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Three Domains of Life Protists

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1 Three Domains of Life Protists
Archea have classified Kingdoms; Bacteria do not (yet) On the contrary, Eukaryota is composed of well-defined Kingdoms including Plants, Fungus and Animals; the exception is Protists which we’ll discover are not monophyletic and include groups that are similar in design, but not in evolutionary processes

2 Three Domains of Life Monophyletic; one c.a.

3 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

4 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

5 Prokaryotes Includes the kingdoms Archaea & Bacteria
Oldest, structurally-simplest, and most abundant forms of life Photosynthesis  Bacterial and Eukaryotic Diversity Important decomposers and symbionts True bacteria; Existed on Earth for 1 billion years before the Eukaryotes appeared

6 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 Although they can transfer genetic material via their plasmids (horizontal gene transfer), however not considered reproduction

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

8 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

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

10 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

11 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

12 Archaea - Extremophiles
Evidence for evolution of life on Earth? Many of the harsh conditions which extremophiles require to survive were characteristic of our early Earth Likely that extremophiles evolved to dwell in such conditions billions of years ago and retained ability to survive today in specific environments Hydrothermal vents?

13 Archaea differ from Bacteria in numerous ways
Plasma membranes are made of different kinds of lipids RNA and ribosomal proteins more like those of Eukaryotes Mostly anaerobic (photosynthetic: cyanobacteria and lithotrophs (Nitrosomonas which oxidizes ammonium) Photosynthetic

14 Domain Bacteria Two types: Refers to the Gram Stain (purple dye)
Gram-positive Gram negative Refers to the Gram Stain (purple dye) Gram-positive bacteria – possess a thicker peptidoglycan cell wall; retain stain Gram-negative bacteria – contain less peptidoglycan; do not retain stain

15 Gram-positive and negative

16 Bacterial Conjugation
Transfer of genetic material Horizontal gene transfer NOT sexually (no gametes) Involves cell to cell contact; does not involve fusion of gametes and the creation of a zygote There is not an equal exchange of genetic material, merely the transfer of genetic material from a donor cell to a recipient Often beneficial to the recipient cell – inc. antibiotic resistance or the ability to utilize a new metabolite Transformation – genetic material transfer that does not involve cell to cell contact; direct uptake from environment Tranduction – incorporation of new DNA from virus

17 Eukaryotic origin The nucleus and endoplasmic reticulum arose from infolding of the prokaryotic cell membrane

18 Eukaryotic origin Eukaryotic organelles arose from a consortium of symbiotic prokaryotes Mitochondria were aerobic heterotrophic prokaryotes Chloroplasts (for photosynthesis) were photosynthetic prokaryotes

19 Endosymbiotic theory Evidence?
Mitochondria have their own independent DNA, and a double membrane Chloroplasts resemble cyanobacteria; also have their own independent DNA and a double membrane Mitochondria generate ATP (powerhouse of cell); DNA analysis shows similarities to bacterial genomes Chloroplasts originated as endosymbiotic cyanobacteria


21 Kingdom Protista (the trouble-maker)
Kingdom Protista is NOT monophyletic The 15 major protist phyla are now grouped into 7 monophyletic groups; There are 60 lineages that cannot be placed with any confidence Paraphyletic – includes common ancestor but not all descendents

22 Kingdom Protista Eukaryotic (must be! Domain Eukarya)
Largely unicellular with some multi-cellular ‘exceptions’ (e.g., kelps, seaweed) May be autotrophic or heterotrophic Debate over classification – Are some protists members of other kingdoms? Would protists best be considered as several different kingdoms?

23 Kingdom Protista Characterized by:
Mode of locomotion (e.g., flagella, cilia) Mode of nutrition (e.g., autotrophic, heterotrophic) Body form (unicellular, multicellular) Pigmentation (e.g., Red, Green, Brown alga) Reproduction (asexual, sexual) Essentially you are a protist if you are not clearly an animal, plant or fungus! Multicellular protists are distinguished from other Kingdoms by their lack of specialized tissues

24 Kingdom Protista Who here eats seaweed?

25 Kingdom Protista Have you ever eaten a protist?, or should I ask, have you ever eaten seaweed??? Just to complicate matters, green algae is categorized as a plant in Kingdom Plantae…

26 Green Plants evolved from Green Algae
We’ll come back to this…

27 Kingdom Fungi

28 Kingdom Fungi Unicellular and multi-cellular ~1.5 million species
Important decomposers Includes many disease-causing organisms Others are important symbionts and fermenting organisms

29 Kingdom Fungi Mycology – the study of fungi
All fungi are heterotrophic Obtain their food by secreting digestive enzymes and absorbing the nutrients released by the enzymes Unicellular fungi may have flagella; multicellular fungi are primarily filamentous in form Cell walls composed of chitin Chitin: what crab shells are made of; a polysaccharide (carbohydrate)

30 Kingdom Fungi Six phyla
Deuteromycetes – imperfect fungi – do not fit into the taxonomic classification; athletes foot, yeast infections, produce antibiotic Penicilin Sexual form of reproduction never observed (only asexual known), sexual structures never seen Six phyla Cytrids (flagellated), Zygomycetes (inc. bread molds), Glomeromycetes (mycorrhizae), Ascomycetes (inc. yeast), Bascidiomycetes (mushrooms), and Deuteromycetes (not pictured)

