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by: Cornelius Reinger Jr.


Cornelius Reinger Jr.
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Date Created: 09/12/15
PB101220 Lecture Outline for Final Exam March 29 2011 Evolution of the Flower 1 Evolution of angiosperms Bryophytes and seedless vascular vascular plants female gametophytes independent of sporophytes require free water for the sperm to reach the egg Gymnosperms plants with naked seeds female gametophytes protected and nurtured by sporophytes development of ovule and seed no free water required for sperm to reach the egg male gametophytes pollen grains carried by wind to the ovule Angiosperms Plants with seeds enclosed within fruits Arose about 150 million years ago Became dominant around 65 million years ago The largest and most diverse group of plants About 250000 identi ed species Magnoliophyta Single common ancestor Pollination by animals Promote outcrossing and genetic diversity Insects play important roles in the evolution of angiosperms Primitive owering plants numerous spirally arranged oral parts not fused variable in number superior ovary owers radially symmetrical magnolia Evolutionary trends of the angiosperms reduction and fusion of oral parts inferior ovary owers became bilaterally symmetrical or irregular orchids 11 What is a ower Flowers reproductive structures produce a new generation through sexual reproduction solitary ower in orescence III Functions of oral parts Sepals lea ike protect oral buds Petals the most noticeable part attraction of pollinators Perianth sepals and petals Stamens lament anther four male sporangia four pollen sacs male gametophyte pollen grains Carpels pistils stigma receptive area for pollen style elevation of stigma ovary ovule female gametophyte 7 cells egg central cell Double fertilization male gametohpyte pollen tubes 3 cells tube cell sperm cells pollen tubes grow through the style down to the ovule convey sperm cells to the ovule both sperm cells undergo fusion sperm and egg zygote embryo sperm and central cell endosperm integument seedcoat ovary wall fruit all members of angiosperms gnetophyte Ovary positions superior ovary on top of the receptacle in primitive owers inferior ovary embedded in the receptacle in advanced owers Nectaries insect and bird pollinated owers nectar sugars reward to pollinators essential oils volatile sweetsmelling attract pollinators IV Our uses of owers Perfumes rosejasmine orange nectaries essential oils Brewing of beer female in orescence of hops a source of desirable bitterness counteract the sweetness beechwood chips Flowershappiness V Reading materials chapters 8 and 23 in Stern s textbook V I Study questions 1 Review the important features evolved in different groups of plants 2 Study the structure of a ower functions of oral parts and examples of our uses of owers 3 Know the following terms primitive owers advanced owers sepal petal stamen anther lament microsporangium microgametophyte carpel stigma style ovary ovule megagametophyte double fertilization binucleate central cell endosperm embryo superior ovary inferior ovary nectary nectar essential oils March 31 2011 Pollination Ecology I Mutualism between flowering plants and pollinators Interaction owering plants and pollinators mutualism both organisms bene t from their relationship Attractants the color of petals leaves bracts scent from nectary Rewards encourage pollinators to move from plant to plant sugars from nectary pollen Coevolution Pollination Fertilization II Pollination by insects Insects the most common group of animals that pollinate owers Bees pollinate more kinds of owers 20000 different species of bees as pollinators the most important pollinators in angiosperms evolution Other pollinators wasps moths butter ies beetles ies ants Beepollinated owers brightlycolored delicately sweet and fragrant petals nectary guides UVabsorbing avonoids toward the center of the ower darker in UV light visible to insects in the sunlight Mothpollinated owers strongly scented night blooming white or creamcolored tubular or trumpet shaped petals longtongue moths Pollinator deception achieve cross pollination through deception orchids owers of ophrys species a wasplike shape hairy petal like the abdomen of the female wasp emit chemicals similar to a sexual attractant secreted by female wasp pollinium a sac of pollen grains male wasps pollinate ophrys owers without rewards III Pollination by bats and birds Flowers that attract bats and small rodents often open at night usually white strongly scented banana cactus Hummingbirds the most common group of owering visiting birds in Americas long beaks nectar at the base of long tubular petals bright red petals generally odorless columbine scarlet monkey owers IV Pollination by wind The most inefficient yet common method of pollination Windpollinated plants produce tremendous numbers of pollen grains improve their chances of pollination lack showy oral parts no strong fragrance wellexposed stamens large stigma a single ovule in each ovary many owers packed into each in orescence grasses many trees oaks sycamore sweetgum birch alder hazel male in orescencecatkin Advantages and disadvantages of self pollination and cross pollination Mechanisms for plants to avoid self pollination V Reading materials chapter 23 in the Stern s textbook V I Study questions 1 Understand the mutualism and coevolution between owering plants and pollinators 2 Study the important features of owers that are adapted to pollination by insects bats birds or wind self pollination and cross pollination mechanisms for plants to avoid self pollination April 5 2011 Evolution of Fruits I How a fruit is formed After fertilization the ovule develops into a seed the ovary wall develops into a fruit A fruit is a mature or ripened ovary Fertilization induces the fruit development Without fertilization owers normally wither and drop no fruit development Exceptions fruits develop from ovaries without fertilization pa1thenoca1py Palthenocarpic fruits seedless pineapples navel oranges supermarket bananas ce1tain varieties offigs and grapes Chemical signals called hormones auxin and gibberellins are secreted by seeds as they develop These hormones induce the ovary to expand and mature into a fruit Applications with fruitpromoting hormones Applied to some crops so that fruits form and mature in synchrony Induce formation of seedless fruits e g seedless grapes in