Week 3 Flashcards
Primary enosymbiosis
The first transfer of oxygenic photosynthesis from a cyanobacteria to a eukaryotic cell
-Diverged over time into the Archaeplastida
First transfer from a prokaryote to a eukaryote
Plastids have two membranes surrounding the chloroplast.
Endosymbiont to Organelle
Host was able to steal a proportion of the sugars being made by the algae through photosynthesis or was acquiring some other essential metabolite
Relationship became more and more interdependent until the algae was reduced to an organelle
Genes moved into the nucleus of the host
What chlorophylls does red algae have
a and c
it is dominant at great depths
Secondary endosymbiosis
Non-photosynthetic eukaryotes picked up photosynthesis by maintaining an endosymbiosis with another eukaryote (specifically a red or green algae)
Spread to 3 out of the 4 supergroups
Structure of red algae
no flagella
mostly multicellular
most have branched filaments (apical meristems)
mucilage secretion layer on exterior
cell walls
-cellulose
-calcification in come cases is critical to coral reef structural strength,
-perhaps as important as dinoflagellate symbionts in reef functioning and diversity
Why is gamete production is greatly enhanced in alternation of generations
Since the zygote is multicellular, multiple cells in each individual can undergo meiosis thereby greatly increasing the total number of gametes and their overall genetic diversity
Importance comes down to the kinds of environments who have species that exhibit alternation of generations - plants, the niche in which they have grown
○ Turbulent water and dry environments makes it hard for gametes to meet - flagella has little benefit so evolution has dispensed with it
Answer: produce lots and lots of gametes
Ecology of red algae
warm and cool mostly marine waters (relatively deep)
usually grow attached to a rock or other algae
resistant to being eaten - antiherbivore terpenoids
What chlorophyll does green algae have
a and b
Ecology of green algae
most freshwater some marine
mostly photosynthetic, important primary producers in lakes
Structure of green algae
form: unicellular, filamentous, multicellular
most have 2 flagella (asymmetrical)
cell walls
- some have cellulose, hemicelluloses and pectic substances
- branched apical growth
- presence of chemical precursors of the cuticle
major features of fungi
Chemoheterotrophs that feed by absorption
aerobic
Rigid cell wall made of chitin
- Helpful in extreme environments
- Example of a trade-off
○ Can’t do phagocytosis
Produce spores
explain the principal distinguishing structural features of the fungi that result in unique spatial patterns and distinct functions
hyphae
-form basic building blocks for fungi
mycelium
-mass of hyphae forming main body of fungi
septal pores
-allow for movement of cytoplasm, organelles and nutrients between
hyphal compartments
all of these allow for the fungi to take up a larger physical location
Why is it that fungi only evolving for a third as long as bacteria and yet have more diversity
They can do sexual reproduction
Environmental diversity
coevolution
what form of meiosis do fungi do
zygotic meiosis
Fungi often exist in two forms
Unicellular (like yeast)
Yeast form to filamentous form
Specialized Hyphae in Mycorrhizal Fungi
Specialized branching hyphae called arbuscules, use to exchange nutrients with plant host
Mutually beneficial
Between fungi and plant roots - relationship called mycorrhizae
Fungi produce spores through sexual or asexual life cycles
Sexual
Union of the cytoplasm’s of two parent mycelia is called plasmogamy
Contain coexisting, genetically different nuclei - enters a dikaryotic stage before they fuse
Retain two separate haploid nuclei until karyogamy occurs and they fuse to produce diploid cells - forms a zygote
Meiosis then restores the haploid condition leading to genetically diverse spores
Asexual
Many grow as filamentous fungi that produce (haploid) spores by mitosis, -Moulds
Some grow as single celled yeasts- cell division or the pinching of bud cells off of a parent cell
Plasmogamy
Cytoplasmic fusion
makes a heterokaryotic organism
Fungi: the significance of not just being microscopically small, but also filamentous
rapid growth
large SA to V ratio
-intimate interaction with environment
the hyphal network: can get nutrients from different hotspots of activity
Ascomycota structure and defining features
unicellular/filamentous
hyphae generally have perforated septa
produce conidia (asexually)
and can reproduce sexually via heterothallic or homothallic hyphae
Karyogamy
Nuclear fusion
Conidia
Multinucleate haploid spores produced by asci in ascomycetes
Basidiomycetes
Important decomposers of wood and other plant material
Long dikaryotic stage
○ Many opportunities for genetic recombination
Periodically in response to environmental stimuli, the mycelium reproduces sexually by producing elaborate fruiting bodies called basidiocarps
Ascomycete extended dikaryotic phase benefit: Compare with Zygomycota
Only one cell undergoes meiosis, but in Ascomycota, many cells undergo meiosis to create genetic diversity
Structure and main features of basidiomycetes
structure
unicellular and/or filamentous
hyphae ALWAYS have perforated septa
most of the life cycle is in the dikaryotic phase
reproduction
Asexual: oidia (haploid spores) from monokaryotic hyphae (infrequent)
sexual: homothallic or heterothallic hyphae
Basidiocarps
Dikaryotic mycelium form compact masses
Lined with basidium that undergo meiosis and develops genetically unique basidiospores
