Exam 2 Study Questions Flashcards
Describe the four processes affecting evolutionary change.
-mutation, genetic drift, migration, natural selection
Describe three conditions that must hold for natural selection to occur.
-1: phenotypic variability (genetic, environmental, or developmental variation)
-2: fitness differences (fecundity, fertility, survivorship)
-3: Heritability
Discuss what are the two steps that natural selection occurs in.
phenotypic selection within a generation and genetic response between generations
Discuss various types of phenotypic selection. How does each of them affect
trait values & what are their population level consequences over time?
directional, stabilizing, disruptive, correlational (see vocab definitions)
Discuss three different patterns of phenotypic adaptation to the environment.
Which of them rely on a single or multiple genotypes?
-Single Intermediate Phenotype: not very efficient in any 1 environment—but functions under a range of conditions, often ephemeral or in disturbed areas—jack-of-all-trades
-Range of Specialized Phenotypes: favored in relatively stable environments, ecotypes across broad & gradual envr gradients—trade-offs, increasing some traits decreases others
-can lead to speciation (separation of
spp in multiple)
-Phenotypic Plasticity of Individual Plants (high in plants—animals move; plants adapt) variation in the phenotype of a single phenotype caused by envr, individuals change forms along with envr,–favored in large temporal variation in range of conditions of very distinct habitats
What are some examples of phenotypic plasticity we covered in the course?
1st ex: emergent (less dissected, large boundary layer, slower CO2 diffusion) vs submerged plant leaves (highly dissected, small boundary layer, more CO2 diffusion)
2nd ex: stem elongation to get light over neighbors
Discuss non-heritable plasticity of plant phenotypes versus heritable genetic
adaptations using the example of jewelweed experiment we covered in class.
jewelweed has directional phenotype between leaf growth rate and relative fitness
Are ecotypes genetic adaptations? Why or why not?
Yes, they are genetically based differences in phenotype based on habitat or location
How may light response curves vary among northern & southern populations
on the northern hemisphere? Why?
northern pops might be more responsive to light since they do not always get as much. Southern populations of plants might be less responsive as they have more traits to protect themselves from excess UV.
What do ecotypes mean for species responses to changing climate?
changing climate means ecotypes will likely have to change in many ways in order to adapt to changing local conditions
How can different barriers to gene flow cause different speciation types?
barriers can isolate populations, leading them to adapting/evolving certain traits to improve fitness and survival. This can eventually lead to different traits and speciation between populations
How would you rank pools and fluxes in global water cycle by their size?
Major pools—1st oceans, 2nd is ice, 3rd groundwater, 4th lakes & rivers, 5th soil, 6th atmosphere, 7th living organisms
Major fluxes—1st precipitation (over ocean, then over land), 2nd evapotranspiration (evap over oceans is actually higher than precip over oceans), 3rd vapor transport, 4th percolation (through soil), 5th surface runoff
How would evaporation, transpiration, and runoff/groundwater recharge differ
between tropical rainforest, temperate forest, grassland, and desert? Why?
ALL DRIVEN BY SOLAR ENERGY
–tropical rainforests—precipitation > Evapotranspiration
–temperate grasslands & deserts, depends a little more on specific ecosystem (some have more evaporation, some have more transpiration)
How would you expect the effects of forest clearance vary between tropical
rainforest, temperate deciduous forest, and Sahel shrubland? Why?
-REMOVAL OF FOREST CANOPY CAN CAUSE EXCESS WATER IN SOME ECOSYSTEMS, IN OTHER PLACES, CAN ACTUALLY CAUSE DRYING EFFECTS
-Rainforests—reduced transpiration can cause reduced rainfall in tropical regions (rainforests can create their own rain through transpiration and encouraging Hadley cells, etc; also less canopy leads to greater heat stress)
-deserts—great heat stress with reduced canopy cover—further desertification
-Deforestation: declines forest cover, remaining forest is often in isolated fragments (agriculture, road development, urbanization)
What is the current mean percent deforestation in Brazilian Amazon and the
deforestation thresholds we discussed as potential tipping points to savanna?
tipping point for Amazon between forest & savanna (20-25% forest loss)—loss is currently abt 17%
What are the main pools and fluxes in global carbon and nitrogen cycles?
Carbon:
-Pools #1 is wetlands, #2 is Boreal forests, #3 is temperate grasslands—lowest is deserts
-Fluxes: -ecosystem respiration, leaching, plant volatile emissions, methane flux, fire, logging, erosion, animal movement
Nitrogen: can’t read slide
-Pools: #1 is soil?
