BIOL1262 Course Organisation Lecture 1 PDF

BIOL1262 Course Organisation Lecturers: – Dr. Chinthapalli Rao (weeks 1, 2 & 6) – Dr. Denneko Luke (weeks 3, 4 & 5)  Teaching Assistant: – Mr. John Laboratory Technician: – Mr. Hughlet Harvey Timetable: – Please note that BIOL1262 & 1263 follow the SAME schedule as for BIO...

BIOL1262 Course Organisation Lecturers: – Dr. Chinthapalli Rao (weeks 1, 2 & 6) – Dr. Denneko Luke (weeks 3, 4 & 5)  Teaching Assistant: – Mr. John Laboratory Technician: – Mr. Hughlet Harvey Timetable: – Please note that BIOL1262 & 1263 follow the SAME schedule as for BIOL1017 & 1018 (from semester I) Taxonomy & Life Cycles 2024/2025 Lecture 1 Dr. Chinthapalli Rao  Taxonomic Ecological  Taxonomy  Earliest forms based on a system of the need for, and the use of plants (& animals)  Plants have often been categorized by: 1. Growth form – herbs, shrubs, trees 2. Life cycles* – annuals, biennials, perennials 3. Articles of diet – fruits, vegetables 4. Medicinal – purgatives, doctrine of signatures 5. Economic / Social – crops, drugs, shade, etc. 6. Reproductive features* – sexual, asexual  Terms associated with Taxonomy  Discipline of classifying organisms and assigning each organism a universally accepted name.  Accumulation of knowledge through the orderly arrangement of living organisms  Taxonomy includes four aspects: 1. Description - Description of the organism 2. Identification - assignment of features of the organism 3. Nomenclature - naming the organism 4. Classification - placing organisms into definite categories 1. Description Description : Providing detailed information about the characteristics and features of an organism to differentiate it from others.  Regarded as characters to each group (or taxon) of organisms being classified, such as: Character Character State (cf. alleles) Petal colour Yellow, red, blue, pink Leaf texture Pubescent or glabrous Bark texture Rough or smooth Leaf shape Elliptical, lanceolate, ovate obovate, etc. 2. Identification Determining the identity of an organism based on its characteristics, often using keys or descriptions, or − If the identification of the unknown is new to science, it is then described and named by the researcher  Identification - method  Taxonomists utilize dichotomous keys in order to identify and describe organisms.  Also inferred are...  shared characteristics, trends  e.g. ancestral cf. derived  evolutionary relationships  predictions based on observed features  Of the many taxonomic keys, the dichotomous taxonomic key is the most widely used method when describing and classifying specimens  Identification All steps of the key are dichotomous (2-branched) throughout: 1. There are a series of lead statements, each containing a pair of similar but opposing characters (couplets) 2. Each couplet must be contrasting so that one fits the situation at hand while the other does not: “1a. Leaves opposite.........go to 3 1b. Leaves alternate...........go to 2, etc.” 3. The key should have enough steps to identify each member of the group 4. The number of steps in the key is one less than the number of specimens 5. You will do an activity for your first tutorial exercise 3. Nomenclature Nomenclature: − The formal naming of taxa according to some standardized system − For the green algae and plants (Kingdom: Viridiplantae), the rules and regulations for naming taxa are formulated by life Scientists who produce the International Code of Nomenclature for Algae, Fungi, and Plants (ICN) − These formal names, also know as the scientific names, are by convention written in Latin. − The scientific name of each organism is expressed in the form of a binomial − e.g., the tree from which we derive bay rum (Pimenta racemosa): Genus name: Pimenta (starts with upper case letter) Species name: racemosa (starts with lower case letter) Nomenclature – In written There is a prescribed convention for writing these names –Both generic and specific names are printed in italics –When hand-written each name is underlined with ITS OWN separate SINGLE, STRAIGHT line –The generic name is capitalised while the specific epithet is all lower case Nomenclature E.g., the scientific name for the nutmeg plant is… – Printed as Myristica fragrans – Hand-written as Myristica fragrans  If you underline the title of a drawing, take care that the name of the organism is NEVER double-underlined! (Myristica fragrans)  These conventions facilitate the ease and accuracy of scientific communication. E.g., the common names “Guinep” and “Ackee” mean different things within the single region of the Caribbean! Nomenclature – special note on the species taxon Please note that the word “species” is the same spelling whether in the singular or plural:  1 species (please NEVER say or write 1 specie!), and,  > 1 species  4. Classification Classification is a general term referring to placing organisms into definite categories (ranks) to achieve some type of orderly study of the entities.  