ecology plws review

what is an example of a community you would find at the beach?

different types of seals, species of birds (gulls ravens, sandpipers) different species of organisms living in a tidepool (seastars, anemones)

why can organisms usually not simultaneously maximize the performance of different functions?

allocation tradeoff → finite amount of resources cannot simultaneously be used to maximize all functions

what are examples of ‘slow’ life history traits, or organisms?

long lifespan, late reproduction, few reproduction events, large body size, low mortality rate

why might species with parental care be more likely to have type I survivorship curves?

parents can care for offspring, limiting juvenile morality (keeps survivorship curve high over a wide range of ages)

how does the principle of allocation explain differences between species with many small offspring versus few larger offspring?

principle of allocation: organisms have finite energy and resources

• experience tradeoffs while investing it in different functions

  • tradeoff between offspring number and offspring size; energy invested in increasing offspring size reduces the total number that can be produced

why are population growth rates useful for determining species distribution limits?

species are declining in locations where their population growth rate is negative; over long time scales → population extinction

• mapping population growth rates in different locations = map potential species range limits

what restrictive assumptions are made to derive the exponential population model

ASSUME: no immigration/emigration, constant rate of population increase that DOESNT depend on the environment, or on the density of the species (big/small populations grow at the same per-capita rate0

how can you estimate R from a graph of population size vs time?

(for exponential growth), slope of the line = R

does exponential growth mean a population is always increasing?

no, depends on ®, if r is 0 = population constant

if r (-) = population is shrinking

what units does r have

number per unit time

why can populations not increase forever at an exponential rate?

some factor becomes limiting to growth, and the existing population experiences a negative feedback that reduces the population growth rate (finite resources → fewer resources being available to catch individuals)

examples of density INDEPENDENT vs density DEPENDENT factors

INDEPENDENT: volcano eruption, change in climate, bulldozing

DEPENDENT: resource competition, fire (if dense tree populations mean hotter/more deadly fires), disease (if disease spreads more easily in denser populations)

in the logistic model, what does the plot of per-capita population growth rate vs N. look like, and how does it compare to the plot of population growth rate vs. N? biologically, how do you interpret these graphs?

per capita: straight line that has a negative slope that crosses the x-axis at N=K

population growth rate: parabola that crosses the x-axis at N=0 and N=K, with a max at N=K/2

• arises because of. balance between N and (K-N/K)

why is negative density dependence common in populations, and what ecological mechanisms cause it?

increased population density = decreased birth rates and increased death rates as a result of limited resource availability, increased competition, a reduction in available resources, increased disease prevalence, and increased risk of predation

what kinds of interactions can be + for one species and - for the other species?

predation, herbivory, parasitism

what strategies do you think squirrels use to prevent being predated by hawks or falcons?

squirrels are camouflaged (dark colored) to blend in as a hiding strategy. They can also run from predators. they can also associate with other species like humans that dissuade predators from hunting them

think of interactions that do not occur for species pairs, but do occur for species triplets?

if species A is a predator, and species B/C are prey, A may switch to preferentially eating B when C is present. or A, B, and C are microbes, A may secrete an antibiotic that harms only B, but the effect of the antibiotic may be diminished if C independently secretes another compound that inactivates the antibiotic

think of an example of mutualism involving fish

a clownfish lives in an anemone. the clownfish gets a safe place to live because the anemone stings other species. the anemone gets protection against predatory fish like butterfly fish because the clownfish will chase them off

what are ways in which individuals of a woodpecker bird species might compete with each other?

competition for insects (food), competition for mates, competition for nesting sites in trees, competition for territories to hunt for insects

give an example of a facilitative interaction in a harsh environment

in alpine environments, cushion plants create warmer, less windy and more moisture-retentive microhabitats that help each other plant species survive harsh conditions

what is a community? what are examples of communities?

community: set of populations (one or more species) that co-occur in a given place and time these populations may or may not interact with each other*

• example: all the fish and microbes in a lake

• non example: rocks and air near a mountain/ polar bears all across the world

why is scarcity a fundamental concept for thinking about ecological competiton?

when a resource is scarce, organisms cannot obtain as much of it as they need and are limited in their fitness by this resource. this leads organisms to change (via behavior. ecological distribution, evolution) to improve fitness.

