Bio 240: Plant Evolution and Life Cycles

List, give the common name, and describe the key differentiating characteristics of each of the major surviving phyla of plants.

seedless plants table

cone

Gymnosperms produce seeds borne exposed (unprotected) on a stem or in a cone. In other words, an ovary wall does not surround the ovules of gymnosperms. Pine, spruce, fir, hemlock, and ginkgo are examples of gymnosperms.

endosperm

In angiosperms, a nutritive tissue, is usually present in the mature seed.

pollination

transfer of pollen from anther to stigma -the transfer of pollen to the female cones, occurs in the spring for a week or ten days, after which the pollen cones wither and drop off the tree.

coevolution

-describes such reciprocal adapta- tion, in which two species interact so closely that they become increasingly adapted to each other as they each undergo evolutionary change by natural selection.

stomata

Tiny pores which dot the surfaces of leaves and stems of almost all plants, facilitate gas exchange.

What organism is believed to be the ancestor to plants? why? what do land plants share with their ancestors? what are new innovations?

-Plants probably arose from a group of green algae called charophytes. this conclusion is based in part on molecular comparisons of DNA and rNA sequences, which show the closest match between charophytes and plants. -Green algae have pigments, energy reserve products, and cell walls that are chemically identical to those of land plants -photosynthetic, with chloroplasts -cell walls with cellulose, although some lack walls -The multicellular forms do not have cells differentiated into tissues, a characteristic that separates them from land plants.

embryo

In plants the fertilized egg develops into a multicellular embryo (young plant) within the female gametangium. Thus, the embryo is protected during its development.

microspore

Microsporangia are sporangia that produce microsporocytes (also called microspore mother cells), which undergo meiosis to form microscopic, haploid microspores. Each microspore develops into a male gametophyte that produces sperm cells within antheridia.

seed

The plant structure that contains a young plant inside a protective covering

tracheid

The wood (secondary xylem) consists of tracheids, which are long, tapering cells with pits through which water and dissolved minerals move from one cell to another.

archegonium

structure that produces eggs, develops on the gametophyte -Gametophytes also produce female gametangia, known as archegonia (sing., archegonium), each bearing a single egg -Embryo development takes place within the archegonium; thus, the embryo is protected as it develops

phloem

Living vascular tissue that carries sugar and organic substances throughout a plant

some ferns exhibit heterospory but it also characterizes gymnosperms and flowering plants

life cycle of heterospory

leaf

the main organ of photosynthesis and transpiration in higher plants

gametophyte

which produces gametes by mitosis. Two haploid gametes then fuse to form a diploid zygote, which divides mitotically to produce a new sporophyte generation.

pistil

The female reproductive part of a flower

pollinator syndrome

"Pollinator Syndromes" describe flower characteristics, or traits, that may appeal to a particular type of pollinator. Such characteristics can be used to predict the type of pollinator that will aid the flower in successful reproduction. A combination of color, odor, quantity of nectar, location and type of pollen, and flower structure can each affect a potential pollinator's ability to locate a flower and its food resources.

angiosperm seed

Seed coat—and carpel—is from the dominant sporophyte food supply from double fertilization—male and female gametophyte.

Mosses

-Each individual gametophyte plant has tiny, hairlike absorptive structures called rhizoids and an upright, stemlike structure that bears leaflike blades, each normally consisting of a single layer of undifferentiated cells except at the midrib -water-conducting cells and sugar- conducting cells, although these cells are not lignified, nor are they as specialized -Alternation of generations -separate sexes, sometime both -important role in forming soil

how did the presence of bryophytes change the ecology of the earth? How did ancient vascular plants change the environment on Earth

-Overcame obtaining enough water and preventing excessive water loss, tolerating high and low temperatures, and adapting to increased levels of solar radiation -Around 450 million years ago, the first plants emerge from the water. They are collectively called the bryophytes and still thrive in moist environments today. These early pioneers are small and simple, yet able to make the first "steps" onto land. -The most important adaptation found in seedless vascular plants, although absent in algae and bryophytes, is specialized vascular tissues—xylem and phloem—for support and conduc- tion. This system of conduction lets vascular plants grow larger than bryophytes because water, minerals, and sugar are trans- ported to all parts of the plant. rue stems with vascular tissues, and most also have true roots and leaves. The two basic types of true leaves—microphylls and megaphylls—evolved independently of each other -megaphylls evolved over a 40-million-year period in the Late Paleozoic era in response to a gradual decline in the level of atmospheric CO2. As CO2 declined, plants developed a flattened blade with more stomata for gas exchange. (More stomata allowed cells inside the leaf to get enough CO2.) -club mosses major contributors to our present-day coal deposits

What were the key challenges that the green algae had to overcome in their adapting to life on dry land? How were these challenges met and in which lineages???

