Ecology Flashcards
ecology come from the word
Oikos- house, place to live
Ernst Haeckel 1869
Ecology interval/range
Organsims-Earth (biosphere)
Behavioural ecology– population ecology– community ecology– deep ecology
Subsection of ecological genetics
genetic variability
natural selection
evolution
ecological genetics
study of genetic/phenotypic variability in natural populations, relationship to ecological processes
If all individuals in a population are homozygous
monomorphic
If any individual in a population has a heterozygous locus
polymorphic
Average percent of loci in a population that are polymorphic
5-15%
genes/individual
~20,000
Genetic variability
percentage of heterozygous loci : population size
increased genetic variability with increased population size
Natural selection in moth species
evolved to mostly black because lichens were less common on trees after industrial revolution
Natural selection of sea snails living on kelp
Yellow snails have advantage over predator below kelp
brown has advantage over predator above kelp
due to light source
evolution of spirit bears
white bears have advantage over darker coloured bears when fishing
zygosity in populations <100
nearly monomorphic
monomorphic populations
increases susceptibility to disease
decrease adaptability to environmental change
Initial genetic variation vs. generations
N = 20, genetic variation = 0 after 200 generations
N=100, variation down to 0.2 ~300 generations
N=1000 small decrease in variation over 500 generations
reduced number of individuals in population
increased inbreeding– increased homozygosity– increased juvenile mortality
MVP
minimum viable population
minimum viable population
smallest possible size at which a biological population can exist without facing extinction
90% of genetic variability after 200 years
MVA
minimum viable area
minimum viable area
minimum land area required to maintain genetic variability after 200 years
MVP then and now
used to think ~500 was viable
now know it must be ~2500-4000
most common park size
~20-50km^2
immigration in regards to genetic variability
even a small amount of migration per generation allows persistence of genetic variability
no immigrants per generation
<60% genetic variability left after 100 generations
1 immigrant per generation
~90% genetic variability left after 100 generations
natural selection 2.0
non-random and differential reproduction of genotypes resulting in preservation of favourable variants
adaptation
physiological, morphological, or behavioural modification that enhances survival and reproductive success of an organism
evolution
serial change over time
descent with modification
Anagenesis
gradual change over time
changing adaptations over time
does not lead to species diversity
Cladogenesis
branching of lineages and formation of new species
usually occurs with geographical or genetic isolation
anagenesis graph geological time vs. trait condition
relatively straight line
cladogenesis graph of geological time vs. trait condition
branching tree
when life began on earth
first life developed on earth ~3billion years ago
total number of species on earth
8-100 million
Subsections of behavioural ecology
optimal foraging territoriality sex and mating systems group living life histories
first hard shelled organisms
542mya explosion of diversity
mass extinction
250mya
~94% of life extinct
diversification of mammals and birds
65mya
Foraging decisions
large/small, soft/hard, plant/animal, sweet/sour, uncommon/common, closer/more quality, opportunistic?
OFT
optimal foraging theory
optimal foraging theory
rules in optimizing choice of food/prey
3 subsets of OFT
preference for food with greatest net energy gain
feed more selectively when food is abundant
low quality food only when profitable food is scarce
optimal foraging, net energy gain
catching difficulty, amount of prey that can be consumed
Pied-wagtail (bird) foraging strategies
beetle size most eaten- not biggest or most common
biggest beetles take longer to eat
7mm beetle provides most calories/handling time
intrinsic quality of food
amino acids, fatty acids, salts, vitamins, trace elements
importance of sodium
primary extracellular ion, major role in body fluid volume, acid-base balance, tissue pH, muscle function, nerve synapse
sodium defficiencies
on average animals are sodium deficient
plants do not contain sodium
why animals are given salt licks
aquatic plants are rich in sodium
primary reason for animals to move to coastal regions
compensation for sodium deficiency
aquatic plant properties
low calories
high Na levels
high moisture (bulk)
Terrestrial plant properties
High calories
Low Na levels
low moisture
Aquatic vs. terrestrial plants in moose diet
low terrestrial would require high aquatic intake for energy
stomach not large enough for high aquatic intake
high terrestrial not enough energy or sodium
small range for optimal diet
bison foraging strategy
migrate to salt lakes
Patch foraging time
food occurs in a patchy distribution and in patches of different size
optimizing foraging time among patches
concentrate foraging activity in most productive patches
ignore patches of low productivity
stay with patch until profitability falls to level equal to average for all foraging patches combined
as time spent in foraging patch increases
energy obtained ‘flattens out’
leave foraging patch when
probability is that the next patch will be more dense
time to spend in foraging patch graph
cumulative net food gain vs. time spent in patch
if it takes a long time to obtain food
animals spend more time on that food
birds that open containers easily didn’t stay long
foraging time vs. predation risk graph
state of hunger dictates willingness to risk predation
starving- straight line, foraging activity is independent of predation risk
very hungry- sloped line, foraging activity decreases linearly with increased predation
slightly hungry- no foraging activity with high predation
Home range
area over which an animal travels in search of food/mates/resources and which is not defended
present in majority of animal species
territoriality
defines of an area and active exclusion of resource use by others through display, advertisement or defense
Territoriality is common in
predators (african lion, cheetah, hyaena, bear, eagle, hawk, owl)
birds during nesting
fish during reproduction
social insects (ants, bees, wasp, dragonfly)
Influences on size of territory
body size, aggressive behaviour, habitat quality, population density, competition with others, ability to share resources
black-capped chickadee territoriality
male sings to mark territory
same species avoid each others territory, other species do not (intraspecific competition)
Great Tit territoriality experiment
Remove individual 3 to see if there would be a change in territories, boundaries expanded, new arrivals came
was 3 dominant to the others? defended territory more..