• competition for resources occurs as not all organisms can obtain a full allocation of resouces. this also leads to tradeoffs as organisms may need to give up other things to be able to gain resources

why does niche partitioning reduce competition and promote coexistence

when organisms use different resources, resource scarcity is alleviated and there is less need for competition

how would you describe the realized niche of a berkeley squirrel?

axes to be thinking of**: temps between 40-90 degrees Fahrenheit, rainfall 5-10 times a year, seeds or nuts of size 1mm-5mm (can’t eat anything larger than that), presence of trees with height > 3m

can a realized niche be larger than a fundamental niche?

yes, potentially → organisms that depend on others to exist, or that can use more habitats than they would otherwise (plants in the desert that rely on other larger plants for shade/cooling)

What is the difference between richness and evenness?

1. Richness = number of species 

2. Evenness = all species present has around the same number of individuals (similarity of abundance)

   1. Or if some species are much more abundant than others

if you increase the grain size of a biodiversity map. would you expect to see more or less spatial variation in biodiversity?

less spatial variation (increased grain size = less area being visible)

• each location averages out more of the variation

if you measured 100 species of plant species in the entire berkeley campus, is 200 species a good guess for the number of plant species in an area twice the size of the berkeley campus?

1. No, because once you double the size of an area you would yield less than double of the number of species 

   1. If we double the search area we are likely to re-encounter some of the same species we have already found in the first search area

which hawaiian island would you expect to have the highest species richness according to the island theory of biogeography?

The big island, because in theory it is the closest to mainland and also had the largest area of land mass allowing for more immigration and lower extinction rates.

based on the global maps of species richness we saw in lecture, what other factors besides latitude might affect biodiversity?

1. Temperature; warmer/wetter climate is better for biodiversity than colder, drier climate 

   1. Peaks of biodiversity in places with mountain ranges

      1. Variation in elevation

why does the tilt of the earth cause seasons?

As the earth goes around the sun, in some parts of the year the northern hemisphere is more in line (tilted closer to the sun) with the light coming from the sun, while in other parts of the year the opposite occurs. This variation in solar radiation causes heating when the tilt is towards the sun, and cooling when the tilt is away from the sun. If the earth were not tilted on its axis relative to its orbital plane, there would not be seasons.

why do more inland areas experience stronger seasonality?

1. Due to the lack of nearby oceans which buffer the climate, there is a higher amplitude of seasonal temperature fluctuations

   1. There is less buffering of climate variation in the ocean

in what biome would you expect to find highest temperatures and highest precipitation?

1. Rainforests near the equator, they are exposed to the sun most often, low elevation and experience many hadley cells increasing precipitation

   1. Tropical rainforest 

why is the western side of the sierra nevada covered in trees but the eastern side is a desert?

1. Moisture filled clouds come from the pacific ocean and are uplifted up the mountains. As they rise, air cools, and is less able to hold water vapor. The excess water vapor condenses into a liquid form and falls as precipitation. By the time the rising air makes it over the mountains most of the moisture has already been lost, so there is less remaining to fall on the interior, eastern side of the mountains. = rain shadow 

is going up a mountain in elevation more similar to traveling to the poles, or traveling to the equator?

1. Traveling to the poles, increased elevation decreases temperature and the poles are at higher latitudes which is also decreasing temperature

   1. (going up means getting colder, roughly the same thing that organisms experience in more extreme northern/southern latitudes)

what are the three major factors that influence species distributions? do they act sequentially or at the same time?

