Term
| Why are the tropics warmer than the temperate zone? |
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Definition
| Due to the spherical curvature of the Earth, the tropics, especially the equator, are closer to the sun so there is a higher number of photons per unit area due to a more direct angle of exposure |
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Term
| Why do air masses from the N and S converge near the equator (the ITCZ)? |
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Definition
| Air masses converge around the equator because the area around the equator is the region most exposed to solar radiation and heat. When air is heated it becomes less dense and moves upwards leaving a void of low pressure behind as it cools and disperses. Since air always moves from high to low pressure, it rushes back and converges near the equator along the surface completing a loop of air flow and forming the ITCZ. |
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Term
| Why does the ITCZ shift during the course of the solar year? |
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Definition
| The earth's axis is tilted, so as it moves about the sun a different latitude is closest to the sun. |
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Term
| What causes dry seasons in the tropics? |
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Definition
| Tropics that are further from the equator will experience a dry season when the ITCZ is far away and the air is cooler. |
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Term
| What is the paradox between tropical net primary productivity and the fertility of tropical soils. |
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Definition
| Tropical soils are usually nutrient scarce. However, the tropical net primary productivity in the tropics is the highest of any place on Earth. |
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Term
| Why does it rain more in the tropics than the temperate zone? |
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Definition
| There are two main reasons why it rains more frequently in the tropics. Solar radiation is strongest near the equator, this has two implications. Firstly, there is a higher rate of evaporation in these areas than in other areas due to this direct exposure (another factor is that the equator is mostly covered by water). Secondly, high temperature warmer air holds more water vapor than cold air accounting for the higher humidity potential present in the tropics. |
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Term
| How is disturbance related to high species diversity in tropical rain forests? |
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Definition
| The intermediate disturbance hypothesis: At low disturbance frequency there will be mostly climax species. At high frequency, there will be mostly pioneer species. At an intermediate frequency, the maximum species diversity occurs. |
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Term
| Rain forest is structurally dominated by trees that block the sun from the forest floor. Yet there are plants that live beneath the canopy. What type of sun light do they depend on, qualitatively and quantitatively? |
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Definition
| They depend on PAR- photosynthetic active radiation, which comes from the visible light spectrum. 50-80 percent of the PAR that hits the floor comes in sunflecks: small patches of direct sunlight. |
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Term
| Which group, pioneer vs. climax tree species is more diverse in the three major geographic regions of tropical rain forest? In which region is pioneer species diversity highest? Why might that be so? |
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Definition
| Climax species are more diverse in all three regions. In the Malaysian tropics, the water surrounding islands provides a boundary that limits the wide spreading of pioneer species seeds, and this limits the gene flow that inhibits pioneer species diversity in other tropical regions. |
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Term
| List the differences between climax and pioneer seeds/seedlings in the following categories: size, abundance in soil, dormancy, germination cues, dispersal distance, growth rate in shade/sun, species diversity of seedlings compared to seeds. |
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Definition
| (Pioneer/Climax): Small seeds/large seeds, high/low, yes/no, shift in radiation & raise in temperature/None (immediate), far/not far, low/slow + steady, fast/slower, low/high. |
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Term
| List the five major mechanisms of evolutionary change, mechanisms that change genetic composition of populations. For each explain, briefly how that mechanism contributes to genetic differentiation of homogeniety between/among populations of a species. |
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Definition
| Mutation (Random diversity), Natural Selection (Adaptations -> diversity), Genetic Drift (Sampling Error), Sexual Selection (Non-Random Mating), Gene Flow (Homogenizes) |
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Term
| What is a keystone species? |
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Definition
| A keystone species is a species whose existence makes the existence of many other species possible and without which those species would not exist. |
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Term
| Describe two factors that make dispersal of seeds away from the parent plant an important issue in evolving an efficient dispersal mechanism. |
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Definition
| 1: The parent plant does not want to compete with its offspring for resources. 2: If all the seeds are close together, it is likely that a predator who finds them will eat them all. |
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Term
| What are the trade-offs in production and animal dispersal of size and number of seeds? |
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Definition
| Size goes up -> Production goes down. Size goes up -> Dispersal goes down. Production goes up -> Dispersal goes up. |
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Term
| List and briefly describe the two major ways plants protect themselves from herbivory. What is the evidence one is more effective than the other? |
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Definition