the absence of fertilization 11 Types of fruits Pericarp the fruit wall that develops from the ovary wall exocaip mesocarp endocarp Simple fruits develop from the ovary of a single carpel or several fused carpels in a single ower Simple eshy fruits when ripe the perica1p is often soft and juicy seed dispersal accomplished when animals eat the fruits tomato grapes oranges melons peaches peaches avocadoes Simple dry fruits the pericarp may be tough and woody or thin and papery Dry dehiscent fruits split open at maturity and so release their seeds peanut pods bean pods cotton capsules milkweed Dry indehiscent fruits do not split open winged fruits of maple and sycamore carried by wind cereal grains Aggregate fruits develop from a single ower with many separate ovaries carpels all of which ripen at the same time raspberry blackberry strawberry enlarged receptacle Multiple fruits develop from the fusion of many ovaries from separate owers on an in orescence pineapple enlargement of the stalk III Functions of fruits Protect developing seeds May help disperse mature seeds inside Seed dispersal self ejection by wind by water by animals IV Our uses of fruits Of the more than 250000 known angiosperms only a small percentage produces fruits that have been utilized by humans Fruits are packed with nutrients and are particularly excellent sources of vitamin C potassium and bers V Reading materials chapter 8 in the Stern s textbook V I Study questions 1 Review the process of fruit formation 2 Study the types and functions of fruits Understand how simple aggregate and multiple fruits are developed April 7 2011 Crop plant evolution and plant breeding I Origins of agriculture The human species Homo sapiens has existed for about 400000 years For most of that time huntergatherers Farming sta1ted about 10000 years ago Agriculture the basis of advanced civilization Population explosion Early sites of agriculture Agriculture arose independently in many parts of the world The NearEastem region early domesticated plants wheat barley apple pear carrot lettuce The Far East region rice soybean tea banana citrus fruits sugarcane Africa coffee sorghum The new world maize potatoes sweet potatoes tomatoes peanuts cacao red peppers pineapple cassava squashes sun ower tobacco cotton unknown outside of the Americas before the time of Columbus the greatest treasure that the Old World acquired from the New world Characteristics of domesticated plants Natural selection promote characteristics that ensure their survival in the environments increase the passage of genes to the next generation Domesticated plants arti cial selection suit human needs do not necessarily have a survival value traits commonly selected better taste larger seeds fruits or tubers nonshattering fruiting heads Maize domesticated over 5500 yr ago in central Mexico teosinte the ancestor of modern corn spike shatters easily at maturity to release kernels modern corn entire ear covered with husks prevent seed dispersal could not survive under natural conditions Carries the genes for resistance to seven of the nine major viruses that infect maize in US for five of these viruses no other source of resistance is known Brassica oleracea the common vegetables broccoli Brussels sprouts cabbage cauli ower kale kohlrabi look very distinct all are derived from wild Brassica oleracea following thousands of years of arti cial selection by farmers Arabidopsis cauli ower mutant caused by mutation of a single gene a MADS box regulatory gene 11 Plant breeding Few crops have been brought into domestication in recent centuries Plant breeders currently devote their effort into improving existing crops Early domestication crop improvement was based on simply selecting and planting seeds from desirable plants Plant breeding is accelerated evolution guided by humans rather than nature based on our understanding of genetics and plant reproduction The primary goal of plant breeding improved yield with disease resistance stress tolerance and other bene cial traits Breeding methods Create hydrid populations by crossing desirable sexually compatible parents Plant genetic engineering transfer desirable genes from any organisms into a crop plant Norman Borlaug the Father of Green Revolution Developed new strains of highyielding wheat in Mexico Crossed normal wheat varieties with a dwarf variety Mexico India and Pakistan quadrupled their wheat production in 1960s by growing these new strains Awarded the Nobel Peace Prize in 1970 Borlaug have saved more lives than anyone in history by increasing grain yields in developing countries Outcrossing in crosspollinated crops Leads to hybrid vigor These plants are larger more vigorous higher reproductive capability higher yielding Self pollination of cross pollinated plants inbreeding depression Plants with smaller size poor vigor low reproductive capability and a high proportion of abnormal plants Due to the expression of deleterious recessive alleles The most dramatic success crop corn maize In 1908 plant breeder GH Shull Cross two inbred lines of corn each of which produced 20 bushels per acre The hybrid offspring yielded 80 bushels per acre a quadruple increase in yield Most of the corn in US is grown from hybrid seed 111 Reading materials chapter 14 in Stern s textbook IV Study questions 1 Know the crop plants domesticated in different regions of the world natural selection and arti cial selection 2 Know the general concept of plant breeding and its benefit to agriculture April 12 2011 Flowering Plants and Civilization 1 Classi cation of owering plants Flowering plants Magnoliophyta two classes Dicotyledones dicots two cotyledons in the embryo leaf venation netlike oral parts tend to occur in 4 5 or multiples of 4 or 5 include many annual plants almost all owering trees and shrubs Monocotyledons monocots one cotyledon in the embryo leaf venation parallel oral parts in 3 or multiples of 3 include species that produce bulbs lilies onions grasses orchids irises palms About 350 families Classi cation mainly based on ower and fruit parts and structure owers and fruits are more reliable indicators of heredity Based on molecular phylogenetic analysis Example key to a few families 1 Flowers with parts in 4 or 5 or multiples of 4 or 5 seeds with two cotyledons dicots 1 Flowers with parts in 3 or multiple of 3 seed with one cotyledon monocots 2 Flowers inconspicuous no sepals or petals the grass family 2 Flowers conspicuous