-Fluxes: human emissions/fertilizer, bacteria
What are the relationships between NPP, leaf biomass, LAI?
The size and area of the leaf relates to the total rate of photosynthesis and thus the amount of energy it can produce—Net Primary Productivity
> NPP = >LAI
What are the average and high NPP in terrestrial ecosystems? Provide units.
-varies greatly on global scale
-temperate forests bt 6-11 metric
tons/ha/yr
-tropical forests bt 16-30 metric
tons/ha/yr
-boreal forests bt 1-4 metric
tons/ha/yr
-deserts bt 0-2.5 metric tons/ha/yr
How do temperature, precipitation, and nitrogen affect NPP (at global scales).
-N is limiting factor for NPP
>temp = >NPP
Moderate precipitation = >NPP
Why is turnover time of soil carbon pools important in soil conservation?
This is amount of time it takes for soil Carbon to become available for plants
How does plant species identity relate to soil carbon pools and fluxes
Different species have different traits like overall biomass, sequestration rates, etc
How would you expect plant growth and survival vary in response to warming
climate across species range? Hint: Think of the Reich & Oleksyn Scots pine
study and productivity trends in taiga/tundra that we discussed in class.
Warming in moderate amounts can actually increase plant productivity and/or growth at least in short term. Large changes in climate will seriously impact growth/productivity—stressing plants. Can also mess with plant phenology timeline.
Contrast the two forms of plant clonal growth.
Phalanx—ramets spatially clumped (like phalanx formation from ancient Rome)
Guerilla—ramets dispersed in space (uses local arrangement in convenient places where they can “pop” up as possible if other plant spp are disturbed/die
Discuss the difference between phenotypic and adaptive plasticity.
phenotypic plasticity focuses on 1 single genotype that is expressed in different ways in different environments. It is an immediate response that is typically not in next generation.
Adaptive plasticity refers to changing of the overall genotype in a population towards specific traits that increase fitness/reproduction. It IS transferred to next generation (can affect fitness/genetics in future if big change occurs)
Illustrate with the example from class how one species can drive adaptive
plasticity in another species.
spearwort without competition had lower angles (sprawled out), in competitive areas angles up toward sun (those with adaptations for competition did it faster though)
What is plant phenology and what does it respond to?
timing/schedule of growth & reproduction during a year
-constrained by seasonality (temp; moisture; wind regime sometimes; pop dynamics of pollinators/seed dispersers, herbivores; seed masting events)
What vegetative modes of reproduction are there in plants?
stolons, rhizomes, root suckers, bulbs, clonal fragments, bulbils
What are the allocation trade-offs between (a) animal & wind pollinated plants
and (b) plants with seeds dispersed by wind vs. those dispersed by animals?
a) Wind-pollinated: less energy towards showy petals, light, very abundant propagules & pollen—lower survival rate (depends on where seeds land)
b) Animal-pollinated: attractive flowers w large petals, nectar, heavy sticky pollen—puts more energy towards flowers = fewer propagules for reproduction
What are the ways by which wind-dispersed seeds can accomplish long
distance dispersal? Are there any tradeoffs there?
-samaras/wings, light tufts that can be blown far in wind
-tradeoffs—seeds go wherever wind takes them, possibly nowhere they can grow =low survival rate
How does plant height and size of seed crop affect the ability of wind
dispersed seeds to reach far away from the maternal plant?
plants that are taller/bigger than others can get their seeds a farther distance away—spreading genetics to other areas (less intraspecific competition, etc)
What plant life history strategies would you expect to be more responsive to
climate warming? Why?
Lin et al 2010, meta-analysis—warming affected different plant types in diverse ways (spore plants, legumes, etc responded the worst; both deciduous & coniferous trees responded the best)
What are the trade-off between seed size and number?
Large seeds:
-more endosperm (nutrient store)
-more defense tissue
-better resistance to seed predators
*(but also easier to find)
-better root development
-better early survival & growth
-worse wind dispersal—but may
invest in water dispersal
-smaller overall number of seeds
-may be less likely to find ideal
conditions
-smaller seeds:
-smaller nutritional stores
-less defense
-lower early survival and growth
-large number of seeds
-may find ideal conditions better
(due to sheer volume of offspring)
-may better escape from predators
(for individuals)
-better for wind dispersal
What seed size is optimal for plants?
seeds slightly larger than medium size tend to do best (large seeds diminish returns due to energy expended) *see chart in notes
What is the C-S-R model? What 3 basic life history story strategies does it
describe? Could you use it to describe other life history strategies? How?