larger territory =
more food, shelter, reproduction
harder to defend
want largest area with lowest cost
determining optimal territory size from benefit/cost vs. territory size graph
optimal size is where there is the largest slope on benefit curve
maximum territory size from benefit/cost vs. territory size graph
where benefit curve flattens out
changes in optimal territory size
ex. predator moves into area
Asexual reproduction
offspring genetically identical to parent
common in bacteria, unicellular eukaryotes, plants
occasional in vertebrates
harder for species to persist
predictor of asexual reproduction
small, short lifespan animals
consistent environment
asexual species using sexual reproduction at particular stages of life
times of stress
Sexual reproduction
majority of species
genotype different from mother and father
in changing environment/niche, new genotypes may have
higher reproductive output than either parental genotype
categories of sexual reproduction
dioecious
monoecious
dioecious
‘two houses’ ‘two sexes’
male/female organs on separate individuals
~equal sex ratio
majority of species
monoecious
‘one house’
m/f organs on same individual
bisexual or hermaphrodite
types of hermaphrodites
simultaneous hermaphrodite
sequential hermaphrodite
simultaneous hermaphrodite
both sets of reproductive organs at same time
common in plants/invertebrates
can’t mate with self
sequential hermaphrodites
m/f reproductive parts at different times
common in coral reef fish
ontogeny
origination and development of an organism, usually from the time of fertilization of the egg to the organism’s mature form
example of simultaneous hermaphrodites
slugs, worms
example of sequential hermaphrodite
Wrasse
small ones- genderless
medium- female (beta position)
large- male (alpha position)
simultaneous/sequential hermaphrodites don’t have
sex determining chromosomes
Mating structures
Panmixis
Polygamy
Monogamy
Panmixis
unrestricted random mating
all individuals equally potential partners
sexes look alike (monomorphic)
eggs and sperm dropped all over the place
panmixis examples
some marine invertebrates
marine schooling fish
Polygamy
many marriages, multiple partners
widespread
sexes look different (dimorphic)
males often larger/more elaborate
types of polygamy
Polygyny
Polyandry
polygyny
female defense polygyny- individual males defend groups of females
resource defense polygyny- individual males defend resources which female seek out
polygyny examples
fish, amphibians, reptiles, songbirds, mammals
female defense polygyny examples
deer, primates
resource defense polygyny examples
fish, songbirds
polyandry
many males, single/few females
males take on ‘mother’ roles- incubate eggs, sexually inactive
sexual genes are down regulated
females compete for males and defend resources
polyandry example
shorebirds
monogamy
serial or lifetime
one marriage, high fidelity to single partner
care for young for a long time, often predators
bi-parental care required to raise young (or they die)
sexes usually look similar (monomorphic)
monogamy examples
carrion beetle, most seabirds, swans, hawks, beavers, weasels, wolves
new data on genetic fingerprinting indicate offspring of monogamous couples
are often sired by more than one father socially monogamous (cheating)
extra pair copulations (EPC)
copulation with a male other than the bonded male, gives birth to offspring whose father is not the bonded male
fitness of offspring is a function of
who female mates with (genetic makeup)
females choosier than males in mate choice
fitness cost is greater than in males (limited eggs 400 vs. unlimited sperm 200 million per ejaculate)
sexual selection
mate choice- tendency for individual to be selective in whom they choose to mate with
male fitness increased by
maximizing number of fertilized eggs (increased number of females)
female fitness is increased by
maximizing genetic quality and genetic variability of their offspring
female mate choice criteria
nuptial gift dominant/strong male preference handicapped male hypothesis parasite free male hypothesis symmetric male hypothesis display evaluation inbreeding avoidance
nuptial gift
males provide gift to female to solicit matings
females use resource characteristics to determine quality of male
examples of nuptial gift
hanging fly
thynnine wasp
song birds
hanging fly
larger prey (gift) = more sperm transferred (longer copulation) sperm is stored in female, she chooses which to use later
Thynnine wasp
female doesn’t fly, releases scent to winged males
males ability to carry female to multiple flowers increases probability of male mating
songbirds (nuptial gift)
gift to female is safe territory for foraging/breeding
male evaluated based on length and complexity of song- correlated with territory size (physically demanding)
examples of Dominant/strong male in sexual selection
ram
elephant seal
damselfly/dragonfly
damselflys dominant sexual selection acts
males engage in aerial combat over pond
winners do the mating
female increases genetic quality of offspring by mating with winner
handicapped male hypothesis
expression of costly elaborate display by males provide female the greatest information on genetic quality of male
“honest signal” of fitness, low possibility of cheating
male survives despite handicap
example of handicapped male hypothesis
peacock
widowbird
widowbird handicap
male tail is longer than body, reduces flight, feeding ability, predator evasion
elephant seal dominant sexual selection act
fight for female attraction
only the winner mates with females for the year
results of widowbird study (handicapped male hypothesis)
lengthened tail of bird- was much more successful reproductively
parasite free male hypothesis
differing susceptibility to disease can lead to mortality in young, males without parasite = better immunological genes- improved physiological ability, immunocompetence heritable
bright displays- parasite free male hypothesis
bright displays are physiologically costly to produce
parasitized birds can’t produce as bright of colours
if females choose these males- provide offspring with genes more resistant to disease
proof parasitized birds can’t produce as bright of colours?
