protistans. once upon a time protozoa = animal one celled organisms and algae = primitive plants...
Post on 22-Dec-2015
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Protistans
Once upon a time
• Protozoa = animal one celled organisms and algae = primitive plants
• Then; all one celled eucaryotic organisms are protists
• Now the group is all eucaryotic cells that are not plants, animals or fungi
Current view, based on biochemistry; three domains Eukarya include protists, fungi, animals and plants
Protista have a single origin = eucaryotic cell complex enough that probably arose only once.
Giardia;
Giardiasis (GEE-are-DYE-uh-sis) is a diarrheal illness caused by a microscopic parasite, Giardia intestinalis (also known as Giardia lamblia or Giardia duodenalis). Once a person or animal has been infected with Giardia, the parasite lives in the intestine and is passed in feces. Because the parasite is protected by an outer shell, it can survive outside the body and in the environment for long periods of time (i.e., months).During the past 2 decades, Giardia infection has become recognized as a common cause of waterborne disease in humans in the United States. Giardia can be found worldwide and within every region of the United States. 2 million cases a year in U.S.
Giardia has a nucleus but no mitochondria. Once thought to be the most primitive protozoan. However, its nucelar DNA has mitochondrial genes = lost mitochondria .
Major new features:
Eucaryotic =nucleus, organelles (mitochondria, chloroplast in some, other things like endoplasmic reticulum.
Cytoskeleton, methods of taking in, dumping stuff
And no cell wallAlso; cells much larger than bacterial cells.
Also; totally new method of reproduction.
Lots of variety;
‘animal like’
Plant like
Fungi like
Locomotion, ciliated, flagella, amoeboid
Hard vs soft covering; diatoms,
Single cell to multicellular = all algae belong here!! (multicellular but without much division of function = almost all cells identical in abilities
(sex cells the exception)
algae include, red, green, yellow green, brown – based on
differences in photosynthetic pigment
Figure 27.9 An Amoeba
Figure 27.5 Foraminiferan Shells Are Building Blocks
Figure 27.32 A Cellular Slime Mold
Why be Eucaryotic??
Perhaps –
1. increasing abilities (metabolism, biochemical pathways, etc. required increasing amount of DNA –
2. Increasing DNA required ‘chromosomes’ = DNA organization
3. Nucleus required to hold DNA
4. Increase in cell size required to hold nucleus, etc.
5. Internal cell organization needed as simple diffusion too slow over bigger distances.
Bacterial reproduction
Single circular strand of DNA makes copies. Copies separate. Cells separate.
Sex is bacteria – haploid (one set of information) ring dna – one dna strand only
Bacteria – a naked circular strand of DNA
Eucaryotes; have DNA organized into Chromosomes
Mitosis –
Involves DNA division, chromosome formation and the development of a ‘spindle’ spindle fibers, etc, to ‘pull’ chromosomes apart to different ends of a cell; then cell division
Traditional cell division in euycaryotes
Dna in strands and two sets of information.
Each makes a copy
Line up in cell
Arms move to opposite ends of cell
Cell division occurs
Result = two cells identical to parent cell.
More information, requires more dna organization.
Mitosis could work with one set of genetic information (divided into pieces)
Advantage in dividing (when spaghetti strand gets too long – hard to keep track of.
So chromosomes and mitosis do not require sex to exist
Why sex?
• “creates more variation” Is this valid or necessary?
• allows more individuals to survive a disease (mutant survival vs recessives
• Allows, through crossover, combination of bad genes and elimination. (bad genes often do bad things, not just inoperative)
• Bigger cells, smaller population, mutation not enough
Needed for Sex.
• Probably nucleus – keep genetic material together
• Diploidy
• Meiosis = maintain level of genetic info.
Basic sexual division - meiosis
0. chromosomes make copies of selves – stay connected
1. Chromosomes line up in pairs = diploid
organism with two sets of information
2. Division 1 = pairs split
3. Pairs line up and split –
4 result – 4 gametes (eggs or sperm)
each haploid – have all information but only one set.
