Population Dynamics Flashcards

The hardy weinberg principle (aka gentic equilibrium) is when if the nessecary factors remain constant, the gene pool will remain contant generation after generation (no evolution). The H.W. equation calculates what a non evolving frequency on traits in a pop. should be. When the equilibrium is upset it is called evolution, this is when what we see in a pop. does not match the H.W. equation.

Micro evolution is when a species has small changes and evolves over a long period of time. Macro evolution is when the changes are so large the two species can no longer make viable babies and speciation has occured. A population is the same species in the same place at the same time. A gene pool is all the alleles in a population (dom or recessive) it is used to calculate gene and allele frequency. 2 alleles are called a genotype (homo dom, homo recessive and heterozygous).

A large population, Random mating (no selctive breeding), NO mutations, NO migration, NO natural selection (equal viability, fertility and mating ability of all genotypes). Gene flow is the net movment of alleles from one population to another (inducing new ones or removing current) gene flow is positive because it creates more diversity. Non-random mating is when one mate has selective adv. over the other. It is likely to occur because organisms have preferred phenotypes and inbreeding can occur. Natural selction is when some indivudals are better able to survive and reporduce than others do to environmental pressure. The succeful gnes are passed on and become more commin. Ex: selective advantages, secual selection, heterozygous advantage.

Genetic drift occurs when there is a change in allele frequency in a breeding population due to random events. Small populations may lose certain alleles (lack of mates, or chance events (predation, disease...) it has the greatest impact on small populations. Gene drift is bad because ir decreases genetic diversity. There are two types of gene drift the founder and the bottleneck effects. In the founder effect a population (gene pool) is formed by a small group of individuals (called founders), that carry a representation of the orginal populations genes. In the bottleneck effect a quick reduction of population occurs do to selective pressures and causes a "bottleneck" in the surviving populations gene pool. It produces less variant offspring and is negative in short term.

• - There is stabilizing selection in which the average phenotypes have a selective advantage over the extreme phenotypes, in this mode of selection the frequency/trait the graphs trait peaks tend to be around the middle
• - Next there is Disruptive selection in which both extreme phenotypes are favoured over the intermediate phenotypes, in this trait/freq. graph the trait peaks are closer to the poles
• - Then there is directional selection in this type of selection the phenotype at one extreme has a selective advantage over those at the other extreme, in this graph the populations traits shift to one extreme.
• - There is also sexual selction which is extreme differences between two genders and it leads to disruptive selection.
• - then there is also artificial selection which is when humans select breeding pairs.

You divide number of organisms by the total area they are. thus tells you the average number of individuals in a defined area.Dp is determined by sampling. There is Random distribution which has no order, no attraction or repulsion among members (lots of resources), then there is uniform order which is when competition among individuals for factors such as light, space, moisture and nutrients spaces out individuals. These are called territories or can be artificially distributed by humans. third there is clumped order, in this individuals are grouped in patches around an attractant or they asexually reproduce (ex: oasis, watering holes, sloughs)

There is natality (b) which is birthrate (+), Mortality (d) which is deathrate (-), Immigration (i) which is moving in(+), Emmigration (e) which is moving out (-). Delta in is the factors that increase population minus the factors that decrease population. In open population migration is possible so we calculate both migration and births and deaths, in closed there is not migration so we only calculate births and deaths.

growth rate is the average a population grows over a time frame, it is found by keeping track of pop. density over an extened timeframe. gr=deltaN/deltaT. Spikes in death are usually caused by war and disease (or other crisises) and a spike in birth rate usually follows. cgr is per capita growth rate (also called biotic potential) it is how much a population grows per organism (deltaN/N). populations can grow fast or slow is affected by the # of organisms present and how fertile each organism is.

The positive factors regulating biotic potential are offspring (max #/birth), Procreation (#times/year reproduction occurs), Capacity for survival (this is the chance of the organism reaching reproductive age), Maturity (age at which reproduction begins) and Life span. The negative factors are apart of environmental resistance, these are all the factors that tend to limit population growth (lack of resources, emigration, competition, climate change, predation, disease). When the positive and negative factors have caused a population to stay relatively stable this means they have balanced out and they have reached their carrying capacity.

