APS 123 - Beckermans Lectures Flashcards
What are the six key processes that drive distribution and abundance?
Births Deaths Extinction Colonisation Immigration Emigration
The growth of a unitary organism is _________
Determinate
Coral reefs and bryozoan collonies are examples of _______ organisms and their growth is _________
Modula
Indeterminate
What is a life history?
Describing when events occur within an organisms life cycle
Death, reproduction, somatic growth rates, birth, maturation and death
What are the two key reproductive patterns
Semelparity - big bang reproduction: large number of offspring produced in one reproductive event
Iteroparoty - organisms reproduce several eggs during reproductive episodes
Describe the dormant phase of an ephemeral species life history
Seeds lay dormant
Reproduce when conditions are ok
Complete life cycle in a few weeks
Site in south Africa with huge plant diversity, give stats about it.
9000 species 70% endemic 5% of south africa 44% of plants in south africa 0.05% of total earth but 3% of global plants
High adult mortality favours which type of reproduction?
Favours reproducing once and early - semelparity
In a life table what is Lx?
Survival to that age
Take value at age x and divide by value at age zero
Define Sx
Age specific survival
Survival between two years
Take value at age x and divide by value at x-1
Define Mx
Age specific reproductive value - must be measured independently
What is fecundity?
Why only females
Number of female babies / reproductive females
Only females generate the input into a population
What is R0? How do you work out the population level net reproduction rate?
The net reproductive rate
= LxXMx
Survival times the number of offspring produced
Population level = the sum of all the R0
R0 = 1
R0 < 1
R0 > 1
What is happening in the above situations
=0 population replaces itself
>1 population growing
< 1 population declining
Define generation time
Average time between births of individuals and the birth of their offspring
(Sum of (age x Lx x Mx))/R0
Define a trade off give a specific example
Negative relationship between two variables
E.g. Reproduction vs survival
- as annual fecundity increases so does the winter mortality rate
How can you increase population growth?
Increase Survival
Increase reproduction
Decrease generation time
What is Fx
Fertility
Fx = Sx X Mx
Describe the count the babies model of measuring fertility
Count the new borns
Adults need to have been born for the babies to reproduce, Sx related to adult survival prior to reproduction.
Fertility at age 2 = the fecundity at age two multiplied by the survival chance from age one to 2
Hence F2= m2Xs1
A general equation: Fx = Sx-1 X mx
Describe the count the fledgling method
Count them at age one See babies that survived one year so S0 Multiply the chance of surviving the first year by the fecundity of the desired age Fx=S0 X Mx No need to vary Sx
Fertility rates can be put into a matrix and from this a dominat eigenvalue is calculated what does this value represent?
Population growth rate ( symbol is upside down y i.e. Lambda
What is significant about the method of finding population growth rate via a matrix?
Tells you at what age population growth rate is the fastest, so you can implement conservation statagies for these ages
When does exponential population growth occur?
Few individuals
No limiting environmental factors
No restrictions on energy and hence reproduction and growth
Give the equation for change in population size per unit time
dN/dt = bN -dN
Change in population per unit time = per capita birth rate time population size - per capita death rate times population size
Can be simplified to
r=b-d
Give the definitions of the following
r
R0
Lambda
r = intrinsic rate of increase
R0 basic reproductive rate
Lambda = population growth rate
What is the limit to exponential growth?
Carrying capacity = k
Density increases = per capita respurces decrease = births decrease and deaths increase
In the logistic equilibrium graph where would you find the carrying capacity?
Where birth and death lines cross
What type of feedback prevents unlimited population growth
Negative feedback
Show the logistic growth equation
Deconstruct the equation and explain it
dN/dt = rN(1-N/K)
dN/dt = change in number per unit time
rN = exponential phase - where numbers are low
The k component adds in density dependant negative feedback which is taken from the exponential phase. But makes it relative to changes in N, disproportionate loss where density increases
Why is the human population not logistic?
Altered our carrying capacity with health care and agriculture
What are the three assumptions of the logistic growth model?
Linear density dependancy
Population approaches carrying capacity smoothly
K is constant - year to year variation
What size should the population start at if it will fit the logistic model?
Small size
What traits are associated with high density dependance ?
Large offspring
Few offspring
Delayed reproduction
Long lived
What traits are associated with low density depednace?
Small offspring
Early reproduction
Small and short lived
What is the competitive exclusion principle?
No two species can share the same resource
What is a fundamental niche and a realsied niche?
Fundamental - intrinsic requirements of a species on its own
Physiological and ecological limits - abiotic or weather
Biotic limits- food and habitat
Realised niche
How other species effect the niche
When competitors are present
Give the equation for population growth taking interspecific competition in to account
Deconstruct the equation
rN1 X (K1 - N1 - alphaN2)/K All that without out N2 is density dependant interspecific competition, the alpha N2 is the interspecific competition coefficient
At carrying capacity in the absence of Predator population growth is 0 manipulate the interspecifc competitom equation into the form of a straight line equation at this point.