-absence of water, Structural changes, Desiccation and Upright Growth -obtaining enough water and preventing excessive water loss, tolerating high and low temperatures, and adapting to increased levels of solar radiation. -signaling molecules, Evolution of multicellular sporophyte embryo within maternal gametophyte tissues -Plants probably arose from a group of green algae called charophytes. this conclusion is based in part on molecular comparisons of DNA and rNA sequences, which show the closest match between charophytes and plants. -before liverworts they created cuticles, multicellular gametetangia, multicellular embryos, before club mosses they became sporophyte dominant and vascular tissues, before gymnosperms they created seeds

conifer

-examples include pine and redwood trees-make female and male cones- female cones are large and woody, two ovules will be produced per ovuliferous scale-Male cones are smaller and pollen grains -can produce a lot of spore baring leaves

gymnosperms

-broken up into 4 phylum cycadophyta, ginkophyta, gnetophyta, coniferophyta-after the evolution of seedless vascular plants a lot of carbon dioxide was removed form the air this caused cooling. -no longer depends on water for reproduction -naked seeds -sporophyte dominant (2n) -Sporophytes kept their spores these spores then grew into gametophyte -Gametophyte dependent on sporophyte -Heterospory: male/female spores created -seed: ovuliferous scale, not protected-MEGAsporangia->MEGAspores(n)->Female gametophyte (n)->Ovule-MICROsporangia->MICROspores (n)-> MALE gametophyte(n)-> Pollen

Bryophyta

-divided into three distinct phyla: mosses (phylum Bryophyta), liverworts (phylum Hepatophyta), and hornworts (phylum Anthocerophyta) -only living nonvascular plants -they have no means for extensive internal transport of water, sugar, and essential minerals -small -require a moist environment for active growth and reproduction, some tolerate dry areas -The earliest colonizers- -450 mya first emerged -Gametophyte is both dominant and independent -need water to reproduce -sporophyte is dependent on gametophyte

ovule

-in gymnosperm (future seed) surrounded by integument (future seed coat) -Seed plants produce ovules, each of which is a megasporan- gium surrounded by integuments, layers of sporophyte tissue that enclose the megasporangium. After fertilization takes place, the ovule develops into a seed, and the integuments develop into the seed coat

angiosperms

-one angiosperm phylum: Anthophyta -innovations include flowers and fruit -flowers increased sperm transport-fruits increased seed dispersal -endosperm: product of double fertilization.-Flowers allowed reproduction with far away plants-Sessile-Not able to attract own species to mate-Use third party to get to male gamete-Animals led to the diversification of this phylum because they act as pollinators/ or perform sexual duties for land plants -Anthophyta divided into 2 -sporophyte is dominant and independent -gametophyte dependent

describe the advantages to having seeds; to having flowers.

-the two groups of seed plants are the gymnosperms and the angiosperms. Gymnosperms produce seeds that are totally exposed or borne on the scales of cones; an ovary wall does not surround the ovules of gymnosperms. -angiosperms are flowering plants that produce their seeds within a fruit (a mature ovary). each seed contains a young plant embryo and nutritive tissue (the endosperm), both of which are surrounded by a protective seed coat -Fruits serve two purposes: to protect the developing seeds from desiccation as they grow and mature and to aid in the dispersal of seeds. -Closed carpels, which give rise to fruits surrounding the seeds, and the process of double fertilization with its resulting endosperm increase the likelihood of reproductive success. -The flower, which may contain sepals, petals, stamens, and carpels, functions in sexual reproduction. Unlike those of gymnosperms, the ovules of flowering plants are enclosed within an ovary. After fertilization, the ovules become seeds, and the ovary develops into a fruit.

