Ecology Final Exam

Front 1

Discuss the pros and cons of descriptive studies as opposed to laboratory studies of the same ecological phenomenon.

Back 1

Descriptive studies attempt to describe what the ecologiest wishes to understand.
Laboratory studies are controlled experiments attempting to provide answers to specific questions that are key parts of an overall explanation of the complex situation.

Front 2

What is a 'natural field experiment'? Why are ecologists keen to take advantage of them?

Back 2

Studies where ecologists observe organisms in their natural environment. Ecologists like these experiments because they can observe species in their natural habitat instead of in a laboratory.

Front 3

How might the results of the Cedar Creek study of old-field succession have been different if a single field had been monitored for 50 years, rather than simultaneously comparing fields abandoned at different times in the past?

Back 3

There may be a different species composition in regards to invader, native praire, annual and perennial species depending on the variation in the nitrogen content for that one field over time.

Front 4

What do you consider to be the essential distinction between natural selection and evolution?

Back 4

Biological evolution: Change in gene frequencies in a population of the same spcies over time. Caused by several processes, one of which is natural selection.
Natural Selection: Improves the performance of species in regards to their environment. Organisms evolve characteristics meant to solve problems in their environment.

Front 5

What was the contribution of Malthus to Darwin’s & Wallace’s ideas about evolution?

Back 5

He wrote An Essay on the Principle of Population that said that the unchecked rate of increase for human population would double every 25 years an overrun the planet. He argued that limited resources, along with disease, wars and other disasters, slowed the growth of populations and placed limits on their size.

Front 6

What are reciprocal transplants? Why are they so useful in ecological studies?

Back 6

Introducing organisms from two or more environments into . each other's environment. Organisms from two or more habitats are taken from their own habitat and reared alongside resident organisms in their own habitat. Transplant experiments are often performed to test if there is a genetic component to differences in populations. They demonstrate adaptations to local conditions.

Front 7

Describe how plants’ requirements to increase the rate of photosynthesis and to decrease the rate of water loss interact. Describe, too, the strategies used by different types of plants to balance these requirements.

Back 7

Water is lost from plants that photosynthesize. Photosynthesis can only happen across surfaces that are wet, as carbon dioxide is allowed in, water vaper leaves. Attempting to reduce water loss reduces carbon dioxide consumption and therefore photosynthesis.
Strategies: Avoiders (like desert annuals) have a short lifespan and only photosynthesize when they can have positive water balance. Tolerators have slower photosynthesis, attempting to increase the efficiency of their water use, or obtaining water from the soil.

Front 8

Account for the fact that the tissues of plants and animals have such contrasting C:N ratios. What are the consequences of these differences?

Back 8

The carbon : nitrogen ratio (C:N ratio) of living things and their residues is essential for determining the outcomes of many processes. The first thing to understand about plants is that the carbon is fairly constant in the break-up, it is the nitrogen that varies. Most trees are about 50% carbon while grasses are about 45% carbon. Like all figures used in plant analysis, this is based on a dry weight.

As the plants are the start of the two food chains, above and below the ground, the C:N ratio of the plants will determine how efficient these other consumption processes are. In plants, nitrogen is necessary for chlorophyll synthesis, and as part of the chlorophyll molecule, is involved in photosynthesis. It is chlorophyll that gives the plant its green colour. Lack of nitrogen and chlorophyll means that the plant will not utilise sunlight as an energy source to carry out its essential functions such as nutrient uptake. A badly managed pasture with low soil carbon levels, and hence lower nitrogen levels, struggles with carbon introduction following rain, due to a lack of nitrogen. Dysfunctional landscapes become increasingly infertile, because they have a low potential for capturing new resources. Carbon / Nitrogen (C/N) ratios are important. Plant and animal residues that
have a C/N of 30:1 and over, have too little N to allow for rapid decomposition.
Therefore, the microorganisms will take ammonium and nitrate out of the soil to
fuel decomposition. This depletes the soil of nitrate and ammonium. Plants and animal residues with low C/N ratios (20:1 and less) have sufficient N for the microorganisms to decompose the residues without taking from the soil. High C/N ratio: Decomposition is slower; microorganism will deplete soil of nitrate and ammonium until they die and release nitrate and ammonium. Low C/N ratio: Decomposition is rapid due to higher nitrogen within the plant; microorganisms are satisfied with plant N. When microorganisms die, nitrate and ammonia are released,
increasing soil N.

Front 9

Explain, with examples, what exploitation, interference and intraspecific competition have in common and how they differ.

Back 9

What they have in common: All forms of competition, which only occurs if there is a negative effect on growth, survival or reproductive rates.
How they differ:
Interspecific Competition: Competition between individuals of the same species. Example: grasshoppers competing for food.
Exploitation Competition: Depleting resources without actually interacting. Example: grasshoppers competing for food that never meet each other.
Interference Competition: Interfering with feeding or ranging. Example: Vultures fighting over a carcus, or birds fighting over territory such that they deny other birds access to that space.

