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• Cell’s control center
• Stores hereditary information--DNA
• Surrounded by a double membrane called the nuclear membrane (or nuclear envelope)
organisms evolve with their symbiotic microbes
symbiotic=close living relatioship
tends to occur because of mutual beneficial actiona
same trait develops independently in different lineages in response to similar selective pressures
Ocean circulation of carbon
Dead decaying materials from surface ocean drifts down to the deep ocean and settles there--> ocean circulation is very slow--> Carbon is stored here for a long time
largest carbon reservoir
Atmospheric Carbon Source
biological inputs (respiration)
mid-ocean ridges and volcanoes
human activities (deforestation)
Atmospheric Carbon Sink
geological removal (chemical weathering)
CO2 in atmosphere produces acid rain (carbonic acid)--> disolves material on rocks--> C flows into rivers--> ocean (as bicarbonate)--> Carbon then taken up by organisms (in form of calcium carbonate) that need hard outer shells (coral reef and clams)
how do plate tectonics recycle carbon?
subduction moves CaCO3 and organic carbon to the mantle (C sink)
seafloor spreading and volcanism bring carbon up from the mantle (C source)
What gives us a record of ancient CO2 levels?
atmospheric levels of CO2 show a steady increase over the years
during the year CO2 is lower in the summer (more photosynthesis) and higher in the winter (less photosynthesis)
Anthropogenic CO2 sources
human additions of CO2
fossil fuel burning
isotopes of carbon provide information about the source of CO2
as the ratio of 13C to 12C declines--> total amount if atmospheric CO2 increases
ice ages and CO2 levels
cold glacial periods correlate with minimum atmospheric CO2 levels
warm interglacial periods correlate with maximum atmospheric CO2 levels
this might be related to deep ocean carbon circulation
3 domains of life
DNA not contained in a nucleus
DNA is a circular chromosome folded on itself floating around in the cytoplasm
What is archaea (a prokaryote) most related to?
What are cyanobacteria?
Is the classification of bacteria that can perform oxygenic photosynthesis.
What is involved in the scientific method?
How does natural selection lead to evolution?
Due to the higher reproductive success of organisms that are more “fit,” the chances that the heritable genes of a particular genetic mutation in organisms will result in a species evolving.
What 2 aspects contribute to variation in a population, and which of these are heritable?
There are environmental variations due to the conditions that a species exists in, and there are genetic variations due to differences in the genetic material of a species. The genetic variation can be passed to offspring and those differences will be inherited.
How does artificial selection result in evolution?
Artificial selection can result in rapid evolution when humans choose to select for certain properties that they are interested in. For example, if a type of corn crop produces more edible material, a human will favor that species of corn and grow more of it, quickly changing the allele frequency of that corn.
What is the tree of life and how is important for the study of biology?
The tree of life shows the 3 classifications we currently use to describe all life. It helps us understand the relatedness of all organisms.
What are the sources of new genetic material in a population?
Genetic material can occur in mutations and recombination. Mutation can be random and may be the result of an error in the formation of new genetic material. Recombination can mix those mutations and create new alleles.
What role can this new genetic material play in the population?
If those mutations are beneficial to the reproductive success of an individual, that may result in the population evolving over time.
What is adaptation and how does it relate to evolution?
Adaptation shows how natural selection can seemingly make a species a perfect fit for an environment. Although evolution does not “choose” to direct species a certain way, over time, species with adaptations that are beneficial to its survival and ability to pass on heritable traits will make it seem like those species were made to exist in that environment when they have actually adapted to do so.
How do we measure genetic variation and changes in genetic variation in a population over time?
Genetic variation and allele frequency was originally measured by noting observable genotypes, or phenotypes, and documenting the variation. Now, we are able to observe genetic variation through electrophoresis.
What is Hardy-Weinberg (H-W) Equilibrium and how is it used to understand evolution in populations?
H-W is the null hypothesis of evolution, showing that the allele frequency of a population will stay at certain frequencies given a set of conditions.
What are the required conditions for H-W equilibrium and would each condition affect the population? How is allele and genotype frequency calculated using H-W, and what can this information tell us?
H-W equilbrium requires no gene flow, no natural selection, no genetic drift, no mutations, and random mating. From allele frequencies, we can also calculate genotype frequency as such: p+q=1, and p2 + 2pq + q2 = 1. If a population is evolving, we can study this population and try to establish which condition of H-W equilibrium is not being met.
How did our understanding of Natural Selection develop?