removal of lice– birds moult— new coat is brighter
symmetric male hypothesis
bilateral species
an excellent genotype can correct asymmetries during development
developmental instability
asymmetries in structure
minor errors in embryological development and growth
can lead to asymmetry
stress, pollutants, parasitism, homozygosity, poor genotype
symmetric male hypothesis bird study
symmetry was altered in male birds tail feathers
female switches her favourite to most symmetric male
symmetric male hypothesis is commonly observed in
insects, fish, birds, mammals
symmetry can be evaluated by
sight and sound
example of symmetry evaluation by sound
crickets having symmetric (monotone) frequency wing harps- indictor of body symmetry
fluctuating asymmetry
random deviation from perfect bilateral symmetry in otherwise symmetrical morphological traits, originates from developmental errors during ontogeny
fluctuating asymmetry reflects
inability of a genotype to buffer itself effectively against environmental perturbations
symmetric male hypothesis fish study
females have significant preferences for fish with symmetric vertical bars
facial asymmetry in rhesus macaques
honest indicator of health
used in mate choice situations
display evaluation
females evaluate quality, complexity, coordination of display (dances, songs)
inbreeding avoidance
all animal/plant species in the wild have mechanisms to avoid inbreeding
animal species can detect genetic kinship based on
pheromones
MHC
major histocompatibility complex
what is MHC
~30 genes coding for proteins in cell membranes essential for immune system, 2 different proteins at each gene, each gene multiple alleles, each individual unique, MHC molecules bind to specific receptors and have distinct odours
females prefer what in regards to MHC
males with the most dissimilar odour (genotype) to themselves
how birth control affects females and MHC
females are attracted to male similar to self– birth control mimics pregnancy– want family close
MHC based mating preference may be affected by
genetic background, sex, early life experience
inbreeding is potentially problematic in all animal species. the major ecological cost of inbreeding is
reduced capacity to cope with environmental changes
increased homozygosity is not an ecological cost
it is a genetic cost
advantages of group living
increased food search efficiency increased capture efficiency of large prey increased detection of predators increased defense against predators selfish herd theory
examples of increased food search efficiency in group living
seed detection by songbirds
fish detection in gulls- repeatedly catching fish signals a good feeding area
examples of increased capture efficiency in group living
wolves, lions
african hunting dogs- pack 20 catch ~80,000 kJ/dog/day, threshold number before a large difference is seen
increased detection of predators in group living
‘many eyes’ theory- Hawks have significantly lower attack successes with large number of pigeons present.
1-10 pigeons = 60-80% success
>50 pigeons = ~10% success
increased defense against predators
mobbing- ex. small birds can mob owls
selfish herd theory
dilution effect- schooling/herding/flocking- if there is an attack on a group it is less likely the attacker will get you
examples of species that exploit selfish herd theory
wildebeest, pronghorn, herring, flamingos
evolution of selfish herd theory
belted kingfisher in a tree above a lake.. if fish are individual and he has one is his sights the probability that he is looking at that one is 1, if that fish joins a group the probability that he the one being spotted is decreased..
Disadvantages of group living
increased transmission of parasites
shared resources and resource depletion
conflicts/stress
yellow-eyed junco group living
flock size 1 = lots of predator scanning, decent amount of feeding, no fighting
flock 3-4 = little predator scan, little fights, lots of feeding
flock 6-7 = slightly more predator scan, more fighting, a little less feeding
results of yellow-eyed junco study
if groups become too large fighting will take up valuable feeding time
reproductive effort
amount of total allocations that an individual makes for reproduction
categories of reproductive effort
r-selected
k-seleceted
r-selected
high # offspring
high population growth potential
boom/bust cycles
usually short lived
k-selected
low # offspring
low population growth potential
stable populations
usually long lived
categories of reproductive effort are
relational categories (rather than absolute) species A is k-selected compared with species B
subcategories of Life History
categories of reproductive effort frequency of reproduction occurrence of parental care clutch size and litter size in k-selected species age of first reproduction
frequency or reproduction
semelparous
iteroparous
semelparous
single reproduction, breed once and then die
iteroparous
repeated reproduction (usually yearly)
semelparous examples
most insects, octopus, salmon
iteroparous examples
plants, snails, most fish, amphibians, reptiles, birds and mammals
occurrence of parental care
absence/presence
amount
parental care absent in
most invertebrate taxa
most fish
most amphibians
most reptiles
parental care common in
social insects small fish dinosaurs birds all mammals
another name for semalparous
‘big bang reproduction’
precoccial
offspring are born without needing care
example of precoccial organisms
caribou babies can run as fast as adults within hours of life
semipalmated plover born with adult size legs
occurrence of parental care - amount needed
absent
precoccial
altricial
altricial
offspring are born helpless and require extensive postnatal care
example of altricial young
social insects, some fish, amphibians, most birds, most mammals
clutch size and litter size in k-selected bird species
birds can only lay one egg a day
all bird species lay fewer eggs in the nest than they are capable of doing
David Lack (1948) proposed that
clutch size represents the maximum number of young parents can successfully raise
clutch size tends to increase with
geographical latitude
why more eggs with latitude
more food, less competition, easier to care for young
test of Lacks hypothesis, collared flycatcher
can lay 8, normal clutch 4
chicks- reduced survival first year, reduced egg production as adults
parents- reduced winter survival, reduced egg production next year
test of Lacks hypothesis, Canada goose
can lay 12, normal clutch 4, added 1
chick- survival similar
parents- delayed molt, delayed migration, reduced weight next year, female bred later next year
results of Lacks hypothesis
clutch size corresponds to maximum number of offspring parents can raise without a net reduction in future reproductive effort
difference in collared flycatcher, canada goose study
collared flycatcher feed young 50 times a day
canada goose does not feed young
age of first reproduction
generation time- major variation
examples of variation in generation time
fish: guppies 3wks, sharks 30yrs
birds: songbirds 6mnths, albatross 6-10 yrs
mammals: mice 3wks, elephant, whale, human 13yrs
fecundity
number of eggs
in most plants and ectothermic animals fecundity is
positively related to size
lay eggs at older/larger stage = more eggs
lay 2 eggs and die at 12 months of age, or lay 10 eggs at 48mnths and die, which is a better strategy?
