Ecology Exam 1

ecology

study of how organisms live, and interact with each other and their environment. Studies all the relationships in nature. The most complex scientific discipline

how to calculate whether a population meets HW

first calculate the observed allele frequencies (number of that kind of allele/total alleles), then use those frequencies as p and q and determine expected genotypic frequencies via HW, then multiply by the population size. If those genotype numbers match what was given in the problem, it meets assumptions.

remember to add new notes and do practice problems

two examples of a relationship

predator-pray, male competition (relationships can be positive or negative)

abiotic factors

minerals, temp, gravity, rain, sunlight

biotic factors

living organisms: animals, plants, fungi, etc.

is a pile of dirt biotic or abiotic

both: has bugs, mircroorganisms, but also organic matter and minerals

is a carcas biotic or abiotic

abiotic

what is the difference between natural history and ecology

natural history is about observing habits and interactions in nature. Ecology involves math, utilizing the scientific method, and predicting relationships and habits in nature, NOT observation

how is multivariate calc involved in ecology?

used to predict how the population of one organism affects another

what are the different scopes/levels of ecology

individual→population→community→ecosystems→biosphere

(a relationship can have an effect on each level)

population

a group of interacting individuals of the same species that generally occupy the same space at the same time

what level of ecology does natural selection happen at

population level

evolution happens within what kind of group

within populations, not an entire species. A species in one population can evolve differently than the same species in a different population

evolution

change in the genetic frequency of a population through successive generations. Typically the genes that promote fitness become more abundant in a population

community

multiple species of things living in the same place at the same time and all interact with eachother

ecosystem

communities of species interacting with each other and abiotic components of the environment (but you can look at abiotic impacts on lower levels too). Can be anything from a cubic inch of water to an entire continent

biome

large scale groups of ecosystems into distinct ecological regions. (land based, the ocean is not sorted into ecosystems)

biosphere

the earth/combination of all ecosystems

evolution vs ecology

evolution observes the environment on a long time scale/over time, where ecology looks at the environment how it is/on a short time scale

mechanisms of evolution (8)

• natural selection: concerns fitness, individuals with heritable traits that improve survival tend to leave more offspring, causing those traits to become more common over generations

• gene flow: movement of alleles between populations when individuals migrate and reproduce in a new population. Alleles become more or less common randomly

• genetic drift: does not concern fitness, allele frequencies in a population change over generations due to random chance rather than natural selection

• mutations: changes in DNA sequences that can create new alleles. Mutations are the ultimate source of new genetic variation.

• artificial selection: concerns fitness, humans choose which organisms reproduce based on desired traits, causing those traits to become more common over generations

• recombination: The reshuffling of genetic material during meiosis that creates new combinations of alleles in offspring.

• genetic inheritance: The passing of genes/alleles from parents to offspring through reproduction

• symbiosis: A close, long-term interaction between two different species. It includes mutualism (+/+), commensalism (+/0), and parasitism (+/−)

allele

form of a gene

genotypic frequency

percent of genotypes in a population

• ex. 20% TT, 70% Tt, 10% tt

phenotypic frequency

% of a phenotype in a population

allele frequency

% of specific alleles in a population, has nothing to do with the individuals or how they combine

p, and its equation

the frequency of the dominant allele within a population

number of dominant alleles/number of total alleles

q, and its equation

the frequency of the recessive allele within a population

(number of recessive alleles/number of total alleles)

Hardy Weinberg equation and its assumptions

p² + 2pq + q² = 1

p + q = 1

gives the expected genotypic frequency in 2 alleles that are equally fit

a null model, requires a population that is isolated, no immigration or emigration ocuring, and a large population

allele frequency in a single generation is…

fixed

true or false: 2 alleles can have the same level of fitness

true

what does it mean if a population is not at equilibrium?

the null and observed values for genotypic frequencies are different, and that shows the population is evolving

do populations ever acheive/stay at equilibrium?

they don’t stay at equilibrium for long, since some mechanism of evolution is always at play

are larger or smaller populations more at risk for genetic drift?

smaller, since random events have a larger impact. If a few individuals die by chance, unique genes can sharply decrease or even disappear completely. For example 5/20 individuals has a greater effect than 5/100.

Genetic bottleneck

occurs in a population that is so small, usually because of a disaster event, alleles have been lost via genetic drift. Even if the population increases again, there will be less diversity.