Front 10

Describe the various changes in climate that occur with changing latitude, including an explanation of why deserts are more likely to be found at around 30o latitude than at other latitudes.

Back 10

The tilt and rotation of the earth determines large-scale patters of rainfall, temperature and solar radiation. Because the equator is tilted towards the sun, equatorial and tropical areas receive more direct sunlight and are warmer than other latitudes. Warm air holds more moisture than cold air, increasing the water-holding capacity of air around the tropics. Air that was warmed in the tropics and lost its moisture as local rain, descends at latitudes of 30 degrees N and S. The air mass warms as it decends, increasing its capacity to hold water and causing the descending air mass to soak up available water from the land. As a result, there is where most of the major deserts are found.

Front 11

The tropical rain forest is a diverse community supported by nutrient-poor soils. Account for this.

Back 11

The tropical rainforest is a woody area dominated by tall trees with a large forest canopy, low forest floor vegetation, limited ground level light, high species diversity, high temperatures and sufficient water supply. The forest area is often collectively joined by vines reaching from the trunk of the trees into the canopy in an attempt to gather light. Surface soil is rich due to decomposition of forest litter from the canopy, but root systems are not deep because they quickly absorb the decomposed nutrients from the litter and stay near the surface of the forest floor. Rainforest soils have been subjected to disparities in geology, landscape, drainage and climate that have made it subject to low mineral content. Most of the nutrients plants need to grow in rainforests are stored within the plant itself, so the soil in the rainforest is severely lacking in compounds like oxygen, carbon, hydrogen and nitrogen. Species diversity is high due to a large number of narrow niche differences in individual populations. Productivity is high as resources grow year round due to a lack of seasonality. Competition is typically between neighboring species for light above the canopy.

Front 12

Discuss some reasons why community composition changes as one moves (1) up a mountain and (2) down the continental shelf into the abyssal depths of the ocean.

Back 12

Mountain: Temperature falls with increasing altitude, and one effect is that vegetation high on a mountain in the tropics tends to resemble vegetation at low altitudes in northern latitudes. Moving up the mountain is like moving from the equator to the pole.
Abyssal: The greatest area of marine productivity is where there is a reliable supply of minerals.The abyssal environment supports very low biological activity of a communityraordinary biological diversity (worms, crustaceans, fish and mollusks found nowhere else) which depends on rain of dying and dead organisms falling from above.

Front 13

Why are broad geographic classifications of aquatic communities less feasible than broad geographic classifications of terrestrial communities? What characteristics of aquatic communities buffer the effects of climate?

Back 13

The dominating characteristics of aquatic envrionments result from the physical properties of water.It remains liquid over a wide range of temperatures and varies little over seasons.

Front 14

Contrast the derivation of cohort and static life tables and discuss the problems of constructing and/or interpreting each.

Back 14

Cohort life table: A life table created by monitoring a group of individuals all born during the same short period, from time of birth through to the death of the last surviving individual. These are difficult to construct because it may be impossible to mark enough individuals early enough in their life so that they can be recognized and followed in subsequent years.
Static life table: A life table created from the age of all individuals in a population at a single moment in time. The difficulty with constructing this is that sometimes we may have to estimate the age of an individual based on certain factors (like condition of teeth in deer). When interpreting this table, one would have to assume that rates of birth and death are, and have previously been, constant - a very big assumption.

Front 15

Describe what are meant by aggregated, random and regular distributions of organisms in space, and outline, with actual examples where possible, some of the behavioral processes that might lead to each type of distribution.

Back 15

Aggregated distribution: The distribution of organisms in which individuals are closer together than they would be if they were randomly or evenly distributed.
Random distribution: Lacking pattern or order. The result of (or indistinguishable from the consequence of) chance events.
Regular distribution: The arrangement of individuals with respect to each other which has some pattern or order that ensures that they are more widely separated from each other than would be expected by chance.

Front 16

What is meant by the carrying capacity of a population? Describe where it appears, and why, in (1) S-shaped population growth, (2) the logistic equation, and (3) dome-shaped net recruitment curves.

Back 16

Carrying capacity: The maximum population size that can be supported indefinitely by a given environment, where intraspecific competition has reduced the net rate of increase to zero. This is an idealized concept not to be taken literally in practice. It appears when density dependent birth and density dependent mortality cross.

S-shaped growth curve has a pattern of growth in which, in a new environment, the population density of an organism increases slowly initially, in a positive acceleration phase; then increases rapidly, approaching an exponential growth rate as in the J-shaped curve; but then declines in a negative acceleration phase until at zero growth rate the population stabilizes. This decline reflects increasing environmental resistance which becomes proportionately more important at higher population densities. This type of population growth is termed density-dependent, since growth rate depends on the numbers present in the population. The point of stabilization, or zero growth rate, is termed the saturation value (symbolized by K) or carrying capacity of the environment for that organism.

