Lecture 4 Flashcards
In general terms, describe the lifecycle of Plasmodium, and state why, despite
extensive research, Plasmodium continues to pose a great risk to human health.
- Caused by the protist Plasmodium, a member of the Apicomplexan lineage of protists.
- Four different species of Plasmodium are capable of infecting humans and causing malaria.
- Plasmodium are probably the best studied protists, but yet we still face challenges in controlling malaria.
Continue to pose a great risk to human health because: Mosquitoes evolve resistance to
insecticides. and Plasmodium evolve resistance to
drugs.
Define a “bloom” and describe why some dinoflagellate blooms are harmful to
human health.
When unicellular species experience rapid population growth and reach high densities in aquatic environments, they are said to
“bloom”.
Harmful? Dinoflagellates contain red pigments (carotenoids); also produce a
toxin to protect themselves from predation
• During a bloom, high levels of toxins can build up in the water, which
in turn builds up in the tissues of shellfish.
• Humans eat these shellfish and get poisoning.
In general terms, describe why protists could possibly help reduce global warming.
A similar effect can be achieved by fertilizing - and thus promoting the growth - of photosynthetic bacteria and protists. • CO2 in water used by phytoplankton. • Phytoplankton either eaten by consumers, die and eaten by decomposers, or die and sink. • If die and sink: become limestone or petroleum carbon sink
Describe the first eukaryote (i.e. what did it look like? Why do we believe this?)
The earliest eukaryote was probably a single-celled organism with a nucleus, an endomembrane system, mitochondria, and a cytoskeleton, but NO cell wall.
We believe this because not all eukaryotes have cell walls
What is the hypothesis of Nuclear envelope and its advantages?
Likely arose as infoldings of the plasma membrane. • These infoldings also gave rise to the endoplasmic reticulum. • Two pieces of evidence support this hypothesis – any idea what they are? 1. Infoldings of the plasma membrane occur in some bacteria living today. 2. The nuclear envelope and the ER of today ’s eukaryotes are continuous.
Advantages… Physically separates transcription + translation –> enables alternative RNA
splicing and more ways to control
gene expression.
What is hypothesis of Mitochondria and how is the evolution of it advantages?
Most likely arose via a process called endosymbiosis.
• Endosymbiosis occurs when an organism of one species lives inside an organism of another species.
• Endosymbiosis theory proposes that mitochondria were formerly small prokaryotes that began living within larger cells.
Under this hypothesis:
• The prokaryotic ancestors of mitochondria probably gained entry to
the host cell (a eukaryote) as undigested prey (or internal parasites).
• Proposed ancestors of mitochondria = aerobic heterotrophic prokaryotes.
• Host = predator capable of only aerobic fermentation.
Advantages: Symbiosis was mutually beneficial
Endosymbiont provided the anaerobic host cell with more ATP than the host could produce on its own.
• Host provided the endosymbiont with protection and carbon compounds from ingested prey (which the endosymbiont could
oxidize to ATP).
What is the hypothesis of Cloroplasts and the advantages?
A lineage of heterotrophic eukaryotes acquired a second endosymbiont.
• This time the endosymbiont was a photosynthetic cyanobacterium.
• Produced sugar and oxygen for the host, making it advantageous for the host not
to digest it.
What is the hypothesis of structures and support and what are the advantages?
Not sure how but advantages for support and protection
Define endosymbiosis and descirbe the evidence that supports the theort that mitochondria and plastids evolved by endosymbiosis?
endosymbiosis: occurs when an organism of one species lives inside an organism of another species.
Evidence:
1. are about the same size as an average bacterium, and replicate via a splitting process that is similar to binary fission in prokaryotes.
2. have inner membranes with enzymes and transport systems that are homologous to those found in the plasma membrane of living prokaryotes.
3. contain a single circular DNA molecule that, like bacteria, is not associated with histones.
4. have gene sequences that are more related to -proteobacteria than eukaryotic DNA
5. have their own ribosomes.
• Size and nucleotide sequence of these ribosomes are more similar to prokaryotic ribosomes then they are to eukaryotic ribosomes.
• Are also poisoned by antibiotics that inhibit bacterial, but not eukaryotic ribosomes.
6. are surrounded by a double-membrane – which would be consistent with
the engulfing mechanism.
State the evidence that sugests that mitochondria were aquired before plastids in eukaryotic evolution .
Serial endosymbiosis suggests that mitochondria evolved before plastids through a series of
endosymbiotic events.
State the two criteria that define multicellularity
- When individual cells cannot survive independently.
- The cells are differentiated, such that different cells perform
different functions.
• i.e. not all of the cells express the same genes
Describe the diversity of growth forms, feeding, locomotion, and reproduction in protist
Growth forms: both colonial and multicellular Feeding: 1. Ingestive feeding 2. Absorptive feeding 3. Photosynthesis
locomotion:
pseudopodia
cillia
flagella
reprduction: sexual and asexual
Explain the role of Secondary Endosymbiosis
Engulf species that already has engulfed cloroplast
Describe two important roles of Photosynthetic protists
- Photosynthetic protists play an important role in marine and aquatic food webs (see earlier slide).
- Also form important symbiotic relationships with other organisms. (EX. Reef building corals and termite gut- help digest wood)
Differentiate between asexual and sexual reproduction
• Asexual reproduction: involves the generation of offspring from a single parent; results in offspring that are genetically identical to the
parent.
• Prokaryotes divide asexually via binary fission.
Unicellular eukaryotes divide asexually via what process? –> mitosis
• Sexual reproduction: two parents give rise to offspring that have a
unique combination of genes inherited from both parents.
• In contrast to asexual reproduction, offspring from sexual reproduction
vary genetically from their siblings and from their parents. They are not exact replicats.
Advantages of Sexual reproduction
genetically variable offspring may be
better able to survive and reproduce if the environment changes.
Define: life cycle and Alternation of Generations
• Life cycle: sequence of events that occurs as individuals grow, mature, and reproduce.
Alternation of Generations : Involves alternation
between multicellular haploid AND multicellular
diploid phases.
Distinguish between “sporophyte” and “Gametophyte” give ploidy for each
The DIPLOID sporophyte produces HAPLOID spores via MEIOSIS
The HAPLOID gametophyte produce HAPLOID gametes via MITOSIS