31 Kingdom Fungi Phylogeny based on the 5 major Phyla (based on mode of sexual reproduction)

32 Kingdom Fungi Multicellular fungi consist of long, slender filaments called hyphae Some hyphae are continuous; others are divided by septa Mycelium – a mass of connected hyphae

33 Kingdom Fungi Mycelium grows through and digests its substrate
Fungi live in their food!



36 Kingdom Fungi Hyphae (mycelium) form complex structures
A mushroom is a spore-bearing body of a fungus; composed of hyphae A puffball is a spore-bearing body of certain species of fungi, including the deadly Death Cap mushroom; composed of hyphae


38 Kingdom Fungi Fungi can also be monokaryotic or dikaryotic
Monokaryotic – one nucleus per cell Dikaryotic – two nucleii per cell Fungi reproduce sexually and asexually During sexual reproduction in some fungi, 2 haploid nuclei fuse creating a dikaryotic (dikaryon) stage, which precedes the normal diploid nucleus

39 Kingdom Fungi Some fungi produce specialized mycelial structures to house spores (e.g., mushroom, puffballs, ‘shelf’ mcycelium on dead trees) Spores can form as a result of sexual or asexual reproduction Spores can withstand degradation and survive for long periods of time; because of their size, they can travel long distances Explains worldwide presence of fungi, how disease spreads so easily


41 Kingdom Fungi Chestnut Blight – a fungal disease which has virtually eliminated the American chestnut Accidentally introduced into the U.S. on imported lumber from Asia The roots of the tree are fairly resistant to the fungus, but the tree succumbs once it grows enough shoots to reproduce Unknown spreading agent (the spores are everywhere!)

42 Kingdom Fungi 1/4th of eastern American trees were Chestnuts, incredibly important for wildlife, only a few surviving – trying to breed resistant (Asian) chestnuts with American to save and restore; cankers caused by fungus cause limb to crack

43 …Jack Frost nippin’ at your nose…
The American chestnut once covered large tracts of forest in the U.S. The chestnut was a very important source of food for wildlife (and the inspiration for at least 1 Christmas song…) At the turn of the twentieth century, one quarter of all trees in the eastern United States were chestnut! 1/4th of eastern American trees were Chestnuts, incredibly important for wildlife, only a few surviving – trying to breed resistant (Asian) chestnuts with American to save and restore; cankers caused by fungus cause limb to crack

44 The Chestnut Blight Only a few mature survivors remain of the American Chestnut, which once consisted of 4 billion trees (that’s over 99.99% gone) If you have ever eaten a chestnut, you had a European import; only our grandparents may have ever tasted an American chestnut The American Chestnut Foundation seeks to restore the great chestnut, but how?

45 The Chestnut Blight Development of blight-resistant American chestnuts is accomplished through a process known as “backcross breeding” Hybrids between American and Chinese chestnuts are repeatedly crossed back onto purely American specimens, yielding offspring which are blight- resistant The resulting offspring are ~94% American (6% Chinese) and disease-resistant

46 Kingdom Fungi Spores are frequently dispersed by wind, but may also be spread by insects and small animals Chytrids are an ancestral group and retain flagella; have motile zoospores

47 Why did the mushroom go to the party?
Many fungi live underground, and can reach great sizes One of the largest living organisms in the world is a fungus! The largest known specimen covers more than 3.4 square miles and is thousands of years old And some species of fungi are bioluminescent! Believed to be 2400 years old

48 Connected underground by hyphae!
Armillaria fungus Connected underground by hyphae!

49 Fungal Ecology Fungi often have interactions or symbioses with other organisms Obligate symbiosis – essential for survival; fungus cannot survive without symbiont Facultative symbiosis – fungus can survive without symbiont Mutualistic relationships – both partners benefit Commensal relationships – one partner benefits, but the other is unaffected

50 Fungal Ecology A lichen is a symbiotic association between a fungus and a photosynthetic partner (usually green algae or cyanobacteria) Inhabit extreme environments – arctic tundra, hot deserts, rocky coasts, rainforests;widespread and long-lived, but subject to environmental disturbance (melanism!)

51 Fungal Ecology Mycorrhizae – association between a fungus and the root of a tree Mycorrhizae function as an extension of the plant root system; the fungus increases surface area for absorption and aids in transfer of nutrients The plant, in return, supplies organic carbon to the fungus 92% of trees

52 Mycorrhizae Very important!
Mycorrhizal plants are more resistant to drought and even microbrial soil-borne pathogens Two types Arbuscular mycorrhizae Ectomycorrhizae Arb – penetrates the outer cells of the plant root Ecto – the hyphae surround but do NOT penetrate the cell walls of the roots

53 Mycorrhizae

54 Fungal Ecology Leaf-cutter ants – an animal symbiont with fungi!
The ants feed on special structures produced by a fungus that they have domesticated The ants feed the fungus leaves and protect it from pests and molds In return, the ants eat the fungus and feed it to their young Fungus grows only in the underground chambers of the ants nest

55 Just in case you didn’t believe me…
I don’t think the smurfs are bioluminescent though!

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