Recap Infomation (Week 1) Flashcards
What is population dynamic
the pattern and processes of change in populations
What is a population?
a population consists of - individuals of a species that interact with one another within a given area at a particular time
What is Demography?
the study of population processes
What are Life History Strategies/ Traits?
A way of describing how time and energy is allocated among various activities throughout an organisms life - They vary dramatically - The variations determine how fast populations grow
Environmental conditions affect life history strategies. what is the simplest population model?
Intrinsic rate of increase (r) r = births - deaths
Intrinsic Rate of Increase: What happens when births exceed deaths (r>0)?
The population grows
Intrinsic Rate of Increase: What happens when deaths exceed Births (r<0)?
The population declines
Intrinsic Rate of Increase: What happens if r=0?
the population is stable
which traits are most commonly influenced by environmental changes?
Age at Reproduction (generation time) Number of broods per female Number of offspring per brood
What are iteroparous species?
Species which reproduce multiple time during their life - typical of organisms whose survival chances are initially low, but increase once they reach maturity. - E.g. Social insect nests are very stable environments (iteroparity is common) Examples include Northern Gannets
What are Semelparous species?
species which reproduce once - Typically produce more offspring at once - Typical of organisms with low survivorship (E.g. some fishes, many insects, all annual plants, Rusty Tussock Moth
Give an example where predation influences Life history strategy.
Guppies (Poecilia reticulata) - Trinidad - Predator fish are excludes by waterfalls and the guppies have a lower mortality rate - Lab: Compare LHS of guppies in high vs. Low predation sites High predation sites: - Mature early, produces more offspring per brood, more eggs compared with low predator guppies Conclusion: adaptation to predation due to natural selection of life history traits
What is expotential growth?
when growth rate remains constant - as population size increases, number of new individuals added per time unit increase
what is the mathmatical equation for Expotenial population Growth?
^N/^t = b-d Change in no. over time = births-deaths dN/dt=(b-d)N dN/dt defines the rate of change in potenial size over time dN/dt = rN Intrinsic rather of increase (rN is sometimes called the biotic potential of a population)
Is exponential populations growth unsustainable?
yes. for short periods of time some populations may grow at an exponential rate usually followed by a population crash. E.g. Reindeer
What factors limit population densities?
Resources become scares/depleted, birthrates drop and death rates increase
How are populations limited?
Carrying Capacity (K): - Number of individuals of a species that can be supported by an environment (Key for sustainablilty)
What happens to a population when it nears the carrying capcity?
It slows down (logisitc growth) which makes an S shape on a graph E.g. sawtoothed grain beetle
What is environmental resistance?
The reduction in population growth due to a known reduction in resources
what is the formula of logistic growth when incoperating carrying capacity?
dN/dt= rN K-N/K r = Intrinsic growth rate N = Population size K = Carrying capacity
what is the Allee effect?
Individuals have a more difficult time surviving or reproducing if the population size is too small E.g. meerkats (Suricatta suricatta)
density-independent factors are:
Abiotic E.g. Deserts, Storms, cold periods of time
Density-dependent factors are:
Biotic E.g. availability of food, predation, disease and migration
What is associated with unpredictable habitats?
High fecundity High intrinsic rate of increase r- strategists
What is associated with Predictable habitats?
Low fecundity Low intrinsic rate of increase K-strategists
What does fecundity mean?
The rate at which offspring is produced.
What are the 4 factors in favour of high density?
- Species that use abundant resources 2. Species with small body size (need less energy) 3. Complex social organization 4. Some newly introduced species
What is a Community?
An assemblage of populations of various species living close enough for potential interaction E.g. carrier crabs carry sea urchins
Classify community intereactions
Interspecific interactions and relationships between species in a community. May have a positive (+) or negative (-) effect, or no effect (0) at all. E.g. Predation, herbivory, symbiosis, parasitism, mutualism, commensalism and facilitation
What sort of interaction is predation?
+/- interaction
What sort of interaction is herbivory?
+/- interaction
What is symbiosis?
A relationship where two or more species live in direct and intermate contact. E.g. Fungi and Algae to make lichen
What sort of interaction is parasitism?
+/- interaction
What sort of interaction is mutualism?
+/+ interaction. there are two types. - Obligatory (one species cannot live without the other - Facultative ( Both species can live alone) E.g. acacia tree and ants
What sort of interaction is commensalism?
+/0 interaction - Hard to document in nature, an example is the Ox and Oxpecker
What sort of interaction is Facilitation?
+/+ interaction - 1 species has a positive impact on another without direct and intermate contact E.g. Black Rush makes soil more hospitable for plants
What is Competitive Exclusion?
- Interspecific competition (-/-) when competing for resources - Strong competition can lead to competitive exclusion, local elimination of a competing species - The competitive exclusion principle states that two species competing for the same limiting resources cannot coexist in the same place
What is an Ecological Niche?
The total of a species’ use of biotic and abiotic resources is called the species’ ecological niche - An ecological niche can also be thought of as an organism’s ecological role - Ecologically similar species can coexist in a community if there are one or more significant differences in their niches
What is the fundamental niche?
A species’ fundamental niche is the niche potentially occupied by that species
What is a Realized niche?
A species’ realized niche is the niche actually occupied by that species
What results from having fundamental and realized niches?
As a result of competition, a species’ fundamental niche may differ from its realized niche – In one classic example, the presence of one barnacle species limits the realized niche of another species (Connell 1961)
What is the trophic structure?
- Trophic structure is the feeding relationships between organisms in a community - It is a key factor in community dynamics - Food chains link trophic levels from producers to top carnivores
