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Environmental Biology Exam 1


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What is the oxygen revolution, when did it occur, and why is it revolutionary?
~ 3.5-3.2 BYA: along with first photosynthetic organisms, atmosphere became oxygen-rich allowing aerobic respiration to become the dominant energy-releasing path
Distinguish the light and dark cycles of photsynthesis
Light: captures light and turns it into chemical energy
Dark: converts CO2 into sugars and other molecules
What is sexual selection and why does it occur?
Selection for traits that increase the ability to attract a mate (occurs more often in males). Can be by female choice. It occurs because if you have traits that attract you to a mate, you will pass on your genes. In other words, males must compete to get attention from females.
What is kin selection and why does it occur?
Altruistic behavior can occur when an individual tries to increase the survival or reproduction of its kin because it helps them pass on their genes
How might we use photosynthetic pigments to measure forest health?
A forest is less healthy when it has more visible pigments, because it means the trees are absorbing less light
Contrast photosynthesis and respiration
Photosynthesis: uses light energy to create sugars

Respiration: breakdown of biochemicals to release energy (opposite of photosynthesis)
Contrast gross primary productivity and net primary productivity
Gross primary productivity: the total amount of photosynthesis in an area over time (i.e. the amount of energy available to producers)

Net primary productivity: the amount of energy invested in new plant tissue and not used for cellular respiration (i.e. the amount of energy available to consumers)
Natural selection
The process by which individuals with certain traits produce more offspring than those without those traits, resulting in a change in the genetic makeup of the population
Contrast Lamarckian and Darwinian evolution
Lamarck: individuals change and pass their traits onto their offspring

Darwin: traits are selected and populations change over time to acquire these traits
What is a p-value and why is it useful?
A high p-value tells you that observed patterns could have arisen by chance, while a low p-value tells you that observed patterns (i.e. differences between samples) are probably real.
When do you use a t-test? What about a regression? ANOVA?
t-test: compare two groups of continuous data. two tail if you don't have hypothesis about a reason for differences between samples, one tail if you do have a hypothesis

regression: how directly related are two variables (i.e. do they increase at the same rate?)

ANOVA: similar to t-test, compares variation between groups, so helpful if you have a hypothesis that knowing what group something is part of is important
What is a null hypothesis?
A hypothesis that states what the results would be if the main hypothesis is wrongs, i.e. that there will be no difference between experimental groups
What is an ecosystem?
The self-contained abiotic and biotic components of a community --> the organisms and abiotic components that affect or exchange material with the organisms
What ecosystems do humans live in? What do we conserve and why?
Humans live in highly productive habitats (ones with lots of resources) and product low productivity habitats
How does nitrogen flow through an ecosystem?
atmosphere --> organic compounds --> plants --> ecosystem
How has the nitrogen cycle changed in modern times? How are we re-arranging the biochemical pools?
Global nitrogen levels are increased by fertilizers, human-grown nitrogen fixing plants, and fossil fuels. Humans don't bring new nitrogen into the world but "unlock" it and put it into other parts of the N cycle
What are limiting resources?
An essential resource whose scarcity in the environment limits growth and reproduction
What factors control net primary productivity?
species richness, limiting nutrients
Contrast primary producers, primary consumers, and secondary consumers
Primary producers: base of the terrestrial food chain

Primary consumers: herbivores; eat plants (producers)

Secondary consumers: carnivores; eat primary consumers
How might the biomass of producers, primary consumers and secondary consumers differ?
Lower trophic levels should have more biomass because they need to be more abundant to support higher trophic levels
Use an energetic argument to argue for and against vegetarianism
Veggie: it's better to eat at lower trophic levels because the grain is supporting you without the intermediate step of supporting the meat

Anti-veggie: it's more efficient to eat at trophic levels close to you because energy is lost through successive trophic levels
What is a species?
a group of populations (evolutionarily independent of other populations) made up of individuals that can mate and produce viable offspring
What is a niche?
the habitat requirements of an organism and its role in a system, so that it can produce viable offspring
What is Hutchinson's n-dymensional hypervolume?
a description of a species' niche (includes all the factors that make up this niche) --> no 2 species should have completely overlapping hypervolumes
What is habitat sharpening?
As we constrict the ranges of habitats of a species, it warps our sense of what habitats are possible for that species to live in
Contrast fundamental and realized niches
fundamental niche: range of possible conditions where you can find a particular species (the niche it would occupy in the absence of predators)

realized niche: the conditions where you actually find that species
How might a niche be altered by the presence of other species? Would it always be contracted?
Predators can kill individuals when they are only in one part of their niche. Species can have relationships with other organisms that alter the niche but don't necessarily constrain it. A mutualistic relationship might expand a species' niche.
Can a species be found outside of its fundamental niche?
Yes, because it is unlikely that a species will have no competitors at all.
Contrast source and sink habitats
Source habitat: allows a species to have a steady or increasing population