5. Gametes meet, get back to diploid fertilized egg.
You now have “sex” = 2 gametes come together
Note: proctista experimented. Some have more than two sexes.
Paramecium reproduction
Under certain conditions, such as overcrowding or environmental stress, Paramecium turns from strictly asexual reproduction to sexual reproduction. Sexual reproduction involves the exchange of genetic material between two individuals of different 'mating strains'. Through a process called conjugation, two paramecia line up side by side and then fuse together. All but one of the cell's micronuclei disintegrate. This micronucleus then divides* into four – one of which will be exchanged during conjugation. (* This process involves meiosis, where the diploid micronucleus divides twice to yield four haploid micronuclei. Three of these disintegrate, while one divides again to produce two swapping haploid micronuclei.)
There are several “odd” ways of doing sex in protists.
Origins???
No neat intermediate forms. You are either a procaryote or a eucaryote
Sexual, asexual, nucleus and chromosomes, or not.
Things to do in transition: first steps
• get rid of outer cell wall, retain cell membrane
• grow in size
• divide dna into chromosomes – develop apparatus for division = mitosis
• develop a nuclear membrane – get endoplasmic reticulum in the process
Things to do in transition – next steps
• develop sex
• add organelles – mitochondria and chloroplasts and ?flagella?
Final Steps:
Begin multicellularity = division of function between cells = intercellular communication.
Figue 27.3 – Part 1
Figure 27.3 – Part 1
figure 27-03a.jpg
Origin of nucleus
Infolding of outer membrane.
Loss of procaryote cell wall = allows intake of things by various means
More shielding from uv light, by ozone layer = don’t need cell wall as protection.
Figure 27.10 Contractile Vacuoles Bail Out Excess Water
Where in animal cells do we see a similar function??
In all views; protista a “grab bag” category – eucaryotes that are not plants, animals or fungi (by new definitions of these groups.
Origin of mitochondria and chloroplasts by endosymbiosis
(internal symbiosis)
Eucaryotic cell; nucleus, organelles, skeleton
Figure 27.3 – Part 2
Figure 27.3 – Part 2
figure 27-03b.jpg
Sperm on egg: ‘nothing’ visible inside. (dna)
Unfertilized egg (rabbit) with ‘stuff’ inside = mitochondria ; basis of maternal
Transmission of information – maternal inheritance.
cytoskeleton
• Back to sex:
• There are several ways to do it – paramecium
• Plants, animals and fungi each do it slightly differently.
• The plant system – found in some algae is the ‘complete’ basic system.
Figure 27.14 Alternation of Generations
The standard or beginning model
Isogamy = male and female gamete identical in size
“cloning” – plants identical to each other
Sexual reproduction- create variation
Why protozoan diseases are often nasty. Example Malaria
Problems with invading the human body
Body defenses = white blood cells, antibodies, etc.
Getting in and getting out.
How to colonize another human body
How to defeat – substances that kill parasite in body hurt body cells
- kill mosquitos = insecticide resistance
-nets – keep mosquitos away
Why Africa so bad for malaria? - mosquitos developed with humans as their main prey.
Malaria. 1. mosquito injects
2. Hide in the liver from blood defenses, multiply
3. Invade blood cells – protected and can divide
4. Get taken up by mosquito – transfers to another host
Many protozoans have very complex life cycles.
Protozoans and disease
The next big step; becoming multicellular
Somewhat simplified version
Summary – eucaryotic advances over bacteria
• Larger size• Cytoskeleton• Nucleus• Diploid – linear discrete chromosomes• Mitosis (like bacteria except for pattern• Meiosis – new• Organelles; mitochondria, chloroplasts• Loss of cell wall – thinner outer membrane.• Living in oxygen atmosphere = protected from damaging
uv light