chapter 41: species interactions Flashcards
what is a biological community?
an assemblage of populations of various species living close enough for potential interaction
what are interspecific interactions?
relationships between species in a community
what can interspecific interactions affect?
the survival and reproduction of each species, and the effect can be summarized as positive (+), negative (-), or no effect (0)
when do interspecific interactions occur?
when species compete for a resource that limits their growth
what can strong competition lead to?
competitive exclusion, local elimination of a competing species
what is the competitive exclusion principle?
two species competing for the same limiting resources cannot coexist in the same place
what is an ecological niche?
the specific set of biotic and abiotic resources used by an organism. can also be thought as an organisms role.
what is evident in the concept of the ecological niche?
evolution
how can similar species coexist in the same place?
ecologically similar species can coexist in a community if there are one of more significant differences in their niches
what is resource partioning?
differentiation of ecological niches, enabling similar species to coexist in a community
what is selective pressure?
any reason for organisms with certain phenotypes to have either a survival benefit or disadvantage
what is a species fundamental niche?
the niche potentially occupied by that species. this can differ from the species realized niche
what is a species realized niche?
the niche actually occupied by that species
what is the type of interaction in predation?
+ for predator and - for prey
what is predation?
refers to an interaction in which one species, the predator, kills and eats the other, the prey. predator-prey interactions can provide a strong selective pressure which results in the evolution of many unique advantages
what are some feeding adaptations predators have?
claws, teeth, stingers, and posion
what are adaptations?
they are not things that animals/ plants can decide to do. adaptations can only exist if they naturally come about because of a mutation
what behavioural defence adaptations do prey have?
hiding, fleeing, forming herds/ schools, and active self-defence
what morphological and physiological defence adaptations do animals have?
cryptic colouration/ camouflage - makes prey hard to find
what is coevolution?
the evolution of 2 or more species which reciprocally affect each other, sometimes creating a mutualistic relationship between the species.
explain the relationship between predator and prey population.
inverse and it flip flops back and forth
what type of interaction is herbivory?
+/- interaction
what is herbivory?
refers to an interaction in which a herbivore eats part of a plant or alga
what adaptations do herbivores have?
in addition to behavioural adaptations, some herbivores may have chemical sensors or specialized teeth or digestive systems
what are some plant defences?
chemical toxins and protective structures
what is symbiosis?
a relationship where 2+ species living in direct and intimate contact with one another/ come across each other a lot - may or may not have an effect on each other
what are the types of symbiosis?
1) parasitism
2) mutualism
3) commensalism
what type of interaction is parasitism?
+/ - interaction
what is parasitism?
a type of symbiosis where one organism, the parasite, derives nourishment from the other organism, its host, which is harmed in the process. the parasite is usually a lot smaller than the host. many parasites have a complex life cycle involving multiple hosts. some parasites change the behaviour of the host in a way that it increases the parasites fitness.
what can parasites affect?
survival, reproduction, and density of host populations
do parasites want to kill the host?
no it wants to get as much nutrition from the host as possible, but does not want to kill the host.
what type of interaction is mutualism?
+/ + interaction
what is mutualism?
an interspecific interaction that benefits both species. in some mutualisms, one species cannot survive without the other. in other mutualisms, both species can survive alone. mutualisms sometimes involve coevolution of related adaptations in both species.
what type of interaction is commensalism?
+/0 interaction
what is commensalism?
one species benefits, and the other is neither harmed or helped. commensal interactions are hard to document in nature because any close association likely affect both species.
what are two fundamental features of community structure?
species diversity and feeding relationships
how is diversity measured?
diversity is measured by 2 different things: species richness and relative abundance
what is the species diversity of a community?
the variety of organisms that make up the community
what are the two components of species diversity?
1) species richness
2) relative abundance
what is species richness?
the number of different species in the community
what is relative abundance?
the proportion each species represents of all individuals in the community
what is simpson’s diversity index formula?
1- the sum of (n/N)^2
what can communities with a higher diversity rate be characterized as?
more productive and more stable in their productivity. able to produce biomass more consistently than single species plots. better able to withstand and recover from environmental stresses. more resistant to invasive species
what are invasive species?
organisms that become established outside their native range
what is trophic structure?
the feeding relationships between organisms in a community
what do food chains do for trophic levels?
food chains link trophic levels from producers to top carnivores
name the basic order of a food chain.
primary producers (ex. plants) - primary consumers (herbivores) - secondary consumers (carnivore) - tertiary consumers (carnivore) - quaternary consumers
what is a food web?
a branching food chain with more complex trophic interactions
what are dominant species?
those that are most abundant or have the highest biomass
what are the hypotheses for dominant species?
1) dominant species are most competitive in exploiting resources
2) dominant species are most successful at avoiding predators and disease
what do ecosystem engineers do?
cause physical changes in the environment that affect community structure
what are keystone species?
they exert strong control on a community by their ecological roles or niches. they are not as abundant as dominant species.
what does the bottom up model of community organization propose?
a unidirectional influence from lower to higher trophic levels
what equation represents the bottom up model?
mineral nutrients (N) -> plants (V) -> herbivores (H) -> predators (P)
what is another name for the top-down model?
trophic cascade model
what is the top-down model?
predators control herbivores, which in turn control primary producers
what is the equation of the top-down model?
mineral nutrients (N)
what is ecological succession?
the sequence of community and ecosystem changes after a disturbance
when does primary succession occur?
when no soil exists when succession begins
when does secondary succession begin?
begins in an area where soil remains after a disturbance
what are the three processes by which early-arriving and late-arriving species may be linked?
1) early arrivals may facilitate the appearance of later species by making the environment favourable
2) early species may inhibit the establishment of later species
3) later species may tolerate conditions created by early species, but are neither helped nor hindered by them
what are the key factors that affect a communities species diversity?
latitude and area
where does a species richness decline?
species richness is great in the tropics and generally declines along an equatorial polar gradient
what are key factors in equatorial polar gradients of species richness?
evolutionary history and climate
why do tropical environments have a greater species richness?
the age
what is the most probable cause of the latitudinal gradient in biodiversity?
climate
what factors of climate correlate with biodiversity?
sunlight and precipitation
what is evapotranspiration?
evaporation of H2O from sol plus transpiration of H2O from plants
what does the species area curve present the idea of?
that all other factors of being equal, a larger geographic area has more species
what are zoonotic pathogens?
they have been transferred from other animals to humans.
what are early arriving species?
Species that arrive first in the newly created environment are called pioneer species, and through their interactions they build a simple initial biological community.