petals and sepals mostly similar in coloration 3 Petals all alike superior ovary the lily family 3 One petal differs in form from the other two inferior ovary the orchid family 11 The Grass Family Poaceae Monocots about 8500 species 25 of the world s vegetation Leaves typically long bladelike with parallel veins leafsheath Stems bear no vegetative branches Flowers small and incomplete lacking sepals and petals pollination by wind most have three stamens and one carpel each ower is born between two bracts the lemma and palea in orescence Grains dry singleseeded fruits endosperm stored food starch large amount of stored food valuable as a food crop the most important family to humans Rice genome sequenced genome organizations among the members of the grass family are similar Cultivated grasses cereals basic food of civilization wheat rice com the three most extensively grown of all food crops other important cereals barley sorghum oats millet rye oat bran has cholesterollowering properties cereals constitute about 70 of the world s food crops The rise of bread wheat our gluten a compleX of proteins elasticity leavening agent allow dough to rise Corn Indian maize an unusual cereal separate male and female in orescence tassel male in orescence at the apeX female in orescence on a lateral stem give rise to the ear of corn Sugarcane a perennial member domesticated in the Far East about 10000 yr ago thrive in moist lowland tropics and subtropics 1520 ft tall store 1215 sucrose in stem cells provide over 50 of the world s sugar supply Columbus introduced sugarcane to the Caribbean islands A major cash crop in Cuba Peru and Brazil 50 of the world production of cane sugar Cane sugar in Brazil biofuel production Switchgrass miscanthus in the grass family Potential cellulosic biofuel crops in US Yield of 265 tonsacre observed in Illinois without irrigation III The Lily Family Liliaceae One of the most important family horticulturally Monocots About 4500 species abundant in tropics and subtropics Floral parts are all in multiples of three usually 3 sepals 3 petals 6 stamens superior ovary with 3 fused carpels Sepals and petals are alike in color and form Examples omamentals lilies tulips sansevieria snake plant vegetables onions garlic asparagus Aloe vera the burn plant evergreen succulent Succulent plants are waterretaining plants adapted to arid climate or soil conditions Succulent plants store water in their leaves stems andor roots The storage of water often gives succulent plants a more swollen or eshy appearance than other plants also known as succulence native to Africa Used for thousands of yrs in Africa as treatment for various skin ailments rashes sunbums minor wounds when cut succulent leaves gt thick sap gt soothing to injured skin Aloe sap contains numerous compounds including several anthraquinone glycosides collectively referred to as aloin Aloe sap promote faster healing with less scarring Stimulates cell growth Inhibits bacterial and fungal infection in injuries Inhibit pain itching and in ammation Has moisturing effects Capitalized by the cosmetic industry skin creams shampoos sunscreen lotions bath oils IV The Orchid Family orchidaceae Spectacularly beautiful owers Monocots About 35000 species the largest family of owering plants most species tropical Ovary inferior Flower bilaterally symmetrical Three sepals often colored similar to petals in appearance color Three petals two lateral ones form wings the third one forms a cuplike lip that is often very large and showy Stamens and carpels united in a unique single structure as the column Anther dispersed as a unit pollinium Each orchid ovary many thousands of minute ovules Orchid seeds cannot germinate until they are invaded by hyphae of the soil fungus Mycorrhizal association an association between a fungus and the underground parts of a plant Epiphytes grow upon or attaches to a living plant Also called quotair plantsquot because they do not root in soil Epiphytic organisms usually derive only physical support and not nutrition from their host Use photosynthesis for energy and obtain moisture from the air or from dampness rain and cloud moisture on the surface of their hosts Roots may develop primarily for attachment Vanilla orchid Vanilla planz39folz39a popular avoring for sweetened food tropical vine orchid native to the New World vanillin a phenolic compound provides the characteristic aroma and taste of vanilla Arti cial vanilla chemically synthesized V Reading materials chapter 24 in Stern s textbook V I Study questions 1 Understand the general concepts about classi cation of owering plants dicots monocots venation 2 Know the important characteristics of each family and examples of our uses of one or two members in each family succulent epiphyte pollinium mycorrhizae April 14 2011 Flowering Plants and Civilization 1 The Sun ower Family Asteraceae Dicots 20000 species the second largest family of owering plants Individual owers orets a compact in orescence straplike extension of corolla Examples sun ower chrysanthemum marigold dandelion daisy Sun ower domesticated about 3000 yr ago in North America wild ancestor highly branched stems small ower heads modern ones singlestalked plants produce up to 1000 seeds per head Sun ower oil among the healthiest oils consumed by people message oil fuel 11 The Legume Family Fabaceae About 13000 species the third largest family of owering plants Flowers radially or bilateral symmetrical five petals a boatshaped keel two wing petals a large banner petal Fruits legume dry dehiscent fruit a pod with one row of seeds seeds contain two prominent foodstoring cotyledons Important crop plants include peas many kinds of beans soybean lentils peanuts alfalfa sweet clover Symbiotic association with nitrogen xing bacteria rhizobium nodules cultivation of legumes enrich the soil nitrogen Rotate with crops that deplete soil nitrogen Seeds of many legumes higher in protein than any other food plant and are close to animal meat in quality 10 essential amino acids arginine histidine isoleucine leucine lysinea methionine phenylalanine threonine tryptophan and valine Peanuts native to the South America After fertilization ower stalk elongates downward pushing the developing fruits into the soil fruits mature into a pod underground Peanut seeds 4550 oil 2530 protein highly nutritious one billion pounds per yr consumed as snack food candy butter in the US Soybeans native to China introduced