Plant Diversity Biological Sciences 2024/2025 PDF

BIOLOGICAL SCIENCES 2024/2025  The course lecturers are:  Ms I. Makhura: 235/225  Prof. B. Moseki, 235/244  Tests and Final Exams:  One CA Test –Plant Diversity only  Includes lecture material and laboratory work Date for Plant Diversity CA Test 1:  Venue and da...

BIOLOGICAL SCIENCES 2024/2025  The course lecturers are:  Ms I. Makhura: 235/225  Prof. B. Moseki, 235/244  Tests and Final Exams:  One CA Test –Plant Diversity only  Includes lecture material and laboratory work Date for Plant Diversity CA Test 1:  Venue and date to be announced  All other information about the course is contained in The Plant Diversity Manual. Read it!!!  BIO 112 - Survey of the Plant Kingdom/land plants Evolutionary approach Start with Simple plants to complex non flowering plants and flowering plants. From aquatic environment to land (terrestrial). Highlight features that have enabled plants to survive and be successful on land.  They are important to life on earth!  LIFE depends on photosynthesis ◦ only plants (algae, cyanobacteria ) can perform photosynthesis  1. Plants as food- directly or indirectly  Base of the food chain  Throughout history, 7000 plant types used as food  12 major food crops- maize, beans, sorghum, rice, wheat etc  Provide Nutrients: grouped into 6 categories:  carbohydrate, protein, lipid (fat), water, vitamins, and minerals  Hence the availability of the following:  Spices, flavouring,  Beverages- beer , tea, coffee  Starch (carbohydrates-sugars)  Oils-unsaturated fatty acids (what is the difference between unsat & sat fatty acids?)  Food additives-to enhance taste (e.g., species)  Food for animals-Feed  2. Source of oxygen  3. Remove carbon dioxide-reduce greenhouse effect (global warming).  4. Regulate water cycle- Move water from soil to atmosphere  5. Aesthetic uses-)  6. Source of natural products  Fibers- cotton (Gossypium hirsutum), Hemp, (Cannabis sativa), also called industrial hemp (plant of the family Cannabaceae cultivated for its fibre (bast fibre) or its edible seeds).  7. Habitat to other organisms  8. Ecosystem services eg: ◦ Soil erosion control ◦ modify temperatures ◦ Nitrogen fixation – legumes (symbiotic relationship)  9. Source of medicine  10. Plants can also be poisonous! ◦ Datura sp., Nerium oliander  Multicellular, photosynthetic, eukaryote  Produce sugars from carbon dioxide in presence of light and gives off oxygen - photosnthesis  Cannot move; responds to environment differently from animals  Cells surrounded by a rigid cell wall (composition?).  Embryo (miniature plant) is protected.  Unique ways of development and regeneration.  Several systems used by botanists This course will follow Sadava et al. 2011 Kingdom Plantae divided into 2 major categories: Vascular Plants (Tracheophytes) - plants with conducting cells called tracheids. Non-Vascular Plants (Non-Tracheophytes) – plants without a conducting system, tracheids. Sadava et al. recognizes 10 groups (clades)  GROUP COMMON NAME 1) NON VASCULAR PLANTS  Hepatophyta(division/phylum) Liverworts  Anthocerophyta (division/phylum) Hornworts  Bryophyta (division/phylum) Mosses  2) VASCULAR PLANTS  (a) seedless tracheophytes  Lycopodiophyta (division/phylum) Club mosses  Pteridophyta(division/phylum) Ferns& fern allies (Monilophyta) Group COMMON NAME (b) Seed tracheophytes (Spermatophyta) (i) Gymnosperms Cycadophyta Cycads Ginkgophyta Ginkgo Gnetophyta Gnetophytes Coniferophyta Conifers (ii) Angiosperms Flowering plants  In this course, we will also discuss organisms called Algae Many botanists include Algae in the Plant Kingdom Sadava et al. does include algae in ‘Green Plants’ Algae have many characteristic features that fit in the definition of a plant  The purpose of course is: to survey the Plant Kingdom to understand their origin and how they have evolved through time We can only understand this by studying the plants or some organisms that came before them- The Algae  Algae have played a big role in shaping the earth  Examples:  1) Algae have been part of the story of the evolution of the eukaryotic cell-  Endosymbiotic theory ? . blue-green algae have played part in origin of chloroplasts- photosynthetic machinery  2) Algae (blue-greens) have been instrumental in creating an oxygen – filled atmosphere :  First true photosynthetic organisms  Produced oxygen, which later accumulated in the atmosphere  Enabled the evolution of aerobic organisms- The Cambrian Explosion!!  3)Algae (green algae) are thought to be ancestors of plants! (see next lecture)**** Lecture 2 Algae refer to:  a wide range of simple oxygen- producing photosynthetic organisms  some prokaryotic and eukaryotic forms  They are important in plant evolution  Body is not specialized into root, stem & leaves ◦ Photosynthesis occurs in the body called thallus ◦ Attachment by rhizoids (root-like structures)  Do not form embryos ◦ Gametes fuse in open waters ◦ Zygote develops into new plant without embryo stage  Reproductive structures not protected ◦ Gametes produced within a single cell, ◦ not protected by sterile envelope/cover as in plants  Mostly aquatic (watery) environments ◦ marine- salt water ◦ freshwater ◦ floating- planktonic (have floating structures) or ◦ attached to objects- benthic  Some are terrestrial (wet soils)  Have mechanisms to survive drying  e.g. the microscopic Oscillatoria sp. Oscillatoria sp.  