work out by adding up population size over months
eventually 2 eggs at 12 months has a greater impact
how many species breed within first year of life
98%
useful to produce early in life?
if higher mortality rate in getting to the older production age (does probability of survival decrease)
mule deer in BC
adult size- 3yrs
can reproduce at 2yrs- body growth reduced, increased winter mortality from predators
without predators most reproduce at 2 yrs
r-selection life history attributes
development- rapid
reproductive rate/age/type- high, early, semelparous
body size- small
life length - short
competitive ability- weak
survivorship- high mortality of young
population size- usually well below carrying capacity
k-selection life history attributes
development- slow
reproductive rate/age/type- low, late, otero parous
body size- large
life length - long
competitive ability- strong
survivorship- low mortality of young
population size- usually at or near carrying capacity
essential features of scientific explanation
testability
falsifiability
scientific experiments
evaluate hypotheses (do not prove)
population ecology
dispersion, movement, estimating population size, life tables, mortality and survivorship curves, population growth and population regulation
dispersion types
regular/hyperdispersion
random
aggregated/clumped
regular dispersion
equidistant
fish school, seabirds
random dispersion
individuals distributed without respect to others
grazing wildebeest, beach clams, forest spiders
aggregated dispersion
most common
2 types
types of aggregated dispersion
coarse grained
fine grained
plants (due to trace minerals left by glacial till)
coarse grained aggregated dispersion
clumps separated by large areas
fine grained aggregated dispersion
clumps separated by short distances
dispersion
how individuals are distributed in habitat
structured by where resources are
dispersion allows
spread/mixing of genetic information
reasons for clumped distribution - plants
local difference in microhabitat- soil moisture, nutrients, sunlight
reasons for clumped distribution- animals
resources are clumped
behaviour which facilitates grouping
animal behaviours that facilitate grouping (clumped distribution)
social context, family groups, predator defense, shelter
types of individual movement
dispersal
migration
dispersal
movement of individual away from place of birth
leads to geneflow
migration
mass directional movement of large number of individuals from one location to next
migration examples
salmon, whales, wildebeest, seabirds, songbirds, monarch butterfly
grey whales migrate south in the fall
calves have high thermoregulation needs, born in Baja where water is warmer so they can store energy
Warbler migration
south in winter for food (no insects in north in winter)
north in spring- easier to raise children in north (less competition)
monarch butterfly migration
migration is multi generational (4 generations for round trip)
adults mate and leave mt.s in mexico in feb, lay eggs on milkweed, die, eggs hatch feed on milkweed, adults migrate north
monarch butterfly eggs hatch in
4 days
monarch pupation to chrysalis
10 days
monarch generations 1-3
adult 2-6 week migration
monarch generation 4
south migration, adult 6-8 months
why milkweed
cardiac glycoside, caterpillar puts toxin in its skin
density
individuals per unit area/volume
estimating absolute density
total counts (photographic)
quadrat sampling
mark, release, recapture estimates
Peterson/Lincoln index for mark, release, recapture
N = Mn / m
variable in Peterson/Lincoln index
N- population size
M- number of marked individuals
n- number of individuals in sample
m- number of marked individuals in sample
confidence intervals in mark recapture
sampling must be repeated to obtain decent confidence interval
problems with mark recapture
50% of released steelheads die of stress
birds target butterflies marked on wings
polar bears marked with paint couldn’t capture prey
assumptions for reliable population estimates in mark recapture
population is largely constant over duration of studies
marked individuals have same chance of getting caught
marked individuals do not incur greater mortality
marks are not lost
population is largely constant over duration of mark recapture studies
no immigration, emigration, births, deaths
only possible in short time frame
marked individuals have same chance of getting caught
assumption of equal catchability
marked individuals do not incur greater mortality
stress-related mortality
mark-associated mortality
problems with flipper bands on penguins
banded birds had 16% lower survival, 39% fewer chicks
non-invasive methods of evaluating density
genotyping / genetic fingerprinting
hair, feathers, faeces, scales, identify individual genotypes
Estimating future population
N_t+1 = N_t + B + I - D - E
variables of future population equation
N_t+1 - individuals in pop. at t+1 year or generation N_t - individuals in pop at time t B- births D- deaths I- immigration E- emmigration
B - births
natality, number of individuals produced
fecundity / fertility
fecundity
ecological concept, number of offspring produced
fertility
physiological concept, females ability to produce offspring per unit period of time
PPP
primary population parameters
B D I E
demography
statistical study of human populations
life tables useful for
estimating mortality rate, survival rates, survivorship curves, average life expectance
types of life tables
age specific
time specific
cohort analysis
age-specific- group of individuals of same age class follow specific cohort from birth to death most useful on short lived species
cohort
group of animals of same species, identified by common characteristic, studied over time as part of scientific/medical investigation
nestling
eggs that hatch
fledglings
birds that can fly from nest
in order to construct age specific life table
follow cohort from eggs to adults for 1 generation
blue tit cohort
50 eggs followed, x eggs lost, y nestlings, x nestlings die, y fledglings, x fledglings die, y new adults, x new adults die, y adults left
survivorship calculated
relative to original cohort
3 new adults left, out of 50 eggs = 6% survivorship
mortality calculated
relative to each stage
3 new adults, 30 fledglings = 1 - (3/30) = 90%
time-specific life table
age structure at single point in time long lived, large animals snapshot in time 'static life table' requires age distribution of a population
determining age for time specific life table
growth rings- mussels/clams/trees/fish scales
cross section of tooth- large animals
horn growth- mt sheep
survivorship in time specific life table
I_x = N_tx / N_t
number entering age class / total count
mortality
1000q_x = ( N_tx - N_tx+1 ) / N_tx number entering age class x, minus number in age class x+1 divided by number entering age class x
life expectancy
e_x - expected number of additional years of life remaining at any specific age
lowest mortality rates
intermediate age- healthiest, predators attack old and young
more information in
mortality rate curve than survivorship curve
Idealized survivorship curves
Type I
Type II
Type III
survivorship curve type I
k-strategists, many mammals, number of survivors relatively constant till later age
survivorship curve type II
many birds, small mammals, lizards, turtles, linear with negative slope, probability of survivorship is same each successive year
survivorship curve type III
many invertebrates, fish, amphibians, plants, r-stratigists, why they lay so many eggs, largely decreasing survivorship at early age
dominant cause of survivorship curve shape
predation
atual survivorship curves
are ~same shape, lower (in survivors) than idealized curves
population growth
occurs when births (natality) and immigration exceed mortality and emigration
ASFR
age specific fecundity rate
ASFR =
average number of male and female offspring produced per female for each class
TFR
total fertility rate
average number of male and female offspring produced per female over her lifetime
TFR =
ASFR x number of years in age class (range)
critical information for population growth
sex ratio- life tables often calculated only for females
importance of sex ratio
A=10 reproductive adults, B=100
A produces 9X more offspring than B?
