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.