Lecture 4 - Protists

Question 1

Briefly explain protista

Answer 1

• Protista literally lie at the crossroads between simple and complex organism
• The kingdom Protista falls under the domain Eukarya
• Photosynthetic Protista support food webs and release oxygen
• Parasitic protists cause diseases.
  Many have industrial uses

Question 2

Explain characteristics of protists

Answer 2

• They are Eukaryotic organisms
• Mostly unicellular
• Metabolically diverse: Some photosynthesize, some are heterotrophs, some are parasites,
• Structurally complex: Some are unicellular, others are multicellular, we find colonial forms as well as filamentous forms.
• Protista primarily reproduces asexually
• Sexual reproduction occur in some

Question 3

What are the supergroups of protists

Answer 3

• Archaeplastids
• Chromalveolates
• Excavates
• Amoebozoans
• Rhizarians
• Opisthokonts

Question 4

Explain the super group archaeplastids

Answer 4

• It includes green and red algae, charophytes
• Green algae has chlorophyll a and b.
• They are found in fresh water and oceans, snowbanks, barks of trees etc.
• Chlorophytes can be unicellular(Chlamydomonas), multicellular like Ulva, or colonial like Volvox.
• Charophytes are filamentous. E.g. Spirogyra
• Red algae (Rhodophyta)are multicellular seaweeds that possess phyco-erythrin and phycocyanin in addition to chlorophyll a

Examples of red algae are Gelidium, Porphyra

Question 5

Explain chlamydomonas fully

Answer 5

• Is a unicellular green alga.
• It reproduces asexually through basic cell division to reproduce. More haploid cells are formed and grow into adult cells
• In unfavorable conditions it will reproduce sexually.
• Haploid gametes are formed and fuse with each other to form a diploid zygote.
• This forms a thick walled zygospore that can withstand unfavorable conditions.
• When conditions are favorable the zygospore will undergo meiosis and give rise to haploid zoospores that will grow and mature.

Question 6

Explain supergroup chromalveolates

Answer 6

• Includes two large subgroups:
  1.Stramenopiles
  2. Alveolates.
• Brown algae are stramenopiles that have chlorophyll a and c and fucoxanthin that gives them their characteristic color.
• Reserve food is stored as a carbohydrate called laminarin

Question 7

Explain brown algae fully

Answer 7

• Brown algae(Phylum Phaeophyta) range from simple filamentous forms to large multicellular forms that may reach up to a 100m in length.

Examples are Laminaria, Ecklonia and Macrocystis.

Question 8

Explain diatoms and straminopiles

Answer 8

• With ornate silica shell resembling a petri dish
• They contain a carotenoid pigment in addition to chlorophyll.
• They form part of phytoplankton, serves as source of oxygen and food for heterotrophs in freshwater and marine ecosystems
• Golden brown(Phylum Bacillariophyta) algae are unicellular or colonial. Many of them are both autotrophic and heterotrophic

Question 9

Explain water moulds ( super group chromalveolates )

Answer 9

• Are stramenopiles that live in water, they parasitize fish or insects and decompose the remains.
• They are saprotrophic.
• They have a filamentous body
  and cell walls of cellulose.

E.g. Phytophthora sp

Question 10

Explain alveolates and sporozoans

Answer 10

• Include Sporozoans such as Plasmodium vivax and Plasmodium falciparum that causes malaria. The secondary vector is Anopheles sp, mosquito.
• Ciliates such as Paramecium
• Toxoplasma gondii causes toxoplasmosis in cats. Toxoplasmosis in pregnant women can give rise to deformed babies.
• Alveolates: alveoli present beneath plasma membrane

Question 11

Explain the plasmodium vivax lifecycle

Answer 11

1. In the gut of female anopheles mosquito gametes fuse and the zygote undergoes many divisions to produce sporozoites which migrate to her salivary gland
2. When the mosquito bites a human the sporozoites pass from the mosquito saliva re glands into the bloodstream and then the liver of the host
3. Asexual spores produced in liver cells into the bloodstream and the red blood cells
4. The red blood cells rapture spores invade and reproduce asexually inside new red blood cells
5. Spores toxins pull into the bloodstream win the red blood cells rapture
6. Song is become male and female gametocytes which enter the bloodstream. If taken up by a mosquito, they become gametes

Question 12

Explain supergroup excavates

Answer 12

• Include the zooflagelates.
• They have atypical or absent mitochondria, a distinctive flagella and/or deep oral grooves.

eg 1 ) Euglena found in fresh water and able to photosynthesize-possess chloroplast

eg 2 )Giardia lamblia that causes severe diarrhea. (spread easily from one person to another or through water, food, surfaces, or objects.)

eg 3 )Trichomonas vaginalis is sexually transmitted and causes vaginitis. Is treatable

eg 4 ) Trypanosoma brucei (a kinetoplastid) is a parasite, transmitted by tsetse flies and causes African sleeping sickness. Causes death or permanent brain damage. Comes from infected humans

Question 13

Explain supergroup amoebozoans

Answer 13

• This group is comprised of protozoans that move by pseudopodia
• They live in aquatic environments, oceans and freshwater lakes and ponds
  E.g. Amoeba proteus found in fresh water.
  - Feeds by phagocytosis.
• Entamoeba histolytica parasites in human intestines, may cause fatal dysentery.
• Includes plasmodial slime molds: a mass of nuclei surrounded by a cell membrane.
• Cellular slime molds exists as haploid feeding cells, feeding on bacteria and decaying vegetation

Question 14

Explain super group opisthokonts

Answer 14

• Animals and fungi are included in this supergroup.
• Includes unicellular and multicellular protozoans

Examples are choanoflagelates which are unicellular and colonial

• And nucleariids

Question 15

Explain super group rhizarians

Answer 15

• This supergroup includes rhizarians and foraminiferans
• They have a skeleton called a test
• Tests of foraminiferans are made of calcium carbonate

Question 16

Explain red tides

Answer 16

• Common name for algal blooms, which are large concentrations of aquatic micro-organisms such as dinoflagellates, diatoms and ciliates.
• Neurotoxins are produced when the organisms increase in numbers in the ocean
• These toxins either kill shellfish directly or concentrate in tissue to make them poisonous (abelone, mussel, oyster)
• Rock lobster and fish die because the O2 is depleted or clogging of gills
• When anoxic conditions arise some anaerobic bacteria convert S to H2S. A black tide develops
• Toxins that are produced: DSP (diarrhetic shellfish poisoning –okadaic acid), PSP (paralytic- saxitoxin et al ), ASP (amnesic – domoic acid)

Question 17

Explain reasons for red tides

Answer 17

• Reasons for red tides are : global warming; increased nutrient enrichment of coastal waters
• Red tides occur along west coast during late summer-early autumn

Question 18

What are the types of red tide organisms

Answer 18

• Dinoflagellates
• Diatoms
• Ciliates