Darwin’s theory of natural selection arose from his curiosity and observations that showed how different species of organisms seemed perfectly adapted to survive in their environments. Combined with the idea that small changes in small timeframes can represent large changes over longer timeframes.
In what ways can natural selection affect change in a population?
Natural selection affects individuals, but over time, a population will evolve.
What is the role of mutations in the process of natural selection?
Beneficial mutations will be positively selected for and harmful mutations will be negatively selected for. This means that those beneficial mutations will be more likely to be passed on to the next generation.
How is sickle cell anemia an example of heterozygote advantage?
Sickle cells in a homozygous form will be very painful to the carrier, and regular blood cells in homozygous form may potentially carry malaria. Sickle cell anemia in a heterozygous form will allow those sickled cells to avoid being affected by malaria.
What is artificial selection and how is it similar and different from natural selection?
Artificial selection is the selective breeding by humans of organisms to favor a certain trait.
How is sexual selection related to natural selection?
Sexual selection is the selection of mate. In many cases, the reason for selection of that mate may be due to the observance of traits that make the mate more fit.
What are the evolutionary tradeoffs in sexual selection?
Sexual selection may help propagate an allele that would otherwise be selected against by natural selection, i.e. peahens select for the large, bright tail of the peacock, which should under most other circumstances should be selected against.
Why does genetic drift affect smaller populations more than large populations?
If genetic drift occurs among a smaller population, a large percentage of that population has drifted. The new population may have a genetic pool that is not representative of the original allele frequencies.
What is the role of genetic drift in bottlenecks and founder events?
Genetic drift due to bottlenecks and founder events could create different allele frequencies in the new populations. If those new populations are small enough, they could undergo fixation due to the small amount of variation in that population.
How can migration affect a population?
Migration can mix populations and introduce new alleles to an existing gene pool.
What is a molecular clock and why is it useful for our understanding of evolution?
A molecular clocks shows us the rate of evolution of a particular allele. We can better understand how fast (or slow) these mutations are taking place.
What are the definitions of a species and why is a species so difficult to define?
A species can be defined in many ways, but it has been hard to find 1 definition that suits every species.
We mainly use the BSC, but what are the complications in using this definition?
Although it is the main speciation concept, it is hard to use in the present time. That requires mating 2 organisms and then observing whether the offspring is capable of mating.
How is the morphospecies concept used and what are the difficulties related to using it?
It suggests that different species look different and same species look the same; however, there is evidence that this concept cannot be applied broadly. There are many species that look like other species, but will not mate with the other species.
What role does reproductive isolation play in maintaining species?
Reproductive isolation can keep species apart and the barriers that create the isolation can be the source of that.
What are examples of pre-zygotic mechanisms of reproductive isolation?
Pre-zygotic mechanisms can be lock-and-key differences, mating behavior differences, and environmental and spatial differences that keep different species apart.
What are examples of post-zygotic mechanisms of reproductive isolation?
How do species diverge and form new species?
Can be from moving (Allopatric), hybridization (Sympatric), co-speciation, polyploidy.
What are the different processes of speciation (both allopatric and sympatric)?
Dispersal and Vicariance
What would you expect relationships between species to be following a vicariance event?
After vicariance, I would expect daughter species that become separated would maintain similarities.
What is an ecological niche?
Is a certain setting that a species can be filled whether it is a habitat or available food source.
What is adaptive radiation and what is the role of natural selection in adaptive radiation?
Adaptive radiation can show how quickly evolution can occur. When a species spreads throughout different ecological niches, a species in each niche will be a new species that is particularly adapted for that niche.
How are parasites and host systems an example of co-evolution? (including malaria – see Case 4)
As a new host species is split from a host population, the parasite that is tied to the new host will be a new species as well. Although with malaria, it is unclear the relationship of the malaria that affected chimpanzees and their most closely related humans.
How can instantaneous speciation occur?
Instantaneous speciation can occur in hybridization, in which two different species produce offspring that can only reproduce with its own new hybrid species and neither of the parent species.
What is reinforcement and how does it affect speciation?
Reinforcement of reproductive isolation occurs when species undergo natural selection in favor of enhanced pre-zygotic isolation to prevent production of less fit offspring.
What information can be learned from phylogenies?
Phylogenies help us observe how species and might be related and how certain traits may have been passed down from shared ancestors.
What is a sister group? Monophyletic group? Paraphyletic group? Polyphyletic group?