Sink habitat: habitat where a species' population is declining
What are keystone species?
A species that alters an ecosystem (for good or bad) when removed
How might immigration vary with the proximity and/or size of an island
Immigration is higher on islands that are bigger and closer to the mainland
How might extinction vary with the size of an island
There is more extinction on smaller islands
What is succession?
Recovery of species in a habitat following a disturbance.
What role does facilitation play in succession?
Facilitation: the presence of an early-arriving species makes conditions more favorable for late-arriving species by providing shade or nutrients. Facilitating species who survive disturbance make it easier for species that arive later to thrive.
What are ecosystem engineers?
A species that alters the ecosystem to fit its own needs, often by creating, modifying, or maintaining habitats (e.g. beavers)
What is a diversity-stability relationship?
Says that simple communities will be more stable than diverse ones in the face of disturbance
What is a diversity-productivity relationship?
Says that more diverse populations are more productive overall (productivity does level off at a certain point)
What is the intermediate disturbance hypothesis?
It states that communities with a moderate amount of disturbance are richest and most diverse, because different species need different amounts of disturbance to thrive
Contrast the relative importance of males and females in population biology
Females are much more important than males in population biology, because you need many more of them (eggs are expensive, sperm is cheap)
What four factors can change population size?
Birth, death, immigration, emmigration
What characteristics distinguish r-selected and K-selected species or populations?
K-selected species produce only a few larger offspring that receive more energy

r-selected species produce large numbers of offspring in a short time, but have a short life span
What is carrying capacity?
The maximum population size of a certain species that its habitat can support
Contrast the logistic and exponential growth models
Logistic growth model: shows how fast a population will grow over time given a certain carrying capacity

Exponential growth model: shows a constantly accelerating rate of increase of a population, not affected by population size/carrying capacity
How might the magnitude of r influence the severity of population fluctuations?
Populations often overshoot their carrying capacity (K), and the larger their rate of increase (r) the larger their oscillations around K
Distinguish between semelparity and iteroparity
semelparity: reproducing only once and investing a lot of energy into the offspring

iteroparity: producing a large number of offspring and investing little energy into them
What sort of information is included in a life table and how is it useful?
A life table summarizes the probability that an individual will survive and reproduce in any given year over the course of its lifetime. It includes number of individuals alive, survivorship, fecundity, and average number of offspring produced per female born
What is a metapopulation?
A population of a single species that is divided into many smaller populations
Why is a population age structure potentially useful for predicting future growth?
Evenness in age structure means growth is likely to be lower in the future, while bottom heavy structures are likely to have higher future growth because there are more reproductive individuals alive
How might a population's "effective size" differ from the number of individuals counted?
*Gender - females are the only gender that counts because they reproduce
*Age - individuals that are too young or too old to produce don't really count
What does it mean to regulate a population?
regulating a population means preventing it from growing too drastically or decreasing too drastically
What sort of forces can regulate a population? What forces cannot?
Density-dependent factors can regulate a population while density-independent factors cannot
Do all density dependent forces have similar influence on a population?
No, predation might affect a population differently than competition for resources.
What is an Allee effect?
If there aren't enough individuals, the population will decrease even if there are enough resources
How do we calculate standard error? How might it change with sample size?
se = standard deviation/square root(n)

standard error decreases as sample size increases (n)
How do you calculate standard deviation?
standard deviation = square root of [1/(n-1) x (x1-x)2] added all together
How do you calculate the Shannon-Wiener diversity index?
H = the sum of Pi log(Pi)

Pi: the proportion of the whole that a particular species takes up
e.g. .97log(.97) + .03log(.03)
How do you calculate the exponential growth model?
dN/dt = rN

r=rate of pop increase
N=# of individuals
How do you calculate the logistic growth model?
dN/dt = rN[K-N)/K]

K=carrying capacity
How do you calculate species-area curves?
S = cA^(Z)

S=# of species

as you increase z, the # of species increases

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