Algae occur in different forms:  Some unicells- single cells with/ without flagella  Some filamentous- cells forming chains  Some colonial- several cells attached together Coenobium- fixed number of cells in a colony  Siphonaceous- (coenocytic) tubular structures, with many nuclei not divided into cells  Parenchymatous- body made up of cells like higher plants; large (macro) algae The Coenobium Volvox aurens 500 to 20,000 individual cells.  Both sexual and asexual reproduction  Asexual:  Fragmentation- breaking away from parent plant  Formation of spores- dispersal structure  Sexual- fusion of gametes  a)Isogamy- fusion of equal size, motile gametes  b)Anisogamy- gametes unequal, small male & large female, both motile  c)Oogamy- small, motile male gamete fuse with large, stationary female gamete  1) Blue-green algae (Cyanophyta or Cyanobacteria)  2) Green algae- Chlorophyta  3) Diatoms  4) Euglenoids  5)Brown algae  6)Red algae  Classified according to the dominant pigment they have  1) Blue-green algae (Cyanophyta or Cyanobacteria)  Oldest group  Earliest oxygen -producing, photosynthetic organisms  Prokaryotic as in bacteria- no organelles  No chloroplasts  Chlorophyll ‘a’ and blue pigments called phycocyanin hence the name blue-green algae  Cell wall similar to bacteria- murein wall  Asexual reproduction by mitosis or fragmentation  No sexual reproduction known  Body form:  Unicells or colonies  Filamentous- cells in filaments surrounded by a gelatinous sheath ◦ Cells in filament may be differentiated into ◦ vegetative cells- photosynthetic ◦ akinetes (spore)- reproduction ◦ heterocysts - nitrogen fixing ◦ eg Anabaena, Nostoc ◦ Many are important in nitrogen fixation like some bacteria  heterocytes akinetes  They are important in the evolution of living organisms-first to produce Oxygen; make atmosphere aerobic  Also in endosymbiosis theory  Origin of chloroplasts and eukaryotic cell  Many blue greens that are harmful form blooms in water  May kill livestock, fish and humans  Largest, most common and diverse group especially in freshwaters  Found everywhere in Botswana  Unicells, filamentous, colonial & parenchymatous  Chlorophyll a & b and carotenoids (accessory pigments)  Cell wall mainly cellulose  Store starch as their food product  Note: Chlorophylls, cellulose and starch also found in plants  Show both asexual and sexual reproduction  Life cycles show alternation of generations (like plants)  a)Diatoms ◦ Silica cell wall (sand cell wall) ◦ Form a glasshouse shell/cover ◦ Most beautiful algae  b)Euglenoids ◦ Unicelluar with flagella ◦ Soft cell covering, euglenoid movement  c)Brownalgae- have chl. a & c and brown pigments  d)Red algae- chl. a and d and red pigments  Brownand red algae mostly marine known as macroalgae or ‘seaweeds’ , produce very useful cpds  1.Primary producers**- contribute 50-60% of primary production on earth especially in aquatic environments (feed fish etc)  2.Some are nitrogen fixers (blue-greens)  3.Some are toxic ◦ Form algal blooms or water blooms or ‘red tides’ in nutrient –rich waters ◦ Some of these are poisonous to humans, livestock and aquatic organisms  4.Some used as food or fertilizers- (green, red/brown)  5.Useful cpds are extracted from brown and red algae e.g. auxins, gibberelins, vitamins, proteins, fibre  6.Agar & carageenans ◦ used as thickening agents ◦ in foods, cosmetics, ◦ ice creams, lotions, creams, microbiological media  7.Diatomaceous earth- remains of dead diatoms  have many uses: ◦ water filters, ◦ beer filtration, ◦ reflective road signs, ◦ abrasives in tooth pastes, ◦ cleaning and polishing materials.  Where did land plants come from?  The Green Algae (Charales) are thought to be ancestors of land plants  Plants evolved from members of the green algae  Green algae and land plants are closely related!  Share some features  How are they closely related? What evidence is there?  1) Biochemical evidence:  Food reserves- starch similar to plants  Cell wall composition- cellulose similar to plants  Photosynthetic pigments- chlorophyll a & b similar to plants  Production of oxygen during photosynthesis  2) Molecular evidence:  rRNA & DNA sequence in some green algal groups similar to plants  Peroxisome contents- break down toxic substances  Similar mechanisms of mitosis and cytokinesis  3) Structural evidence:  Presence of plasmodesmata in cells  Retention of eggs and protection of young sporophytes  Chloroplast structure- grana  Branch and grow from the tip- (like plants)