A= 1 male, 9 females
B= 99males, 1 female
NRR
net reproductive rate
NRR =
Ro = ∑ Ixmx
Ixmx
survivorship of reproductive females in any age group * number of daughters produced for each age class of female
Ro
number of breeding daughters that will be produced by each breeding female in the population per generation
Ro < 1
population is decreasing
each female produces ~<1 breeding daughter by end of reproductive period
Ro = 1
population is stationary
Ro > 1
population is increasing
each female produces ~>1 breeding daughter by end of reproductive period
if Ro = 1.33
population of 100 females will grow to 133 females per generation
population growth without restraint
geometric growth
if Ro is unknown
use lambda- geometric rate of increase, finite multiplication rate, finite rate of increase
lambda =
N_t+1 / N_t
estimate geometric growth of population in to future
N_t = N_o * lambda^t
useful for non overlapping (discrete) generations
semelparous species
population growth of iteroparous species
dN/dt = rN dN = rate of change in numbers dt = rate of change in time dN/dt = rate of population increase r = per capita rate of population growth (intrinsic rate of natural increase) N = population size
r ??
b - d
number of births/thousand yrs
number of deaths/thousand yrs
alternative estimation of r
r ~ ln Ro / Tc
Tc = generation time, mean time elapsing between birth and first reproduction
If r < 0
population declines
If r = 0
population is stable
if r > 0
population increases
to determine N at some point in future, for population with overlapping generations
N_t = No * e ^ rt
overlapping generations vs. discrete generations
over. Nt = Noe^rt
discret. Nt = No*lambda^t
projected population in 100 years if r=0.01 and No = 7 billion
19.6billion
Nt = No e^rt
why can populations not grow indefinitely
finite resources run out
renewable resources are limited
K
carrying capacity
carrying capacity
total numbers of individuals of a species that be sustained in a habitat in the long term
determining carrying capacity
often estimated indirectly as the average population numbers of the species observed across multiple years
many factors are involved, usually determined in hindsight
logistic growth
population ‘flattens out’ as it approaches K
types of / variations in logistic growth
ideal logistic growth (smooth response) damped oscillations (up and down before settling at k) stable limit cycle (up and down around k without settling) chaotic (extreme up and down, rise and crash)
logistic growth equation
dN/dt = rN [ ( K - N ) / K ]
carrying capacity of habitat is influenced by
most limiting resource
if populations exceed K
resources decline– morality increases– birth rate decreases– population decreases
factors limiting population growth
density-dependent population regulation
density-independent population regulation
density-dependent population growth
due to intrinsic (natural) factors
due to individuals (birth rate, mortality)
mechanisms for density-dependent effects when population exceeds K
intraspecific competition delayed breeding/reduced offspring production territoriality dispersal parasites/disease predators
intraspecific competition (populations exceeding K)
occurs when required resources are in limited supply (food, space, mates)
types of intraspecific competition
interference competition
differential ability to secure resources
Inference competition
individuals interfere with others for limited resources
leads to one individual having less
examples of inference competition
gulls stealing from others
lions excluding others from a kill
differential ability to secure resources
law of constant final yield- only a certain amount can be sustained in certain area, ex. start with 1000 or 100 plants, end with ~same amount
delayed breeding or reduced offspring production (populations exceeding K)
applicable to almost every bird and mammal
increased population = agonistic encounters = stress– females reabsorb embryo
agonistic
combative, conflicting, aggressive/submissive interaction
how stress can be birth control
stress triggers hyperactivation of hypothalamus, pituitary and adrenocortex- alters secretion of growth and sex hormones– suppression of body growth, reproduction, immune system– pregnant females enlarged adrenal glands, kidney inflammation, uterine mortality, reduced lactation
young born to stressed mothers
low body weight, poor survival, delayed puberty, low reproductive rate
delays puberty in juveniles born during periods of high population density
odour of female urine
increased territoriality (populations exceeding K)
territorial defense by dominant individuals leads to reduced access to resources by sub-dominant individuals
leads to reduction in # of non-territorial individuals (reduced reproduction)
dispersal (populations exceeding K)
migration
w/o migration population exceeds K and crashes
with migration population can ‘flatten’ at K
example of parasite/disease controlling population
Myxomatosis introduced in European rabbits in Australia, 99% mortality
example 2 of parasite/disease controlling population
gastrointestinal nematodes– reindeer– negative impact on female reindeer becoming pregnant– parasites have potential to regulate population dynamics– in presence of parasite populations = stable dynamics
average number of parasite species per host
fish ~2 birds ~8 mammals ~15 bugs, beetles, flies 4-6 butterflies, moths ~10 trees 95
Predators (populations exceeding K)
major source of mortality in survivorship curve
increased density of prey = predator expansion = proportionately greater predation on prey
parasitic wasp
~1mm, lays one parasitic eggs in each aphid, rapidly controls population
analysis of density dependent population regulation
parasites and disease - ~50% insects
predators - ~40% insects
mortality from limited food- ~40% small mammals/birds, ~50% insects, ~90% large mammals
mortality from limited space- 100% small mammals/birds
density-independent population regulation
reduction in carrying capacity of habitat
mainly due to extrinsic factors
mortality due to severe external conditions
mostly independent of NK
examples of density-independent population regulation
winter, severe draught, fire
lynx abundance
correlated to snowshoe hare abundance- increased food source
snowshoe hare abundance
correlated with 11yr cycles sunspots– higher solar output, more plant life, more food for winter
why don’t hare, lynx, sunspot curves match all the time
many factors are working together- plants produce anti-grazing chemicals, lynx produces stress changes in hares, hares reproduce less
a population of 50 female deer with stable age distribution has a Net Reproductive Rate of 1.1, if generation time is 2yrs, population is increasing by how many female individuals per generation
2
if population = 50, NRR = 1.1, generation time = 2yrs, population increases by 2 individuals per generation, how many will there be in 20 years?
