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Lectures 1 - 6 Notes

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Biology 2217B
Richard Gardiner

Lecture 1: Introduction Can Plants Move?  Yes – respond to touch, motion  Has to do with ions leading to potassium gated channels - related to osmolarity What about Harsh Times?  Resurrection plant o Can preserve itself over a long period of time o Closes up when no water is present and vice versa Predators  Venus Fly Trap – when an insect lands on the leaf, little hairs stimulate the plant to close, trapping the insect inside; enzymes are then released, completely consuming and digesting the insect  Low in nutrients – therefore, most nutrients and proteins are obtained from the insects that are consumed o For example, the Pitcher Plant – insects walk on the edge of the plant and fall inside Stranglers  Bind weed, kudzu  Fast growth rate  Grows over other plants, buildings  Could be major pests Poisonous  Used in cases where crops need to be protected (for example, Chrysanthemum is used to keep rabbits away)  Also used for medicinal purposes  Hydrangea – vomiting, weakness, sweating, coma  Lily-of-the-Valley – nausea, vomiting, heart palpitations Vampires  Stem parasite – where seeds germinate  Forms a specialized structure called hostori o Green = Hemi-parasite o No color = Holo-parasite  Cannot produce chlorophyll on their own  Obtains/steals water from neighboring plants/trees, attacks the roots or vascular tissue to obtain water that it needs Not a Plant  Lichens are a symbiotic association of two different organisms – not a plant  Fungi – multicellular organism  Could be grown in labs  Made of algae and fungi – usually named for the fungal component rather than the algal component Lecture 1 Readings: (1) Plants in Our Lives (Pgs. 2 – 5) The Flowering Plants  Angiosperms – flowering plants, most abundant and diverse plants in the environment  More than 250,000 known species  Characterized by flowers and fruits  Typical angiosperm flower consists of four parts: sepals, petals, stamens and one or more carpels o Stamen and carpel = sexual reproductive structures o Fruits and its seeds develop from the carpels  Angiosperms are divided into two groups – monocots and dicots The Non-Flowering Plants  Range from small mosses and ferns to giant redwood trees (largest organism on earth)  Gymnosperms – seed-bearing plants, but seeds are not formed in fruits, but rather generally in cones The Algae  Diverse group of photosynthetic organisms found in marine and freshwater habitats where they serve as the base of food chains  Algal blooms – dangerous when algae are capable of producing toxins The Fungi  Includes mold, mildews, yeast and mushrooms  Generally have threadlike body, the mycelium, and propagate by reproductive structures called spores  Non-photosynthetic organisms, obtaining their nourishment from decaying organic matter as saprobes or as parasites of living hosts  Play an essential role as decomposers, recycling nutrients in the environment Scientific Method  Often begins with an observation, which lead to questions and speculations  Hypothesis is a possible explanation or working assumption for the original observation  Once hypothesis has been stated, it is tested through experimentation  Use of scientific method leads to development of scientific theories – accepted explanation for natural phenomena that is supported by extensive and varied experimental evidence Lecture 2: Plant Kingdom What is a Plant?  Kingdom plantae  Body type: multi-cellular with cell walls made of cellulose  Eukaryotic  Food consumption: photosynthesis (absorbs light) – vast majority are photosynthetic  Reproduction: both sexual and asexual  Environments: land and water  Autotrophic – produce their own food  Sedentary – do not move around, must develop number of characteristics to protect themselves from climate, predators, etc. Aquatic Environments  In water  Supported by buoyancy  Not dry  Absorb nutrients  Sperm swims  Float near surface for light Land Environments  Need minerals  Fight gravity  Grow higher for more light  Adaptations for dry environments  Reproduction differs  Roots to anchor and absorb minerals  Water transport system (for larger plants), water loss systems  Pollen and seeds Alteration of Generations  Haploid and diploid plants of the same species are present  Haploid phase – gametophyte  Diploid phase – sporophyte  Sporophyte will eventually go through meiosis and produce gametophyte Evolutionary Trend from Haploid to Diploid What is in a Name?  