The simple Logistic Equation is a formula for approximating the evolution of an animal population over time. Many animal species are fertile only for a brief period during the year and the young are born in a particular season so that by the time they are ready to eat solid food it will be plentiful. For this reason, the system might be better described by a discrete difference equation than a continuous differential equation. Since not every existing animal will reproduce (a portion of them are male after all), not every female will be fertile, not every conception will be successful, and not every pregnancy will be successfully carried to term; the population increase will be some fraction of the present population.This model produces exponential growth without limit. Since every population is bound by the physical limitations of its surrounding, some allowance must be made to restrict this growth. If there is a carrying-capacity of the environment then the population may not exceed that capacity. If it does, the population would become extinct.

Net recruitment is the number of births minus the number of deaths in a population over time. When densities are low, net cruitment will be low becase there are few individuals available eiether to give birth or to die. Net recruitment will also be low at much higher densitites as the carrying capacity is approached. Net recruitment will be at its peak, then, at some immediate density. The result is a "humped" or "dome-shaped" curve. This curve reflects the essence of net reccruitment patterns when density-dependent birth and death are the result of intraspecific competition.

Front 17

Some experiments concerning interspecific competition have monitored both the population densities of the species involved and their impact on resources. Why is it helpful to do both?

Back 17

Because they are looking at which species are more effective exploiters of resources, and whether or not they will develop niche differences. The competive exclusion princple says that if to competing species coexist in a stable environemnt, then they do so as a result of niche differentiation. If, however, there is no such differentiation, or if it is precluded by the habitat, then one competing species will eliminate or excluse the other.

Front 18

Define the fundamental niche and the realized niche. How do these concepts help us to understand the effects of competitors?

Back 18

Fundamental niche: the combination of conditions and resources that allow that species to exist, grow and reproduce when considered in isolation from any other species that might be harmful to its existence.
Realized niche: the combination of conditions and resources that allow it to exist, grow and reproduce in the presence of other specified species that might be harmful to its existence - especially interspecific competitors.

Species can coexist when both are provided with a realized niche by their habitat; but even in locations that provide species with the requirements of its fundamental niche, that species may be excluded by another, superior competitor that denies it a realized niche there.

Front 19

Explain how environmental heterogeneity may permit an apparently “weak” competitor to coexist with a species that might be expected to exclude it.

Back 19

Environmental heterogeneity is resource patchiness. A species that is a "weak" competitor in a constant environment, might, for example, be good at colonizing open gaps created in a habitat by fire, or a storm, or the hoofprint of a cow in the mud - or may be good at growing rapidly in such gaps immediately after they are colonized. It may then coexist with a strong competitor, as long as new gaps occur frequently enough.

This explains the co-occurence of species that in constant, homogeneous environments would probably exclude one another. The environment is rareley unvarying enough for competitive exclusion to run its course or for the outcome to be the same across the landscape.

Front 20

What is the “ghost of competition past?” Why is it impossible to prove an evolutionary effect of interspecific competition?

Back 20

Ghost of competition past: A term coined by J.H. Connell to stress that interspecific competition, acting as an evolutionary force in the past, has often left its mark on the behaviour, distribution or morphology of species, even when there is no present-day competition between them.

By invoking something that cannot be directly observed (in this case evolution), it may be impossible to prove an evolutionary effect of interpecific competition, in the strict sense of proof that can be applied to mathematical theorems or carefully controlled experiments in a lab.

Front 21

With the aid of examples, explain the feeding characteristics of true predators, grazers, parasites, and parasitoids.

Back 21

True predator: A predator which kills other organisms (their prey) more or less immediately after attacking them, killing several or many over the course of its lifetime. Example: lions, tigers and bears

Grazer: A consumer which attacks large numbers of large prey during its lifetime, but removes only a part of each prey individual, so that the effect, although often harmful, is rarely lethal in the short term, and never predictably lethal. Example: cattle, sheep, locusts, blood-sucking leeches

Parasite: An organism that obtains its nutrients from one or a very few host individuals causing harm but not causing death immediately. Example: tapeworms, mistletoes

Parasitoid: Insects (mostly wasps and flies) in which the adults are free-living, but eggs are laid in, on or near an insect host (or rarely, a spider or isopod), after which the parasitoid larva develops in the host (itself usually a pre-adult), initially doing little apparent harm, but eventually consuming and killing the host before or during the pupal stage. Example: flies and wasps whose larvae consume their insect larva host from within

Front 22

True predators, grazers and parasites can alter the outcome of competitive interactions with their “prey” populations; discuss this assertion using one example for each category.

Back 22

When there is plenty of good food, and no competition, the effects of predation should be detectable. When food is short and competition is intense, predation may relieve competitive pressures and allow individuals to survive who might not otherwise do so.

True predators: Spiders and grasshoppers in fertilized field. Large predators concentrate on the old and young, who don't contribute to reproduction.

Grazers:

Parasites:

Front 23

Explain why an understanding of life-history trade-offs is central to an understanding of life-history evolution. Explain the contrasting trade-offs expected to be exhibited by r-selected and K-selected species.