• FORM OF GENETIC DRIFT

founder effect

a new population has less genetic diversity than its parent group because they migrated and started with small numbers, and is therefore prone to genetic drift

• TPYE OF GENETIC DRIFT

all individuals have the same chance of mating when…

genotypes have no difference in fitness

do recessive alleles increase or decrease fitness

can do both, but typically reduce

equation for frequency of dominant allele after 1 generation

p’ = p / (1-sq²)

p’= freq of dominant allele after 1 generation

p= freq of dominant allele

s= selection coefficient, shows % decrease in fitness of recessive phenotype relative to dominant

q= freq of recessive allele

1= fitness of dominant allele

1-s= fitness of the recessive allele

fitness

success of a genotype at contributing alleles to the population (more about parents passing to offspring, a DIRECT way of passing alleles)

evolutionary stable strategy

a strategy that allows a genotype to be optimally fit so that it is not replaced by other genotypes in the population. Fitness will usually increase over generations as it is passed through reproduction until almost all members have the genotype that codes for this strategy, and then it is said to be stable.

the strategies are not intentional, just coded by the genes

will not be replaced by another alternative strategy because this one is the most fit and effective for survival and repoduction

altruistic behavior

enhances the fitness of a genotype at contributing its alleles or copies of them to the population, at the expense of the individual performing the behavior

inclusive fitness

sucess of a genotype at contributing its alleles or copies of them to the population (more about parents passing to offspring AS WELL AS other relatives passing copies of alleles to offspring, so direct AND indirect)

ex. horn bills: aunts and uncles help raise offspring. Even though they aren’t having direct offspring themselves, they are still aiding in contributing their own genotypes to the population (r=.25)

coefficient of relationship (r), and how it relates to altruistic allele equation

the average proportion of genes shared by 2 individuals

parent/child: .5

siblings: .5

cousins: .125

all altruistic allele will increase in fitness if k > 1/r

k= inclusive fitness gained/inclusive fitness lost

physical resource

physical abiotic components that must be assimilated for survival

ex. O2, CO2, light, water, nutrients, minerals

not every organism needs every single one of these

physical factors

environmental CONDITION that affect where an organism can live.

Ex. temp, pH, light (don’t necessarily have to be assimilated)

limiting resource

a resource that isnt abundant enough for an organism to survive (ex. not enough calcium for crayfish)

limiting factor

a environmental condition that is beyond an organisms range of survival (for example extreme heat that causes a plant to shrivel)

what does low temp do to the body, in mild and extreme cold?

slows metabolism, and in extreme cold it freezes the body and cellular fluids

homeothermic

an organism whose metabolic rate is high enough to keep a constant body temperature regardless of the external environment. These organisms are called endothermic, or informally, “warm blooded”

ex. humans, polar bear, whale, duck

ectothermic and example

organisms that have a metabolism too slow to have a constant body temp, instead it is controlled by the external environment. Informally, “cold blooded” or poikilothermic

ex. lizards, frogs

Q10 rule

math function that described the increase in an organisms metabolism as ambient/environment temp increases by 10C

Humans is usually 2, meaning our metabolic rate doubles for every increase in 10 degrees

Q10 trap

the issue of the activity of ectothermic organisms being dependent on ambient temp, so they are very sensitive to temperature changes

strategies for Q10 trap/increasing metabolism in cold ambient temperatures: sunlight positioning, huddling, insulation, and counter current heat exchange

do endotherms eat more or less as it gets colder

more, to increase their body temperature to maintain a constant internal temp

do ectootherms eat more or less as it gets colder

less, since their metabolism is slower so they need less food

sunlight positioning

positioning body in the sun to absorb UV rays that raise body temp and metabolism above ambient temp, utilized by many ectotherms

huddling

grouping together to maintain body heat, decreases surface area relative to volume

insulation and examples

specialized tissue to hold in body heat, very important for homeotherms/endotherms

ex: fur on a wolf, blubber on a walrus, duck down

counter-current heat exchange

used in tuna, basically makes themselves from an ectotherm to endotherm

they swim to create friction in their muscles, which creates heat. Therefore, warm blood travels out of and away from muscles, while cold blood comes out of heart into muscles. These blood vessels carrying warm and cold blood run countercurrent to eachother. The warm blood heats the cold blood as it enters the muscles, to keep muscles receiving warm blood.