life cycle of ferns

1. Fern Sporophyte 2. Sorus with sporangia 3. Spores 4. Germinating spores 5. Young prothallus 6. Prothallus gametophyte 7. Antheridium 8. Archegonium and egg 9. Sperm 10. Young sporophyte

monocot

An angiosperm that has only one seed leaf. -palms, grasses, orchids, irises, onions, and lilies -class Monocotyledones -mostly herbaceous plants with long, narrow leaves that have parallel veins (the main leaf veins run parallel to one another -flowers usually occur in threes -Monocot seeds have a single cotyledon, or embryonic seed leaf; endosperm, a nutritive tissue, is usually present in the mature seed.

root

An organ in vascular plants that anchors the plant and enables it to absorb water and minerals from the soil.

megaspore

Megasporangia produce megasporocytes (also called mega- spore mother cells). When megasporocytes undergo meiosis, they form haploid megaspores, each of which develops into a female gametophyte that produces eggs in archegonia. The development of male gametophytes from microspores and of female gametophytes from megaspores occurs within their respective spore walls, using stored food provided by the sporophyte. As a result, and unlike the gametophytes of other seedless vascular plants, the male and female gametophytes are not truly free-living. Fertilization is followed by the development of a new sporophyte.

eudicot

Member of a clade consisting of the vast majority of flowering plants that have two embryonic seed leaves, or cotyledons. -include oaks, roses, mustards, cacti, blueberries, and sunflowers -either herbaceous (such as a tomato plant) or woody (such as a hickory tree) -class Eudicotyledones -Eudicots are more diverse and include many more species (at least 200,000) than the monocots -Their leaves vary in shape but usually are broader than monocot leaves, with netted (finely branched) veins -Flower parts usually occur in fours or fives or multiples thereof -endosperm is usually absent in the mature seed, having been absorbed by the two cotyledons during seed development

cotyledon

Monocot seeds have a single cotyledon, or embryonic seed leaf -A "seed leaf" which develops as a part of the seed. It provides nutrients to the developing seedling and eventually becomes the first leaf of the plant.

define coevolution and pollination syndrome. How had the evolution of angiosperms influenced the evolution of insects?

One reward for the animal pollinator is food. Pollen grains are a protein-rich food for many animals. -Some nectars contain alkaloids such as nicotine to prevent animal pollinators from drinking all the nec- tar in a single visit. (Nicotine is poisonous.) Thus, pollinators are encouraged to visit multiple flowers, and each flower has multiple pollinator visitors. -Plants pollinated by insects often have blue or yellow petals. The insect eye does not see color the same way the human eye does. Most insects see well in the violet, blue, and yellow range of visible light but do not perceive red as a distinct color. So, flowers pollinated by insects are not usually red. -Insects see ultraviolet radiation as a color called bee's purple. -Insects have a well-developed sense of smell, and many insect-pollinated flowers have a strong scent that may be pleasant or foul to humans.

alternation of generations

Plants have a clearly defined alternation of generations in which they spend part of their lives in a multicellular haploid stage and part in a multicellular diploid stage .1 The haploid portion of the life cycle is called the gametophyte generation because it gives rise to haploid gametes by mitosis. When two gametes fuse, the dip- loid portion of the life cycle, called the sporophyte generation, begins. The sporophyte generation produces haploid spores by the process of meiosis; these spores represent the first stage in the gametophyte generation. Let us examine alternation of generations more closely. The haploid gametophytes produce male gametangia, known as antheridia (sing., antheridium), in which sperm cells form (FIG. 27-3a). Gametophytes also produce female gametangia, known as archegonia (sing., archegonium), each bearing a sin- gle egg (FIG. 27-3b). Sperm cells reach the female gametangium in a variety of ways, and one sperm cell fertilizes the egg to form a zygote, or fertilized egg. The diploid zygote is the first stage in the sporophyte genera- tion. The zygote divides by mitosis and develops into a multicel- lular embryo, the young sporophyte plant. Embryo development takes place within the archegonium; thus, the embryo is pro- tected as it develops. Eventually, the embryo grows into a mature sporophyte plant. The mature sporophyte has special cells called sporogenous cells (spore-producing cells, also called spore mother cells) that divide by meiosis to form haploid spores. All plants produce spores by meiosis, in contrast with algae and fungi, which may produce spores by meiosis or mitosis. The spores represent the first stage in the gametophyte genera- tion. Each spore divides by mitosis to produce a multicellular gametophyte, and the cycle continues. Plants therefore alternate between a haploid gametophyte generation and a diploid sporo- phyte generation.

