot is “apical” meristem
Bryophytes
Mosses Liverworts
•Lack vascular tissue•Reproduce with spores
Classes of Bryophytes
Bryophyte ClassesHornwortsLiverwortsMossesSee page 608 in Textbook
Objectives5.Describe the life cycle of mosses, and compare their
gametophyte and sporophyte generations. 6.Discuss the features that distinguish ferns and other
seedless vascular plants from algae and bryophytes. 7.Describe the life cycle of ferns, and compare their
sporophyte and gametophyte generations. 8.Compare the generalized life cycles of homosporous
and heterosporous plants. 9.Name and briefly describe the four phyla of seedless
vascular plants.
Life Cycle of Mosses
Mosses – Comparing generations
Sporophyte Generation
◦ Temporary◦ Dependent upon
the gametophyte◦ Taller, grows from
the top of the gametophyte
◦ Not photosynthetic
Gametophyte Generation
◦ Permanent/Long lived
◦ Independent◦ Shorter, grows from
the soil/anchored with rhizoids
◦ Photosynthetic
Tracheophytes – Vascular plants
Vascular tissue provides advantages◦ Efficient transport of water and nutrients◦ Structural support
Tracheophyte phylogeny Tracheophytes
include all plants with vascular tissue
The tracheophytes are subdivided into seedless plants and seed plants
Seed plants are subdivided into gymnosperms and angiosperms (flowering plants)
Vascular Seedless Plants
Ferns and Horsetails• Have vascular tissue• Reproduce with
Sporeshttp://www.youtube.com/watch?v=xN8c_X0LNcg
Fern Life CycleThe gametophyte
generation is small, flat and nonvascular, resembling a liverwort
The gametophyte dies once the sporophyte is established
The sporophyte is the prominent generation◦ Vascular◦ Long lived
Ferns – Comparing GenerationsSporophyte
◦ Permanent/Long lived
◦ Independent once established
◦ Produces a rhizome for storage and asexual reproduction
◦ Forms “fronds”
Gametophyte◦ Temporary, dies
once the sporophyte is established
◦ Nonvascular, small and low to the ground
◦ Resembles liverwort
◦ Flattened form captures and holds water
Homosporous and Heterosporous
Homosporous Plants◦ Most seedless
vascular plants◦ Single type of
spore◦ Spores give rise
to monoecious (bisexual) gametophytes
Heterosporous Plants◦ All seed plants and
some seedless vascular plants
◦ Two types of sporangia, each producing a different type of spore
◦ Megaspores give rise to the female gametophyte
◦ Microspores give rise to the male gametophyte
Seedless Vascular PlantsLycophytes
◦Most ancient group of vascular plants◦“club mosses” and “spike mosses”◦Superficially resemble mosses, but vascular
Whisk Ferns◦Branching stems, but no roots
Horsetails◦Photosynthetic stems with rings of branches or
small leavesFerns
◦Horizontal stems with large “fronds” divided into leaflets
Lycophytes
Whisk Ferns
Horsetails
Ferns
AP BiologyChapter 30Seed Plants: Gymnosperms and Angiosperms
Chapter 30 Objectives1. Compare the features of seeds with those of
spores and discuss the advantages of plants that reproduce primarily by seeds rather than by spores.
2. Trace the steps in the life cycle of a pine, and
compare its sporophyte and gametophyte generations.
3. Summarize the features that distinguish
gymnosperms from bryophytes and ferns. 4. Name and briefly describe the four phyla of
gymnosperms.
Seed Plants
Conifers – Pine seeds Flowering Plants – Apple seeds
Seeds provide many advantages over spores• Multicellular embryo • Stored food• Protection• Mechanisms for dispersal
Life Cycle TrendsAlternation of generations continues
in the seed plants, but the gametophyte is diminished to the point of being microscopic
By enclosing the gametophyte entirely within the sporangium, the need for a film of water for transport of sperm is eliminated. The pathway is fully enclosed.
Motility in sperm is lost in most seed plants and diminished in others
Life Cycle of the PineThe Pine tree is the sporophyte
generationGymnosperms are heterosporous.
The megasporangium is located in an ovulate cone. The microsporangium is in a pollen cone.