Back 23

Life history theory says that the schedule and duration of key events in an organism's lifetime are shaped by natural selection to produce the largest possible number of surviving offspring. These events, notably juvenile development, age of sexual maturity, first reproduction, number of offspring and level of parental investment, senescence and death, depend on the physical and ecological environment of the organism. Organisms have evolved a great variety of life histories, from Pacific salmon, which produce thousands of eggs at one time and then die, to human beings, which produce a few offspring over the course of decades.

r species: Those species with the ability to multiply rapidly in environments that are short-lived, allowing organisms to colonize quickly and exploit new resources. They produce large numbers of progeny, early in the life cycle, rather than investing heavily in either growth or survival. Their habitats are called r-selecting.

Kspecies: Organisms that surviv in habitats where there is intense competition for limited resources. Those that are successful leave behind dependents because they were able to capture and hold on to the larger share of resources. Their populations are crowded and they win a struggle for existence because they've grown faster or larger or spent more of their resources in aggression or some other activity that favors their survival in crowded conditions. They spend most of their lives bumping up against the limits of environmental resources. Their habitats are called k-selecting.

Front 24

In a mark-recapture exercise during which a population of butterflies remained constant in size, an initial sample provided 70 individuals, each of which was marked and then released back into the population. Two days later, a second sample was taken, totaling 123 individuals of which 47 bore a mark from the first sample. Estimate the size of the population. State any assumptions that you have had to make in arriving at your estimate.

Back 24

Initial sample was 70; all marked. 2nd sample was 123, with 47 marked. 47/123 = 38% that were found marked. Since 70 were initially marked, 70 is 38% of 184.

Front 25

Discuss the ways that plants may “compensate” for the effects of herbivory.

Back 25

Herbivory: The consumption of living plant material.

The removed leaves can improve the balance between photosynthesis and respiration. After an herbivore attack, plants can compensate by utilizing reserves stored in a variety of tissues and organs, or by altering the distribution of photosynthate within the plant. They can increase the rate of photosynthesis per unit area of surviving leaf, or have compensatory regrowth of defoliage when buds that would otherwise remain dormant are stimulated to developed. There can also be a reduced death rate of the surviging plant parts.

Front 26

Discuss the pros and cons, in energetic terms, of (1) being a generalist as opposed to a specialist predator, and (2) being a sit-and-wait predator as opposed to an active forager.

Back 26

Generalist: Pro: Can get nectar or pollen from any source and distribute it to any source. Con: ineffective pollinator because fertilization may not occur on correct plant.
Specialist: Pro: Developed adaptations to get nectar and pollen from specific sources, and as they feed on more of those specific sources, effectively fertilize new plants of the same species. Con: Pollinator must be forced into a position where he maximizes the efficiency of pollination.

Sit and Wait: Ambush predators or sit-and-wait predators are carnivorous animals that capture prey by stealth or cunning, not by speed or necessarily by strength. These organisms usually hide motionless and wait for prey to come within striking distance. They are often camouflaged, and may be solitary. This mode of predation may be most efficient when a predator cannot move faster than its preferred prey; otherwise, active hunting is more efficient. (Example: Frog and fly) Pro: Expend less energy. Con: Have to wait for prey.

Active Forager: Active foraging is favored when the cost of moving is small or the difference between good and poor sites is large. Pro: Can move from a poor site to a good one. Con: expend more energy in predation.

Front 27

You have data that shows cycles in nature among interacting populations of a true predator, a grazer, and a plant. Describe an experimental protocol to determine whether this is a grazer-plant cycle or a predator-grazer cycle.

Back 27

Check Chapter 7

Front 28

Why are some plants more likely than others to be involved in arms races with their insect herbivores?

Back 28

Plants can produce plant-defensive chemicals that are divided into qualitative chemicals that are poisonous, can kill in small doses and teend to be induced by herbivore attakes, and quantitative chemicals that are digestion-reducing, relying on an accumulation of ill effects. Plants relying on toxins are more prone to becoming involved in arms races with their herbivores than those relying on more quantitative chemicals, because these chemicals will select for adaptations in herbivores that can overcome them.

Front 29

Account for the decline in virulence of the myxomatosis virus in European rabbits after its initial introductions into Europe and Australia

Back 29

Rabbits were favored by natural selection in the presence of the myxoma virus. It was intially thought that parasites evolved towards becoming benign to their host to prevent their host from dying and eliminating its habitat. That was incorrect. In actuality, the virus was blood-corne and transmitted from host to host by blood-feeding insect visitors. In the first 20 years aftr its introduction, the main vectors were mosquitoes, which feed only on live hosts. The virus killed the host so quickly that there was only a short time for the mosquito to transmit the disease. Thus, selection was for increased transmissability and increased fitness so the disease could be transmitted.

Front 30

Discuss the following propositions: ‘Most herbivores are not really herbivores but consumers of the byproducts of the mutualists living in their gut’ and ‘Most gut parasites are not really parasites but competitors with their hosts for food that the host has captured.’