Explain how this equation works in absence and presence of another species
Set it equal to 0
Multiply both sides by K
Divide both sides by rN
N1=K1 - alphaN2
In the absence of another species alphaN2 = 0 hence N1=K1 which makes sense
Where N2 is present the population is reduced by some function of N2 population size
There is a _______ decrease in carrying capacity with an increase in _______specifc competition
Linear decrease
Interspecific competition
How can coexistence occur between two species?
Where the interspecific competition is greater than intraspecific competition
What are the four possible outcomes of coexistence
Competitive exclusion for species 1
Competitive exclusion for species 2
Stable equilibrium - where inter>intra
Unstable - k outside other lines
Give examples of direct methods of competition
Overgrowth
Chemical
Territorial - defensive
Encounter - events over a specifc resource e.g. Fighting over food
Where the isolines of two interspecifc competition lines dont cross what happens?
Which ever species has the higher carrying capacity wins
Give some direct forms of competition
Exploitation - depleting resources
Pre emptive - using space depleting space
Scramble and contest - interference
Give five reasons why predation is important?
Structure and dynamics of commitmities Evolution - behaviour physiology etc Agriculture- pest contol Conservation - predator control Biodiversity
Give some examples of prey defenses
Colouration Morphology Spatial arrangement Batsian (harmless mimics poisonous) and mullerian (harmful mimic other harmful) mimics Camoflauge - crypsis
How can you test if an animal forages optimally?
They would eat what they encounter therefore you could gather contents of the gut, contents if not optimal should be in proportion to the abundance of organisms in the environment
What are the three factors involved in prediciting animal diet choice.
The objective - e.g. Reduce time and maximise energy
The currency - time and energy
Constarints - search time and amount of energy gained
Describe how the contingency model of foraging works
An organism will add prey choosing the most profitable ignoring search costs until the cost of searching and handling items is greater than the profit of the new prey
How do we know that consumers are choosey?
Profitability does not equal availability
Yet consumers are choosing the most profitable items
Hence they are foraging optimally
What is meant by the functional response when referring to predator prey relationships?
How the predators consumption rate varies with prey density
- plotting consumption on the y axis and prey density on the x axis
Describe the type one functional response
Type one is a linear relationship
- the gradient of the line = prey mortality rate
- therefore mortality rate is constant
Doesnt seem likely - digestive constraints i.e. If predator eats 10% of a size 100 population it eats 10, to keep this rate the same it would have to eat 1000 in a 10,000 size population
Describe the type 2 functional response
Attempts to capture the idea of digestive capacities
- non constant
- steep at low prey density
- then plateaus
Death rate does not increase as prey density increases hence this model doesnt follow the rule of density dependance
- mortality rate increases then decreases with density
What is the type three function response
Mirrors type 2 for the first portion
But implements the idea that with increasing density organisms are easier to spot winde less space inbetween
- slope and therefore mortality is steepest in the middle
Mortality increases then decreases with density
Which functional response would allow a movement towards stable communities?
Type 3 as it has an element of negative feedback
Which functional response is the most common? What does this suggest?
Type 2
- inverse density dependant mortality
- suggests predators are destabilising
Which of the following will lead to a stable community? Type1 FR and logistic growth Type 1 FR and exponetial growth Type 3 FR and exponetial Type 2 and logistic
A,C and D
For coexistence to occur there must be a source of ____________ this can either be ________ or _________
Negative feedback
Functional response 3 or logistic growth
Similar to how coexistence occurs between two competitors for coexistence to occur between predator and prey can occur when?
Intraspecific competition is stronger than the effects of predation
Describe using Paine’s 1966 study how predation can work to add structure to a community. Also breifly describe Tansleys study on rabbits that came to similar conclusions
Paine looked at rocky intertidal communities
Muscles were the dominat competitor and were predated on by piaster fish
- in the absence of predation the diversity dropped to one or two species because the muscles could outcompete the others
With predators the diversity remained at 18
Tansley saw that if rabbits were excluded from a grassland habitat then the diversity went down. Rabbits ate the dominat competitor
When will predation increase biodiversity?
Where the predators predate on the dominat competitor
When would predators reduce biodiversity?
When they are generalist competitors
What are the three possible effects of predation on a community?
Keystone predation = diversity increases
Generalist predation = diversity decreases
Change the ranking of biodiversity but not the diversity
What is a trophic cascade?
Pattern of interactions between predator and prey and resources
Describe the otter story in terms of a trophic cascade
High otter abundance
Eat sea urchins so low urchin abundance
Urchins eat kelp so high kelp forest density
Overfishing = not enough fish for killer whales
- killer whales turn to otters
- more sea urchins
- reduced density of kelp forests
Hence an organism 4 trophic levels away is determing the kelp forest biomass
A test was done with spiders with glued mouths, these couldnt kill the grasshoppers. The glued spiders had a similar effect on veg abundance than normal spiders, what is happening here?
The spiders are causing a change in behaviour of the grasshoppers, the grasshoppers are less active and therefore dont move. Without moving they cant eat the grass