130
anti grazing chemicals
phenols, bitter, less delicious, less nutritious
subcategories of interactions
competition, niche concepts, predation, defenses
Interspecific competition
any use or defense of a resource by one species that reduces the availability of that resource to other species
resource
any substance that leads to individual/population growth if substance is increased
resources
food, water, trace elements, space, elements (O2, CO2)
is air a resource
not generally (unless it was limited)
Liebigs law of the minimum
we often don’t know what the limiting resource is
what did Justus von Liebig do
discovered that nitrogen is the major nutrient for plants
competitive exclusion principle
Gause’s Law of competitive exclusion
2 species with same niche cannot coexist
Gause’s discovery
paramecium grown separately had logistic growth curves, grown together one species crashed, one species always outcompeted the other
evidence of interspecific competition
habitat shifts in allopatry and sympatry
character displacement and resource partitioning
habitat differences and resource partitioning
allelopathy
character displacement
feeding structures, breeding times, changing bill size, displacement of characters reduces competition
alpha
competition coefficient
per capita competitive effect of species 2 on species 1
measure of inhibitory effect “
alpha = 1
one individual of species 2 equals one individual of species 1
alpha = 0.1
then 10 individuals of species 2 equals one individual of species 1
total competitive effect of species 2 on species 1 =
alpha * N2
N2 - population size of species 2
competition model
dN1/dt = r1N1 [ (K1 - N1) - alphaN2] / K1
to coexist 2 species must have
alpha ~ 1.3 difference (ratio) in feeding parts
paradox of the plankton
limited range of resources supports wide range of planktonic organisms, paradox results from competitive exclusion principle, which suggests when 2 species compete for the same resource, only one will persist
grain beetle competitive exclusion
just a 3.2ºC difference in habitat switches competitive ability of two beetle species
allopatric speciation
populations of same species become isolated from each other, prevents genetic interchange
sympatric speciation
new species evolve from single ancestral species while inhabiting same geographic region
habitat shifts in allopatry and sympatry
allopatric populations habitat whole area, sympatric populations stick to one area, ex. when fish species are mixed one species lives in middle of lake, other around edges and bottom
character displacement (interspecific competition)
two allopatric species have same size feeding structures
species in sympatry have different size feeding structures
hutchinsons ratio
character displacement, size differences between similar species when living together compared to when isolated
average hutchinsons ratio for sympatric species
1.28
sympatric monkeyflowers (reproductive character displacement)
mean divergence of reproductive structures was greater in sympatric than allopatric, P values of reproductive structures <0.05
types of habitat differences and resource partitioning
the ghost of competition past
competition in the present
the ghost of competition past
at some point in the past, several species inhabited an area, all of these species had overlapping niches, through competitive exclusion, the less competitive species were eliminated, leaving only the species able to coexist
example of ghost of competition past
desert plants- developed different root systems to coexist
competition in the present
exotic species- artificially introduced, displacement of native species
examples of competition in the present
European starlings introduced to New York, most common nesting bird in US and south Canada, Scotch Broom from Europe threatening Vancouver island
allelopathy
chemical competition in plants and animals
release of chemicals by one species in order to reduce growth/survivorship of another
examples of allelopathy
antibiotics, poisons penicillin by mild jug lone by black walnut tree terpines by salvia corrals produce defenses to stop overgrowth from others
juglone
highly toxic, kills/injures other plants species within 20m, toxic to herbivore insects, reduces growth of weeds
species resistant to juglone
corn, maple, birch
salvia study
salvia produces terpines when predation is a problem
doesn’t when it is not (when caged)
habitat
physical place where an organism lives
niche
how an organism makes its living (carnivore, herbivore)
Elton’s niche
the role of a species in a community
Hutchinson’s niche
all biophysical conditions that characterize the life of a species
fundamental niche
entire multidimensional space that represents the total range of conditions within which an organism can function without limiting factors (prospective ecospace)
realized niche
actual multidimensional space that a species can occupy taking into account biotic factors such as predators, competitors and parasites (actual ecospace)
variable in quantifying niche space
d = distance between two species in average resource use (peak to peak, between species) w = measure of resource spectrum breadth of a species (peak to one side of curve, each species) K = resource availability
d/w < 1 (quantifying niche space)
no co-existance
d/w > 1 (quantifying niche space)
full co-existance
resource spectrums
most species have narrow resource spectrum
specialists have VERY narrow resource spectrum
ex. pandas only eat bamboo
Hutchinson’s concept of niche space
viewing overlap between species in multi dimensions
ex. foraging height, size of prey, time of day
n-dimensional hypervolume
increases organisms ability to coexist
biophagy
predation
types of predation
carnivory
herbivory (grazing, browsing)
parasitism (pathogens, parasitoids)
detritivores (dead plant/animal)
FRC
functional response curves