into North America in 1765 US 60 ofthe world s supply of soybean about 20 oil up to 50 protein among the richest foods known Soy foods iso avones phytoestrogens lower cholesterol levels lower blood pressure reduce the risk of cardiovascular disease reduce symptoms of menopause inhibit tumor formation and growth III The Rose Family Rosaceae About 3000 species oftrees shrubs herbs Flowers basal parts fused into a cup sepals petals and stamens attached to the cup s rim commonly ve sepals ve petals except for ornamental cultivars usually many stamens Enormous economic impact Fruits Simple fruits apples pears cherries plums apricots Aggregate fruits strawberry blackberries raspberry Omamentals rose Perfume oil rose Perfume worker are rarely reported to develop respiratory disorders IV The Nightshade Family Solanaceae About 300 species concentrated in the tropics of Central and South America Flowers usually 5 sepals 5 petals fused petals stamen laments fused to the corolla Examples food plants tomato white potato eggplant pepper ornamentals petunia drugs tobacco Capsicum pepper native to the New World cultivated for at least 9000 yr by American Indians capsicum annuum sweet bell peppers hot peppers Biting taste in capsicum peppers seven alkaloids capsaicin prevalent one capsaicin heat trigger the same painsensing nerve bers hot Applications pepper spray analgesic cream relieve the pain of arthritis cluster headaches Pepper fruits excellent sources of vitamin C Tobacco native to the New World leaves used for chewing smoking by Native Americans for centuries Nicotine the major alkaloid in tobacco the most addictive drug in widespread use one of the most toxic plant poisons insecticide Tobacco smoke a complex mixture of over 2000 chemicals harmful to health V The Poppy Family Papaveraceae Flowers tend to have numerous stamens usually two whorls of petals most have a single ca1pel Most have milky or colored saps All members produce alkaloid drugs Opium poppy significant impact on society native to the Middle East Opium milky liquid from capsules over 20 alkaloids morphine codeine deaden pain suppress cough widely used in medicine central nervous system depressant strongly addictive overdose deadly Heroin semisynthetic derivative of morphine introduced in 1898 by the Bayer Company as a cough suppressant thought not to be addictive but sixtime more addictive than morphine laststanding drug and crime problem V I The mustard family Brassicaceae About 2500 species owers four sepals four petals six stamens petals in the fonn of a cross fruits dry dehiscent siliques Pungent smell and taste attribute to mustard oil glycosides mustardsmelling volatiles Among the widely cultivated edible plants of mustard family Cabbage Chinese cabbage cauli ower brussels sprouts broccoli radish turnip horseradish Canola oil obtained from rapeseed a source of low LDL fats Mustard a mixture of ground dried seeds of 2 species of Brassica Phytochemicals which occur naturally in vegetables fruits grains and seeds have their protective action in prevention of cancer and other diseases Mustard family vegetables excellent source of a class of phtochemicals mustard oil glycosides dithiolthiones Prevent tumor growth via activate liver enzymes that destroy carcinogens in the body Phytochemicals most effective if eaten in foods rather than in supplements Arabidopsis thaliana The model plant for molecular and genetic analysis Arabidopsis cauli ower mutant caused by mutation of a single gene a MADS box regulatory gene The whole genome was sequenced in 2001 26000 genes gt to make a owering plant V II Caffeine rich plants Stimulating beverages in many cultures Caffeinerich plants Coffee cola native to Africa Tea native to Asia Cacao native to Central and South America Caffeine an alkaloid Psychoactive drug central nervous system stimulant addictive Alleviate fatigue promote alertness and endurance Constrict blood vessels gt painrelieving effect Appetite suppressant many diet pills Speed heartbeat increase blood pressure stimulate respiration Coffee Co eaArabica native to Ethiopia Small evergreen tree or shrub Seeds coffee beans are used in production of coffee Coffee aroma the essential oil caffeol ground coffee refrigerated to preserve avor Decaffeinated coffee extracted with methylene chloride to remove caffeine Genetic engineering low caffeine coffee tree Tea Camellia sinensis small tree or shrub native to China and India Dried tip leaves gt tea Green tea dried leaves without fermentation Black tea leaves fermented Tea avor essential oils theol tannins gt bitterness Green tea Flavonoids Inhibit cancer formation Lower cholesterol level Cacao Theobroma cacao a tree native to tropical Central and South America Fruit pods formed directly on the main trunk Seeds used to make cocoa chocolate Chocolate High energy food 60 carbohydrate 30 fat Stimulating effects alkaloids gt caffeine and theobromine toxic to dogs Phenylethylamine increase in human brains when one falls in love Cola Cola m39tida a tree native to West Africa Belong to the same family as cacao Seeds caffeinerich CocaCola Dr John Pemberton a pharmacist Atlanta GA In 1886 CocaCola Cola seed extract caffeine Coca leaf extract cocaine sugar caramel for coloring carbonated water Instant success Brain tonic cocaine removed since 1903 V 111 Plant Secondary Products Primary plant metabolism all pathways necessary for the survival of the cells e g photosynthesis respiration Secondary plant products produced in some specialized cells not necessary for the cells but may be useful for the plant as a whole Terpenes Essential oils perfumes for pollinator attractants peppermint oils coffee aroma caffeol tea aroma theol Pine resins Alkaloids Morphine codeine depressants Caffeine nicotine cocaine stimulants Phenolic compounds Vanilla cinnamon tannins iso avones avonoids Glycosides Mustard oil glycosides Aloe sap Functions discourage herbivores from feeding inhibit bacterial and fungal pathogen Essential oils in owers and fruits attractants for pollinators and fruitdispersal animals IX Reading materials chapter 24 in Stern s textbook X Study questions 1 Know the important characteristics of each family and examples of our uses of one or two members in each family April 19 2011 Evolution 1 Charles Darwin and the theory of evolution Theory an explanation that organizes all of the known evidence about a particular subject has predictive powers is well supported by scienti