Classical system today – binomial system of naming things o Applies to same plant all over the world  System is devised to allow us to know what plant is being discussed, no matter what the common names are  Some Latin names for the important plants we study in this course must be memorized Latin Names  Not obtuse  Same everywhere in the world  Always written in Latin  We can know a specific plant name written anywhere on Earth International Code of Botanical Nomenclature  Uniqueness – only one correct name for any group  Type principal – specimen deposited in herbarium  Priority – first name counts  Authorities – certain letters follow a name Plant Taxonomy  Group things by similarities – taxonomic organization o In order to compare  Monocots vs. dicots (class)  By learning endings, one could understand what major taxonomic group is being referred to  Descriptive name – names in commemoration, names that describe some sort of physical quality, names that indicate use, and names that indicate origin – refer to table 8.1, 8.2, 8.3 Kingdom Plantae  12 divisions of plants  Organized into 4 groups o Mosses and liverworts – Bryophyta o Gymnosperms – Spermatophyta o Ferns and fern-allies – Pteridophya o Angiosperms – Division Magnoliophyta Plant Phylogeny  Retention of embryo o Fertilized egg develops into multicellular embryo in female gametagium o Retained within the plant – embryo is protected during development o In algae, the fertilized egg develops away from gametagnium  Stomata o Allow for gas exchange and control of water loss o Needed for larger multicellular structures that leaves became  Vascular tissue o Specialized vascular tissue for support and conduction (to all parts of plant) o Xylem conducts water o Phloem conducts carbohydrates o Allows for larger growth  True leaves o Thallus (body) not differentiated into leaves, stems or roots o Arose as fusion of small branch stems o Specialized organs of photosynthesis o Designed to collect light efficiently under varied condition  Seeds o Spores – haploid reproductive units that give rise to gametophytes o Seeds – an important adaptation for life on land  Embryonic sporophyte plant, nutritive tissue and protective coat o Superior to spores:  Seed has well developed young plant  Seed contains abundant food supply  Multicellular seed coat allow seeds to survive extended periods  Gymnosperms = naked seed o Seeds are totally exposed or borne on scales o No ovary wall surrounds them  Flowers and fruit o Angiosperm = seed enclosed in a vessel or case o Seed produced in a fruit o Ovules enclosed within an ovary o Interdependency on insects, birds and bats to pollinate o Also better developed vascular systems Mosses and Liverworts (Bryophyta and Others)  No vascular tissue  Dominant stage gametophyte (n)  Typically small  Reproduce via spores  Swimming sperm  Peat moss Ferns and Fern Allies (Pteridophyta and Others)  Club mosses, ferns, horsetails  Swimming sperm  Vascular  Separate gametophyte (n) and sporophyte (2n) in ferns  Reproduce via spores Gymnosperms (Coniferophyta and Others)  Vascular  Pollen allows for not needing water for  Male and female gametophytes reproduction  Reproduce via naked seeds  Conifers, Cycads, Ginko, Gnetophytes Flowering Plants (Magnoliophyta)  Vascular  Seeds are enclosed within an ovary (fruit)  Male and female gametophytes  The flowering plants  Reproduce via seeds  Earth’s dominant form Lecture 2 Readings: (8/9) Plant Systematics and Evolution / Diversity of Plant Life (Pgs. 121 – 128) How Plants are Named – Common Names and Scientific Names  Names are sometimes used only in a limited geographical area, while on the other hand, different plants may share the same common name  Each kind of organism is known as a species, and similar species form a group called a genus  Each species has a scientific name in Latin that consists of two elements – the first is the genus and the second is the specific epithet  A complete scientific name also includes the name/names of the author/authors who first described the species or placed it in a particular genus o For example, the complete scientific name for corn is Zea mays L – the L indicates that Linnaeus name this species  Scientific name is unique, referring to only one species and universally accepted among scientists Taxonomic Hierarchy  Phylogenetic system is used to group plants – info is gathered from morphology, anatomy, cell structure, biochemistry, genetics, and fossil record to determine evolutionary relationships and group plants  Species with many characteristics in common, based on shared vegetative and reproductive characteristics – grouped into a genus  Next higher category, or taxon, above rank of genus is the family – composed of related genera that share combinations of morphological traits o Family represents natural group with common evolutionary lineage o Each family is assigned one name (ending in –aceae)  Families are grouped into orders, orders into classes, classes into divisions (phyla), and divisions into kingdoms  Domain is above the kingdom level, most inclusive taxonomic category What is a Species?  