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58 Cards in this Set
- Front
- Back
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Seed plants originated...
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360 million years ago
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Similarities in all seed plants
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●Reduced gametophytes
●Heterospory ●Ovules ●Pollen |
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Advantages of reduced gametophytes
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●The gametophytes of seed plants develop within the walls of spores that are retained within tissues of the parent sporophyte
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Gametophytes and Sporophytes in...
Mosses and nonvascular plants Ferns and other seedless vascular plants Seed plants |
G- dominant
S- reduced, dependent on gametophyte for nutrition G- reduced, independent S- dominant G- reduced, dependent on surrounding sporophyte tissue for nutrition S- dominant |
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Ovules
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●consists of a megasporangium, megaspore, and one or more protective integuments
●Gymnosperm megasporangia have one integument ●Angiosperm megasporangia usually have two integuments |
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Microspores develop into...
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●pollen grains, which contain the male gametophytes
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Advantage of pollen
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●Pollen eliminates the need for a film of water and can be dispersed great distances by air or animals
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What happens after pollen germinates?
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● it gives rise to a pollen tube that discharges sperm into the female gametophyte within the ovule
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Evolutionary advantages of seeds
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●develops from the whole ovule
●A seed is a sporophyte embryo, along with its food supply, packaged in a protective coat |
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Seed advantage over spores...
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●They may remain dormant for days to years, until conditions are favorable for germination
●Seeds have a supply of stored food ●They may be transported long distances by wind or animals |
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Gymnosperm seeds
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seeds are exposed on sporophylls that form cones
Conifers |
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Angiosperm seeds
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seeds are found in fruits, which are mature ovaries
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Key features of gymnosperm life cycle
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●Miniaturization of their gametophytes
●Development of seeds from fertilized ovules●The transfer of sperm to ovules by pollen |
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Life cycle of pine tree
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●The pine tree is the sporophyte and produces sporangia in male and female cones
●Small cones produce microspores called pollen grains, each of which contains a male gametophyte ●Larger cones contain ovules, which produce megaspores that develop into female gametophytes ●It takes nearly three years from cone production to mature seed |
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Devonian period
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Fossil evidence shows some plants began to aquire features in land plants
●For example, Archaeopteris was a heterosporous tree with a woody stem, but it did not bear seeds |
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When did gymnosperms appear on the fossil record and when did they dominate?
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appear 305 million years ago and dominated Mesozoic terrestrial ecosystems 251-65.5 million years ago
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Why were gymnosperms good?
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●Gymnosperms were better suited than nonvascular plants to drier conditions and served as food
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Recent fossil discoveries show that
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●that gymnosperms were pollinated by insects over 100 million years ago
●Angiosperms began to replace gymnosperms near the end of the Mesozoic |
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Gymnosperm phylas
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●Cycadophyta (cycads)
●Gingkophyta (one living species: Ginkgo biloba) ●Gnetophyta (three genera: Gnetum, Ephedra, Welwitschia) ●Coniferophyta (conifers, such as pine, fir, and redwood) |
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Cycadophyta
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●Individuals have large cones and palmlike leaves
●Unlike most seed plants, cycads have flagellated sperm ●These thrived during the Mesozoic, but most of the few surviving species are endangered |
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Ginkgophyta
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●single living species, Ginkgo biloba
●Like the cycads, this group also has flagellated sperm ●It has a high tolerance to air pollution and is a popular ornamental tree |
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Gnetophyta
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●This phylum comprises three genera: Gnetum, Ephedra, and Welwitschia
●Species vary in appearance, and some are tropical whereas others live in deserts |
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Coniferophyta
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●This phylum is the largest of the gymnosperm phyla
●Most conifers are evergreens and can carry out photosynthesis year round |
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Anthphyta classified
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Single phylum called anthophyta
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Adaptations of anthophyta
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Flowers and fruits
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Flower
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●an angiosperm structure specialized for sexual reproduction
●Many species are pollinated by insects or animals, while some species are wind-pollinated |
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Floral organs
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●Sepals- enclose the flower
●Petals- brightly colored and attract pollinators ●Stamens- produce pollen ●Carpels- produce ovules |
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Stamen
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●consists of a stalk called a filament, with a sac called an anther where the pollen is produced
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Carpel
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●consists of an ovary at the base and a style leading up to a stigma, where pollen is received
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Symetry in flowers
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●Radial symmetry- through the central axis divides the flower into two equal parts