Cataloguing and expressing relationships between life forms  Each rank is hierarchical (i.e., inclusive of other ranks beneath it): - Kingdom__ e.g., Viridiplantae - Phylum (aka. Division)__ e.g., Magnoliophyta - Class__ e.g., Liliopsida hierarchy - Order__ e.g., Arecales - Family__ e.g., Arecaceae - Genus__ e.g., Cocus - Species__ e.g., nucifera More Taxonomic Terms Phylogeny: – Phylogeny refers to the evolutionary history and relationships among species or groups of organisms. It illustrates how species have evolved from common ancestors, i.e. a “tree of life” or phylogenetic tree Cladistics: Cladistics is a method of classifying organisms based on common ancestry, emphasizing the branching order of the evolutionary tree without considering the degree of difference. Systematics: Systematics is a broader field that encompasses both taxonomy (the classification and naming of organisms) and phylogenetics (the study of evolutionary relationships).  Systematics: modern taxonomy The systematic approach has overtaken the traditional phenotypical (phenetic) taxonomical approach. Scientists rely principally on evidence from the evolutionary history of an organism(s) from sources such as: 1. Paleontology: the branch of science concerned with fossil animals and plants 2. Comparative anatomy: study of similarities and differences in the anatomy of different species 3. Comparative embryology: comparison of embryo development across species 4. Comparative biochemistry: comparison of the basic chemistry and processes that occur in cells 5. Molecular genetics: the structure and function of genes at a molecular level 6. Geographic distribution of organisms in question  Progress of Taxonomic Systems Scientist(s) Approach Linnaeus, 1735 Animalia, Vegetabilia (2 Kingdoms) Haeckel, 1866 Protista, Plantae, Animalia. (3 Kingdoms) Chatton, 1937 Prokaryota, Eukaryota (2 Kingdoms) Monera (prokaryotes), Protoctista, Plantae, Copeland, 1956 Animalia (4 Kingdoms) Monera (prokaryotes), Fungi, Protista, Plantae, Whittaker, 1969 Animalia (5 Kingdoms) Eubacteria, Archaea, Protista, Fungi, Plantae, Woese et al., 1977 Animalia (6 Kingdoms) Woese and Fox, 1999 Eubacteria, Archaea, & Eukaryotes (3 Domains) How is life rearranged and classified? The Three-Domain Model (Woese and Fox 1999) Carl Woese George Fox c. 1977  Life Cycles  The series of changes in the growth and development of an organism from its beginning as an independent life form to its mature state in which offspring are produced.  Life cycles are governed by reproduction and reproduction can occur in two ways: 1. Asexual reproduction: formation of new individuals from a single individual without the involvement of gametes. 2. Sexual reproduction: formation of new individuals (zygotes) by the fusion of female and male gametes. Asexual Reproduction in Algae  Both asexual and sexual reproduction can occur during the life cycles of algae. 1. Some unicellular forms of algae like Euglena reproduce by mitosis (eukaryotic fission). ▪ The parent cell divides (longitudinally or transversely) into two similar parts. ▪ These two cells develop as organisms and are similar to the parent cell: Euglena sp. Asexual Reproduction in Algae 2. Some algae use the process of fragmentation ▪ e.g. Ulva,Sargassum and also filamentous algae (e.g. Spirogyra) ▪ the parent body breaks up into two or more fragments that grow into new organisms Asexual Reproduction in Algae 3. Sporulation - formation of spores in normal vegetative cells or specialized cells known as sporangia.  The spores swim away (zoospores) from the parent, settle down and develop directly into new filaments.  e.g. Chlamydomonas, Chlorella and Ulothrix  Some other spores are non-motile (→ aplanopores) Sporulation in Ulothrix sp.  4. Autocolony Formation  Daughter colonies form within the parent colony  e.g. Volvox sp.  These are produced inside the hollow internal space of the parent colony.  New daughter colonies form from certain cells (initials) in the surface of the colony  Eventually, the parent colony will rupture and release the mature daughter colonies. Sexual reproduction in the algae  Although most algae reproduce asexually under normal circumstances, environmental disturbances may initiate sexual reproduction.  Usually some disturbance / instability in the environment initiates sexual reproduction Sexual Reproductive Cycles  Sexual reproduction is manifested through three types of life cycles. ▪ These are distinguished on the basis of when meiosis takes place within the life cycle: a) Zygotic meiosis: meiosis in the zygote (the only 2n in the cycle) ▪ mainly in freshwater Chlorophyta b) Gametic meiosis: for the production of gametes ▪ in mainly marine Chlorophyta & Phaeophyta c) Sporic meiosis: for the production of spores ▪ involves an alternation of generations (sporophyte to gametophyte and back to sporophyte). ▪ marine Chlorophyta, Phaeophyta & Rhodophyta. a) Zygotic meiosis  Mature, dominant adult organism is a haploid individual which produces gametes by mitosis  These haploid gametes combine to form a diploid zygote.  Zygote divides immediately by meiosis to form 4 haploid cells. ▪ The zygote may develop into a zygospore to ‘ride out’ unfavourable environmental conditions, then divide into the haploid cells when normal conditions return Zygotic meiosis n n mitosis n 2n Raven, Evert & Eichhorn, 2005 Zygotic meiosis  aka. the haplontic or haploid life cycle the dominant adult individual in the life cycle is haploid (n), i.e., the gametophyte ▪ Since the zygote undergoes meiosis = zygotic meiosis. ▪ e.g. Chlamydomonas, Volvox, Spirogyra Chlamydomonas sp.  