Functional response curves
rate of food consumption and density of prey
FRC#I, FRC#II, FRC#III
FRC#II
positively sloped, flattens out
single prey species
consumer is limited by its capacity to process food
only needs so much , satiated, caloric requirements met
FRC#III
standard logistic curve
multiple prey species
increases slower than II
threshold of security
occurs when there are multiple prey species
minimum density under which no further predation occurs- asymptote at lower end of curve
why threshold of security
when there are a rare amount of prey, go to new location or find other prey species to consume
FRC#1
increasing linearly
single prey species
assumes time needed by consumer to process food is negligible, consuming food does not interfere with searching for food
mostly theoretical, can apply to species with very high metabolism
low prey densities
reduced search efficiency
prey switching
search image
aggregated responses of predators
search image
predator develops ‘image’ of what to search for based on first prey it sees (likely most common)
proportion of prey population taken by predator predicts that
predators are rarely able to overexploit the prey
age class of prey taken by predators
virtually all predators target juveniles and post-reproductive adults
lowest cost of injury
salmon field study (removal of predators)
removal of predatory birds- twice as many smolts made it to ocean but same number returned, exceeded carrying capacity
grouse study (removal of predators)
removal of predators had no effect on grouse population
‘law of minimum’, prey not controlled by predators
mink predation on muskrat populations
most predation occurred on muskrats that had sen excluded from territories due to infraspecific competition, predators took prey where N>K
predators did not control population
wolf predation on caribou
without wolves caribou exceed K and population crashes
wolves keep caribou numbers from exceeding K
predator controls prey population in some sense
Isle Royal
wolves all homozygous, been studied since 1959, going extinct, moose population greatly increasing
parasitic wasp
2 stings to adult cockroach, 1 buckles front legs, 2 into brain, uses sensors along stinger to guid through brain, venom eliminates escape reflex, wasp leads cockroach by antennae, ‘zombie’ led to wasps burrow, wasp lays egg on underside of cockroach, plugs up burrow, egg hatches, larva chew hole in cockroach and climbs in, grows inside, devouring
do predators limit/control prey density
in some circumstances
no if Leibigs law of minimum is acting
yes if carrying capacity has been exceeded
yes but limits tendency of prey population to exceed K
yes when native prey have no defences against non-native predators
dingo - kangaroo relationship
no dingos = higher density of kangaroos present
dingo - wild pig relationship
with dines absent, biggest increase in population density was in babies
the biomass ratio of predator to prey in a community of endothermic predators and prey would be
~ 1:250
why is endothermic biomass ratio so high
endotherms have high energy requirements for thermoregulation
ectotherm biomass ratio
20:100 (1:5)
exploitation rate of prey by predator
average 5% for each predator species (mostly new born and old)
exploitation rate is low because
there are multiple predators per prey
why predators can coexist
increase in exploitation can be seen
up north (less predators)
highest exploitation rate
humans.. by far
only predator that take reproductive adults (target the reproductive capital)
escape tactics
camoflouge, disruptive colouration, crypsis, aposematic, mullerian mimicry, batesian mimicry
aposematic
be conspicuous
advertising poison/pain
predators learn to minimize contact
warning signal
mullerian mimicry
many poisonous species develop same conspicuous colour patterns (mimic each other), similar patterns among poisonous species (7 poisonous butterflies with same colour pattern)
batesian mimicry
non-stinging/edible species mimics stinging/poisonous species, very precise
ex. hoverfly mimics yellowjacket wasp
post-capture defenses
speed, agility, stamina, protean behaviour, autotomy-limb release, spines/armor/behaviour, reflexive bleeding, venomous
protean behaviour
unpredictable escape response (predator can’t adapt)
one of most common escape responses of prey
autotomy
lizard removing tail, crab releasing claw
reflexive bleeding
beetle with 2 separate chemical pouches, can combine them and spray at predator- hot, chemical reaction, blinding
effects of herbivory on plants
defoliation
loss of plant vigour, loss of competitive ability
young leaves consumed first (less lignin, most nutrients)
growth rate of plant reduced by up to 25%
young leaves consumed first
less lignin
most nutrients
less bitter
taste better
plant structural defenses
cactus spikes- protect water supply
plant chemical defenses
unpleasant odour contact irriation bitter taste neurotoxins proteinase inhibitors growth hormone mimics psychotropic effects
anti-browsing chemicals
alcohols, alkaloids, quinones, glycosides, flavenoids, raphides
plant unpleasant odour
mustard
plant contact irritation
poison ivy
plant bitter taste
very common
Red Ceder- tannins
plant neurotoxins
dinoflagellates (marine algae), paralytic shellfish poisoning
plant proteinase inhibitors
cotton, chickpea, potato
stops digestion
growth hormone mimics
catnip:
nepetalactone (mosquito/tick repellant)
iridodial (attracts aphid eating lacewing)
psychotropic effects
peyote (mescaline)
marijuana (THC)
coffee (caffeine)
animals utilizing anti-browsing chemicals
monarch butterfly- milkweed
poison dart frog- leaf cutter ant
antibrowsing compounds in spider food
mescaline– irregular web
caffeine– VERY irregular web
selective browsing of plants with anti browsing compounds
leaf veins are under positive pressure with toxins
don’t bite veins!