Back 30

Check Chapter 8

Front 31

Compare the roles of fruits and nectar in the interactions between plants and the animals that visit them.

Back 31

Plants and insects have complex, integrated ecological systems that have been studied for years. The core of their symbiotic relationship is the concept of flower visits by insects for food consumption that ultimately serves the purpose of plant pollination. Plants are unable to reproduce themselves without cross-pollination of their species that can only occur through wind transmittal, water transmittal or through the distribution of pollen. In order to survive, they must rely on a mutualistic relationship with insects occurring through natural selection. These insects serve as pollinators to other members of the same species within their community, and can also transport pollen to new ecosystems where flowers can be birthed as a new species in another community. Animals distribute pollen when it sticks to their feathers or hairs (which the animals later scratch off on another plant of the same species). Since most insect individuals go to plants in order to enjoy the nectar inside, they brush against the flowers as they feed. During this process pollen is attached to the insects, and as they travel to different communities, many plant species are mistakenly or consciously presented into new bionetworks. Pollination via insects is more effective than wind or water processes, because it delivers more pollen directly to members of the same species and does not waste the pollen on the ground or on non-species individuals. This is primarily due to the foraging behavior of insects, or the nature in which they look for, eat and store food, all of which is strongly determined by natural selection. Focusing on the habitat the plant individual is located in, the patch where the flower is located and the food the plant is offering, insects tend to forage in such a way that they make the most of their nutrient opportunities and reduce the threat to their survival. Through the selection process, insects forage plant species and individual flowers based on the color of the petals, the shape of the flowers, the size of the individual and the smell or amount of nectar. Plant individuals have developed these indicators to attract plant visitors and to notify them that nectar or food is available for their consumption. Charles Darwin studied Aquilegia and insects attempting to retrieve the nectar from plants. He discovered that the more successful insects had long tongues able to extract the liquid from the nectaries. Because the plants were attempting to have their pollen delivered more effectively to plants of their same species, they evolved even longer nectaries which made access to the nectar more difficult. In return, the more successful plant visitors evolved longer tongues in order to forage the longer plant nectaries for food. As the insects flew from plant to plant of similar species consuming the nector, they more effectively delivered the pollen for Aquilegia to the corresponding members of their species. This coevolution allowed forager and flower to both develop a beneficial mutualistic relationship that aided both species survival.

Front 32

What are mycorrhizas and what is their significance?

Back 32

A commonly mutualistic and intimate association between the roots of a plant and a fungus.
Ectomycorrhiza: An association of a fungus and the root of a plant (usually a tree) in which the fungus forms a sheath around the root and penetrates between the cells of the host
Vesicular arbuscular mycorrhiza (VAM): An intimate and perhaps usually mutualistic association between a fungus and a plant root in which the fungus enters the host cells and also usually extends widely into the surrounding soil

Front 33

Construct a flow diagram (boxes and arrows) with a named population at its center to illustrate the wide range of abiotic and biotic factors that influence its pattern of abundance.

Back 33

Selected species in tropical rainforest.
Abundance: The number of organisms in a population, combining 'intensity' (density within inhabited areas) and 'prevalence' (number and size of inhabited areas
Abiotic: Non-living; usually applied to the physical and chemical aspects of an organism's environment.
There are more species in the tropics because the tropics have existed longer than any other biome (they were part of the Pangaea before the Continental Drift); tropic species are more productive, and are able to have more biomass and support greater diversity.
Biotic: Living; usually applied to the biological aspects of an organism's environment, i.e. the influences of other organisms. Heterogeneity - the more spacially diverse, the greater the species richness; competition - species are natually selected for that environment, so those less successful either go extinct, move to a new environment, or develop adaptations that develop into a new species that allows them to be more successful in that environment; predation - creates niches for possible prey to evolve into.

Front 34

What is meant by a “metapopulation” and how does it differ from a simple “population”?

Back 34

Population: A group of individuals of one species in an area, though the size and nature of the area is defined, often arbitrarily, for the purposes of the study being undertaken.
Metapopulation: A population perceived to exist as a series of subpopulations, linked by migration between them. However, the rate of migration is limited, such that the dynamics of the metapopulation should be seen as the sum of the dynamics of the individual subpopulations.

Front 35

What are meant by bottom-up and top-down control? How is the importance of each likely to vary with the number of trophic levels in a community?

Back 35

Top-Down Control: He has also found that the removal or population decline of large carnivores can alter plant species composition, particularly the balance between large- and small-seeded plants, due to increased seed and seedling predation by superabundant herbivores that are normally regulated by large carnivores.

Bottom-Up Control: driven by energy moving up the food web (trophic levels) from plants to herbivores to carnivores.

The trophic level of an organism is the position it occupies on the food chain.

Level 1: Plants and algae make their own food and are called primary producers.
Level 2: Herbivores eat plants and are called primary consumers.
Level 3: Carnivores which eat herbivores are called secondary consumers.
Level 4: Carnivores which eat other carnivores are called tertiary consumers.
Level 5: Apex predators which have no predators are at the top of the food chain.

