Three Domains of Life Protists

Three Domains of Life

Changes in Classification The ‘old school’ method of classification included 5 Kingdoms (what I learned in school) –Monera –Protista –Fungi –Plantae –Animalia Today, advances in molecular technology expanded our understanding (and interpretation) of systematics

Modern Systematics Three Domain classification of life Numerous, virtually countless Kingdoms Bacteria and Archaea are now 2 distinct Domains (once included together in Kingdom Monera) Protista, Fungi, Plantae, and Animalia remain classified as distinct Kingdoms, although classification of the kingdom Protista has been met with complications

Prokaryotes Includes the kingdoms Archaea & Bacteria Oldest, structurally-simplest, and most abundant forms of life Photosynthesis  Bacterial and Eukaryotic Diversity Important decomposers and symbionts

Prokaryotes Unicellular Typically 1μm or less (1000 μm = 1mm; 1000mm = 1 meter) No membrane-bound nucleus; instead a single circular chromosome made of DNA Asexual reproduction by binary fission Photosynthetic bacteria utilize oxygen or chemical compounds, such as sulfur

Prokaryotic Cell Structure Three basic forms: –Bacillus – rod-shaped –Coccus - sphercal or ovoid-shaped –Spirillum – spiral or helical

Prokaryotic Cell Structure Prokaryotes have a tough cell wall and other external structures Cell wall consists of peptidoglycan; a rigid network of polysaccharide strands cross-linked by peptide side chains; unique to Bacteria Maintains the shape of the cell and protects it from swelling and rupturing

Prokaryotes can have 1 or more flagella (much less complex than in Eukaryotes) Some Prokaryotes possess pilli, which helps fasten cell to host membrane

Domain Archaea Once considered a subdivision of the Kingdom Monera, now its own domain Like all prokaryotes, Archaea are single-celled microorganisms that lack a nucleus and membrane-bound organelles Best known for the “extremophiles” – Archaea which thrive in extremely harsh environments

Archea - Extremophiles Thermophiles – thrive at 60-80°C (>176°F!) Acidophiles – thrive at pH at or below pH 3 Xerophiles – grow in extremely dry conditions Halophiles – require extremely high concentrations of salt

Dr. Anastasia’s lecture starts here

13 Molecular Classification

Bacteria and Archae differ fundamentally Cell Wall –Bacterial cell walls are made of peptidoglycan, Archae are not Gene expression –Archaea may have more than one RNA polymerase (Transcription: reads DNA to make RNA), and these enzymes more closely resemble the eukaryotic RNA polymerases than they do the single bacterial RNA polymerase

16 Eukaryotic Origins The nucleus and endoplasmic reticulum arose from infoldings of prokaryotic cell membrane

Endosymbiotic theory Eukaryotic organelles evolved from a consortium of symbiotic prokaryotes –mitochondria were aerobic heterotrophic prokaryotes –chloroplasts were photosynthetic prokaryotes

Kingdom Protista Eukaryotic Most are unicellular (there are some simple multicellular ones) Originally consisted of all unicellular eukaryotes was paraphyletic The 17 major protist phyla are grouped into six major monophyletic groups

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ciliates Apicomplexans ArchaeaEubacteriaChromalveolataRhizariaArchaeplastidaExcavataAmoebozaOpisthokonta Parabasalid Dinoflagellates AlveolataStramenopila RhodophytaChlorophytesDiplomonadsEuglenozoa Choanoflagellates Animals Fungi AmoebozoaLand plants Charophytes Cercozoa Foraminifera Radiolara Brown algae Diatoms Oomycetes Fig Paraphyletic – includes common ancestor but not all descendents

Characteristics Used to Classify Protists Mode of locomotion mode of nutrition overall body form pigments & others…

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Second flagellum Stigma Contractile vacuole Paramylon granule Nucleus Chloroplast Flagellum Pellicle Mitochondrion Basal bodies Reservoir b. a. 6 µm Fig a: © Andrew Syred/Photo Researchers, Inc.

A ciliated protozoan

Too diverse for one kingdom: a diatom, a unicellular "alga"

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ptychodiscus Noctiluca Ceratium Gonyaulax Fig

Too diverse for one kingdom: Australian bull kelp (Durvillea potatorum)

Fig

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. + Gametangia Gametophyte (n) Gametes +Gametangia +Gametophyte (n) Spores Sporangia Sporophyte (2n) Germinating zygote n 2n2n Zygote MEIOSIS FERTILIZATION Fig © Dr. Diane S. Littler

Too diverse for one kingdom: Amoeba proteus, a unicellular "protozoan"

Too diverse for one kingdom: a slime mold (Physarum polychalum)

Kingdom Fungi Eukaryotes, mostly multicellular, heterotrophic, have cell walls (chitin) decomposers, food, some cause disease Acquire nutrients through absorption

Mycologists believe there may be as many as 1.5 million fungal species Fungi are classified into 5 major phyla based on mode of reproduction -Chytrids (aquatic, flagellated, ancestral) -Zygomycetes (bread molds) -Glomeromycetes (mycorrhizae) -Ascomycetes (bread yeast, truffles) -Basidiomycetes (mushrooms) Kingdom Fungi

Table 32.1

33 General Biology of the Fungi Multicellular fungi consist of long, slender filaments called hyphae -Some hyphae are continuous -Others are divided by septa

34 General Biology of the Fungi A mass of connected hyphae is called a mycelium -It grows through and digests its substrate

Fungal mycelia

37 Fungal Parasites and Pathogens Largest Organism? Armillaria –a pathogenic fungus – 8 hectares

Fungi Reproduction spores are produced either sexually or asexually hyphae and spore nuclei are haploid –except for a brief diploid stage that occurs during sexual reproduction

Figure 31.3 Generalized life cycle of fungi (Layer 1)

Figure 31.3 Generalized life cycle of fungi (Layer 2)

Figure 31.3 Generalized life cycle of fungi (Layer 3)

Figure 31.6 The common mold Rhizopus decomposing strawberries

43 Zygomycetes

Lichens Mutualism between fungi and algae or cyanobacteria Sensitive to pollution due to absorption capabilitues

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a.b.c. Fruticose LichenCrustose LichenFoliose Lichen a: © Ken Wagner/Phototake; b: © Robert & Jean Pollock/Visuals Unlimited; c: © Robert Lee/Photo Researchers, Inc.

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Algal cells Fungal hyphae 40 μm © Ed Reschke

Mycorrhizae Mutualism between fungi and the roots of 90% of all vascular plants Increases absorption of phosphorous, zinc & other nutrients

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a.b. Root 50 µm5 µm Arbuscular MycorrhizaeEctomycorrhizae a: © Eye of Science/Photo Researchers, Inc.; b: © Dr. Gerald Van Dyke/Visuals Unlimited