A sister group is two species descended from a common ancestor. A monophyletic group is an ancestor and all of its descendants. A paraphyletic group is an ancestor, and not all of its descendants. A Polyphyletic group includes species that don’t have a shared ancestor.
What is a character and a character state?
Characters are anatomical, molecular, or physiological features based on genetics. Their state is their observed condition i.e. whether or not a trait is present.
What are homologous and analogous traits? How are homologies and analogies represented on a tree?
Homologous traits are traits that are derived from a common ancestor. Analogous traits are similar traits that evolved independently of each other, much like the wings of bats and birds.
What is a synapomorphy and how is this related to homologous traits?
A trait derived from a common ancestor.
How are phylogenies determined, and how is parsimony a component of these determinations?
Phylogenies are hypotheses of relationships between species. Parsimony suggests that the simplest answer, the tree with the least # of changes is the most likely.
How are fossils used in determining evolutionary relationships?
Fossils can help describe the changes in species, particularly over time. They can help show what changes occurred for species and how the environment shaped the different species.
How do fossils form and what biases exist in the fossil record?
Fossils are formed from the remains of organisms in sedimentary rock. Because a certain set of circumstances must be met to create fossils, there can exist a lot of bias as to what is fossilized. If organisms exist in a time where there is not a lot of rock present. Organisms without bone or hard tissue that can be fossilized. If there is an abundance of a certain organism, but that organism cannot be fossilized, then they may not be represented in our history.
How is fossil age determined (both relative and radiometric)?
Fossil age can be determined based on what layer of rock it is in. With a basic understanding of the different layers of sediment and when they existed, we can determine when an organism that is fossilized in that sediment existed. We can also determine the amount of C14 in an organism. With knowledge of the half-life of C14, we can make an estimation on to the age of the fossil.
How do transitional forms found in the fossil record contribute to our understanding of evolution?
Transitional forms can show us the path that organisms evolved in. They can show the gradual transition from long-ago species to what we recognize today.
How have past mass extinctions affected evolution (especially the post-Permian and Cretaceous)?
The post-Permian and Cretaceous extinctions eliminated a significant portion of life on our planet, and with it a significant amount of the gene pool. The Permian extinction eliminated 90% of marine life and opened those previously occupied habitats for the surviving 10%. Similarly, when dinosaurs were wiped out during the Cretaceous extinction, those habitats in which they were predators became habitable by other organisms (notably, mammals)
What is the significance of the carbon cycle to all life on earth?
The carbon cycle is extremely important in showing how energy is transferred from organisms and the environment. It illustrates the main driving factor that determine how organisms interact with the environment.
Explain the short-term carbon cycle – photosynthesis and respiration – and the role of these processes in atmospheric CO2 concentrations.
Photosynthesis consumes CO2 and produces carbohydrates for energy and releases oxygen. Organisms, like humans, consume carbohydrates in an aerobic process (requiring oxygen).
How do we determine recent and historical atmospheric CO2 concentrations, and what is the relationship between these concentrations and temperature?
We can measure CO2 concentrations in fossilized material or in blocks of ice that trap CO2 from a long time ago. The concentrations of CO2 have steadily increased over time. Temperature cycles through different time periods. The concentrations may fluctuate during the year depending on the season. During the summer months, CO2 concentrations decrease due to the increased activity of plant life. During the winter months, CO2 concentrations increase due to the decreased activity of plant life.
What are the major sources and sinks of CO2?
The major sources of CO2 are from the burning of fossil fuels and deforestation. The sinks, or where CO2 accumulates in the oceans, lands, and in the atmosphere.
How does carbon cycle through the earth? What are the major reservoirs and fluxes of carbon?
A major reservoir is in rock, but organisms, the sea, and the atmosphere also serve as reservoirs. The major flux of carbon occurs from sedimentary rock, which is the largest reservoir.
Why are shell-building animals and corals considered a sink of carbon?
They are formed by Calcium Carbonate which form shells and corals.
What are the geological processes involved in the cycling of carbon?
Plate tectonics play a role in cycling carbon. As plates rub against one another, material can enter magma under the earth’s surface and be expelled into the atmosphere through volcanos.
What roles do humans play in the carbon cycle?
Humans respirate, consuming oxygen, and exhale CO2 into the atmosphere. But more importantly, humans burn massive amount of fossil fuels and deforest the earth, creating more CO2.
How does carbon cycle through a community?
As a food web, we can recreate the path that carbon is cycled through a community. It is produced by plants, algae, and photosynthetic bacteria, which is then consumed by primary consumers.