Heat gets recycled back to muscles, warming core temp above ambient temp

torpor

breif lowering of metabolism during the coldest part of the day. Utilized when it is so cold that Q10 strategies don’t work, but makes organisms more vulnerable to predators.

preserves energy by dropping metabolism and body temp

ex. hummingbirds and chickadees

hibernation and example

lowering of metabolism during the coldest part of the season (ex. hedgehogs and dormice)

• lowers caloric need

• bears are not true hibernators, they give birth and nurse in the winter

supercooling and example species

lowering body temp below the freezing point without freezing body fluids and endangering life, utilizes “antifreeze” like glycerol and alcohols to prevent blood from freezing and maintain a metabolism that is still low yet active. NOT a kind of hibernation because it helps them keep functioning in extreme cold rather than reach a full dormant state, like what would happen in hibernation

ex. arctic ground squirrels, snow fleas

extracellular freezing and example

a kind of hibernation, freezing all body fluids except those in the cells, adds a nucleating agent outside of cells for ice to form around outside of the cell (NOT inside). The goal is to get water outside of the cell to make the cell itself harder to freeze. Metabolism is as low as possible for the organisms to stay alive, the animal literally does nothing

ex. wood frog

life history strategy

an organism's overall “strategy” for surviving and reproducing

for example, K and R selected species (“slow” vs “fast”)

metamorphisis, why it is effective

great change of the body form during the maturation process.

• juveniles and adults may not be recognizable as the same species

• ex. tadpoles and frogs, caterpillars and butterflies

intraspecific competition: effective because there is little intraspecific competition, since juveniles and adults fill different specific niches so that resources are better partitioned (ex. caterpilar is on the ground and eats all day, butterflies fly around for mates food and travel farther

habitat exploitation: also beneficial because juvenilles can better exploit their temporary habitat, since adults don’t occupy the exact habitat in the exact same way

diapause

prolonged dormancy including lowering of metabolic rate and supression of protein synthesis

• hibernation is a specific type of diapause to avoid cold

• but overall diapause can be used to avoid unfavorable conditions in general, not just extreme cold

R and K selection, draw the population graphs of each.

two theoretical extremes in reproductive and ecological factors, but many species have elements of both

• both graphs initially grow exponentially to the carrying capacity, but then K levels out and only goes slightly above or below. It is stable. Whereas R tends to overshoot then experience exponential decline, then shoots back up again when resources replenish.

R selected species

have a high reproductive rate, mate early in their lifespan (reach sexual maturity quickly), mate often, have a lot of offspring with little to no parental care

• often undergo large fluctuations in population and have an exponential growth rate

• have a Generalist niche, can live in many types of environments (however in a stable environment often outcompeted by species with a specialist niche)

• short lifespan (hours to months)

examples: dandelions, mosquitoes, frogs, bunnies

K selected species and example

low reproductive rate, mate when older, mate rarely but regularly, have less offspring at a time, live longer

• take great care of offspring, they are less likely to die

• K= carrying capacity, how much the environment can sustain

• populations remain fairly stable since mortality rate is lower, so long as the environment is stable they have specific niches that make them very successful in their environments

• live in more specific types of environments and eat more specific types of diets than R selected→they are specialists

ex. koalas: specialists in eating eucalyptus leaves, almost no other organisms do so they have very little competition, helps them be successful and maintain stable population

what happens if a niche a K selected species specializes in is lost? provide an example

the population will decline and may go extinct

ex. spotted owl, specialized in old woody forests but many populations were lost in California as these forests were utilized for resources

is it better to be R or K selected

depends on the environment. If its stable, then K, because the environment is able to support the specific niches of the K selected species. Their population will remain fairly stable because of lower birth rates and lower offspring mortality. If not, then R, because they are more adaptable and generalists, and are able to utilize a variety of resources rather than relying on a specific one or few. They can rapidly colonize an environment due to high reproduction and offspring per birth.

population demography

quantitative descriptions of a population

ex. size, density, age structure, dispersion (how they are organized), sex ratio, birth rate, death rate

population growth

rate at which a population is growing or shrinking

carrying capacity

K →number of individuals of a species that can be supported indefinitely by a habitat. Can go over K, but not long term sustainable

exponential growth (draw a graph)

growth in which the rate of growth increases as size increases

common in R selected species

population overshoot

when a population grows larger than the carrying capacity of its environment, so its resources become depleted, usually followed by exponential decline

exponential decline occurs when

resources become depleted, especially because the population continues to reproduce. Common in R selected species after exponential growth

• therefore the high reproductive rate of R selected species is both good and bad

exponential growth model

Nt = N0e^rt

Nt→pop size at a defined time

N0→beginning size of population

r→rate of growth

t→time

r= birth rate - death rate

(if you get a negative number, its negative growth)

deme

singe genetically distinct population characterized by random mating within it, it is at equilibrium

• basically organisms within a population who are closer to each other and therefore more likely to mate, so kind of like a sub population