Life 103-Week 5 notes
Life 103-Week 5 notes Life 103
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This 8 page Class Notes was uploaded by Addy Carroll on Friday February 19, 2016. The Class Notes belongs to Life 103 at Colorado State University taught by Dr. Dale Lockwood and Dr. Tanya Dewey in Winter 2016. Since its upload, it has received 22 views. For similar materials see Biology of organisms-animals and plants in Biology at Colorado State University.
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Date Created: 02/19/16
Life 103 Notes *adapted from the lecture notes of Dr. Dale Lockwood* Gymnosperms ctn. (see week 4 notes for the rest of the notes) • Phylum Gnetophyta -This phylum comprises three genera (see week 4 notes for different genera) -Species vary in appearance, and some are tropical whereas others live in deserts • Phylum Coniferophyta (see textbook figure 30.4 for life cycle of a pine) -This phylum is by far the larges of the gymnosperm phyla -Most conifers are evergreens and can carry out photosynthesis year round Angiosperms • Angiosperms (see textbook figure 30.12 for life cycle) -Single phylum ~Note, gymnosperms have multiple phyla, however, angiosperms make up the majority of plants on the earth ~Anthophyta ~The root “Antho” comes from Greek for flower -Seed Plants -Flowers -Fruits • Flowers (see textbook figure 30.8) -Specialized structure for sexual reproduction -Pollination by animals (insects, mammals, birds) and wind ~Pollinator has a large effect on the adaptations of the flower -Color -Shape -Scent ~Gymnosperms are primarily wind pollinated because they don’t have much to attract a pollinator -Huge diversity in flower color and form -Diversity linked to pollination methods • Amorphophallus titanium -Titan arum -Largest unbranched inflorescence ~Grows about 5-6 feet tall -Corpse flower ~Smells like rotting flesh when blooms -Flies serve as the pollinator -Only blooms for a couple days, making it very popular to watch during that time -Only found on Sumatra • Rafflesia schadenbegiana -Largest flower ~1 meter diameter -Bloom lasts 5-6 days -Corpse flower (see reasoning and pollinator in section above) -Indonesia and Malaysia • Wolffia arrhizia -Smallest flower • The Carpel -A carpel consists of an ovary at the base and a style leading up to a stigma, where pollen is received ~Note, the pollen tube that grows from the pollen, contrary to gymnosperms, has to travel a long way, all the way down the style to the ovary -Sometimes carpel is referred to as pistil ~Much confusion regarding these terms ~Pistil can be multiple fused carpels ~If there is one carpel, then it is also a pistil -The female gametophyte, or embryo sac, develops within an ovule contained within an ovary at the base of a stigma • The Stamen -Modified microsporophyll -Male part of flower -Anther ~Microsporangium-pollen sacs • Floral Structure -Complete Flower ~Has all four modified leaves (sepals, petals, carpels, stamens) ~Incomplete is missing one or more -Perfect flowers ~Have both male and female parts ~Imperfect flowers are missing one or both -Note, all perfect flowers aren’t complete flowers but all complete flowers are perfect flowers • Selfing Plants -Perfect flowers can theoretically self pollinate ~Some plants have a very high frequency of selfing -Plants can have mechanisms to prevent selfing; (inbreeding; there may be more reproductive success, but potentially less fitness) ~Gametophytic Self Incompatibility -Proteins prevent tube from growing ~Heterostyly -Stamens and Carpels are of different lengths ~Sporophytic Self Incompatibility • Pollen -Male gametophyte -Pollen structure influenced by dispersal methods -Exterior composed largely of Sporopollenin • The Life of a Pollen -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 -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 -The endosperm nourishes the developing embryo • Cotyledons -Within a seed, the embryo consists of a root and one or two seed leaves called cotyledons ~The first leaves that emerge from a seed ~Gymnosperms have 2-24 cotyledons -Hypogeal cotyledons stay below ground and do not photosynthesize ~Often used for storage -Epigeal cotyledons expand on germination and push off seed shell, photosynthesizing above ground -Cotyledons often bear little resemblance to the other leaves on the plant • Fruit -A fruit typically consists of a mature ovary but can also include other flower parts -Fruits protect seed and aid in their dispersal ~Serve to attract animals to eat them and then disperse their seeds through digestion -Mature fruits can be either flashy or dry • Types of Fruits -Simple Fruits ~Ripened single or compound ovary within a single carpel -Dry fruits ~Achene: dandelions, strawberries ~Legume: pea, peanut, bean ~Samara: maple, ash, elm ~Nut: acorn, beech, hazelnut ~Fibrous Drupe: coconut, walnut -Simple fleshy fruits ~Berries: grapes, tomatoes, oranges ~Drupes: stone fruits, olives, mangoes -Aggregate fruits ~Single flower with multiple carpels ~Blackberries, raspberries -Multiple fruits ~Pineapple, breadfruit • Achene -Small, hard, dry fruit -Fruit is on the outside ~Ex.) Strawberry • Legume -Simple, dry fruit -Splits open when mature • Nut -Simple, dried fruit -The outside of the ovary becomes a hard shell -Doesn’t split open when mature (opposite of legume) • Drupe -Contains a fleshy exocarp and mesocarp -Hard endocarp ~Fleshy on outside, hard on inside -Stone fruits, coconuts, mangoes, olives • Berries -Fleshy fruit from a single ovary -Pepo: special berry with hard rind on outside ~Ex.) Watermelon, squash • Multiple fruits -Inflorescence ~Cluster of flowers ~Each flower becomes a fruit ~All fruits merge into one mass • Angiosperm Diversity (see textbook figure 30.16) -The two main groups of angiosperms are monocots (one cotyledon; see notes above) and eudicots (“true” dicots) -The clade eudicot includes some groups formerly assigned