Ecology Test 3
Chapter 15
Consumptive effects
Predators kill to each and the prey they kill limits the population size
Non-Consumptive effects
This is when the behavior of being prey effects the popluation size rather than the act of being preyed upon
Cycles of predator and prey populations
Both Consumptive effects and non consumptive effects will drive the prey populations
For example when prey population goes up the predator population will also go up but then the prey population will go back down due to more predators being born since the predators are just eating a lot, then it will go back down due to the prey population declining. This will repeat forever. This is called a popiulation lag
Lotka Volterra model is a way to predct the change in a prey population size. The given formula is \frac{dN}{\differentialD t}=rN-cNP
dN/dt= the intstantenous rate of increase prey
R = the intrinsic growth rate of prey per capita
N= number of prey
C= Fraction of prey pulation caught by each predator
P = number of predators
Predictiing preadtor populatoin growth
Lotka Volterra model also has a way of predicting the predator population size d\frac{dP}{\differentialD t}=acNP-mP
dP/dt= the instantenous rate of increase in predators
a= efficiency of converting 1 prey to 1 predator offspring
c,n, and p= the same thing as in the prey formula
m= mortality rate of predators per capita
Deviations from Lotka Volterra in nature
the problem with the mathmatical models is that the model assumes that hte predators are going to have a constant capture effiency across all the prey population sizes but this simply isnt the case
Functional Response Cruves allow people to visualize what the catpure effiency changes look like based on the size of the prey populatoin
Type 1 functional response is when a predators consumption efficiency linearly increases with prey density until the predator is full and cannot eat anymore
Ex: 100 salmon pass a bear and it eats 10, 400 pass a bear and the bear eats 40, 1000 pass the bear but the bear eats only 40.
Type 2 functional response is when a predators effiecney gradually reaches a plateu as the populatio ndensity increases
for example: there is 1 fish in the bay and you catch a fish an hour, there are 13 fish in the bay and you catch 10, now there are 20 fish in the bay but you catch 12 an hour
Type 3 functoinal response is when the predators effiency starts low but increase rapidly when the prey density becoems more dense
Defenses against predation
There are 4 types of defenses against predators by prey
behvioral defenses- yelling, avoidances,
Chemical defenses- Compounds in the prey which are hard to digest or not plesent for the predators
Structural defenses- things like a shell, or hardened skin which makes it for predators to consume the prey
Coloration defesnese- such as camouflauge or colors that blend into the surrounding
Warning coloration also called aposematic coloration have patterns/colors which warn preadtors of their distatefulness
Posin tree dart frogs are brightly colored and this shows the predators that they are bad to eat
mullerian micmicary is when a species will mimic the color of another species in order to also show that they are not good tasting which will increase their likelyhood of sruvival
Batesian mimicary is the same thing however they arent actually harmful but instead just trying to pretended that they are.
Competition
Competition arises due to the limited resources that a habitat sets. the carrying capcity for a given habitat is called (K)
The competitive nature leads one species to push another species out called competitive exclusion
if this happens between two different species it is called interspecific but if it is between two creatures of the same species it is called intraspecific
Exploitative competition is when individuals of a species consume too many resources and dont leave enough for other creatures, in the same species or different
This doesnt have to involve direct interactoins
Interference competition occurs when an infiduvdal directly alters the resoruce attating the behavior of other species can either be interspecific or intraspecific
Interference through agrreesive interactions
Example: a species of ants will go to other colonys and block their entrance so that they cant get out for a while
interference throguh chemical itneractions
Example: black walnut trees induce a chemical around them changing the soil pH which makes it harder for other species of plants to grow
Apparent competition is when two indivduals that do not directly compete for resources affect each other by being the prey for the same predator
R sleected species are often out compteted by K slected species in a habitat however R sleceted speceis can leave the area through disperial giving them a better chance
K selected species- Slwoly growing and having few off springs
R slected species- have high offspring but they die off quick and only some surivive
Species living in the same habitat can reduce competition thorugh spatial nitche partitioning, where species that eat the same food will occupy different microhabitats within the habitat
Example: squirrel eating acorns at the top of the tree and rats eating acorns at the bottom of the tree
Dietary niche partioning- is when species that occupy the same microhabitat eat different prey
example: two species livign in a pond, but one species eats the food at the bottom of the lake, while one eats the flies on top of the water
Lotka volterra competion model dN/dt\frac{dN}{\differentialD t}=rN\left(1-\frac{N}{K_{}}\right)
dn/dt= growth rate
r= intrinsice growth rate
n= popilation size
k=carrying capcity
Lota Volterra competion takes into account the two different species
A is the effect of an indivdual of species 2 on the rate of pulation growth of species 1
B is the same thing but is for species 1 on the rate of the growth of the poulation of species 2
if A or B>1 then it is intersepcific> intraspecific
which means that you need more than 1 species to equal the comeptivie effect of the other species