How much energy moves on to the next tropic level and how does this affect biomass of the next level?
As we move through the trophic levels of the pyramid, the amount of energy that is available is roughly 10%
What changes occurred in oxygen levels on earth over time?
Only relatively recently in earth’s history has oxygen been available in an amount that is able to sustain the organisms we recognize today. The availability of oxygen helped with the diversity of life that is now sustainable on our planet.
What are the features of the prokaryotic cell?
A prokaryotic cell has no membrane-bound nucleus and no organelles.
What are the evolutionary relationships between the two domains of prokaryotes and the eukaryotes?
Although prokaryotic cells were originally dismissed as simple, the diversity of prokaryotic cells and abundance of them have shown them to be highly evolved organisms.
How does diffusion limit prokaryotic cell size?
Because prokaryotes rely on diffusion, they tend to be smaller in size. A smaller cell allows for greater surface area relative to the cell size. The volume of a cell increases exponentially faster than the surface area, so a larger cell becomes untenable.
Why is it difficult to use the biological species concept to determine bacterial species and their relationships?
Because bacteria reproduce asexually, the BSC does not apply. Also, it is hard to track species in such a simplified way as the transmission of DNA in bacteria can occur in many different ways, including conjugation, transduction, and transformation.
What are the different approaches to metabolism in prokaryotes (i.e. energy and carbon sources)?
Prokaryotes can be photoautotrophs (acquire carbon from and use sunlight as energy), chemoautotrophs (gain carbon from CO2, energy from chemical reactions), photoheterotrophs (use sunlight for energy, but acquire carbon from chemical), and chemoheterotrophs.
What are the conditions needed for fermentation?
Fermentation will typically occur in oxygen-poor environments, but with a large amount of available organic matter.
How is sulfur cycled through biological systems and why is this important to living organisms?
Sulfur is an important component of amino acids in our bodies. Sulfur is available to us through the things that we eat, which is made available to plants by assimilation. For assimilation to occur, there must be bacteria that can oxidize H2S to SO4. Decomposition and reduction can take the sulfur and convert it to H2s.
How is nitrogen cycled through biological systems and why is this important to living organisms?
Nitrogen is important to the growth of plants and is extremely important in our body as a key component of proteins and nucleic acids.
What is the significance of nitrogen fixation and where does this process occur?
Nitrogen fixation is an important part of the nitrogen cycle in which bacteria convert nitrogen gas to ammonia which is then biologically available to plants, either as ammonia or nitrate. Anammox or denitrification can also take these products and convert them back to N2 gas.
What are the roles of nitrogen fixation and denitrification in moving nitrogen between the atmospheric and biological reservoirs?
Where are the aerobic and anaerobic locations most likely to be in a microbial mat?
Aerobic prokaryotes in microbial mats would most likely be found nearer to the surface, where oxygen is available to them. Anaerobic prokaryotes, which don’t need oxygen to respire will be found away from the surface.
How do scientist determine diversity in the prokaryotes, and what are the challenges?
Because bacteria and archaea separated over a billion years ago, it is hard to determine what traits evolved independently and what was shared over common ancestry. Horizontal gene transfer also complicates the process.
How are archaea similar and different from bacteria?
Archaea and bacteria are both prokaryotic in cell structure, but their membrane and cell composition allow for survival in extreme conditions or conditions where energy is less available to an extent where bacteria and eukaryotes would not be able to survive.
What are the extreme lifestyles of the archaea that have evolved? How could natural selection have played a role in the evolution of these extreme abiotic tolerances?
Thermophilic, Hyperthermophilic, Halophilic, and Acidophilic. It is believed that Archaea may have existed in times when less oxygen was available, so anaerobic metabolism allowed Archaea to survive in extreme conditions.
What are the extreme lifestyles of the archaea that have evolved? How could natural selection have played a role in the evolution of these extreme abiotic tolerances?
What are stromatolites?
Are essentially fossils of bacteria. They are layered structures that record the existence of bacterial mats.
History of microbial communities
early record of life on earth
can cut through rock and see banding that has occured as a result of many years of seasonal growth of cyanobacteria and sediment
What are stromatolites?
Formed by sedimentation of microbial mats
Showed that ancient blue-green cyanobacteria were one of the earliest forms of life in the oceans
How is co-evolution of symbiotic prokaryotes with eukaryotes similar and different to co-evolution in parasite-host systems?
Coevolution in prokaryotes and eukaryotes may be much more symbiotic in that benefits are provided to both. For example, the bacteria in the stomach of animals may help make different material biologically available to the animal, while the animal provides a steady stream of nutrition.