Pterifophytes

Pterifophytes Phyla: Lycophytes, Ferns, horsetails, whisk ferns -Sporophyte dominant (2n) -Independent -Vascular Seedless -horizontal underground stem, or rhizome, that bears leaves, called fronds, and true roots -sperm have flagella -reproduction relies on water -First Tracheophytes -contains lignified tissue -these tissues help w/water transport and strengthening -xylem transports waters and minerals-phloem transports sugars -Sporophtye and gametophyte stages are independent of one another -alternation of generations

seeds over spores

Seeds are reproductively superior to spores for several rea- sons. First, a seed is further along in its development before itis released to survive on its own: a seed contains a multicellular young plant with embryonic root, stem, and one or more leaves already formed, whereas a spore is a single cell. Second, a seed contains an abundant food supply. After germination, food stored in the seed nourishes the plant embryo until it becomes self-sufficient. Because a spore is a single cell, few food reserves exist for the plant that develops from a spore. Third, a seed is protected by a multicellular seed coat that is very thick and hard in some plants, as, for example, in lima beans. Like spores, seeds live for extended periods at reduced rates of metabolism and germinate when conditions become favorable.

what are stomata? What is their purpose? In what lineage of plants did they first evolve?

The leaf epidermis contains minute openings, or stomata (sing., stoma), for gas exchange between leaf cells and the environ- ment; the stomata are evenly spaced to optimize this gas exchange. -Opening and closing of stomata affect carbon dioxide availability Stomata are adjustable pores that are usually open during the day when CO2 is required for photosynthesis and closed at night when photosynthesis is shut down The opening and closing of stomata are controlled by changes in the shape of the two guard cells that surround each pore. The guard cells' shape is determined by their rigid- ity. When water moves into guard cells from surrounding nonguard cells, the guard cells become turgid (swollen) and bend, producing a pore. When water leaves the guard cells, they become flaccid (limp) and collapse against one another, closing the pore. Under drought, plants may also close their stomata to limit the amount of water that evaporates from their leaves. However, this strategy introduces new dilemmas. Because plants must exchange gases through their stomata, closing them prevents plants from taking up carbon dioxide (CO2). -bryophyta

what characteristics differentiates the tracheophytes from the non-tracheophytes? Why are the non-trachophytes generally, small and close to the ground?

The main difference between bryophytes and tracheophytes is that the bryophytes are nonvascular plants while the tracheophytes are the vascular plants. Furthermore, bryophytes include mosses, liverworts, and hornworts while tracheophytes include ferns, gymnosperms, angiosperms. Because they have no means for extensive internal transport of water, sugar, and essential minerals, bryophytes are typically small. They generally require a moist environment for active growth and reproduction, but some bryophytes tolerate dry areas.

floral structure

This cutaway view of an Arabidopsis flower shows the details of basic floral structure. Each flower has four sepals (two are shown), four petals (two are shown), six stamens, and one long pistil. Four of the stamens are long, and two are short (two long and two short are shown). Pollen grains develop within sacs in the anthers.

sporophyte generation

When two gametes fuse, the diploid portion of the life cycle -The sporophyte generation produces haploid spores by the process of meiosis; these spores represent the first stage in the gametophyte generation. -forms haploid spores by meiosis each spore divides mitotically to form a multicellular haploid

zygote

a diploid cell resulting from the fusion of two haploid sex cells, or gametes

antheridium

alternation of generations more closely. The haploid gametophytes produce male gametangia, known as antheridia (sing., antheridium), in which sperm cells form

Vessel element

in angiosperms, xylem cell that forms part of a continuous tube through which water can move -Gnetophytes share certain features that make them unique among the gymnosperms. For example, gnetophytes have more efficient water-conducting cells, called vessel elements, in their xylem. Flowering plants also have vessel elements in their xylem, but of the gymno- sperms, only the gnetophytes do.

ovary

ovary, an enlarged structure that contains one or more ovules

xylem

vascular tissue that carries water upward from the roots to every part of a plant