Grimes (1977) C-S-R model—3 broad groupings of individual life history characteristics (competitors, stress tolerators, and ruderals)
*see both charts in notes
What are the characteristics of the 3 basic life histories in the C-S-R model?
-competitive plants grow fast and live longer, are abundant (small seeds) and often persistent, produce lots of leaf litter, and flower near time of maximum productivity
-stress-tolerant plants grow slowly and live longer, small seeds, leaves persist for longer
-ruderals (disturbance) are typically short-lived annuals, have large seeds, flower at end of favorable period
*see chart in notes
What is fast-slow continuum? What plant characteristics (traits) it may be
missing based on a more recent work (cf. Salguero-Gomez 2017)
traits farther to right of graph are “slow” and take longer
-Salquero-Gomez– They discovered that the pattern was more complicated than a simple fast-slow continuum (Figure 7.11). The first axis did align with the predictions of the fast-slow continuum. But it explained only 35% of the variation among species. The second axis explained another 25% of the variation and was related to reproductive strategy
*see chart in notes
How can bet hedging lead to traits that seem suboptimal in the short-term?
-plants that produce a large number of seeds but do not have high germination success—it points to seedbanking potential—the plant is stocking seed over time (bet hedging on later reproductive success with ideal conditions)
-decreases variance in fitness
What is masting and what theories were put forward about what controls it?
fruiting synchrony across years and locations (independent of plant density)
—seeds are overproduced so predators will not consume all of them—thereby increasing success rates for germination (Predator satiation)
-Other scientists think it’s more likely due to wind factors: wind pollinating spp tend to mast more
What environmental cues may control plant flowering in different biomes?
-Flowering synchrony artifact—plants may need to overcome:
a) pollen limitation
b) depleted resources
c) regional weather/environment
—case in point it varies by species and implicating factors
What environmental factors control seed germination?
-temp (ex: winter vs summer desert annuals)
-moisture
-light (esp. weedy spp)
-smoke (in chaparral)
What it the basic formula for predicting population size and how does the
interpretation of its individual terms differ between plants and animals?
n(t+1) = n(t) + B(t) - D(t) + I(t) - E(t)
n: current population size
t: previous population size
B: births
D: deaths
I: immigration
E: emigration
-plants are sessile so they have to make it work with conditions they’ve got
-plants can have clonal colonies that complicate measuring individuals: genets, ramets
Contrast the exponential and logistic growth models and discuss how
realistic are they assumptions for plant populations
-Exponential growth model formulas—on slide (assumes resources are NOT limited)
-Logistic Growth models (tend to be more realistic)—takes into account carrying capacity, etc (assumes resources ARE limited and that carrying capacity is sensitive to the # of individuals instead of overall biomass)
How do plants disperse as individuals? How do they disperse genes?
propagule dispersal (veg fragments, seeds—some trade-offs between [only so many resources—environmental context, dispersal methods, genetic diversity—clones as fragments, etc: some plants produce both)
What is the difference between age and stage structured population
models? Which would be more suitable for plant populations and why?
-age structure—-plants are unique due to growth processes that do not relate to age
-stage structure (developmental classes) defined by life history stages—tend to be usually better at characterizing plant population patterns
How would you measure population structure of a tree species in the field?
-Life Stage Structure: better reflects population processes than age structure
-earlier stages defined by 50 cm height increments (2-7); later stages may vary much more (8+)
What is a reverse J curve and where would you likely find it? Why?
relates to the greater rate of death amongst juveniles over time–more vulnerable to array of stressors, stochastic events, and competition.
What are stage classes and their relation to plant age in pink lady’s slipper?
a) 1 leaf plant (1-2 yrs) b) dormant corm (6-7 yrs) c) 2-leaved plant (7-8 yrs) d) flowering plant (13+ up to 30 yrs!)
What is a life cycle graph and it’s components? Can you draw one?
looks at probability that an individual plant with move to next life stage, stay where it is, or even reverse track
*see chart in notes
What is a life table? How and what data would you collect to construct one?
literally like graph but in table form
-collect survival rate, # seeds produced at each stage, avg # seeds produced, reproductive rate per individual…
What is λ and what does it tell us about population growth and extinction
probability? What do you need to know about λ to understand it’s effects?
used in transition matrix to find growth rate (lamda value)
> 1 = growing population
<1 = declining population
What is the role of environmental stochasticity in population dynamics?