to the paraphyletic dicot (two cotyledons) group ~All eudicots share the same ancestor; not all “dicots” do -Basal angiosperms are less derived and include the flowering plants belonging to the oldest lineages -Magnoliids share some traits with basal angiosperms, but are more closely related to monocots and eudicots • Basal Angiosperms -Three small lineages constitute the basal angiosperms -These include Amborella trichopoda, water lilies, and star anise • Magnoliids -Magnoliids include magnolias, laurels, and black pepper plants -Magnoliids are more closely related to monocots and eudicots than basal angiosperms • Monocots -More than one-quarter of angiosperm species are monocots ~60,000 species ~Flower parts come in multiples of 3 -Ex.) 6, 9 ~Often have parallel leaf veins • Palms -Monocot -Evolved at the end of the Cretaceous -2,600 species -Tropical, subtropical, and warm climates -Example ~Talipot Palm ~Leaves up to 5 meters in diameter ~Largest inflorescence of any plant • Grasses -Monocot -Family Poaceae -9-10,000 species -Ex.) Bamboo, wheat, sugar cane, rye, maize • Orchids -Monocots -Not only considered the largest single family of monocots, but the largest single family of angiosperms (Asteraceae is comparable) - Approximately 22,000 species -Bilaterally symmetric -One pollinator • Eudicots -More than two-thirds of angiosperm species are eudicots -Very diverse species • Evolutionary Links Between Angiosperms and Animals -Pollination of flowers and transport of seeds by animals are two important relationships in terrestrial ecosystems -Clades with bilaterally symmetrical flowers have more species than those with radially symmetrical flowers -This is likely because bilateral symmetry affects the movement of pollinators and reduces gene flow in diverging populations • Plants and Humans -No group of plants is more important to human survival than seed plants -Plants are key sources of food, fuel, wood products, and medicine -Our reliance on seed plants makes preservation of plant diversity critical • Products from Seed Plants -Most of our food comes from angiosperms -Six crops (wheat, rice, maize, potatoes, cassava, and sweet potatoes) yield 80% of the calories consumed by humans -Modern crops are products of relatively recent genetic change resulting form artificial selection -Many seed plants provide wood -Secondary compounds of seed plants are used in medicines • Threats to Plant Diversity -Destruction of habitat is causing extinction of many plant species -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 Plant Structure • Plant Anatomy (see textbook figure 35.2) -Plants, like animals, are composed of organs made up of tissues, which are composed of cells -Three main organs include roots, leaves, and stems -Roots supply water and minerals to the plant -Leaves supply sugars to the plant -Stems supply support structure and transport systems • Roots -Roots are multicellular organs with important functions ~Anchoring the plant ~Absorbing minerals and water ~Storing organic nutrients -In most plants, absorption of water and minerals occurs near the root hairs (see textbook figure 35.3), where vast numbers of tiny root hairs increase the surface area • Types of Roots -Taproot system ~One main vertical root ~Lateral roots, or branch roots -Adventitious roots ~Can arise from stems or leaves -Fibrous Roots ~Seedless vascular plants and monocots ~Thin lateral roots with no main root • Modified Roots (see textbook figure 35.4) -Prop roots ~Aerial roots ~Add structural support -Strangling roots ~Grow around objects supporting the plant -Strangler Figs ~Epiphytes ~Roots grow down and around tree ~Stem grows up to sunlight -Pneumatophores ~Roots that rise up in the air ~Pores allow gas exchange ~Mangroves -Buttress roots ~Support large trees -Storage root ~Tap root ~Lateral root -Haustorial roots ~Parasitic pants -Examples: mistletoe, dodder, snow plants ~Absorb water and nutrients from other plants -Climbing root ~Adventitious root ~Supports climbing plants ~Negatively phototropic -Grows away from light ~Examples: Ivies • Stems -A stem is an organ consisting of ~An alternating system of nodes, the points at which leaves are attached ~Internodes, the stem segments between nodes -Axillary bud ~Can form a lateral shoot, or branch (in other words, where growth sideways occurs) -Apical bud, or terminal bud ~Located near the shoot tip and causes elongation of a young shoot (in other words, where growth upward occurs) -Apical dominance ~Dormancy in most nonapical buds • Modified Stems (see textbook figure 35.5) -Corm ~Short underground storage stem ~Examples: Taro, gladiolus, saffron -Rhizome ~Horizontal stem ~Usually underground ~Sends out roots, shoots (adventitious roots) ~Examples: Ginger, poison oak, Bermuda grass -Stolon ~Horizontal stem ~At the ground surface or just underground ~Adventitious roots ~Produces clone at the end of the stem ~Examples: Strawberry, many grasses -Bulbs ~Underground stems ~Have modified leaves -Storage when dormant ~Examples: Garlic, onion • Leaves (see textbook figure 35.6) -The main photosynthetic organ of most vascular plants -Generally consist of a flattened blade and a stalk called the petiole, which joins the leaf to a node of the stem • Modified Leaves (see textbook figure 35.7) -Bracts ~Associated with the reproductive structure ~Often brightly colored ~Examples: Bougainvillea, poinsettia -Tendrils ~Used for attaching for climbing ~Can photosynthesize ~Can be thigmotropic -Grows toward touch ~Example: Pea plant -Spines ~Used for defense ~Common in xerophytes ~Thorns and prickles are not the same as spines because they aren’t modified leaves -Thorns ~Modified stems -Prickles ~Modified epidermis ~Example: Roses -Storage Leaves ~Can store water, nutrients, and toxins ~Succulents have these storage leaves -Examples: Cacti, ice plants, agave
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