APS123 Beckerman Flashcards
Organismal ecology is concerned with the … … … traits that mediate interactions among individuals, between species and with the environment
behavioural, physiological and morphological
A population is a…
group of individuals of the same species living and interaction in a given area
Population ecology examines factors that … … population size and composition
limit and regulate
A community is…
all the individuals of all the species that inhabit a particular geographic area
Community ecology examines..
the interactions among populations
- how factors such as predation, competition, disease and environmental factors affect community structure and organisation
Ecosystems also involve..
abiotic factors
Unitary organisms have … form
determinate
- e.g. a sheep has 2 eyes, 2 ears, 4 legs
Modular organisms have … and … growth, which occurs by repeated production of …
indeterminate, unpredictable, modules (leaves, polyps etc)
- not dead until all modules are dead
The traits that affect the birth, maturation, reproduction and death schedule make up the…
life history
What is semelparity?
Large numbers of offspring are produced in a reproductive event, after which the individual often dies
- e.g. annual plants, many insects
What is iteroparity?
some organisms produce several eggs/offspring during repeated reproductive episodes
- most perennial plants
Some seeds are viable for up to…
1600 years
Annual plants spend part of the year dormant as..
seeds, spores, cysts or eggs
Ephemeral species…
lie dormant until environmental conditions are adequate for reproduction
Generally speaking, high juvenile mortality favours…
iteroparity - mortality risk once reached adulthood not high any more so can invest in reproduction many times
so high adult mortality favours semelparity
nx =
Number of individuals at age x
lx =
survival rate to age x (from age 0)
Sx =
age specific survival (survival between ages x and x-1)
- put answer in row that is coming from
- put dash if n/a
mx =
fecundity. Number of female babies/reproductive female (per capita).
Often 0 in early ages - before reached maturity
R0 =
net reproductive rate (sum of lx * mx)
- average number of offspring produced per individual (female) OVER HER LIFETIME
- if >1 pop increase
- if <1 pop decrease
- if =1 stable pop
The average number of people that one sick person will infect is also called…
R0
Generation time =
Average time between birth of individuals and birth of their offspring
Sum of(xlxmx)/R0
Population growth can be increased by increasing survival, increasing reproduction, or decreasing generation time, but…
all cannot be done at once - allocation of limited resources - trade-off
Removing eggs … clutch size the following year.
Adding eggs … clutch size the following year
increased
decreased
Change in population size during a time interval =
Births during time interval - deaths during time interval
When does exponential population growth occur?
In an environment with no limiting factors, no restriction on available energy and no restriction on growth or reproduction
change in N/change in t = bN - dN
b = per capita birth rate d = per capita death rate N = population size t = time
if there are 34 births in one year in a population of 1000 individuals, what is b (per capita birth rate)?
0.034
r =
b - d
therefore: change in N/change in t = rN
if b = d, r =
0
r > 0 leads to pop growth
r = 0 leads to stable pop
r < 0 leads to pop decline
K =
carrying capacity
- maximum stable population size that can be supported over a long time
Why does density affect population growth rate?
Crowding and resource limitation can reduce per capita birth rate and per capita death rate may increase when energy is low
What is the most common determinant of K?
Energy/resource limitation
+ availability of nesting sites, roosting sites, territories, refuges from predators
As density increases…
per capita resource declines
as density increases and per-capita resource declines…
births decline and deaths increase
Negative feedback prevents…
unlimited population growth
Also, change in N/change in t =
rN(1-N/K)
therefore
= rN - rN^2/K
intraspecific competition
- disproportionate losses as population increases
rN is the…
exponential phase
straight horizontal line on per capita growth rate graph
logistic growth (involving negative feedbacks) gives an…
S-shaped curve
and a negative slope on per capita growth rate
What traits are associated with high density?
Large, few offspring
Delayed reproduction
Large size
Long lived
What traits are associated with low density?
Many small offspring
Early reproduction
Small
Short-lived
When do individuals compete?
When resources are limited
How do we measure competition?
Change in population growth rate or size caused by another population
What is the competitive exclusion principle?
No two species can share the same resource and coexist - one will always outcompete other
What is the fundamental niche?
Intrinsic requirements of a species on its own
What is the realised niche?
What happens to “limits” when other species are around. Competitors may get sections of niches from others
No two species can occupy the same…
niche
Two species cannot coexist when…
they have identical needs of a limited resource
How do you incorporate interspecific competition into
rN1(K1-N1)/K1 ?
rN1(K1-N1-aN2)/K1
exponential growth - intraspecific competition - interspecific competition
N1 =
K1-a12N2
a12 is the gradient
Exclusion: isoclines…
do not cross
What is exploitation?
Depleting resources
What is overgrowth?
Species growing over another and depriving the other of light
What is territorial behaviour?
Fighting or behaviour in defence of space
What is an encounter?
Transient interaction directly over a specific resource
Coexistence: isoclines..
cross
Coexistence occurs when interspecific competition is…
weak
No two species can coexist unless they…
use different resources, use the same resource in different locations, or use the same resource at different times
Why is predation important in ecology?
Structures communities and changes dynamics (macarthur paper)
Why is predation important in evolution?
Major driver, selection pressures change morphology, physiology, behaviour
Why is predation important in agriculture?
Pest control and pesticides
Predators can promote…
biodiversity - richness and evenness
Optimal foraging: animals will eat the most … item, i.e. the item with the most energy per…
profitable, unit time of foraging (searching and handling)
Predators add new items (item 2) if…
the profit of the item 2 is >= the cost of ignoring it and searching for another of item 1
Add items until the profit of new items is…
less than the average cost of searching and handling items currently in the diet
Do consumers choose the most profitable items?
Yes
Are the most profitable items the most common?
No - non-random selection of food
Prey death function =
predator growth function
-conversion of prey into predators
Type 1 functional response is a..
straight line. Whatever the density of prey, 10% will get eaten for example (the same proportion) - consumption rate constant
Type II functional response…
plateaus - accounts for satiation effects - if very high prey density then not enough predators to eat them all, so consumption rate is lower
Type III functional response is an..
s-shaped curve - accounts for difficulty finding prey at low density - more space between
Which is the most common functional response?
Type II
In the absence of a predator, it allows certain competitors..
to dominate
Keystone predation…
increases diversity
Generalist predation can…
decrease diversity
Sometimes predation can change the … of competitors, but not change diversity
ranking
What is a trophic cascade?
Predators have an impact on the trophic levels below them, including more than one trophic level below (indirect impact)
What is the behaviourally mediated trophic cascade?
Predators simply scaring prey has an effect on the trophic levels below
How do spiders alter grasshopper activity?
Compress activity to certain (hotter) parts of day, rather than many spread out points. And overall less activity (even more reduction in juveniles)
The spiders with less active (sit and wait) hunting behaviours (nursery web spiders) lead to..
different plant diversity, NPP, decomposition rates and N mineralisation than active hunting spiders (wolf spiders)
