Lecture 4 - Protists Flashcards
Briefly explain protista
- 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
Explain characteristics of protists
- 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
What are the supergroups of protists
- Archaeplastids
- Chromalveolates
- Excavates
- Amoebozoans
- Rhizarians
- Opisthokonts
Explain the super group archaeplastids
- 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
Explain chlamydomonas fully
- 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.
Explain supergroup chromalveolates
- 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
Explain brown algae fully
- 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.
Explain diatoms and straminopiles
- 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
Explain water moulds ( super group chromalveolates )
- 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
Explain alveolates and sporozoans
- 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
Explain the plasmodium vivax lifecycle
- In the gut of female anopheles mosquito gametes fuse and the zygote undergoes many divisions to produce sporozoites which migrate to her salivary gland
- 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
- Asexual spores produced in liver cells into the bloodstream and the red blood cells
- The red blood cells rapture spores invade and reproduce asexually inside new red blood cells
- Spores toxins pull into the bloodstream win the red blood cells rapture
- Song is become male and female gametocytes which enter the bloodstream. If taken up by a mosquito, they become gametes
Explain supergroup excavates
- 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
Explain supergroup amoebozoans
- 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
Explain super group opisthokonts
- Animals and fungi are included in this supergroup.
- Includes unicellular and multicellular protozoans
Examples are choanoflagelates which are unicellular and colonial
- And nucleariids
Explain super group rhizarians
- This supergroup includes rhizarians and foraminiferans
- They have a skeleton called a test
- Tests of foraminiferans are made of calcium carbonate