●In bilateral symmetry, can only be divided into two equal parts by a single imaginary line |
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Location of stamens and carpels
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●Most species have both both functional stamens and carpels, but in some species they occur on separate flowers
●Flowers with stamens may be on the same plant as those with carpels, or they may occur on different plants |
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Fruits
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Formed when overy wall matures and thickens which protects seed and aids dispersal
Can be fleshy or dry ●Various fruit adaptations, Seeds can be carried by wind, water, or animals to new locations |
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Angiosperm life cycle
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●The flower of the sporophyte composed of both male and female structures
●microsporangia of anthers produces pollen grains which contain male gametophytes ●The female gametophyte, or embryo sac, develops within an ovule contained within an ovary at the base of a stigma |
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Angiosperm pollination
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●Most flowers have mechanisms to ensure cross-pollination
●A pollen grain that has landed on a stigma germinates and the pollen tube of the male gametophyte grows down to the ovary ●The ovule is entered by a pore called the micropyle |
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Angiosperm fertilization
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●Double fertilization occurs when the pollen tube discharges two sperm into the female gametophyte within an ovule
●One sperm fertilizes the egg, while the other combines with two nuclei in the central cell of the female gametophyte and initiates development of food-storing endosperm which nourishes embryo. |
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Cotyledon
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●Within a seed, the embryo consists of a root and two seed leaves
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Angiosperms originated
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●at least 140 million years ago and began to dominate terrestrial ecosystems by 100 million years ago
●Chinese fossils of 125-million-year-old angiosperms share some traits with living angiosperms but lack others ●Archaefructus sinensis, for example, has anthers and seeds but lacks petals and sepals |
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Angiosperms and gymnosperm diverged about
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305 million years ago
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Angiosperms may be closely related to
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●Bennettitales, extinct seed plants with flowerlike structures
●Amborella and water lilies are likely descended from two of the most ancient angiosperm lineages ●Based on the features of ancestral and basal taxa, including Amborella, early angiosperms were likely small-flowered shrubs with simple water-conducting cells |
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How do animals influence evolution in plants?
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●animal herbivory selects for plant defenses
●interactions between pollinators and flowering plants select for mutually beneficial adaptations |
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Bilateral symmetry affects...
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●Bilateral symmetry affects the movement of pollinators and reduces gene flow in diverging populations
●Plants with bilateral symmetry may have increased rates of speciation ●This hypothesis can be tested by comparing the number of species in closely related “bilateral” and “radial” clades |
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Angiosperm diversity
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Comprise more than 250,000 living species
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Previously angiosperms were divided into...
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Monocots- one cotyledon
Dicots- two cotyledons DNA suggests that diets are paraphyletic |
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Clade Eudicot
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Includes most dicots and the rest form small lineages
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Basal angiosperms
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●include the flowering plants belonging to the oldest lineages
●Three small lineages which include include Amborella trichopoda, water lilies, and star anise |
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Magnolids
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●share some traits with basal angiosperms but evolved later
●include magnolias, laurels, and black pepper plants ●more closely related to monocots and eudicots than basal angiosperms |
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Monocots
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●More than one-quarter of angiosperm species are monocots
●The largest groups are the orchids, grasses, and palms |
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Eudicots
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●More than two-thirds of angiosperm species are eudicots
●include the large legume family and the economically important rose family |
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Seed plants are key sources of
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●food, fuel, wood products, and medicine
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Most of our food comes from angiosperms
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●Six crops (wheat, rice, maize, potatoes, cassava, and sweet potatoes) yield 80% of the calories consumed by humans
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Atropine
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Belladonna plant, eye pupil dilator
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Digitalin
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Foxglove, heart medication
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Menthol
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Eucalyptus tree, throat soother
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Quinine
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Cinchona tree, malaria preventative
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Taxol
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Pacific yew, ovarian cancers drug
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Tubocurarine
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Curare tree, muscle relaxant
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Vinblastine
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Periwinkle, leukemia drug
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Threats to plant diversity
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●In the tropics 55,000 km2 are cleared each year
●At this rate, the remaining tropical forests will be eliminated in 200 years ●Loss of forests reduces the absorption of atmospheric CO2 that occurs during photosynthesis ●Loss of plant habitat is often accompanied by loss of the animal species that plants support ●At the current rate of habitat loss, 50% of Earth’s species will become extinct within the next 100–200 years ●At the current rate of habitat loss, 50% of Earth’s species will become extinct within the next 100–200 years |