c investigations Theory of evolution provides a scienti c explanation about how the rst forms of life diversi ed into the organisms of today how the many different kinds of plants animals and microorganisms arose on ea1th Evolution implies change in living things over time Evolution the change in the inheritable characteristics of a group of organisms over the course of generations Throughout the recorded history people have wondered how the great variety of earth s organisms came to be Before Darwin beliefs that all organisms were static and didn t evolve The foundation for understanding how biological change occurs and how such change forms new species rests on the theory of evolution This theory is most closely identi ed with Charles Darwin 18091882 the most famous and in uential naturalistphilosopher in history His ideas about evolution may have impacted a wider array of human endeavors than any other scienti c achievement in history Charles Darwin born in 1809 in Shrewsbury England From 1831 to 1836 Darwin served as naturalist aboard the HMS Beagle on a British science expedition around the world He spent much of his time on shore collecting plants and animals and making geological and biological observations The geographic distribution of South American organisms both fascinated and puzzled Darwin He wondered why they were so diverse and different from organisms in England Charlie Lyell s principles of Geology the earth was very old and constantly changing Convinced Darwin to embrace the idea the organisms that fascinated him may have changed that is evolved along with a slowly changing environment over a long period time In 1838 Darwin was inspired from a book An essay on the principle of population by Thomas Malthus Populations has an inherent tendency to increase in geometric proportions resources to support this growth may increase slowly or not at all Because continued growth of a species would outstrip needed resources especially food supply there would inevitably be a struggle for existence Darwin adopted Malthus s ideas that populations tend to increase geometrically and outstrip their resources Darwin also observed that wild organisms have variable traits He reasoned that in a resourcelimited environment the hardiest or bestsuited individuals have a competitive and reproductive advantage over weaker individuals As a result the bestsuited organisms would live longer and be more likely to reproduce than weaker organisms Thus traits of welladapted individuals would increase in successive generations and traits of poorly adapted individuals would decrease Darwin called this process natural selection He saw a similar mechanism in he modern world among plant and animal breeders who practice arti cial selection Charles Darwin published his famous book The Origin of Species in 1859 11 Evidence for evolution Evolution explains the unity of living organisms 7 ie why many characteristics are shared by all living things including the composition of proteins and DNA Evolution also explains the diversity of life on earth 7 how millions of species of organisms have descended with modification from different lineages of common ancestors This suggests that all forms of life are related by unbroken chains of descent that all living species can be traced back through time to fewer and fewer common ancestors Ample evidence indicates the earth is over 45 billion yrs old If evolution occurs gradually then the earth must be old enough to allow it to happen Darwin s day the earth was believed to be only a few thousand yrs old too brief for all living things to have evolved from a single common ancestor Age of the earth estimated by comparing ratios of radioactive to nonradioactive elements in rocks Earth is between 45 to 50 billion yrs old Meteorites found on earth are also estimated to be 45 billion yrs old support the idea that the earth was formed simultaneously with other parts of the solar system Vascular plants have left fossil evidence about their evolution The oldest organisms either were not preserved as fossils because they were too small or too soft or we can t recognize their preservation in rocks The oldest recognizable fossils are of bacteria that lived at least 38 billion yrs ago This age establishes a minimum time span for biological evolution this is long enough for the evolution of all of the organisms of today Darwin predicted that if evolution happened the fossil record would contain links among related organisms from ancient to progressively more recent species The information about fossils that subsequently has been gathered supports Darwin s prediction The most complete record of plants is for those with vascular tissue 4lOmillionyrold fossils of the first vascular plants look like they share a common ancestry with certain groups of living vascular plants Homologous structures are derived from a common ancestors Ifdifferent species have evolved from a common ancestor they may possess features that are homologous ie the features have the same evolutionary origin and come from the same ancestor In owering plants the ovary surrounding the seeds gt all of these plants inherited the ovary from a common ancestor All plants have chloroplasts for photosynthesis cellulosic cell wall embryo gt descended from a common ancestor of the plant kingdom green algae Chara Plants also have features that are homologous with features of other kinds of organisms Cells with nuclei chromosomes with histones and genes with introns gt inherited from the common ancestor of plants animals and fungi Convergent characteristics occur in unrelated organisms living in similar habitats Not all similarities are due to homology Stem succulence of cacti and euphorbia Succulent stems provided descendants of a cactus ancestor an adaptation to an arid environments in America Likewise descendants of a euphorbia ancestor with succulent stems became adapted to the arid environments of Africa The succulence seen today in cactus and euphorbia is not a homologous characteristic but a convergent one because two distantly related groups of plants evolved similar characteristics in similar environments Natural selection helped shape these organisms in similar ways Biogeography provides evidence for evolution Biogeography study of the geographic distribution of organisms reveal the movement of organisms and their change through time Adaptive radiation migration to new environments followed by adaptation