Exam 2 Study Questions

Question 1

Describe the four processes affecting evolutionary change.

Answer 1

-mutation, genetic drift, migration, natural selection

Question 2

Describe three conditions that must hold for natural selection to occur.

Answer 2

-1: phenotypic variability (genetic, environmental, or developmental variation)
-2: fitness differences (fecundity, fertility, survivorship)
-3: Heritability

Question 3

Discuss what are the two steps that natural selection occurs in.

Answer 3

phenotypic selection within a generation and genetic response between generations

Question 4

Discuss various types of phenotypic selection. How does each of them affect
trait values & what are their population level consequences over time?

Answer 4

directional, stabilizing, disruptive, correlational (see vocab definitions)

Question 5

Discuss three different patterns of phenotypic adaptation to the environment.
Which of them rely on a single or multiple genotypes?

Answer 5

-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

Question 6

What are some examples of phenotypic plasticity we covered in the course?

Answer 6

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

Question 7

Discuss non-heritable plasticity of plant phenotypes versus heritable genetic
adaptations using the example of jewelweed experiment we covered in class.

Answer 7

jewelweed has directional phenotype between leaf growth rate and relative fitness

Question 8

Are ecotypes genetic adaptations? Why or why not?

Answer 8

Yes, they are genetically based differences in phenotype based on habitat or location

Question 9

How may light response curves vary among northern & southern populations
on the northern hemisphere? Why?

Answer 9

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.

Question 10

What do ecotypes mean for species responses to changing climate?

Answer 10

changing climate means ecotypes will likely have to change in many ways in order to adapt to changing local conditions

Question 11

How can different barriers to gene flow cause different speciation types?

Answer 11

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

Question 12

How would you rank pools and fluxes in global water cycle by their size?

Answer 12

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

Question 13

How would evaporation, transpiration, and runoff/groundwater recharge differ
between tropical rainforest, temperate forest, grassland, and desert? Why?

Answer 13

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)

Question 14

How would you expect the effects of forest clearance vary between tropical
rainforest, temperate deciduous forest, and Sahel shrubland? Why?

Answer 14

-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)

Question 15

What is the current mean percent deforestation in Brazilian Amazon and the
deforestation thresholds we discussed as potential tipping points to savanna?

Answer 15

tipping point for Amazon between forest & savanna (20-25% forest loss)—loss is currently abt 17%

Question 16

What are the main pools and fluxes in global carbon and nitrogen cycles?

Answer 16

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

Question 17

What are the relationships between NPP, leaf biomass, LAI?

Answer 17

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

Question 18

What are the average and high NPP in terrestrial ecosystems? Provide units.

Answer 18

-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

Question 19

How do temperature, precipitation, and nitrogen affect NPP (at global scales).

Answer 19

-N is limiting factor for NPP
>temp = >NPP
Moderate precipitation = >NPP

Question 20

Why is turnover time of soil carbon pools important in soil conservation?

Answer 20

This is amount of time it takes for soil Carbon to become available for plants

Question 21

How does plant species identity relate to soil carbon pools and fluxes

Answer 21

Different species have different traits like overall biomass, sequestration rates, etc

Question 22

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.

Answer 22

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.

Question 23

Contrast the two forms of plant clonal growth.

Answer 23

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

Question 24

Discuss the difference between phenotypic and adaptive plasticity.

Answer 24

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)

Question 25

Illustrate with the example from class how one species can drive adaptive plasticity in another species.

Answer 25

spearwort without competition had lower angles (sprawled out), in competitive areas angles up toward sun (those with adaptations for competition did it faster though)

Question 26

What is plant phenology and what does it respond to?

Answer 26

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)

Question 27

What vegetative modes of reproduction are there in plants?

Answer 27

stolons, rhizomes, root suckers, bulbs, clonal fragments, bulbils

Question 28

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?

Answer 28

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

Question 29

What are the ways by which wind-dispersed seeds can accomplish long distance dispersal? Are there any tradeoffs there?

Answer 29

-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

Question 30

How does plant height and size of seed crop affect the ability of wind dispersed seeds to reach far away from the maternal plant?

Answer 30

plants that are taller/bigger than others can get their seeds a farther distance away—spreading genetics to other areas (less intraspecific competition, etc)

Question 31

What plant life history strategies would you expect to be more responsive to climate warming? Why?

