Ecological interactions Flashcards
The physical place where an organism lives
habitat
ex. tropical forest, grasslands
niche
how an organism makes its living
ex.carnivore-hunts at dusk versus daylight
herbivores- feeds on woolly plants vs grasses
Competition has —- and —- competition.
interspecific and intraspecific (within)
Leibig’s Law of the Minimum
pop. numbers can be regulated by a single resource that has the greatest relative scarcity
ex.phytoplankton has limited iron and nitrogen
Grinnell-1904 and Gaussian-1932
Evidence for interspecific competition
-give two species of paramecium and fixed amount of bacteria as food
-both showed logistic growth curve when separated but together one takes over the other
TWO SPECIES WITH THE SAME NICHE CANNOT COEXIST
If competitive exclusion is true, why are there so many species in the same habitat using the same resources?
habitat diversity
Grain beetles
Calandra beetle takes over the rhisopertha in 29.1C but in 32.3C Rhiso takes all resources
-temp is always changing maybe this is why they can coexist
Evidence for interspecific competition in nature?
1.Habitat shifts in allopathy and sympatry
2.Character displacement(ecological and reproductive)
3.Habitat differences and resource partitioning
4.Allelopathy
EVIDENCE OF INTERSPECIFIC
- Difference between allopathic and sympatric pop.
Allopatry= different home ( trout and char in separate lakes spread throughout)
Sympatry=same home( trout and char in same lake char only stays on bottom close to the shore and trout in center)
EVIDENCE OF INTERSPECIFIC
- What is character displacement?
the tendency for two species to diverge in form when in sympatry
ex. House Finch and black-headed Grosbeak -different size beaks b/c they live together
EVIDENCE OF INTERSPECIFIC
- What is the Hutchinson’s ratio?
Average Hutchinson’s ratio for sympatric species is 1.28
Mixed success in allying this
EVIDENCE OF INTERSPECIFIC
- Habitat differences and resource partitioning
-what is the ghost of competition past
It may look like there is competition but for example a forest how does all the different trees live in the same niche, they don’t have the same one. The roots under the soil take up different depths.
EVIDENCE FOR INTERSPECIFIC
- Habitat differences and resource partitioning
What is competition of the present?
-exotic species-artificial introducing a species into habitats they weren’t, leads to the displacement of native species that occupy similar habitats
ex. Scotch bloom introduced from Europe and now threatening native Garry Oaks
EVIDENCE OF INTERSPECIFIC
4. What is alleopathy?
What is Salvia?
What other things in ocean do this?
chemical competition in plants and animals
-the release of chemicals by on species in order to reduce growth or survivorship of another species
ex. Black walnut trees secrete Juglone from the roots
Crops like barley secretes alkaloids which reduces weeds
Salvia produces volatile terpines(bad smell)- two boxes with cucumber seeds- add Salvia to one doesn’t grow, b/c birds came to eat
Coral reefs- alleopathy among corals creating levels
Elton’s niche?
the role of a species in a community
Hutchinson’s niche?
What are the two niches in this?
-all biophysical conditions that characterize the life of a species
1-Fundamental niche
2-Realized niche
Fundamental vs realized niche
Fundamental- is the entire multidimensional space that represents the total range of condition within which an organism can function without limiting factors
Realized- the actual multidimensional space that a species can occupy taking into account biotic factors such as predators, competitors and parasites
what is Lotka and Volterra competition model-1926
effect of species 2 on pop. growth of species 1
rN(K-N)-aN2/K
N2= pop. size of species 2
a=competition coefficient(alpha)
-if species 1=2. a=1
What is biophagy?
consumption of bio material
Survivorship Curves are largely due to..
predation
What is the Functional response curves(FRC) measure?
rate of food consumption and density of prey
What is Compensatory predation in FRC curve?
At low prey densities
a) reduced search efficiency
b) prey switching
c) search images(predator has a better image for more common prey)
d) aggregated responses of predators
What is the threshold of security in a FRC curve
minimum density under which no further predation occurs
What is the most important curve in FRC?
FRC #111- Multiple prey species eaten
What age class do predators target?
mostly all predators target juveniles b/c of lowest cost of injury
-major exception to this trends is humans which target the largest
Do predators limit maximum prey density?
Yes no. Predators don’t control prey density in long term. No statistical difference in numbers( Leibig’s law of minimum)
ex. took all predators out of forest no different long term
ex. Wolves keep caribou from exceeding K so yes they control density( if carrying capacity has been exceeded)
ex. Muskrats that didn’t have territories are killed more
No: if Leibig’s law of the minimum is acting
Yes: if carrying capacity has been exceeded
Yes: when native prey have no defenses against non-native predators
Do predators limit maximum prey density?
Parasitic wasps(parasitoids)
important natural source of biological control of population numbers in insect host
wasp stings prey and control their movements into their burrow. Then wasp lays eggs, eggs eat organs for prey and make cocoon before breaking out
Do predators limit maximum prey density?
Non-native predators preying on native or non-native species
No opportunity for co-evolution between them and natural equilibrium is disrupted
ex. Wild dogs(Dingos) preying on kangaroos. Dingos totally control density of kangaroos
Relative abundance of predator and prey in a community
What are the ratios?
Endothermic predators(warm blood).- 1:300 ratio for predator to prey
Ectothermic predators( Relays on environment around them for body temp)- 60:300
Exploitation rate of prey by each predator
species
Average 5% for each predator species
Biological interest= targets weak and young
Biological capital- reproductive adults (Humans do this)
Defences of prey against predators-
First escape?
Camouflage or crysis
Conspicuous
Defenses of prey against predators
Conspicuous, Why stand out?
Mullerian?
Batesian?
Warning(aposematic) colouration
-usually poisonous
Mullerian mimicry- when poisonous species mimic each other
Batesian mimicry- when a harmless species mimic a harmful one
Defenses of prey against predators
What mechanism is the most frequent in arthropods(insects)?
Chemical
Defence of plants against herbivores?
A) Plant structural defences -pointy
B)Plant chemical defences-odour,irritation,bitter(very common)
Animal defences against plant chemical defenses.
a) mixed function oxidaze
b)concentration of toxins
c) selective browsing