and formation of new species Adaptation characteristics of an organism that increase its chances for survival and for reproduction Evolution can be observed Some evolutionary changes happen fast enough for people to observe over a relatively short period of time Hundreds of species of cropeating insects have evolved resistance to insecticides Evolution also can be observed as a result of experimentation especially with rapidly growing bacteria that are exposed to high temperature chemicals and antibiotic which are used as selective agents to identify tolerant individuals 111 Mechanisms for evolution The theory of natural selection proposed by Darwin explains the primary mechanism by which evolution occurs Natural selection individuals best adapted to their environment produce the most offspring and pass their desirable genes to the next generation Natural selection is a fundamental process in nature and a cornerstone of biology Four principles of natural selection 1 Organisms have a tendency to produce more offspring than survive 2 Only a fraction of the offspring in a population live to produce offspring In nature most plants die as seeds or seedlings Conditions for germination or growth may not be good enough pests may destroy seeds or seedlings or a freeze or drought may wipe them out 3 Individuals in a population vary and these variations are inherited by their offspring In a field of corn which may appear uniform certain features very from one plant to another This was shown in a longterm experiment in artificial selection that began in 1896 at the Illinois Agriculture Experimental Station At the beginning of the experiment protein content per kernel 109 selected for the high and low protein corn lines After 50 generation the high protein line gt 194 the low protein line gt 49 4 Individuals with favorable traits produce on average more offspring that survive to reproduce than those with unfavorable traits In nature if a plant is disease resistant a good competitor for resources and an efficient photosynthesizer then we expect it to reproduce more frequently than plants that are not so disease resistant or competitive in the same environment Natural selection is meaningful only in the context of the environment e g Succulent stems may promote reproductive success in a desert by not in a rain forest Environmental conditions are the forces that determine the outcome of natural selection these environmental conditions are called selection pressures Genetic variation is necessary for natural selection No variation no natural selection Where does genetic variation originate Mutation Changes in genes or chromosomes A mutation of a gene may involve a change in one or more nucleotide pairs Changes within chromosomes may occur as deletion translocation inversion Mutations occur constantly in all living organisms at an average estimated to be roughly one mutant gene for every 200000 produced Some of the mutations may produce a characteristic that help the organism survive changes in its environment Sexual reproduction It is probably the most important factor that promotes genetic variation in plants and animals It provides new combinations of genes so offspring are always different genetically from but similar to their parents IV Speciation Species a group of individuals that are morphologically similar to each other and capable of breeding successfully with each other Darwin was convinced that a group of similar individuals population 7 could give rise to a new species by accumulating adaptations to a new environment New and different adaptations were especially likely when a species became separated into populations isolated by geographical barriers such as mountain ranges or bodies of water Each of the separated populations might then reproduce and change in response to local environmental conditions in the different locations As an isolated population became adapted to its new environment its members would become increasingly different from the ancestral population After many generations an isolated population would be different enough to be a new species V Reading materials chapter 15 in Stern s textbook V I Study questions 1 Know how Charles Darwin formulated atheory of natural selection to explain the diversity of life on earth 2 Understand evidence for the evolution of living things convergent evolution adaptation 3 Understand the four principles of natural selection how genetic variations originate speciation April 21 2011 Ecology What is ecology Ecology from the Greek oikos meaning home this is the same root as that for economy which also involves resources and interactions The study of organisms in relationship to their environment Environment biotic living factors abiotic nonliving factors Ecologists investigate processes such as the change in numbers of individuals of a particular species how species are adapted to their environment and affected by climate changes how organisms interact With other species how nutrients and energy move through an ecosystem 1 Population community and ecosystem Population A group of individuals of the same species sharing the same territory or range at the same time and interbreeding or reproducing with each other Members of the same species may be widely distributed and divided into many populations A population is speci c to a given area and members of a population must be close enough to interbreed and form offspring together Community Consists of populations of different species living and interacting in the same location Plants are the producers in the community All organisms in a community depend either directly or indirectly on producers for a source of energy Organisms in a community are linked by their use of energy and nutrients food chain and are grouped into trophic or nutritional levels Producer herbivore carnivore and decomposer levels Producers and form a food web r J of many interlocking food chains A community and its abiotic nonliving factors constitute an ecosystem The distribution of a plant species is controlled by abiotic factors and the effects of other organisms biotic in the ecosystem Nutrients light water Herbivores parasites mutualistic interactions 11 Energy flows through an ecosystem Energy in the form of light enters a food chain at the producer trophic level and ows to levels of and J 1 r in an ecosystem Only 1 of the total light energy striking a temperate zone community is used in photosynthesis