Evolution 3 Flashcards
What is Krebs definition of ecology?
“Ecology is the scientific study of interactions that determine the distribution and abundance of organisms”
What does the intrinsic rate of growth depend on? (r)
Life-history traits such as birth rate, age of maturity, clutch size etc.
What are the ways in which species can be connected through resources?
They might compete for the same resource, they might serve as a resource to another or might collaborate to increase their resources.
What are the names in which species are connected through resources?
Competition, predation and mutualism.
What is Liebig’s law of the minimum?
The idea that each population should increase until the supply of most limiting resource constrains further growth.
What are the two types of competition?
Intraspecific and interspecific.
What are the two ways in which competition can occur?
Indirectly (through shared resources - plants for sunlight) and directly through defending resources such as physical combat.
Who did experiments with Paramecium?
Gause.
What did the experiments with Paramecium show?
If they were grown separately they reached maximum capacity, but if they were grown together the carrying capacity of the first population will be reduced by their own population and the competitor. (N1 and N2).
What is the equation for the logistic growth of a single population?
dN/dt=rN(K-N)/K.
What does the growth of the first population depend on, in terms of the second population?
How many of species 2 is present and the amount of resource species 2 takes away compared to another n1.
What is the equation for growth of population 1 in the presence of population 2?
dN/dt = r1N1(K1-N1-aplha1,2 N2)/K1.
What is an isocline?
A region where the population is stable and there is no growth.
In what case can populations coexist but the equilibrium is unstable?
One in which the two populations are strong interspecies competitors but there is weak intraspecific competition.
What is the competitive exclusion principle?
That is two species are using the same resource and share the same habitat, one competing species will eventually exclude the other.
What is a niche?
The resources that plants/animals use.
What is the fundamental niche?
The range of resources within a species is able to survive and reproduce.
What is the realized niche?
Competitors and predators may restrict the potential range for the niche.
When does competition occur?
When the niches of two different species overlap.
How can two organisms that share the same niche allow for coexistance?
They can specialise on differences within the niche.
What is resource partitioning?
Using different resources in nature as a response to competition.
Who did experiments to test the competitive exclusion principle as to whether it explained geographic distribution?
A. G. Tansley with bedstraws.
What was the result of the experiment to test the competitive exclusion principle?
That it was competition and not differences in ecological niches.
What are the evolutionary consequences of competition?
If there is genetic variation within a population for increased competitivity, competitiveness can evolve. If there is variation in resource, selection within the population may favour avoidance of competition with other species by evolving different traits.
What is the character displacement hypothesis?
The idea that when 2 species utilise the same resource and have an overlapping geographic distribution, their morphology may shift to avoid competition.
What was the hypothesis on the type of interaction between ferns and saplings?
Ferns compete with tree saplings for light, thus altering forest long term competition.
What was the alternative hypothesis for the interaction between ferns and saplings?
Ferns provide a good habitat for rodents who eat the tree seeds.
What was the result of the experiments with ferns and saplings?
Ferns provide shelter for the rodents and sapling mortality is only correlated with the presence of ferns when rodents are allowed in the plot. This is apparent competition.
What happens when two populations of different species compete for the same resource?
They reduce each others growth.
What is the most common stable equililibria between two populations?
When either drives the other to extinction.
How can a stable coexistence be achieved with interspecific competition?
When each population limits its own growth more than the growth of its competitor (bigger intraspecies competition).
Despite resource partitioning being an explanation for differential use of resources in nature, what else might be an explanation?
The observed difference might be due to separate evolution (allowing the species to live together) or differences among species may be irrelevant to competition - resources are not limiting or competition is not related to the differences we observe.
What are evolutionary consequences of competition?
If there’s genetic variation within population for increased competitivity, competitiveness can evolve. If variation in resource use exists, selection within the population may favour avoidance of competition with other species by evolving different traits.