Biological species concept – first proposed by Ernst Mayr in 1942, which defines a species as “a group of interbreeding populations reproductively isolated from any other such group of populations” o Problem with this definition – many closely related plant species that are morphologically distinct are able to interbreed o Single plant species may have diploid and polyploid individuals that may be reproductively isolated from each other – estimated 40% of flowering plants may be polyploids  Thus an alternative concept was suggested – ecological species concept recognizes species through role in biological community as defined by set of unique adaptations within particular species to its environment  Genealogical species concept – utilizes distinct genetic history of organisms to differentiate species Lecture 3: Plant Cells Plasma Membrane  Responsible for what comes in and out of the cell  Fluid mosaic model o Phospholipids can move around o Composed of many different proteins  Phospholipid bilayer is not a membrane, by biological definitions  Do not mix up with the cell wall, cell wall has more of a structural purpose  Why would plants want cholesterol in the membrane? o Sterol will prevent phospholipids from getting too tight together o This can also be done by changing the saturation of phospholipid chains Cytoplasm  Material surrounding nucleus, bordered by plasma membrane  Always in motion o Cytoplasmic streaming o Movement of organelles inside the cell o Actin and myosin interactions allows organelles to move around o Facilitates exchange of materials in the cell Nucleus  Controls ongoing activities of cell  Repository of the cells genetic information  Porous double-membrane o Complexes  Filled with nucleoplasm  Continuous with ER at several junctions  Haploid (n), diploid (2n), poloypoid – 3n, 4n, 5n, etc.  Chromosomes with chromatin (DNA + proteins)  Nucleolus (RNA + proteins)  Nuclear pores allow communication from the nucleus out in the cytoplasm Plastids  Various kinds of plastids o Chloroplasts, chromoplasts, leucoplasts  Characteristic of plant cells  Double membrane  Example – stroma, thylakoids (used in photosynthesis)  Semiautonomous organelles – divide on their own, stimulated by requirements of the cell o Endosymbiosis – bacteria either absorbed or ingested  Bacterial genome: o Nucleoids (circular DNA) o Small genome o 70s ribosomes o Divide like bacteria – binary fission  Mesophyll cells Chloroplasts  Responsible for photosynthesis o Contain chlorophyll, carotenoids  Number of chloroplasts can vary, depending on the specie  Broad surface lies parallel to cell wall  Starch granules are formed during photosynthesis (formed in the day time, and taken apart at night)  Numerous copies of DNA (100 proteins encoded) Other Plastids  Proplastids or eoplasts o Small and colorless plastids o Undifferentiated  All plastids in adult plant derived from single parent o Identical genome o Binary fission (asexual) Chromoplasts  Carotenoid pigments (yellow, orange, red) o Flower colour, autumn leaves, fruit  Loses thylakoids, chlorophyll, rRNAs, ribosomes o Storage Leucoplasts  Uniform, colorless stroma o Roots and other non-photosynthetic tissues  Starch storage (amyloplasts)  Proteins (proteinoplasts)  Fats (elaioplasts)  Potatoes have a single starch grain Mitochondria  Used to produce ATP through cellular  Inner convoluted respiration o Cristae for maximum surface area  Smaller than plastids  In constant motion o Around 0.5 mm in diameter  One or more circular chromosomes o Round bodies  Semiautonomous  Double membrane  Maternally inherited  Matrix – similar to the cytoplasm of chloroplasts Vacuoles  Unique to plant cells  Meristematic cells contain small vacuoles that o May have more than one type later fuse o Storage, lytic compartments  90% volume in mature cell o Multifunctional organelles  Consists of cell sap (water) o Diverse in size, content and function  Storage compartments  Tonoplast  Likely form ER (endomembrane) Ribosomes  Protein and RNA synthesis – similar to animal  Small and large subunits cells o Polysomes  17 – 23 nm in size  Most numerous cellular structures Endomembrane System  All cellular membranes  Continuous 3D membrane system o Permeates cytosol  Internal space o Lumen Cytoskeleton  3D network  Microtubules o Structural integrity  Actin/myosin Cell Wall  Distinguishes plant from animal cells  Cellulose in microfibrils (4 – 10 nm)  Characterizes plants o Wind together to macrofibrils  Determines size and shape of cell o Tensile strength approaches that of  Cell types identified by their walls steel  Plays a role in defense  Embedded in a matrix of polysaccharides (e.g. pectin)  Walls vary in thickness Plasmodesmata  Cytoplasm strand connecting cells  Cell wall creates symplast and apoplast  Cell-to-cell passage o Interconnected protoplasts form  Analogous to gap junctions in animal cells continuum Cell Cycle  Ordered sequence of events from dormancy to division  