How diverse in the microbial community in humans? (also see Case 5)
The bacteria that exists in humans can be very different depending on the region the human is in. This may help our understanding of the development of allergies and immunities.
In what ways can bacteria be harmful or beneficial to humans?
Bacteria is important to help us digest different types of food sources. Bacteria is also responsible for nitrogen fixation to help grow crops.
can live in extreme conditions
1. Thermophilic- heat loving
2. hyperthermophilic- very heat loving (up to 122°C)
3. halophilic-salt loving
4. Acidophilic- acid loving
diversity of archaea
What is this?
communities of bacteria and archaea that form on submerged or moist surfaces and create color banding
can help differentiate types of species that are present
What is this?
structural framework between cytoskeleton in the cell that can alter cell shape so that it can move
non living chemical and physical parts of the environment that affect living organisms
microbial mat communities have vertical gradients of abiotic factors
look at light, oxygen, sulfur penetraron to determine the form of metabolism used there
H2S increases as O2 decreases
proteins need sulfur to form
sulfur doesnt have an atmospheric component
advantages of sexual reproduction
new combinations of alleles
can produce new genotypes
produce variation with new allele combinations
clears deleterious mutations
maintains genetic diversity produce new variation
eukaryotic, but not animal, plant, or fungi (paraphyletic group)
photosynthetic protist- algae
heterotropic protist- protozoans
What is this process?
process by which a single-celled eukaryotic heterotroph can engulf food particles
forms a vesicle around the food that is made from the cell membrane
cells that have 2 flagella- 1 hairy and 1 smooth (at some point in their life)
N2 cannot be utilized by organisms--> converted by bacteria and archaea to inorganic nutrients (ammonium/ammonia)
Nitrogen fixation vs. Denitrification
Denitrification= Loss of N: NO3---> N2O and N2
nitrogen fixation=source of N: N2-->NH4+ (ammonium)
performed by cyanobacteria, heterotrophic bacteria, archaea, and symbiotic heterotrophic bacteria
these organisms can fix nitrogen in low N
adaptive advantages of simple multicellularity
avoid protozoan predators
better maintain position on a surface or in water
relationship between O2 and complex multicellularity
increase in atmospheric oxygen--> evolution of simple mulitcellular systems--> once oxygen level is high enough complex multicellularity begins to evolve
Eukaryotic life cycle
alternation btw sexual or asexual
alternation btw haploid and diploid phase
eukaryotic cells changes from prokaryotic cells
cells can grow larger because they are not dependent on diffusion
vesicles transport materials-> allows for larger cells than prokaryotic cells
E metabolism occurs in mitochondria and chloroplasts
approximately same size as proteobacteria
replicate via fission (an replicate inside of the cell)
have their own genomes that are circular
have double membranes
one thing living inside another
marine and freshwater
prey on bacteria
protist that is most closely related to animals
have flagella for movement in an aquatic environment
plasmodial slime molds
coenocytic-one cell with multiple nuclei (nucleus divides but not the cell wall)
cellular slime mold
feed on soil bacteria
starvation --> cells aggregate and form a blob on top with stalk--> flops over--> disaggregates--> eat in new environment
coralino red algae- have calcium carbonate walls
can live deeper in the ocean due to accessory pigments that funnel energy to chlorophyll A
halimeda forms calcium carbonate plates
all algae are used as a stabilizer and thickening agent
ecologically important--> 25% of photosynthesis on earth
precipitate silica out of water to form cell walls--> hard parts leave a fossil record in sediments
important for recycling carbon back into the environment
tons of hairy projections (cillia)
cellulose cell walls
2 smooth flagella
can form red tides
produce neurotoxin that cannot breakdown--> reaches high levels after a few trophic levels
bioiluminescence- chemical response to produce glow
shells with holes
calcium carbonate shells
use pseudopodia to move and feed
live in soil
dictyostelid slime molds
plasmodial slime modes
Green algae (land plants)
all are photosynthetic--> have chlorophyll A
important in recycling carbon from bacteria
take carbon from water and store in shells--> stored in fossil record
free living, symbiotic, or parasytic- need a host to survive
development of photosynthetic eukaryotes
chloroplasts evolved from cyanobacteria living as endosymbionts with eukaryotic cells