Zygotic meiosis life cycle of Chlamydomonas Haploid cells Zygote divides immediately by meiosis to form 4 haploid cells. Each haploid cell divides by mitosis producing a multicellular haploid individual. ZYGOTIC MEIOSIS Haploid individual produces gametes. 2 haploid cells combine to give a diploid zygote http://kentsimmons.uwinnipeg.ca/2152/lb3pg1.htm  Zygotic meiosis life cycle of Chlamydomonas Each haploid cell Zygote divides Haploid cells divides by mitosis immediately producing a by meiosis to multicellular haploid form 4 haploid individual. Haploid individual cells. produces gametes. 2 haploid cells combine to give a diploid zygote  Zygotic meiosis  A special form of zygotic meiosis referred to as conjugation, happens in some freshwater green algae  Some of the filamentous forms of algae like Spirogyra reproduce by the conjugation method of sexual reproduction  Two normally vegetative cells in adjacent filaments of Spirogyra suddenly behave as gametes → fuse via a conjugation tube → form a zygote → meiosis to form four new (haploid) cells → grow into new Spirogyra filaments Conjugation in Spirogyra (a freshwater filamentous alga) a. Formation of conjugation tubes between two adjacent filaments. b. Cytoplasmic contents of each cell form a compact mass (an isogamete). which migrate from one filament to the other through the conjugation tubes c. The two isogametes unite to form a zygote which undergoes meiosis to form four haploid cells. One haploid cell will form a new filament by mitosis. b) Gametic meiosis  Mature, dominant adult is a diploid individual  Diploid individual undergoes meiosis giving haploid gametes.  Each pair of haploid gametes combine to form a diploid zygote.  Zygote develops into the diploid individual.  Since gametes are produced by meiosis → gametic meiosis.  aka. the diplontic diploid life cycle  the dominant adult individual in the life cycle is diploid (2n).  e.g., Acetabularia Gametic meiosis Raven, Evert & Eichhorn, 2005 n n n 2n  Gametic meiosis life cycle of Acetabularia 2 haploid gametes combine to form a diploid zygote Diploid individual undergoes meiosis in reproductive organs giving haploid gametes Diploid individual Zygote divides to produce a diploid individual. http://universe-review.ca/R10-34-anatomy2.htm Gametic meiosis life cycle of Cladophora glomerata  c) Sporic meiosis  The mature adult may exist either as a haploid gametophyte or as a diploid sporophyte ▪ The gametophyte produces the gametes → 2 haploid gametes combine to form a diploid zygote → Zygote divides to produce a sporophyte (an autotroph which produces spores) ▪ The sporophyte produces haploid spores within sporogenous tissue via meiosis. ▪ since meiosis gives rise to spores = sporic meiosis. ▪ The spores then develop by mitosis into multicellular haploid individuals (new gametophytes)  aka. the haplodiplontic cycle or the Haploid-Diploid life cycle: ▪ There are two types of generations, the one haploid and the other diploid, within the life cycle of the species. Sporic meiosis Raven, Evert & Eichhorn, 2005 n n n 2n Sporic meiosis & Alternation of Generations (a-o-g) 1. Isomorphic alternation of generations ▪ In many marine green algae that reproduce via sporic meiosis, the sporophyte and gametophyte individuals are appear the same in external appearance ▪ Chlorophyta: Ulva 2. Heteromorphic alternation of generations: The sporophyte and gametophyte individuals are appear the quite different in external appearance ▪ Derbesia and Bryopsis Isomorphic alternation of generation in Ulva http://www. brainkart.co m/article/Ch lorophyta--- Structural- characteristi cs-of-algal- protists_172 85/ Heteromorphic alternation of generations Life cycle of Bryopsis  Sporic meiosis  The life cycle of all land plants proceeds by means of alternation of heteromorphic generations.  Since some green algae show this type of life cycle which is similar to that of land plants  May suggest that certain algal groups evolved into land plants.  hence Viridiplantae  Viridiplantae - origin  Along with the Chlorophyta, Plants share the following: 1. Presence of chlorophyll a and b 2. Presence of "plant" carotenoids such as beta-carotene, xanthophylls 3. Cell walls containing cellulose 4. Presence of starch in chloroplasts 5. Phragmoplast formation during cytokinesis 6. Oogamy within a sporic life cycle (egg and sperm) o Alternation of generations 7. Sporopollenin - a protective substance that covers spores & pollen grains 8. Development of alternation of generations  Terminology - revision  Gametophyte  haploid stage of an autotroph that develops from a spore and produces gametes by mitosis  Gametangium  a “case” where gametes are produced and stored, produced by the gametophyte  Gamete  collective term for sperm and egg (sex cells)  Sporophyte  diploid stage of autotroph that grows from the zygote and produces spores by meiosis  Sporangium  the “case” holding spores, produced by the sporophyte  Spore  haploid, single cell produced by meiosis