Front 36

How do keystone species help maintain species diversity? Give examples of different types of keystone species operating at different levels of a food web.

Back 36

Species who enrich ecosystem function in a unique and significant manner through their activities, and the effect is disproportionate to their numerical abundance. Their removal initiates changes in ecosystem structure and often loss of diversity. These keystones may be habitat modifiers (ie. cottonwoods, rushes and ironwood), keystone predators (ie. puma and coyote) or keystone herbivores (ie. prairie dog and beaver).

classic keystone species is a small predator that prevents a particular herbivorous species from eliminating dominant plant species. Since the prey numbers are low, the keystone predator numbers can be even lower and still be effective. Yet without the predators, the herbivorous prey would explode in numbers, wipe out the dominant plants, and dramatically alter the character of the ecosystem.

Example: Sea otters in the kelp forest food web. Because they lack the blubber of other marine mammals, individual sea otters need to consume a huge amount of food each day to stay warm and healthy.

Front 37

Explain species richness, diversity index and the rank-abundance diagram and compare what each measures.

Back 37

Species richness: The number of species present in a community.
Diversity index: A mathematical index of species diversity in a community.
Rank - abundance diagram: A graphical plot of differential abundances of species in a community.

Front 38

Explain, with examples, the contrasting effects that predation can have on species richness.

Back 38

Predation is an interaction between species in which one species uses another species as food. Predation is a process of major importance in influencing the distribution, abundance, and diversity of species in ecological communities. Generally, successful predation leads to an increase in the population size of the predator and a decrease in population size of the prey. These effects on the prey population may then ripple out through the ecological community, indirectly changing the abundances of other species. One example of such indirect effects of predation involves the trophic cascade. As the name implies, a trophic cascade occurs when the effects of predation "cascade" down the food chain to affect plants or other species that are not direcrtly eaten by the predator. Typically, a trophic cascade involves a predator feeding on herbivores and reducing their abundance, which then releases plants from grazing pressure and increases the biomass of vegetation.

Predation can either increase or decrease the number of species that coexist in a community, depending on the favorability of the environment and on the competitive status of the preferred prey species. For example, a keystone predator is one that feeds on a competitively dominant prey species. By reducing the dominant prey's abundance, the keystone predator releases competitively inferior prey from suppression by that dominant species. As a result, keystone predation allows more prey species to coexist within the community than would be possible in the absence of predation, and thus increases species richness within the community (predator-mediated coexistence). Conversely, when a predator feeds preferentially on competitively inferior prey species, predation can further reduce the number of species in the community. In environments that are favorable for prey, competition among prey species will be stronger, such that keystone predation can be important in reducing competitive exclusion among prey and thus increasing species richness. In unfavorable environments, on the other hand, most prey species are stressed or living at low population densities such that predation is likely to have negative effects on all prey species, thus lowering species richness

Front 39

Researchers have reported a variety of hump-shaped patterns in species richness, with peaks of richness occurring at intermediate levels of productivity, predation pressure, disturbance and depth in the ocean. Review the evidence and consider whether these patterns have any underlying mechanisms in common.

Back 39

Productivity: The rate at which biomass is produced per unit area by any class of organisms.
Disturbance: In community ecology, an event that removes organisms and opens up space which can be colonized by individuals of the same or different species.

Humped shaped patterns show that species richness may be highest at intermediate levels of productivity. Species richness declines at the lowest productivities because of a shortage of resources, but also declines at the highest productivities where competitive exclusions speed rapidly to their conclusion. When communities differing in productivity but of the same general type were compared, a positive relationship was the most common finding in animal studies, whereas with plants, humped relationships were most common, with smaller numbers of positives and negatives. There were also U shaped curves - cause unknown.
Increased productivity leads to increased or decreased species richness - or both.

Front 40

Describe how theories of species richness that have been derived on ecological timescales can also be applied to patterns observed in the fossil record.

Back 40

TBD

Front 41

Why does the equilibrium theory of island biogeography predict that species richness should be related to larger island size? Be sure to explicitly discuss the assumptions of the models when comparing a set of neighboring islands, and the principles of population ecology that underlie the model.

Back 41

Equilibrium theory: A theory of community organization that focuses attention on the properties of the system at an equilibrium point, to which the community tends to return after a disturbance.
Biogeography: The study of the geographical distribution of organisms.
Population ecology: The study of the variations in time and space in the sizes and densities of populations, and of the factors causing those variations.

Front 42

Describe the general latitudinal trends in net primary productivity. Suggest reasons why such a latitudinal trend does not occur in the oceans.

Back 42

Primary productivty: The rate at which biomass is produced per unit area by plants, the primary producers. It can be expressed either in units of energy or of dry organic matter.

Gross primary productivity: The total fixation of energy by photosynthesis .

Respiratory heat: heat respred away from the plant during photosynthesis.