| Morphology: Having tough leaves, undesirable to chew on. Chemical: Having nasty chemicals in the leaves. In one experiment, young plants with high chemical defense were more susceptible to herbivory than older plants with better morphological defense. So morphology is more effective. |
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Term
| Why do we call such things as alkaloids, terpenoids, and phelonics in plant tissues secondary plant compounds? |
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Definition
| Primary compounds are central to life processes. By contrast while secondary compounds may have various helpful functions such as protection from herbivory, they are not central to metabolism. |
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Term
| What is the Red Queen Hypothesis? How does it apply to plants and herbivores that eat them? |
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Definition
| "It takes a lot of running to stay in the same place". Plants evolve defense mechanisms -> Herbivores evolve ways to overcome such mechanisms -> Plants evolve better mechanisms and so on. These animals continue evolving without gaining any relative competitive advantage. I.e. an arms race. http://www.youtube.com/watch?v=CCYvPUChnIo |
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Term
| Why might tropical rainforests of Africa be less diverse than either the Neotropics or Malaysia. |
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Definition
| The African flora probably underwent considerable bouts of extinctions due to drying that occurred on that continent, some due to mountain building that interrupted the flow of warm moist air across the continent, mountains caused by continental drift. |
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Term
| Describe the structure of typical lowland evergreen rain forest. [How tall is it, how many layers of plants, how many species compared to other types, what do the trunks of trees look like, ground vegetation, presence/absence of vines and epiphytes?] |
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Definition
| The tropical lowland evergreen rainforest is characterized by abundance. It is a lofty, dense, everfreen forest 45m or more tall characterized by a large number of tree species. This formation typically has three layers. Ground vegetation is sparse and patchy. Tree trunks are almost cylindrical and reach 4.5m in girth. Vines and epiphytes are occasional. See descriptions of formations page 15 on. |
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Term
| 7. There are many categories of tropical rain forest types based on a description of the plant types, sizes, evergreen/deciduous, etc. but what causes the difference between monsoon/ semi-evergreen rain forests and lowland evergreen/lower montane/ upper montane rain forests* |
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Definition
| The first division between different forest formations is that of climate. Forest formations can be separated into those that are seasonally dry, as are the monsoon and semi-evergreen rain forests. By contrast lowland evergreen/lower montane/upper montane rain forests are everwet (perhumid). Other characteristics by which forest formations are classified include soil type, the amount of water in the soil, and elevation. See page 14 |
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Term
| There are two fundamental reasons why the tropical regions are where they are. The first we talked about long, long ago and is related to the curvature of the earth. What is the second? Explain. |
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Definition
| Continental Drift—w/ the breakup of Gondwana (southern continents) the tropical regions of SA, Afr, and Maylasia/NE Australia drifted into their current positions. |
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Term
| Given the geographic separation of the major tropical regions and the limited dispersal ability of plants, how could there possibly be any similarity in their floras? |
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Definition
| Continental Drift—because the three regions used to be part of a common land mass it was possible for each region to have many taxa in common prior to break up of the continent. |
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Term
| Tropical rain forest has a dense canopy, limiting the amount of light that reaches the forest floor. What impact has this environment had on the evolution of forest ungulate behavior and social systems? Recall that ungulates are even and odd-toed (hoves), herbivorous mammals. |
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Definition
Forest ungulates live in a dark, shadowy world where they escape predation by not being noticed. They are solitary – fewer individuals are harder to detect than a herd
They freeze when they detect a predator—running away might make you more conspicuous
Their color pattern blends in with the light flecks/shadows of the forest
When detected, run in zigzag pattern, not straight line (forest anyway, running in straight line might be hard) |
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Term
| Considering the global and geographic positioning of tropical regions and the migration of “modern-looking” humans out of Africa perhaps 200,000 yrs ago, trace the migration of humans into the major tropical regions of the globe. Approximately how long have humans been in the Neotropics? How do we think they got there? |
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Definition
| Origins in Africa, spread into Europe and Asia, into Australia and North America, then down into S America last. Been in neotropics between 6 and 15 thousand years. They crossed by land via the Bering Straight when sea level was lower creating Beringia and possibly by sea using craft similar to the boats used by Eskimos/Inuit along the edge of ice flows prior to the land bridge. |
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Term
| What is some of the evidence that humans have lived in tropical rain forest for thousands of years with out the extensive devastation to diversity that we are seeing in modern times? |
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Definition
| First, evidence of human habitation in these areas and the existing biodiversityif humans destroy diversity, these areas of high diversity where humans have/are living wouldn’t be there. Second, evidence of farming/cultivating food plants in areas of high biodiversity…where the way indigenous peoples used the areas actually increased the diversity. Cultivated rare useful plants more common as a result of cultivation. 3rd—indigenous people in all 3 areas use shifting agriculture, not slash and burn. Shifting agr preserves diversity. Fields of differing ages (fallow ground) harbor different species in successional series. |