-can determine extinction probabilities related to total relative environmental stochasticity
-extinction probability increases for each spp w/ envr stochasticity
-but the increase is steepest with spp with small pop growth rates
Why do young saguaro cacti often grow in association with desert shrubs?
-shrubs act as nurse plants and can provide juvenile cacti protection from sun
How do nurse plants affect marsh elder seedlings in a salt marsh? Why?
-reduces heat stress in juvenile alders in area with little availability of fresh water
Explain how competition between two species may turn into facilitation due
to environmental context (resources) or response variable (or life stage).
- Mark Bertness and Ragan Callaway (1994) predicted that positive interactions should be particularly common under conditions of high abiotic stress or high levels of herbivory
- Many of the hypotheses about competition in unproductive environments have often implicitly focused on low nutrient levels. But inadequate water supply is one of the most important factors limiting productivity globally. Low productivity may also be due to cold temperatures, short growing seasons, saline soils, or toxic materials in the soil that inhibit growth, such as heavy metals.
What does self-thinning law postulate?
initial plant density neg affects final individual biomass (linear relationship bt density & weight on a log-log scale) W = cN-3/2 (W = weight, N = survivor density, c = constant)
–mean individual weight will decrease (plants are smaller due to high competition)
What are the effects of herbivory on plant species realized niche? Can you
provide an example? How may this affect plant response to climate change?
herbivory can change where plants are ex: deer cages show amount of vegetation that is suppressed by constant herbivory although neither side of fence is “natural”
What is coevolutionary arms race between herbivores and plants? Discuss
some examples.
plants and herbivores locked in coevolution to ‘fight’ each other—each can develop chemical/physical defenses against natural enemies (acacia has tough tissue to minimize damage, ruminants with symbiotic cellulose-digesting bacteria/continuous tooth growth, monarch caterpillars sequestering toxins from milkweed to protect them from predators)
What are some physical defenses that plants have against herbivores?
trichomes, toxic substances
What are the effects of herbivory on plant species richness, productivity in
grasslands? Would you expect this to depend on the number of herbivores?
-grazing increases aboveground (21%), belowground (35%) & total productivity (32%)
-overcompensation—after grazing, plants grow a lot more to produce new vegetation
Provide examples of the effects plant pathogens on plants and ecosystems.
-can cause death, size reduction, lower reproductive fitness in individuals
-in populations/communities–<pop growth; less abundance/isolation of pops; chg in pop age or size-class structure; shifting community composition; effects on ecosystem processes; evolutionary chg
How do animals disperse seeds?
frugivory, nut caching, myrmecochory
What are the current trends in many animal populations? How may this
affect plants?
-Declines in insects & birds threaten pollination & seed dispersal
-75% of flying insects in German nature reserves have vanished since 1980s
-farmland birds declined 55% in 28 European countries since 1980
How may deforestation & forest fragmentation in the tropics affect seed
dispersing birds & tree populations dispersed by birds?
forest fragmentation in tropics declines bird spp and young tree abundance of spp that require them for seed dispersal—this is especially true for smaller fragmented segments (more isolated, less useful habitat for birds)
What is mycorrhizae/its benefits/costs? How does it work? Why is it
important? What are the types of mycorrhizae; where would you find them?
helps plants to extend their reach past just their own root capacity (abt 80% of angiosperms and all gymnosperms)
-enhances water/nutrient uptake, improve plant resistance/resilience to envr stress, can possibly improve access to C from other plants, pathogen protection
-fungus gets carbs in exchange
What plant taxa are epiphytes? How do epiphytic and parasitic plants differ?
orchids, bromeliads, ferns
plants that grow on another plant & are not rooted to the ground—commensal relation
parasitic plants actually take nutrients/water from host, lowering fitness—+/- relation
Discuss how final plant biomass per area AND per plant may change for a
agricultural crop if planting density is increased by a little vs. by a lot? Why? How would the answer to the above question change if you were following
plants over time (e.g., through a growing season) or added fertilizer?
high density would decrease biomass of individual plants–would decrease survival in large amounts due to intraspecific competition and over time as dominant plants get even bigger. Adding fertilizer may somewhat slow down detrimental effects by increasing nutrient availability