if A or B <1 it is interaspecific
which means that it is less than the comeptive effect of the other specieis
parastism
Ectoparasites live on the outside of organisms
The advantages of living otuside the hosts allow the organisms to move between hosts and not be exposed to the immune sysrtem
Disadvatnages is that its exposed to the environements and exposed to predators and parasties
endoaprasites live inside their horts
advantages: protected inside the hosts body, can easily eat wihout worry
Disadvatnages: cant move between hosts and exposed to the immune system of hosts
Emerging infectous diseases are new strains of dieases or new diseases which have new mutations which allow it to jump from hosts to host
White nose syndrom was a diseases caused by a fungus which infected bats
Zoonotic diseases are diseases which jump from non humans to humans and are one of the main diseases which infects us
THe SIR model predicits the transmistion rate of a diseases, NOT wheather or not it will happen
S- suspetiable to the pathogen
I- Infected population
R - immunity or resistance
In between S and I is the transmisstion rate (g)
Between I and R is the recover rate (B)
we can use a mathmatical model to predicat changes in hte population of infected hosts
\frac{dI}{\differentialD t}=\beta SI-Ig
-
BSI is the gains added to the infected class and it depends on hte average number of the suspcetible indivudals infected by one infectipus individual per unit of time, the number of people who can be infected, and the number of people currently infected
Ig- is the loss to the infected class where I represents the people who are currently infected and G represents thoses who are recovered per unit of time
if R0>1 then the infectoin will continune to spread through the population
if R0< 1 then the infection will not repsread
How do we get R0<1
we try to lower the transmition rate from the S to I and this means quarninting, socially distinicng
we also vaccinate
Mutualism
Obligate mutlaists is where the interaction of two species are needed in order for both to surive
Figs and wasps, the fig needs the wasps to carry its seeds and the wasps needs the figs in order to have a nest
Faculative mutalists is wheere two species two species dont need the to interact in order to survive, however if they do it is benefical for their survival rate
Root nodules are organisms which convert N2 from the atmosphere into usuable forms for the plants
Community interactions and disturbances
in a trophic pyramid the primary producer level holds the most energy and biomass so organims such as flowers or fruits
When the number of rophic levels is lmited by the ammount of energy avaible it is controled from the bottom up control
When the number of trophic levels is limited to by predation it is under top down control
Speceis can affect each other through indirect and direct effects
Community diversity is the species richness and the number of species in a cmmunity and species evenness, is the proportion of inidivudals in a community represented by each species
A rank abundace curve is used to visualize both species richenss and species eveness within a community
Species diversity can be affected by the presence or absence of one keystone species
community diveristy can be affected by distubance patterns
By the intermediate disturbance hypothesis more species are in communities where there are lots of disturabnces than thoses that dont have alot
Sucession is the change in speceis compsition over time which often occurs after a disturbance
There are two types of sucession primary and secondary
Primary start from bare rock and no soil and there are pionner species
secondary sucession is when there is a big disturbance but there is still soil and nutrients for the next sucession to start so it happens alot faster, taken over by r selected speices
Primary producitvity: processes and limitations
The biomass of a tree mainly comes from the carbon dioxide in the air
Plants absorb light within the visible spectrum (400-700 nm) for photosynthesis
in eukaryotic primary procuders photosyntehsi is carried out by chloroplasts
Chlorplasts contains clorophylls and carotenoids which capture energy from the light
Chlorophylls only absorbe red and violet light and reflect green and yellow light
Carotenoids capture blue and green light and reflect yellow, orange, and red light
Primary producitivty is a charcteristic of the primary producers of the ecosystem and determines how much energy will be avaible to higher trophic levels per unit of time
this is catagory is split into two types
Gross primary producitviy (GPP) is the ammount of energy captured in an ecosystem
Net primary producitivty (NPP) is the ammount of energy that is actually put into the new growth and reproductoin NPP=GPP- Respiration rate
Energy flow and carbon cycle
In each location NPP determines how much of the energy at the bottom is avaible to the higher levels
global patterns in terrestrial net primar producitvity are associated with biomes and abiotic conditions
Global patterns i naquatic net primary producitivty are associated with nutrient avaibility as well as the presence of nutritent pollution
Trophic pyramids are models which help us see the ammount of energy and biomass avabile in a system
in a terrestrial ecosystem there is a more energy and biomass at the primary procuder level
in an aquatic ecosystem there is more energy at the primary producer level and there is a more biomass at the teriary consumer level
Energy transfer between trophic levels is lost due to a multiude of reasons
Consummers cannot absorb the whole organisms, some is lsot as waste, and others is lost as respiration
The carbon cycle balance shifted when humans started burning fossil fuels
Burning these fossil fuels puts lots of carbon dioxide in the air which increases the global warming
disturbances such as natrual events like wild fires also affect hte ammount of CO2 in our air
Humans have developed a way to turn direct air into usuable forms of CO2 for us