Net primary production (NPP): The difference between GPP and R. Represents the actual rate of production of new biomass that is available for consumption by heterotrophic organisms (bacteria, fungi, mammals).

Front 43

What evidence suggests that the productivity of many terrestrial and aquatic communities is limited by nutrients?

Back 43

TBD

Front 44

. Outline the role played by bacteria and fungi (decomposers) in the flux of energy and matter through a named ecosystem. Imagine what would happen if bacteria and fungi were magically removed- describe the resulting scenario in detail.

Back 44

Responsible for the majority of secondary production, and therefore respiratory heat loss in every community of the world.

The decomposer system plays its greatest role where vegetation is woody - forests, shrublands, and mangroves.

Bacteria and fungi start the process of decomposition if a scavenger animal does not eat the dead resource immediately. Decomposistion breaks material back down to carbon dioxide and minerals to be entered back in to the environment.
Decomposers: Organisms that breakdown complex, energy-rich organic molecules to simple inorganic constituents.

Front 45

The hydrological cycle would proceed whether or not a biota was present. Discuss how the presence of vegetation modifies the flow of water through an ecosystem.

Back 45

Hydrological cycle: The movement of water from ocean, by evaporation, to atmosphere, to land and back, via river flow, to ocean.
Biota: The fauna and flora together; all the living organisms at a location.
Ecosystem: The plants and animals in a habitat and all the physical and chemical components of the immediate environment or habitat which together form a recognizable self-contained entity.

Front 46

What is sustainability? Is it possible to have sustainable population growth? Sustainable use of fossil fuels? Sustainable use of forest trees? Justify your answers.

Back 46

The ability for an activity to be continued or repeated for the foreseeable future.

No, because we cannot go on using these resources indefinitely without impact. They are not inexhaustible. We would have to create more resources to support the population growth (technological advances may help this, but it doesn't meet the foreseeable future requirement). We cannot create new fossil fuels. We can plant new trees, but not at a rate fast enough to replish all we use if we have unrestricted growth.

Front 47

. Contrast the ways in which “fixed quota” and “fixed effort” harvesting strategies seek to extract maximum sustainable yields from natural populations.

Back 47

Through fixed quota MSY harvesting, the same amount, the MSY, is removed from the population every year. If the population stayed exactly at the peak of its net recruitment curve then this would work: each year the members of the population, through their own growth and reproduction, would add exactly what the harvesting removed. But, if by chance the numbers feel even slightly below those at which the curve peaked, then the numbers harvested would exceed those recruited. Population would decline to below the peak of the curve, and if the MSY quota was maintained, the population would continue to decline until it was extinct. Also, if the MSY harvesting rate was slightly overestimated, the harvesting rate would exceed the recruitment rate and extinction would again occur.

Fixed effort is an attempt to increase the amount harvested with the size of the population so that if density drops below the peak, new recruitment is larger than the amount harvested and the population recovers.

Front 48

Discuss the pros and cons of agricultural monocultures. Describe the features of indigenous shifting cultivation systems that make them sustainable but unattractive models in most contexts. (note-this is a change from the original text).

Back 48

Agricultural monocultures: dense populations of single species (like rice or cattle raised specifically for food). Pros: This allows them to be managed in specialized ways that can maximize their productivity so that it meets our human demand.

Con: There is a high price for the methods used, such as the spread of disease because animals are kept at such high density levels.

Front 49

Weigh up the advantages and disadvantages of the chemical and biological control of pests.

Back 49

Chemical control of pests: Advantages: kills unwanted pests, keeps pests from causing economic injury, keeps them from attacking crops. Disadvantages: Can kill more species than the one targeted and become a pollutant, can cause the enemy population to be killed and increase the target population, can increase the rise of potential pests kept at prey by their enemies, can have the pests evolve resistance to them, and there are social and health costs for using them.

Biological pest control has similar Pros as the Chemical pest control. Cons: Introduction of new species to control a target species can inadvertently affect a non-targeted species.

Front 50

What are the features that distinguish human pollution of the environment from that by other social organisms?

Back 50

We degrade our environment at a much faster rate due to our activities:
Soil loss from mass agriculture
Chemical degredation from pesticides and fertilizer
Burning fossil fuels
Fisheries overexploited
Loss of tropical resources
Acid rain from pollution

Other organisms' pollution levels are small: feces, dead bodies, fallen debris,etc.

Front 51

Describe the causes of acid rain and the way in which it damages terrestrial and aquatic communities.

Back 51

Acid rain is rain containing acids that form in the atmosphere when industrial gas emissions (especially sulfur dioxide and nitrogen oxides) combine with water.

Human activities are the main cause of acid rain. Over the past few decades, humans have released so many different chemicals into the air that they have changed the mix of gases in the atmosphere. Power plants release the majority of sulfur dioxide and much of the nitrogen oxides when they burn fossil fuels, such as coal, to produce electricity. In addition, the exhaust from cars, trucks, and buses releases nitrogen oxides and sulfur dioxide into the air. These pollutants cause acid rain.