Answer 31

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)

Question 32

What are the trade-off between seed size and number?

Answer 32

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

Question 33

What seed size is optimal for plants?

Answer 33

seeds slightly larger than medium size tend to do best (large seeds diminish returns due to energy expended) *see chart in notes

Question 34

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?

Answer 34

Grimes (1977) C-S-R model—3 broad groupings of individual life history characteristics (competitors, stress tolerators, and ruderals) *see both charts in notes

Question 35

What are the characteristics of the 3 basic life histories in the C-S-R model?

Answer 35

-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

Question 36

What is fast-slow continuum? What plant characteristics (traits) it may be missing based on a more recent work (cf. Salguero-Gomez 2017)

Answer 36

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

Question 37

How can bet hedging lead to traits that seem suboptimal in the short-term?

Answer 37

-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

Question 38

What is masting and what theories were put forward about what controls it?

Answer 38

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

Question 39

What environmental cues may control plant flowering in different biomes?

Answer 39

-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

Question 40

What environmental factors control seed germination?

Answer 40

-temp (ex: winter vs summer desert annuals) -moisture -light (esp. weedy spp) -smoke (in chaparral)

Question 41

What it the basic formula for predicting population size and how does the interpretation of its individual terms differ between plants and animals?

Answer 41

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

Question 42

Contrast the exponential and logistic growth models and discuss how realistic are they assumptions for plant populations

Answer 42

-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)

Question 43

How do plants disperse as individuals? How do they disperse genes?

Answer 43

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)

Question 44

What is the difference between age and stage structured population models? Which would be more suitable for plant populations and why?

Answer 44

-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

Question 45

How would you measure population structure of a tree species in the field?

Answer 45

-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+)

Question 46

What is a reverse J curve and where would you likely find it? Why?

Answer 46

relates to the greater rate of death amongst juveniles over time--more vulnerable to array of stressors, stochastic events, and competition.

Question 47

What are stage classes and their relation to plant age in pink lady’s slipper?

Answer 47

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!)

Question 48

What is a life cycle graph and it’s components? Can you draw one?

Answer 48

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

Question 49

What is a life table? How and what data would you collect to construct one?

Answer 49

literally like graph but in table form -collect survival rate, # seeds produced at each stage, avg # seeds produced, reproductive rate per individual...

Question 50

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?

Answer 50

used in transition matrix to find growth rate (lamda value) >1 = growing population <1 = declining population

Question 51

What is the role of environmental stochasticity in population dynamics?

Answer 51

-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

Question 52

Why do young saguaro cacti often grow in association with desert shrubs?

Answer 52

-shrubs act as nurse plants and can provide juvenile cacti protection from sun

Question 53

How do nurse plants affect marsh elder seedlings in a salt marsh? Why?

Answer 53

-reduces heat stress in juvenile alders in area with little availability of fresh water

Question 54

Explain how competition between two species may turn into facilitation due to environmental context (resources) or response variable (or life stage).

Answer 54

- 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.

Question 55

What does self-thinning law postulate?

Answer 55

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)

Question 56

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?

Answer 56

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”

Question 57

What is coevolutionary arms race between herbivores and plants? Discuss some examples.

Answer 57

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)

Question 58

What are some physical defenses that plants have against herbivores?

Answer 58

trichomes, toxic substances

Question 59

What are the effects of herbivory on plant species richness, productivity in grasslands? Would you expect this to depend on the number of herbivores?

Answer 59

-grazing increases aboveground (21%), belowground (35%) & total productivity (32%) -overcompensation—after grazing, plants grow a lot more to produce new vegetation

Question 60

Provide examples of the effects plant pathogens on plants and ecosystems.

Answer 60

-can cause death, size reduction, lower reproductive fitness in individuals -in populations/communities--

Question 61

How do animals disperse seeds?

Answer 61

frugivory, nut caching, myrmecochory

Question 62

What are the current trends in many animal populations? How may this affect plants?

Answer 62

-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

Question 63

How may deforestation & forest fragmentation in the tropics affect seed dispersing birds & tree populations dispersed by birds?

Answer 63

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)

Question 64

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?

Answer 64

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

Question 65

What plant taxa are epiphytes? How do epiphytic and parasitic plants differ?

Answer 65

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

Question 66

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?

Answer 66

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