Most plant cells uninucleate Mitosis in Plants  Similar to animal cells  Most higher plant cells do not contain visible centrioles  An analogous region of the plant cell acts as the microtubule-organizing centre (MTOC) Lecture 3 Readings: (2/4) Plant Cell and Cell Division / Plant Physiology (Pgs. 16-23, 24-27, 47-68)  Cell Theory – recognizes the cell as a basic unit of life and states that all organisms are composed of cells, and all cells arise from pre-existing cells The Cell Wall  Cell wall encloses all other parts of the plant cell, collectivity called the protoplast  Plant cell walls may consist of one or two layers o Primary wall – formed early in the life of a plant cell, composed of many polysaccharides, principally cellulose, in the form of fibrils o Secondary wall – lignin is a major component of the walls, in addition to cellulose and other polysaccharides, only certain types of plants have secondary walls (those specialized for support, protection or water conduction)  Lignin is known for its toughness – gives wood its characteristic strength and provides protection against attack by pathogens and consumption by herbivores  Cell wall is not a solid structure – minute pores, known as pits, allow for transfer of materials through cell walls  Cytoplasmic connections between adjacent plant cells often occur – called plasmodesmata – pass through the pits in cell wall, allow for movement of materials from cell to cell  Sticky layer called middle lamella can be found between walls of adjacent plant cells – acts as cellular cement, gluing cells together o Composed of pectins, additive used in making fruit jellies The Protoplast  Defined as all of the plant cell enclosed by the cell wall – composed of nucleus plus cytoplasm  Cytoplasm consists of various organelles distributed in the cytosol, a matrix consisting of large amounts of water, proteins, other organic molecules and ions  Also in the cytoplasm is a network of proteinaceous microtubules and microfilaments that make up the cytoskeleton – a cellular scaffolding that helps support and shape the cell, involved in cell movement  Membranes o Outermost layer of protoplast – plasma membrane, which is composed of phospholipids and proteins o Fluid mosaic model – membrane structure, consists of a double layer of phospholipids with scattered proteins, some of which go through lipid bilayer (integral proteins), while others are on either the inner or outer surface (peripheral proteins) o Some membrane proteins/lipids have carbohydrates attached – called glycoproteins/glycolipids o Plasma membrane serves as a permeability barrier, allowing some molecules, but not others, to pass through  Moving Into and Out of Cells o Diffusion – spontaneous movement of particles or molecules from areas of higher concentration to areas of lower concentration o Membrane is differentially permeable – permit the diffusion of some molecules but present a barrier to the passage of other molecules o Osmosis – diffusion of water across cell membranes o If plant cell is left in a highly concentrated, or hypertonic, solution – water will leave and protoplast will shrink away from cell wall  Cell is said to be plasmolyzed o If plant cell is in pure water or a very weak, hypotonic, solution – water will enter until vacuole is fully extended, pushing the cytoplasm up against cell wall  Cell is said to be turgid o If plant cell is placed in solution of the same concentration, isotonic – no net movement o Diffusion/osmosis take place when molecules move along concentration gradient from higher to lower concentration  Organelles o Chloroplasts – double membrane-bound, contain several pigments of which the most abundant are chlorophylls, making leaves green  Carotenes and xanthophylls are present – orange and yellow pigments which are visible in autumn, when chlorophylls break down before leaves are shed  Pigments are located within internal membranes of chloroplasts and are most concentrated in stacks called grana  Individual grana are interconnected and embedded in the stroma  Photosynthesis occurs in chloroplasts o Two other organelles found in plant cells are leucoplasts and chromoplasts – all collectively called plastids  Leucoplasts – store various materials, especially starch  Chromoplasts – contain orange, red or yellow pigments and are abundant in colored plant parts o Mitochondrion – site of many of the reactions of cellular respiration (process in which glucose is chemically broken down to release energy in a useable form, ATP) o Most mature plant cells are characterized by large central vacuole – contains the cell sap, a watery solution of sugars, salts, amino acids, proteins and crystals o Internal membrane system also occurs in plant cells – consists of ER, Golgi apparatus, and microbodies which are all involved in the synt
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