What similarities are there between Embryophytes (land plants) and Charophytes (green algae)?
chlorophyll (photosynthetic pigments)
What differentiates algae from land plants?
- lacks many complex plant tissues
- lacks a multicellular embryo (i.e seeds)
- not adapted to land
- zygote develops separate from maternal tissues
What similarities are there between bryophytes and Charophytes?
- no true root system
- no stems/leaves
- no vascular system
What evidence is there to support brown kelp having parallel evolution with plants?
- has specialized tissues/cells that resemble that of plants (i.e sieve cells)
What can we learn about from the model organism Chlamydomonas r.?
- how organisms sense light and undergo photosynthesis
- what genes are responsible for forming cilia (animals) and flagella (plants)
- evolution of multicellularity
What is the evidence behind how phylogenetic trees are created?
- shared traits among species will be more abundant the closer they are related
- species will have accumulated traits from their ancesters
- historically went off of visible traits (macroscope or microscope)
What were the five kingdoms Whittaker proposed?
bacteria, animals, fungi, plants and protists
How did Whittaker classify his kingdoms?
bacteria = cells without organelles
animals/plants/fungi = nutritional modes
protists = whatever was left over
Where did algae fall in Whittaker’s classifications?
cyanobacteria –> bacteria
eukaryotic algae –> some in plants, some in protists
How does genetic classification sort species?
- ribosomal DNA sequence similarities
- similar nucleotide/amino acid sequences
- the farther apart species are related, the more mutations will be present between the two
What is the difference between conserved and variable sequences?
conserved = critical for gene function so are less changed, differences are more clear in species distantly related
variable = change often throughout evolution, differences are more clear between closely related species
Why does horizontal gene transfer make phylogenies difficult?
DNA sequences may only be found on one subset of the tree, without suggesting inheritance and can also be suddenly lost
What two types of symbiotic relationships do algae have?
- endosymbiosis (one organism is within the cell of another)
- side by side
What is an example of a side by side symbiosis with algae?
lichens
- cyanobacteria fixes nitrogen
- green algae provides photosynthesis
- fungi anchor and process nutrients
What is an example of endosymbiosis with algae?
coral
- zooxanthellae within coral polyps provide photosynthesis
- coral provides nutrients and can pass down algae to offspring
Explain the endosymbiont theory
- a free living bacterium was engulfed by an archaean cell
- the bacterium’s genome became integrated with the eukaryote via gene transfer
- the bacterium became unable to live independently from the eukaryote, and formed the mitochondria
- cyanobacteria after developing oxygenic photosynthesis were absorbed by mitochondria containng eukaryotic cells, becoming chloroplasts
What makes cyanobacteria different from eukaryotic algae?
- cyanobacteria lack nuclei and other membrane bound organelles
- photosynthesis occurs in cyanobacteria membranes (thylakoids) vs the chloroplast
- cyanobacteria are much smaller
What evidence is there than cyanobacteria evolved before eukaryotic algae?
plastids in photosynthetic algae are derived from symbiotic cyanobacteria that were engulfed by ancient eukaryotes
What ecological functions do cyanobacteria have?
- nitrogen fixation
- primary production
- soil stabilization (i.e biocrusts)
- stress tolerance
- symbiosis with fungi/plants
- blooms (aquatic)
How do cyanobacteria do diazotrophy?
- heterocyst cells create anaerobic conditions that activate nitrogenase
- nitrogenase converts atmospheric N2 into organic NH3/NH4
How do heterocysts maintain anaerobic conditions?
- no photosystem II (oxygen producing stage)
- thick cell walls and mucilage to limit gas exchange
- high respiration rates
What photosynthesis components do all algae share?
2 photosystems, 1 cytochrome complex, 1 electron transport chain and ATP synthase
What are phycobilisomes and where are they found?
- antennae like structures on thylakoids that contain light collecting pigments
- found in cyanobacteria and red algae
What is the general rundown of photosynthesis?
- PSII captures light
- light energy gets transfered to chlorophyll a molecules
- excited electrons are passed to plastoquinones
- electrons are recharged by splitting water
- PQ moves excited electrons to the cytochrome complex
- electrons are used to create a proton gradient to move proteins from outside thylakoid to inside
- PC brings the used electrons to PSI