The female gametophyte develops entirely within the megasporangium
The male gametophyte is enclosed within the pollen grain
Gymnosperm Life Cycle
MicrosporangiumThe pollen
cone contains microsporangia, which will produce the pollen grains
The male gametophyte is within the pollen grain
MegasporangiumThe ovulate cone
contains the megasporangium
The female gametophyte is enclosed within it
Pollination results in the growth of a pollen tube into the ovule, directly depositing a sperm cell
Same deal, different diagram
Evolutionary significanceThe gymnosperms had advantages
over seedless plants:◦With the gametophyte protected and
sperm delivered directly by the pollen tube, gymnosperms were able to survive in much drier environments than any of the seedless plants.
◦The climate became drier in the Mesozoic, giving the advantage not only to the gymnosperms, but also to the reptiles over the amphibians
Concept check 30.1 p. 6211. Contrast sperm delivery in
seedless plants with sperm delivery in seed plants
2. What features not present in seedless plants have contributed to the enourmous success of seed plants on land?
3. If a seed could not enter dormancy, how might that affect the embryo’s transport or survival?
GymnospermsVascular, seed
producing plants“naked seed” –
seeds are not completely enclosed by the ripened ovary
Generally have needle-like (pines) or scale-like (cedars) leaves
Gymnosperm Phylogeny (p. 622-3)Cycads
◦Resemble palms, but are gymnosperms. The cycads were the prominent large plants of the mesozoic
GnetophytesGinkgoes
◦A deciduous gymnosperm, only one species still exists
Conifers◦Pines, spruce, redwoods . . . The most
diverse group of gymnosperms
Chapter 30 Objectives5. Summarize the features that distinguish
flowering plants from other plants 6. Diagram the parts of a flower. Describe
the structure and function of each part 7. Briefly explain the life cycle of a
flowering plant and describe double fertilization.
Angiosperms (Flowering Plants)Vascular seed plantsHave a wide variety
of adaptations for transferring pollen
Seeds mature inside of the ripened ovary of the flower, forming “fruit” which protects, nourishes, and aids dispersal of the seeds
Parts of a Flower
What parts can you recognize?
Double FertilizationDouble fertilization occurs only in
the angiospermsThe pollen grain will produce 2
sperm cells, one which will fertilize the egg to form the zygote (2n) and another which will fertilize the diploid female gametophyte, producing a triploid cell which will form the endosperm
The Endosperm and Cotyledons
The endosperm contains stored food (mostly starch) which will contribute to the early growth of the embryo
The endosperm will form either 1 or 2 seed leaves called cotyledons
Angiosperms are categorized as either monocots or dicots based on the number of cotyledons
Angiosperm life cycle
Chapter 30 Objectives8. Define fruit. Discuss adaptive advantages of
fruits. Give examples 9. Contrast dicots and monocots, the two classes
of flowering plants. 10. Discuss the evolutionary adaptations of
flowering plants. 11. Summarize the evolution of gymnosperms
from seedless vascular plants, and trace the evolution of flowering plants from gymnosperms
FruitFruit is the
ripened ovary of a flower
Fruit may contain stored food and moisture
Fruit provides a mechanism for seed dispersal
Monocots vs. Dicots
Monocots vs. Dicots
Advantages of Flowering PlantsMany flowering plants attract animal
pollinators, which increase the likelihood of pollen grains actually resulting in pollination
Seeds of flowering plants contain far more stored food than the seeds of gymnosperms. The endosperm provides for rapid growth of the embryo after germination
Fruit facilitates seed dispersal through a wide variety of mechanisms: wind, water, animals
Trends in Plant EvolutionAnimal pollinators greatly increase the
rate of cross-pollination, which in turn increases the amount of genetic recombination and variation that occurs within a species
Greater variation results in both more opportunities for adaptation and a more rapid rate of evolution
The connection between flower and pollinator results in co-evolution. The flower and the pollinator both evolve in relation to each other
Pollinator/Flower CoevolutionWasp mimicry
◦https://www.youtube.com/watch?v=-h8I3cqpgnA
The hoverfly◦https://www.youtube.com/watch?v=
MQlq5QtRI9oOverdramatic artistic pollinator
representation◦https://www.youtube.com/watch?v=
MQlq5QtRI9o
Concept Check 30.3 p. 632
1. It has been said that an oak is an acorn’s way of making more acorns. Write an explanation that includes these terms: Sporophyte, gametophyte, ovule, seed, ovary and fruit
2. Compare and contrast a pine cone and a flower in terms of structure and function
Concept Check 30.3 p. 632
3. Do speciation rates in closely related clades of flowering plants show that flower shape is correlated with the rate at which new species form, or that flower shape is responsible for this rate? Explain.