Lecture 5: Algae Flashcards
Where is photosynthesis widespread?
Photosynthesis is widespread (polyphyletic) in Eukaryotes
What are algae?
Algae are photosynthetic eukaryotes other than land plants
Describe most algae
- Most algae are aquatic (both freshwater and marine)
2. Many are unicellular
Describe most multicellular species
Most multicellular species produce bodies in which all cells are in contact with the environment (simple multicellularity)
What two things are closely related? What is the group they form called?
Plants and green algae are closely related and together form a monophyletic group.
What features of land plants are present in some green algae?
Many of the…
1) key physiological
2) structural features
of land plants are present in some green algae
The ____________, ______________, and _________ are the green algae most closely related to land plants.
1) Charales
2) Coleochaetales
3) Zygnematales
What do the Charles, coleochaetales, and zygnematales all have?
1) All occur in freshwater
2) All have a haplontic life cycle
3) All produce sporopollenin in the cell walls of the zygote
What are the six features found in the green algae and in plants that are thought to have played a role in the transition to land?
Great POMPS
1) The use of the enzyme Glycolate oxidase in photoresipiration
2) Phragmoplast
3) Oogamy
4) Matrotrophy
5) Plasmodesmata
6) Sporopollenin
What is oogamy?
Oogamy is a mode of fertilization where a nonflagellated gamete (the egg) is fertilized by a flagellated gamete, as in humans
What is matrotrophy?
Matrotrophy is the retention of the fertilized egg (the zygote) and supply of “maternal” care to it
What is sporopollenin?
Sporopollenin is a complex polymer hat serves a protective function
What is the phragmoplast?
The phragmoplast is the cytoskeletal structure responsible for the deposition of the cell plate
What are plasmodesmata?
Plasmodesmata are microscopic channels that allow communication between cells
What is glycolate oxidase?
Glycolate oxidase increases the efficiency with which 2-Carbon molecules produced during photorespiration are recycled
What is a phylogeny?
A phylogeny is a starting point of the evolutionary diversification of plants and a way to organize information about the past
A hypothesis of the evolutionary relationships among species or other entities
What does a node indicate?
A node indicates the last common ancestor
What does monophyletic mean?
A group consisting of all the descendants of a common ancestor
- MUST all have the SAME last common ancestor
What is a paraphyletic group?
A paraphyletic group includes some, but NOT all, descendants
When are paraphyletic groups useful?
Paraphyletic groups can be useful when they refer to organisms that are functionally similar
- For example, Turtles, Lizards, and Crocodiles are not all descendants but are functionally similar
Within a Eukaryotic tree, which relationships are unresolved?
the deepest relationships are unresolved (polygamy)
- It’s therefore harder to know who’s related to who
What is polygamy?
a flat line indicating we don’t know the relationship
What are algae?
Algae is an informal term for photosynthetic eukaryotes that are not “land plans” and are typically aquatic
- polyphyletic
What is polyphyletic?
when you group an organism by characteristics
Describe rhodophyta
- Red Algae
- Mostly multicellular
- Chlorophyll (a & c) and phycobilins (red pigment)
- Some crustose red algae grow at a depth of 250 meters
What are two traits of algae that are of interest
1) Cellulose in cell walls (occurs in all of these groups)
2) Sporopollenin (found in cell walls of some chlorophytes and in land plants and close green algal relatives)
Describe green algae
- Chlorophyll a and b
- starch stored in chloroplasts
- 2-7 thylakoids stacked in grana
- stellate flagella
State 3 types of green algae
1) Chlorophyta
2) Volvox
3) Dasycladales
4) Ulva (sea lettuce)
What is chlamydomonas?
a unicellular chlorophyte with a haplontic life cycle (vegetative - doing photosynthesis and metabolic activity)
Describe gametes
gametes can’t live very long - if they don’t fuse then they die
- spores can survive much longer
What is ulva?
Sea lettuce
- a multicellular chlorophyte with alternation of generations
All plants have ______________ and are distinguished by __________
All plants have alternation of generations and are distinguished by ploidy
All _____________ have a haplontic life cycle
All streptophyte algae have a haplontic life cycle
Features found in all streptophyte algae
- fresh water
- haplontic
- sporopollenin (zygote)
- phragmoplast
- plasmodesmata
- open mitosis
- glycolate oxidase
What feature did all 3 candidates of the closest alga relative to plants share?
the presence of sporopollenin in the wall of the zygote
What is sporopollenin?
Sporopollenin is the most degradation resistant polymer known
- protection from UV radiation, desiccation, damage
Where do green algae grow?
green algae grow in freshwater habitats where water levels fluctuate
Filaments type of cell division
filaments, single plane of cell division
Sheets type of cell division
Sheets, two planes of cell division
Parenchymatous type of cell division
Parenchymatous, three planes of cell division
_________ and ________ allow for complex multicellular development
phragmoplast and cell plate allow for complex multicellular development
What are plasmodesmata?
span two cell walls and their connections together - control what moves between them
All cells have _____________-
intercellular connections
What moves between cells?
There are intercellular movements of proteins, mRNA, small molecules, and virus particles
What happens in “open” mitosis?
In “open” mitosis, the nuclear envelope breaks down before the chromosomes separate (and then reforms around the two sets of chromosomes)
- fungi and animals
What happens in “closed” mitosis?
In “closed” mitosis, the nuclear envelope remains intact (later pinches to form two nuclei)
What is rubisco?
rubisco is the enzyme that catalyzes the entry of CO2 into the Calvin cycle
What can rubisco also catalyze?
Rubisco can also catalyze a reaction with O2 (instead of CO2) which leads to a loss of carbon and energy
- this is because rubisco has trouble distinguishing O2 and CO2
- higher rates at higher temperatures
What is glycolate oxidase?
an enzyme that helps mitigate against the losses in carbon and energy that occur when rubisco reacts with oxygen
- deals with temperature fluctuations
- selectivity comes with speed –> if very selective also very slow
What are oogamous and what does it mean?
Choleochaete and Chara/Nitella are oogamous meaning they make eggs and swimming sperm
What are conjugating algae and what does it mean?
Zygnematales are conjugating algae - fertilization involves cytoplasmic bridges between cells
- eggs don’t move and sperm/male component moves
Where are gametes produced?
gametes produced in gametangia
Where are sperm produced?
sperm produced in the antheridium
Where are eggs retained?
eggs retained in the oogonium
All green algae have _________ via ________
all green algae have haplontic life cycles via mitosis
What are chara lifecycles triggered by?
chara lifecycle triggered by stress
form a diploid
What is matrotrophy?
wall ingrowths indicate nutrient transfer to zygote
What do zygotes undergo and what does this produce?
zygotes undergo meiosis which produce four haploid daughter cells that undergo 2 to 3 mitotic divisions which produce haploid “meiospores” that then disperse
How can haploid alga also reproduce?
can also reproduce asexually (mitotically produced zoospores)
What are zygnematales?
1) no swimming sperm
2) dismiss floating around and have to come into contact with a spirogyra
What is desiccation tolerance?
the ability to survive drying and go back to metabolic processes when rehydrated
What is photorespiration?
when rubisco acts on oxygen with an acceptor carbohydrate molecule
Gamete vs. spore
Gamete: always fuse
- no independent existence
Spore - grow up on its own
- persists
What is alternation of generations?
genetically distinct in policy
