Download Protists

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 wall
Also; 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
Invasive algae caulerpa = all one cell!
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.
figure 27-03a.jpg
Origin of nucleus
Infolding of outer
membrane.
Figue 27.3 –
Part 1
Figure 27.3 – Part 1
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??
Origin of
mitochondria and
chloroplasts by
endosymbiosis
(internal symbiosis)
In all views; protista a “grab bag” category – eucaryotes that
are not plants, animals or fungi (by new definitions of these
groups.
Eucaryotic cell; nucleus, organelles, skeleton
figure 27-03b.jpg
Figure 27.3
– Part 2
Figure 27.3 – Part
2
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
“cloning” –
plants
identical to
each other
Isogamy =
male and
female gamete
identical in size
Sexual
reproductioncreate
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.
Many protozoans have
very complex life cycles.
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
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