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Term
| What is different? How is it that only recently (last 100-200 yrs) humans are having a devastating impact on tropical ecosystems? |
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Definition
| Industrial Revolution—greater ability to exploit natural resources (formerly via animal power). More people (growing global population due to increased efficiency due to industry revol) needing more food, building materials, etc. |
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Term
| How are climax tree species defined? |
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Definition
| Climax species are shade tolerant species which can grow below the canopy. They produce larger seeds either annually or less frequently. Slower and denser growing. |
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Term
| How are pioneer tree species defined? |
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Definition
| Pioneer species are light-demanding (shade intolerant) species who only germinate and establish in canopy gaps open to the sky and exposed to full sunlight. They often produce a lot of small seeds copiously and continuously and their seeds can often lie dormant. Aggressive and opportunistic growers. |
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Term
| How is the fig tree a keystone species? |
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Definition
| The fig tree provides food all year round, most importantly during the dry season, when many other plants do not. Thus a lot of animals are dependent on the fig tree for survival during the dry season. |
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Term
| 2. In slash and burn or shifting agriculture, what is perhaps the single most important change in tropical soil due to burning? Why? |
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Definition
| The biomass of the forest contains plant mineral nutrients which when burned remain in the ash and become available to other plants. The pH is raised by the release of this pulse of nutrient cations reducing the acidity of the soil. Phosphorous alumnium and iron become more insoluble and locked in the soil after repeated use leading to a residual decline in crop yield and soil value. |
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Term
| 1. Describe cyclic agriculture. Traditionally, who does i/did it? Is it sustainable? If so, how/why? |
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Definition
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Term
| What factor determines initial soil nutrient level --- what makes soils nutrient rich vs nutrient poor? |
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Definition
| Soluble cations such as K+, Ca2+, and Mg2+ as well as Nitrogen and Phosphorous accumulate, whether by the decomposition of litter, rock, volcanic ash, or rain. |
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Term
| Relate this to nutrient evels in the soils of the Amazon Basin vs the foothills of the andes. |
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Definition
| Because the farmers in the foothills of the andes in western amazonia have no real experience forest farming they are competely depleting the soils balance of nutrients. When farmers slash and burn the forest and grow crops on the released nutrients year after year unti the soils is exhausted then desertification can set in where nothing can grow except weeds. |
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Term
| Describe two ways diverse species groups manage to decrease competition among them |
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Definition
| Specialization in Time and Space. Ex: Toucans find their prey in the canopy, Wrens find it on the ground. Food Preferences. Ex: Neotropic bats have 9 "food guilds" including Frugivores, Insectivores, Sanguivores (blood). |
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Term
| Why might animal pollination be more common/effective in tropical rainforests compared to wind |
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Definition
| wind poination is random and polen may only travel short distances. Animal pollination will often disperse further distances and the animal is likely to visit other flowers completeing the pollination process |
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Term
| Describe the characteristics of an animal pollinated flower for a plant that lives beneath the canopy |
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Definition
| The flowers are either white (so they are visible in the dark) or have a strong odor. Moths and bats attracted to light colored fruit. Carrion fly attracted to stinking flower. |
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Term
| How is flower shape important in determining the type of pollinator that visits a flower? |
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Definition
| different flower shapes are acessible only to certain pollinatiors. A flat landing pad works for many insects, while flowers with long tubes only allows insects/birds with longue tongues. In addition specialized flowers with curved tube may only alow birds with certain beak shapes. |
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Term
| DO ANIMALS EXPLOIT SECONDARY PLANT COMPOUNDS? IF SO GIVE AN EXAMPLE: |
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Definition
| a) euglosiine bees use secondary plant compounds from some orchid species as an aphrodisiac. b) monarch butterfly incorporates milkweed compounds into exoskeleton. |
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Term
| Ant/Acacia Relationship. How does the Acacia help the ant, vise versa? |
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Definition
| Acacia help ant: Housing (Ants can remove pith from swollen thorns or stems), food (beltian bodies on leaflets, extrafloral nectaries). Ant help Acacia: Protects from herbivores + competition plants, gets nutrients from dead ants + other dead things ants bring. |
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Term
| What are the five things required for model/mimic relationship to work? |
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Definition
a- visual predator so that the predator can see the aposematic coloration in the model/mimic
b- a predator with a good memory so that they can remember and learn from previous experiences
c- a rare mimic and a common model