animal defense against plant chemical defenses
mixed function oxidaze
concentration of toxins
selective browsing
top anti predator mechanisms
- chemical- reflexive bleeding, toxic chemicals 46%
- fighting- stinging, biting, kicking, 11%
- crypsis- camoflouge 9%
- escape- running/flying, 8%
- mimicry- batesian/mullerian, 5%
interaction categories
competition, niche concepts, predation, defenses
ecological succession
continuous unidirectional sequential change in the species composition of the community
primary succession
initial establishment of plant and animal communities on substrates lacking living organisms
ex. bare rock, lava, sand dune, glacial melt pond, rainwater
alder trees
fix nitrogen, can grow on bedrock
die, make soil, others can grow
ecological succession
1º - from original material (rock slide/lava)
2º - change of an established community
secondary succesion
ponds/lakes accumulate sediment
vegetation develops on shoreline
eventually replaced with terrestrial community
each sequential community in ecological succession
seral stage
climax
last serial stage that has long duration and changes very slowly
early stage succession of pond
sedges and reeds, quaking bog
seral stage
not discrete stage
not always sequential, cycle back due to environmental factors (flood, fire, heavy storm, volcano, glaciation)
identifying succession
yearly pollen influx settles to bottom of pond
take core sample
identify pollen species
reconstruct vegetation history
radiocarbon dating
amplify minute quantities of DNA
animal/plant species determination
radiocarbon dating
CO2- >99% C12
C14, half life 5730yrs, decays to 14N
sedaDNA
securely dated DNA, molecular presence of species that appear absent in macro fossil record
allogenic succession
abiotic disturbance
autogenic succession
biotic disturbance
beaver dam, virus outbreak, invasive species
lodgepole pine
has been replaced by douglas fir
from pond sediment cores
species richness vs. seral stage
increases linearly to maximum, flattens out
young forest
high plant diversity, low animal diversity, very dense, low sun, few habitats
mammal/bird species diversity in forest after clear cutting
summer- immediately after, very high, dips, rises again
winter- immediately low, increases, flattens
total biomass in seral stages following clearcutting
large increase, small decrease, levels off
why decrease in total biomass following clear cutting
takes time for decomposers to reestablish, break down biomass
problem with reestablishing clear cut forest
takes time for soil community to reestablish
reestablishing communities in warm/wet climate
~100 yrs
Krakatau near Java
15m hot lava
reestablishing communities in cold/dry climate
~20,000 yrs
Yukon
glaciation
secondary growth forests have
almost no predatory insects
~1000 yrs to reestablish insect communities
ecological mechanisms for succession
stochastic events
facilitation
inhibition
tolerance
stochastic events (ecological mechanisms for succession)
unpredictable, who gets there first
facilitation (ecological mechanisms for succession)
species creates conditions favourable for a succeeding species but not itself
major process in early stages
leads to assembly rules
facilitation example
clover growth without soil– clovers produce soil for other plants to grow which shade out clover
assembly rules
regular and sequential shift in species
species B cannot establish till species A is present
examples assembly rules
predators cannot colonize successfully unless prey are present
pollinators can not colonize successfully unless flowering plants are present
inhibition (ecological mechanisms for succession)
species inhibits the colonization of subsequent colonists
slows succession and prolongs a seral stage
inhibition examples
allelopathy- plants/corals
competitive exclusion- intertidal communities
gigartina abundance
red marine algae- high density if Ulva removed, low if Ulva present
tolerance (ecological mechanisms for succession)
members of serial stage are those that co-exist due to use of different resources
combines facilitation + inhibition = ghost of competition past
early seral stages
seed dispersal - good plant efficiency low light- low resource acquisition - fast biomass- small stability- low diversity- low species life history - r seed dispersal- wind seed longevity - long shoot to root ratio- high
late seral stage
seed dispersal - poor plant efficiency low light- high resource acquisition - slow biomass- large stability- high diversity- high species life history - k seed dispersal- animals seed longevity - short shoot to root ratio- low
trophic levels
the sequence of steps in a food chain or pyramid
what are the trophic levels from lowest
primary producer– primary consumer– secondary consumer– tertiary consumer
why trophic levels (food chains) are unrealistic
because real life situations involve food webs
what determines food web complexity
number of trophic levels
chain length
connectance
linkage density
what is chain length (in food web complexity)
number of links running from a primary producer to a top predator
what is conductance (in food web complexity)
actual number of links in a food web divided by the total number of possible links (N)
N = (in food web complexity)
[ n (n - 1) ] / 2
linkage density (in food web complexity)
number of links per species
has the largest effect on a system (food web)
species with high linkage density
types of trophic pyramids
by numbers
by biomass
by energy
number trophic pyramids
how many individuals per trophic level- tertiary consumer is on top (1 consumer : 250 prey)
how many individuals are supported- top is biggest level, bottom is small (one tree maybe)
dominant species
a species with an effect on the community proportional to its biomass
umbrella species (indicator species)
species used for conservation decisions, supporting an umbrella species can save the ecosystem
examples of umbrella species
grizzly, panda, spotted owl, Garry oak
example of dominant species
cod
keystone species
a species with an effect on the community that is disproportional to its biomass or abundance
example of keystone species
sea otter- without them sea urchins take over– eat kelp– nursing grounds collapse– entire sub tidal community shifts
keystone molecule
DMS- dimethyl sulphide- produced when plankton feed on algae– attract bird/fish– they poop–nutrients increase algae growth
the major advantage to breeding earlier in life rather than later is
is shortens generation time
experimental removal of fish eating birds from a salmon river in eastern Canada led to which important ecological observation?
number of adult salmon returning to the river did not change
today, there are about 7billion humans on the planet. the yearly mortality rate is ~1% and generation time is about 15years. If each female produced one daughter in her life, the earths total population would be closest to which one of the rolling in 50 years assuming these rates remain similar
4 billion