chloroplasts are surrounded by a double membrane like mitochondria and in addition have a third membrane in the interior, the thylakoid membrane
thylakoid membrane- where light reactions take place
stroma- surrounding fluid where dark reactions occur
origin of chloroplasts
symbiosis- chloroplasts evolved from cyanobacteria living as endosymbionts with eukaryotic cells
primary and secondary endosymbiosis
2 endosymbiotic events
cyanobacteria engulfed by a eukaryotes via phagocytocis--> forms green algal cell--> green algal cell engulfed by a second eukaryotic
secondary- 4 membranes
nucleus from photosynthetic protist is lost
evidence of eukaryotes acquiring photosynthesis multiple times by endosymbiosis
phylogenetic relationships based on chloroplast genes
symbiotic relationship between unicellular eukaryotes and bacteria
-anaerobic bacteria generate H2S
-bacteria surround eukaryotic cell and metabolize H2S
-bacteria protect host cell from low oxygen and high H2S conditions
fossil record of protists
fossil record can show reminence of algal lineages
can look through layers of sediment to see how they have changed over time
coccolithophore- source of carbonate sediments to sea floor
phytoplankton blooms- chalk cliffs
little communication or transfer of resources between cells
little or no differentiation of specialized cell types
most cells have all functions, including reproduction
every cell is in contact with the external environment
nuclei divide but no cytokinesis (no cell walls form)
one large cell with many nuclei
convergent evolution of multicellularity
evolved 6 separate times:
Green algae--> plants
highly developed mechanisms for adhesion btw cells
specialized structures for cell communication
tissue and organ differentiation
a small subset of cells contribute to reproduction
cell or tissue loss can be lethal for the organism
diff in&out envr
-high adhesion between cells
-specialized structures for cell communication
-tissue and organ differentiation
-a small subset of cells contribute to reproduction
-cell or tissue loss can be lethal for the organism
-presence of both interior and exterior cell (3 dimensional)
evolutionary adaptations for multicellularity
diffusion--> bulk transport
requirements for complex multicellular life
communicate with one another
plants- plasmodesmata (connects cytoplasm and ER)
animals- gap junctions
participate in a network of genetic interactions for cell division and differentiation
water dependent for fertilization
disperse via spores (1n)
• Gametophyte dominant
• H2O dependent for fertilization
• Disperse via spores
adaptation for spore dispersal
provides: UV protetion and desiccation protection
– UV protection
– Desiccation protection
major component of peat bogs
changes pH of water
peat blogs store large amounts of organic C--> coal formation
-major component of peat bogs
-changes pH of water
extinct tree-sized lycophtes 320 mya
change in climate dried out swamp habitats--> coal deposits
extinct tree sized lycophytes 320 mya
-change in climate dried out swamps habitat
Ferns and horsetails
40 of ferns are epiphtic (plant grows on another plant)
spores grow on the underside of the fern leaves
vascular system--> sporophyte dominant
water dependent for fertilization
disperse via spores (1n)
• H2Odependent for fertilization
• Disperse via spores
conifers: pines, junipers, redwoods
pollen--> water independent for fertilization
disperse via seeds (sn)
3.conifers:pines, junipers, and redwoods
-pollen h2o independent for fertilization
-dispersal via seeds (2n)
pines, junipers, redwoods.
pollen--> water independent for fetilization
disperse via seeds (2n)
-h20 independent for fertilization
-disperse via seeds
outer 2 whorls (petals and sepals) serve to attract pollinators and to protect the flower as it develops
central 2 whorls (carpels and stamens)- produce ovules and pollen respectively
embryo has one cotyledon
flower petals are in multiples of 3
major leaf veins are parallel
scattered vascular tissue
-embryo has one cotyledon
-flower parts in multiples of 3
-major leaf veins are parallel
-scattered vascular tissues
responsible for the decomposition of plant and animal tissues
Since fungi depend on pre-existing organic molecules for both carbon and energy, they are called ____________.
How do fungi ingest food and break it down?
absorb organic molecules directly through their cell walls
What two major problems does fungi face with their mode of feeding?
1. complicated molecules cannot pass through cell walls
2. finding food in the environment (no locomotion)
What permits fungi to explore their environment for food resources?