d- a predator's previous bad experience with a model
e- this experience must have not killed the predator as this would greatly limit social learning |
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Term
| Define and provide examples for the two types of model/mimic relationships. |
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Definition
| Batesian: Good-tasting mimic (Viceroy + Monarch butterflies) Mullerian: Bad-tasting mimic (coloration of bees) |
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Term
| explain what a drip tip is and where it is common. Also, explain why it exists |
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Definition
| Pointed leaf tip for water runoff. Common in the tropical rain forest. Prevents water + "crud" buildup which block sunlight. |
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Term
| describe the differences between climax and pioneer wood and state the reason for this difference. Because of the differences in wood type there have been different uses for climax and pioneer wood, briefly outline each use for both rich individuals. |
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Definition
| Climax trees grow slowly and, therefore, have durable wood with anti-fungal/insecticide compounds. Pioneer trees grow rapidly and have less durable wood. Individuals with money can use climax wood as construction wood to build houses and decks (due to its anti-fungal/insecticide and durable properties). They can also use it in water craft sports, for example, teak. Rich people can use pioneer trees as construction wood for recreational airplanes (ex. balsa wood) and paper products. |
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Term
| Which biome is most productive for human food production? Why? |
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Definition
| Temperate grasslands because nutrients remain in the soil (rather than in the vegetation as in tropical rain forests) making the cultivation of crops more productive. |
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Term
| Early on critics of international organizations like the World Bank and IMF claimed that these institutions were exacerbating rather than alleviating degradation of tropical rain forests. Why? |
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Definition
| The World Bank funded infrastructure developments like road and dam building creating access for poor campesinos just looking to maintain their livelihoods to use these roads to cut into virgin vegetation and clear forests. |
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Term
| What is the distinction between annual and diurnal temperature variation? Which is most prevalent in the tropics? |
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Definition
Annual temperature variation refers to temperature variation throughout the year. Temperate climates are cold in the winter and hot in the summer.
Diurnal temperature variation refers to temperature variation over a 24 hr period.
In tropical regions diurnal variation may exceed annual variation. |
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Term
| What are cauliflory and ramiflory? In which forest vegetation type are they most readily found? |
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Definition
Cauliflory are flowers on trunks while ramiflory are flowers on stems/branches
Most common in lowland evergreen rainforest |
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Term
| Where do most indoor plants originate from? |
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Definition
| They are shade tolerant plants from the tropics, many are epiphytic or bromeliads |
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Term
| Unlike some other sciences like physics or chemistry, biology has no concrete laws but there is one concept that comes close to being a law, what is it? |
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Definition
| The species area curve – the number of species increases as you expand the area studied. |
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Term
| What are 3 ways in which plants have evolved strategies to evade seed predation? |
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Definition
| 1) toxic chemicals in seeds, 2) tough, durable seed coverings, 3) irregular seeding cycles |
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Term
| Why don’t mammals in the tropics store their food like their temperate counterparts? |
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Definition
| No dry season so they don’t have to store food, predictable rain of seeds and fruits, and other predators might find their food before they do, fungal infestation in warm, humid tropics. |
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Term
| What is stochastic extinction? Provide an example of what might cause this to occur? |
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Definition
| Stochastic extinction involves a population threshold. When populations decline to or below a certain level the probability of extinction increases dramatically. This is likely to occur with species that already have small populations and rely on specific habitats that are quickly disappearing, like orangutans in the Malaysian tropics. |
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Term
| What is Wallace’s line and how does it relate to continental drift? |
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Definition
| Located between Borneo and Sulawesi and discovered by Alfred Russel Wallace, Wallace’s line signifies an ecological barrier between the Asian and Australian groups of species of Laurasian and Gondwanan ancestry, respectively. This intangible boundary relates to continental drift because Wallace’s line exists as a result of the break-up of Pangea into Gondwanaland and Laurasia, which each contain distinct ecological diversity due to their different continental origins. |
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Term
| Why have Amerindians historically experienced significant difficulties preventing industrial encroachment into their Amazonian home? |
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Definition
| Amerindians do not possess the political influence to compete with the corporate interests of loggers, miners, large-scale farmers, and dam owners, who employ considerable skill, resources, and experience to control local politicians. Moreover, many Amerindians do not likely have the familiarity with government structures, nor the needed contacts to get their needs and concerns addressed. |
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