to convert C02 into sugar Only a very small portion of energy stored in one trophic level will ow to the next level Most energy is lost as M during respiration As a result life on earth relies on the constant supply of energy from the sun lt10 of the energy stored in plants that are eaten by cattle is converted to animal tissues Most of the remaining energy dissipates as heat during the normal activities of the animal When we eat beef our bodies use less than 10 ofthe beef s stored energy for our growth and maintenance Important implications Yields N440 usable pounds of meat gt 1000 7ounce servings Option Bake the 2500 pounds of grain and 350 pounds of soybeans into bread and casseroles gt 18000 8ounce servings A vegetarian diet uses energy more efficiently than does a diet based on meats gt90 of the energy is lost as heat at each level of a food chain The greater the number of carnivores in a community the greater the number of producers is necessary to provide energy for the herbivores that are eaten by the carnivores One large sh may depend on a billion tiny algae to meet its energy needs every day So few hawks compared to many hundreds of mice in a eld The number of any kind of organism that an ecosystem can support is limited The maximum number of individuals that can survive and reproduce in an ecosystem is the ecosystem s ca ing capaci As a population increases the competition for nutrients water and light increases Every ecosystem has a limit to the number of plants animals and trophic levels that it can support 111 Nutrient cycle through an ecosystem In the food web decomposers recycle the nutrients into the air and soil from where the nutrients come The cycling of water and minerals such as nitrogen and carbon is essential to all living things in an ecosystem Nitrogen cycle Photosynthesis and respiration are key processes in the carbon cycle IV Humans drastically affect the ealth s ecosystems The earth remains constant in size but humans have occupied more of its land over the the past few decades When feeding clothing and housing themselves humans have greatly affected the environment Clear natural vegetation pollute poison We disrupt every ecosystem we inhabit How do we human activities affect the productivity and succession of ecosystems Acid rain contributes to the degradation of forests Acid rain occurs after the burning of fossil fuels releases sulphur and nitrogenous compounds into the atmosphere Sunlight converts these compounds to sulphur and nitrogen oxides and they combine with water to become acid rain mostly sulphuric acid nitric acid Acid rain can lower the pH of lakes and streams and kill many organisms in them It also affects the soil and injures plants upon which it falls Global warming The earth has gone through cycles of wa1ming and cooling in the prehistoric past Human activities are accelerating the rate at which global wa1ming is now occurring The hottest 10 yrs in the last century have all occurred since 1980 As a result glaciers are shrinking permafrost is disappearing and sea levels continue to rise as warm water expands and glacier melts extinction of organisms Greenhouse effect the accumulation in the atmosphere of gases that permit radiation from the sun Greenhouse gases lt1 of the atmosphere C02 methane nitrous oxides and chloro uorocarbons byproducts of the manufacture of refrigerants plastics aerosol cans Use of fossil fuels coal petroleum oil and natural gas releases the stored carbon contributing to the increase in C02 in the atmosphere Doubling of the C02 level the earth s surface Tem increases an average of between 15 0C and 45 0C Loss of biodiversity Most plants and animals adapted sometimes in subtle ways to the habitats in which they occur When their natural habitats are destroyed a few species may be able to adapt to new habitats but most will ultimately perish One of the many consequences of such losses pertains to the origins of our crop plants Virtually all food fiber medicinal and other useful plants have been developed from wild species The gene pools of wild species have developed over millions of years irreplaceable V Reading materials chapter 25 in Stern s textbook V I Study questions 1 Know the concepts of ecology population community and ecosystem 2 Understand energy ows and nutrient cycle through an ecosystem 3 Know the causes of acid rain global warming and loss of biodiversity April 26 2011 Biomes Terrestrial ecosystems are classi ed into m on the basis of the similarities of their vegetation and physical environments I Tundra The word tundra is derived from a Russian word meaning treeless marshy plain Distribution It occupies 25 of the earth s land surface primarily north of the Arctic Circle with some extending farther south Climate Fierce drying wind freezing temperature can also reach 270C during a mid summer day Annual precipitation averages lt10 inchesyr Soil Shallow 5 to 75 cm deep nutrientpoor clay soils water logged Water logged primarily because permafrost permanently frozen soil beneath the surface prevents water from draining deep into the soil Oxygendeficient Vegetation Growing season lasts only 2 to 3 months Primarily consists of grasses mosses liverworts and lichens mostly evergreen Usually treeless low shrubs do survive including willow birch and blueberry lt1 meter tall at maturity The ora of tundra also include low perennials that produce brightly colored mats of owers during the brief growing season Adapted to the harsh growing conditions having 10 their mass aboveground the remainder below the surface and above the permafrost Leaves small protected by a thick cuticle and dense hairs trichomes Cells are exceptionally tolerant of the dehydration that occurs as the freezing draws water from the cells Exceptionally fragile A vehicle driven across it compresses the soil enough to kill lichens mosses and roots of plants vehicle tracks remain for decades II Taiga Also referred to as northern conifer or boreal forest Distribution Occurs mostly adjacent to the arctic tundra across large areas of North America and Eurasia Climate Snow accumulates during winters which are long and cold In midwinter 6 hr sunlightper day Tem may drop to 50 C In summer Tem may reach 27 C daylight can last up to 18 hr Soil Usually acidic and nutrient poor making them unsuitable for most agriculture activities other than timber and cranberry farming Vegetation Relatively uniform and dominated by a few genera