-highly branched filmanets
-slender & long
-provide fungi with a large surface area for absorbing nutrients
How do hyphae maintain their slender form?
by growing only at their tips
When resources are low, what happens to the hyphae?
growth is slow or may stop entirely
When fungi encounter a rich food resource, ....
hyphae grow rapidly and branch repeatedly, forming a mycelium
network of branching hyphae
What is key to hyphal growth and nutrient transport?
strong, flexible cell wall
-makes up fungi cell walls
-modified polysaccharide that contains nitrogen
Properties of fungi cell walls
1. thinner than plant cell walls because of chemical make up of chitin
2. prevents cells from rupturing when exposed to dilute solutions
3. keep cells from expanding as water flows into the cytoplasm by osmosis
What force allows fungi to explore their surroundings as the hyphal tip is pushed deeper into the local environment?
positive turgor pressure from inflow of water by osmosis
Fungi transport materials within their _____.
Transportation of food and signaling molecules across long distances in mycelia allows for fungi to ...
1. grow between resource patches
2. produce reproductive structures
What does transport by bulk flow allow?
-hyphal elongation across nutrient-poor locations (carrying materials in nutrient-rich locations)
-fungi to build relatively large reproductive structures aboveground
What is essential for the long-distance movement of materials within mycelia?
Properties of early-diverging groups of hyphae
-no cell walls to separate them
In later-diverging groups, nuclear divisions are accompanied by the formation of _____.
-walls that partially divide the cytoplasm into separate cells
-contains one or more pores that allows water and solutes to move freely between cells
-play an important role when hyphae are damaged
What does the septa do when the hyphae are damaged?
sealing mechanisms are activated that plugs pores in the septa, preventing loss of pressurized cytoplasm
Two roles of hyphae
1. exploring environment
2. transporting materials
-found in moist, nutrient-rich environments (hyphae are unnecessary)
representatives in Ascomycetes and basidiomycetes
single celled--> asexual reproduction
divide by budding
animal skin and gut--> yeast infections
yeast fermentation--> carbs into CO2 and alcohols
Lack of hyphae is an example of _________ _________.
Most yeasts divide by _______.
a small outgrowth increases in size and eventually breaks off to form a new cell
Where are yeasts common?
1. surface of plants
2. (lesser extent) surface and gut of animals
Fungi are _________ __________ of plant tissues.
What do fungi use as their source of energy and raw materials?
dead organic matter
(Dead tissues on and within the soil/ Living biomass) contains more organic matter.
dead tissues on and within the soil
How are fungi critical elements of the carbon cycle?
Convert dead organic matter into carbon dioxide and water
Why do fungi have the advantage on a forest floor or in soil?
hyphal growth allows fungi to search actively trough the soil for new food resources
Why are bacteria at a disadvantage on the forest floor and soil when compared to fungi?
flagella is not functional when local resources become depleted (must wait for new food to appear)
What are the most abundant biomolcules on and within the soil?
*principal components of cell walls
Properties of cellulose
1. rich source of carbon and energy
2. difficult to degrade
Why is cellulose difficult to degrade?
1. individual polymers bound tightly to one another
2. occur in intimate association with lignin (hard to get at)
3. lacks a regular chemical structure
To break down lignified plant cell walls, fungi require ______.
Why does decay proceed slowly?
oxygen concentrations are low in water-logged environments
What happens when woody biomass is submerged in water?
1. woody biomass accumulates
2. buildup of partially decayed plant material as peat
3. peat becomes coal
Fungi are important _____ and ______ pathogens.
What is the key to success for plant pathogens?
How do fungi usually infect plants?
3. penetrate epidermal cells directly
How do fungi infect epidermal cells directly?
1. degrade the wall with enzymes
2. push hyphae into the plant interior by turgor pressure
The extent of infection depends on ...
ability of hyphae to expand into new tissues
How are plant infections transmitted aboveground?
fungal spores carried by wind or on the bodies of insects
How is infection transmitted belowground?
hyphae that penetrate the root
Hyphae can feed on organic matter in the soil until ...
the root of a suitable host plant is encountered
The persistence of fungal hyphae in soils means that ...
populations of pathogenic fungi can build up in soil
How are fungal pathogens thought to play an important role in maintaining high levels of species diversity?
favoring establishment of seedlings of less-common species
How do fungi exploit living animals?
1. sticky traps with hyphae
2. lasso prey
How does fungi lasso prey?
hyphae forms rings that can inflate within seconds, trapping anything within the ring
Why is fungal infection rare in vertebrates (mammals)?
Fungi grow poorly at mammalian body temperatures
Many fungi form _________ associations with plants and animals.