1. Can the species disperse to locations? Are the biotic and abiotic environments suitable for the survival, growth, and reproduction of the species? They all occur AT THE SAME TIME

   1. Can be useful to think about them as acting sequentially when explaining a given species’ distribution

what process might cause dispersal limitation?

1. Organismal behaviors, fear of movement or inability to move

   1. Limited dispersal distance (plants with heavy seeds), need to modify conditions before new locations are suitable (after glacier retreat), long lifespans or slow reproduction.

when two species have similar distributions, can we be sure that the same factors limit both of their ranges?

1. No! 

   1. The same pattern could be caused by different processes 

      1. Sometimes it is useful to think about common drivers as a starting hypotheses (perhaps both species are both limited by cold temperatures in the same way)

what environmental gradients might exist around the bay area?

Cooler on the coast, warmer on the interior (Berkeley to Orinda); more rain near mount tam, less rain near Berkeley. Drier soils in the hills, wetter soils in the flats

In lecture, we learned that Hadley cells are driven by pressure gradient changes of warm, moist air rising and subsequently cooling. Based on that, why do you think storms are more common in some latitudes than others, and which latitudes would you expect them to be more common in?

Storms are more common in regions where warm, moist air rises because rising air creates low-pressure systems, which promote condensation and cloud formation. In the Hadley cell, air rises near the equator due to intense solar heating. As it rises and cools, moisture condenses and produces precipitation and frequent storms. Therefore, storms should be most common near the equator. In contrast, around 30 degrees north and south latitude, air descends, creating high-pressure, dry conditions that suppress storm formation.

Why do fluxes in = fluxes out of a stock at equilibrium?

At equilibrium, the stock does not increase or decrease, so therefore the inputs (fluxes in) must be equal to the outputs (fluxes out), so there is no net flux, making the stock at equilibrium; otherwise the stock would change.

is the residence time of the water longer in the ocean or in the atmosphere?

longer in the ocean, which means water is recycles quickly in the atmosphere and slowly in the ocean

can plants use nitrogen gas available in the atmosphere?

Yes, but not directly; plants use microbial organisms that directly turn atmospheric nitrogen into ammonium and nitrates that plants benefit from. ‘Nitrogen fixing’ bacteria are one key group that is often also associated with plant roots.

What are some ways humans could reduce fluxes of nitrogen into streams and lakes?

1. Reduce the burning of fossil fuels

2. Cotton crops rapidly deplete nitrogen resources in the soil. Peanut plants have nitrogen-fixing bacteria, which can replenish soil stores of nitrogen from the atmosphere. Switching from a nitrogen drain to a nitrogen source can ensure the long-term productivity of the soil.

Why do gases like carbon dioxide in the atmosphere contribute to climate change?

As more carbon dioxide gets into the atmosphere, it is trapped, and not emitted, contributing to the increased absorption of solar radiation causing warming and climate change.

What are the main carbon cycle fluxes that are affected by human activities?

Fossil fuel emissions (direct, carbon dioxide, methane) and land use change (indirect, urbanization, land clearance, intensification of agriculture in particular)

Why do scientists forecast future climates under different RCP scenarios?

There is substantial uncertainty in what policymakers and politicians and voters will decide to do regarding future emissions. As a result the different scenarios are able to describe the variation in outcomes for different potential decisions

What is an example of  positive feedback and negative feedback in the climate system?

Positive feedback: vegetation feedback: warming = increased tree mortality = more CO2 in atmosphere = more warming

Negative feedback: cloud feedback #2: warming = more low altitude tropical clouds = reflection of solar radiation = cooling

In a RCP 8.5 scenario, what is the expected climate change for India, based on the maps we saw in lecture?

India is forecast to become warmer, and also to receive more precipitation. Thus climate change does not uniformly cause hotter/drier conditions, though it is likely to in Western North America.

What potential consequences might arise from changes in phenological events?

If plants go to fruit early, harvest times would change. If animals mate/give birth early there may not be enough resources at the corresponding time.

• temporal isolation