Acid rain on the forest floor makes the soil more acidic. It damages the leaves on trees and deprives them of vital nutrients. In aquatic systems, acid rain can harm or kill individual fish, reduce fish population numbers, completely eliminate fish species from a waterbody, and decrease biodiversity

Front 52

Define the characteristics that make some pesticides particularly dangerous pollutants.

Back 52

They containt Persistent organic pollutants (POPs) or organic compounds that are resistant to environmental degradation. They are toxic, stay in the environment for an extended amount of time, can pass through the food chain and can cause cancer.

Front 53

Define the greenhouse effect and list the pollutants that contribute to it.

Back 53

Greenhouse gases are gases in an atmosphere that absorb and emit radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The main greenhouse gases in the earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide and ozone.

Front 54

Species may be “rare” on three counts: what are these? Use either examples from the book or your own experience to illustrate these (note-this is a change from the original text).

Back 54

1. Geographic range is small
2. Its habitat range is narrow
3. Local populations are small (perigrine falcon)

All three are small for the panda, which is why it is considere to be close to extinction.

Front 55

Unpredictable temporal variability is a feature of most ecosystems. How can conservation biologists allow for such uncertainty when they devise species management plans?

Back 55

Temporal variation: Variability in conditions, such as temperature, on an hourly, daily or seasonal basis.

Match agricultural inputs and practices to localized conditions within a field. Manage using site-specific management recommendations and accurate input control technologies. Understand the economic, environmental, and social impacts on the farm and adjacent ecosystems.

Front 56

Explain, with examples, how the loss or introduction of a single species can have conservation consequences throughout a whole ecological community?

Back 56

TBD

Front 57

Why is restoration ecology said to be an “acid test” of ecological understanding?

Back 57

Restoration ecology: The science concerned with the deliberate colonization and revegetation of derelict land, especially after major damage from activities such as mining and waste disposal and after land has been released from agricultural use.

Front 58

What is a Minimum Viable Population, and how does Population Viability Analysis assist in developing species conservation plans?

Back 58

Minimum viable population (MVP) is a lower bound on the population of a species, such that it can survive in the wild. Population viability analysis (PVA) is a species-specific method of risk assessment frequently used in conservation biology. It is traditionally defined as the process that determines the probability that a population will go extinct within a given number of years. More recently, PVA has been described as a marriage of ecology and statistics that brings together species characteristics and environmental variability to forecast population health and extinction risk. Each PVA is individually developed for a target population or species, and consequently, each PVA is unique. The larger goal in mind when conducting a PVA is to ensure that the population of a species is self-sustaining over the long term.

Front 59

Wednesday Section question

Back 59

TBD

Front 60

1. In many species, both survivorship and reproduction are density-dependent.
a) Draw two lines showing these relationships on a single graph below; be sure to label the axes.
b) What is the significance of the point where they intersect?

Back 60

TBD

Front 61

The earth’s biomes can be plotted on a graph of average minimum monthly temperature against total annual rainfall. Label the axes on a graph and indicate on the graph where typical values of these two variables for savanna, tropical forest and tundra are located.

Back 61

TBD

Front 62

. Plot curves for a) exponential and b) logistic population growth and write the equations for each.
c) define all the terms in these equations.

Back 62

TBD

Front 63

One tradeoff in life-history evolution is the allocation of resources to either growth or reproduction. Illustrate this for a hypothetical oak tree. Be sure to specify the variables for the two axes.

Back 63

TBD

Front 64

Show on a graph how the probability of extinction is related to population size for a) a large mammal (bears, primates, etc.) vs. an insect population. Draw two lines showing these relationships on a single graph below; be sure to label the axes.

Back 64

TBD

Front 65

On one graph, draw two lines showing how the number of bird species is expected to vary with island size for a) low elevation islands formed by uplifted coral deposits; and b) mountainous islands derived from continental shelf geology.

Back 65

TBD

Front 66

Show graphically how the equilibrium number of species is determined on islands of varying size and distance from a source of colonizing species. Be sure to label the axes of the graph.

Back 66

TBD

Front 67

How has the atmospheric concentration of carbon dioxide changed over the last 250 years?

Back 67

TBD

Front 68

Draw the population fluctuations of a hypothetical insect pest over time, indicating where its equilibrium abundance and hypothetical economic injury level might occur.

Back 68

TBD

Front 69

Draw a curve showing the growth in the Earth’s total human population size from year 0 to present, and contrast this with curves fitted to both exponential and logistic population growth. What explains the discrepancy?

Back 69

TBD

Front 70

Draw graphs specifying how plant species richness changes with:
a) latitude; b) elevation at a specific latitude; c) productivity; d) age of an old field vegetative succession

Back 70

TBD

Front 71

Draw graphs specifying how plant species richness changes with:
a) latitude; b) elevation at a specific latitude; c) productivity; d) age of an old field vegetative succession

Back 71

TBD