Two main types of mycorrizhal fungi
hyphae surround, but do not penetrate root cells
hyphae penetate into root cells, where they produce highly branched structures that provide a large surface area for nutrient exchange
-fungi that lives within leaves
-hyphae grow within cell walls and in spaces between cells
Why are endophytes recognized as beneficial?
help host plant by producing chemicals that deter pathogens and herbivorous insects
Mutual association between fungi and insects
Insects grow fungi for food
-Fungi benefit with provided shelter, food, and protection form predators and pathogens
-symbioses between a fungus and a green alga/cyanobacterium
-look, function, and even reproduce as single organisms
mutualism between fungi and algae or cyanobacteria
fungal hyphae that take up water and nutrients from the soil
often live in arid regions--> slow growth
algal cell forms a thin layer just under surface of lichens
mutualism between fungi and algae or cyanobacteria
-15% of all fungal species grow as lichens
-100 species of photosynthetic symbionts
-consist mostly of fungal hyphae that take up water and nutrients from the soil.
Lichens consist mostly of ...
fungal hyphae, with the photosynthetic algae or cyanobacteria forming a thin layer under the surface
The function of the hyphae in lichens:
1. anchor lichen to a rock or tree
2. aid in uptake and retention of water and nutrients
3. produce chemicals that protect against excess light and herbivorous animals
What does the photosynthetic partner contribute in the symbiotic relationship with lichens?
source of reduced carbon
What does cyanobacteria living in lichens provide?
source of fixed nitrogen
How do the two symbiotic partners exchange nutrients?
fungal hyphae that tightly encircle or penetreate the walls of the photosynthetic cells
What influences the form and shape of the fungus?
chemical signals from the photosynthetic partner
How do lichens spread asexually?
2. formation of dispersal units consisting of a single photosynthetic cell surrounded by hyphae
Photosynthetic cells reproduce asexually by ....
mitotic cell division
Lichens are remarkable for their ability to ...
grow on the surfaces of rocks and tree trunks
How do lichens obtain resources needed in barren environments?
1. obtain nutrients from rainfall
2. secrete organic acids that help release some nutrients from rocky surfaces
Given their small size and exposure to environment, lichens must be able to tolerate ...
-high tolerance to dessication
-tolerate wide fluctuations in temperature and light
Why is lichen growth used as an indicator of industrial pollution?
sensitive to air pollution (SO2)
Like plants, fungi face two challenges in completing their life cycles.
1. to maintain genetic diversity
2. must be able to disperse from one place to another
What are the fungal adaptations for dispersal?
rely on wind, water, or animals to carry spores through the environment
We must often come into contact with fungi through their ...
Fungi proliferate and disperse using ______.
Why must fungi be able to disperse from one food source to another?
-living/dead tisues that support fungal growth are sometimes hard to come by and have a patchy distribution
-extensive networks of hyphae within soils or host organisms can spread locally but not spread over great distances
Properties of spores that are disperssed over habitats unsuitable for growth
encased in a thick wall that protects them
Why do fungi prouce huge numbers of spores?
the probability that any given spore will come to rest in a favorable habitat is low
Spores allow fungi to use resources that are patchy in ____ and ______.
One of the cues that triggers spore formation is ...?
shortage of resources
How can spores form?
1. meiotic cell division (sexual reproduction)
2. mitotic cell division (asexual reproduction)
-forms at the ends of erect hyphae
-asexual spores are produced
-facilitate relaese of spores into the air
What faciliatates the dispersal of sexually produced spores?
multicellular fruiting bodies
-highly ordered and compact
-constructed entirely of hyphae
fungi and carbon cycle
decomposers--> important for C cycle
can digest lignin and cellulose
release CO2 back into atmosphere via respiration
Wht ensures dispersal of spores from the fruiting bodies of fungi?
1. elevation above the ground or growth from the trunks of dead trees
2. forced ejection of spores
3. external forces: raindrops, animals
layer of still air that lies close to the ground that the spores must escape to be picked up by the wind
Escape from the boundary layer is easier if spores have a size and shape that ...
The fungal life cycle often includes a stage in which ...
haploid cells fuse, but nuclei do not
Fungi have life cycles that include ________ and ________ stages.
haploid (1n), diploid (2n)
The nuclei in fungal hyphae are _______.
In haploid-dominant organisms, asexual reproduction involves the ...
production of haploid spores by mitosis
nuclei from 2 different mating types
2 genetically distinct haploid nuclei
ascomycetes and basidiomycetes
In haploid-dominnt organisms, sexual reproduction involves ...
fusion of haploid cells (gametes) to form a dipoid zygote, which undergoes meiosis as its first division
-association with plant roots (form endomycorrhizae)
fungal group cannot live independently of plants