of coniferous trees including spruce fir and in some places pine Deciduous trees such as birch poplar aspen willow alder and tamarack often occur in some of the wetter areas such as the margins of may lakes ponds and marshes in taiga A thickwalled epidermis sunken stomata and a thick cuticle have evolved in leaves of taiga conifers Adapt these trees to the rigors of the harsh winter climate Coniferous forests Also occupy vast areas of the Paci c Northwest and extend south along the Rocky mountains the Sierra Nevada and the California coast range although not considered part of the taiga Trees in these forests tend to be large particularly in the west of the Cascade Mountains of Oregon and Washington and on the western slopes of the Sierra Nevada Part of the reason for the huge size of trees such as Douglas fir is high annual rainfall which exceeds 100 inches in some areas of the Paci c Northwest III Deserts Sand heat oases and camels are features commonly associated with the most well known deserts Distribution Occur both north and south of the equator in the interior of Africa and Eurasia Cover 5 of North America Climate and soil Deserts form whenever precipitation is consistently low or where water passes quickly through the soil Many deserts get lt4 inches of precipitation per yr Some desert areas with porous soil in southwestern US and Northwestern Mexico may receive 10 inchesyr The low humidity of deserts causes large uctuations in daily Tem During the summer daytime Tem can exceed 38 C and often fall below 15 C the same night Vegetation Many desert plants have adapted to desert conditions through the evolution of crassulacean acid metabolism CAM photosynthesis and C4 photosynthesis gt help plants conserve water while producing sugar CAM plants fix C02 into malate during the night convert into sugar during the day cactus pineapple jade plants Other adaptations thick cuticle fewer stomata succulent stems and leaves leaves with a leathery texture and reduced size Cacti have small leaves or nonphotosynthetic leaves in the form of spines which reduce transpiration their stems are photosynthetic Such plant species adapted to low precipitation and high Tem are called xerophytes Annuals in deserts provide a spectacular display of color and variety particularly during an occasional season with aboveaverage precipitation The seeds of annuals often germinate after a rain and then grow and reproduce within a month before the water in the soil dries up Desert ecosystems like those of the tundra are fragile and recover from disturbance often takes many years IV Reading materials chapter 26 in Stern s textbook VI Study questions 1 Know the physical environments of different biomes vegetation and adaptations of plants living in tundra taiga and deserts permafrost xerophytes CAM plants April 28 2011 BiomesII Terrestrial ecosystems are classi ed into biomes on the basis of the similarities of their vegetation and physical environments IV Temperate deciduous forests Deciduous trees are broadleaved species that shed all their leaves annually during the fall Distribution In North America temperate deciduous forests occur from the Great Lakes region south to the Gulf of Mexico and from near the Mississippi River to the eastern seaboard Climate Temperature within the area vary greatly but normally fall below 4 C in midwinter and rise to above 30 C in the summer Precipitation averages between 36 to 90 inches per yr and occurs mostly during the summer Vegetation Trees usually have thick barks become dormant before the onset of cold weather Well adapted to subfreezing temperatures Some of the most beautiful of all broadleaved trees Sugar maple American basswood and the stately American beech predominate in moist temperate climates In drier parts of the deciduous forests oak and hickory are dominant During the summer trees of deciduous forests form a closed canopy that prevents most direct sunlight from reaching the oor Many of the showiest spring owers such as bloodroot hepatica Dutchman s breeches buttercup trillium violets open before trees have leafed out fully completing most of their growth within a few weeks V Grasslands Distribution Natural grasslands cover the interior of most continents Tend to integrate with forests woodlands or deserts at their margins depending on the amounts and patterns of precipitation Climate Usually receive less precipitation than do deciduous forests from 10 to 40 inches per yr Air temperature range from 50 C in midsummer to 45 C in midwinter Vegetation Fires often clear the standing dead grass leaves and young tree seedlings in the dry season Fires do not kill grass plants because of their underground rhizomes modified stems Fires destroy saplings of trees fires and inadequate rainfall prevent the establishment of trees in this biome In north American natural grasslands or prairies were once grazed by huge herds of bison Today large areas of prairie are now used for growing cereal crops and for grazing cattle Thus native grasses of the prairie have been replaced by economically important grasses such as wheat and corn and native herbivores have been replaced by domesticated animals V 1 Tropical rain forests The greatest biological diversity on earth gt50 of the earth s living species in this biome Distribution 7 of the earth s surface representing nearly half of the forested areas of the earth In North and South America gt the Amazon Basin of Northern South America much of Central America and the Caribbean Climate Occur throughout areas of the tropics where annual rainfall ranges between 80 and 160 inches daytime temperatures ranges between 25 C and 32 C with night temperature seldom dropping gt5 C lower than those at noon Relative humidity seldom drops below 80 Soil Organic matter is sparse in tropical soils acidic Deficient in important nutrients potassium magnesium calcium and phosphorus Decomposers rapidly degrade leaves and other organic material on the forest oor nutrients released by decomposition are quickly recycled or leached by heavy rains Vegetation Such climate conditions favor and support a diversity of plants and animals Dominated by broadleaved evergreen trees Trunks are often unbranched for as much as 40 meters or more Form a beautiful dark green and multilayered canopy Shallow root systems Buttress root large roots on all sides of a tall or shallowly rooted tree broader bases


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