There is a J-curve in which large growth occurs and keeps accelerating, it is exponential unrestricted growth (ex: mosquitoe growth) it is usually followed by a sharp decline in population. Second is an S curve, aka restricted growth in this type of growth curve on a graph, growth begins by accelerating then achieves its point of maximum growth and begins to slow down until it reaches the carrying capactiy of the environment in which the population stays relatively stable (occurs in large mammal pop growth). First comes the Lag phase in which the population grows slowly (deltaN = (n+i) is slightly greater than or equal to (m+e)). Next is growth phase in which large growth occurs (deltaN = (n+i) are much greater than (m+e)). Third is the plateau/stationary phase in which growth slows down and pop stays stable (deltaN = (n+i) = (m+e)). Last is the death/decline phase in which the population is hit with biotic or abiotic (density dependent or density independent) environmental resistance and the population declines (deltaN = (n+i) is less than (m+e).

Density independent factors affect population regardless of size, they are mainly abiotic and include things like floods, weather, sunlight, drought, temperature...). With Density dependent factors and increase in population = an increase in these factors, examples are diesease, parasites, food, competition). The law of the minimum states that of all essential substances required for growth, the one in shortest supply controls population numbers. Shelfords law of tolerance states that too little or too much of any factor can be harmdul to an organism (ex: salinity, temp.) tolerance = survivability.

They are also called age pyramids and are useful to study animals with a life span of more than a couple years to see if the population will grow, stabilize or decline in the coming years. We can also use them to study the population in terms of its age structure and porportion of males to females, it does not show immigration and emmigration numbers. The three shapes are 1. pyramid which means rapid growth but usually shorter lifespan, rectangle which is slow growth with a long lifespan and an upside down trianglish shape which means negative growth (more seniors than kids).

r species (also called opportunists) are highly reproductive and their main limiting factor is their short life span/how much they can reproduce. They have a small body size, create large numbers of offspring that mature and grow fast and have little parental involvement with their offspring. The main examples are bugs. R-species show a J-curve in their growth curves. K-species (also called equilibrium) main limiting factor is the carrying capacity of their environment (K). They have a large body size, create a small number of offspring that are slow growing/maturing and require large amounts of parental involvement. The main examples are large mammals such as humans, bears, elk, etc. K-species show an s-curve in their growth curve graphs.

• 1. Does it have a long life?
• 2. What is the maturation rate of the offspring, long or short?
• 3. How many offspring are produced?
• 4. What is the organisms body size?
• 5. How much are the parents involved with the babies?

1. Competition (short term +/-, long term +), 2. predation (+/-, includes death of an organism), 3. mutualism is when both species benefit (+/+), 4. commensalism is when one species benefits with no effect to the other (+/0), 5. parasitism (+/-, usually does not involve death) it is when one species benefits (parasite) while harming but not killing the other (host)

It is density dependent competition between the same species for resources. You can avoid it by having offspring being different from the parents, or sending your seedlings far away (wind, fleshy fruit). Interspecfic competition is between different species for the same resources, it is caused by overlap of niches. An example is introduced species (non-native/invasive). The solution to it is specialization. Gause's law stats that if 2 populations have the same niche one will be eliminated (competitive exclusion).

• 1. Resource partitioning, which is when sympatric species consumer slightly different foods or use other resources in slightly different ways (splitting resources)
• 2. Character displacement which is when sympatric species tend to diverge in those characteristics that overlap, they undergo a NICHE SHIFT.

• Predation is the relationship between predator and prey, it leads to co-evolution (species adapting due to pressures exerted on each other). defense mechanisms are:
• 1. camouflage (cryptic colouration) which is when an organism blends in with its environment in form, shape or behaviour (ex:hares in winter)
• 2. Biochemical: which is when an organism is bitter tasting or toxic to its consumer (monarch butterfly)
• 3. Armour: which are thorns, spines, hairs and shells (ex: porcupine)
• 4. Warning (aposematic colouration): which are natures warning colours (red, yellow and black) on an organisms body to warn of threat (ex: wasps, venomous snakes)
• 5. Mimicry, which is when an organism develops a similar colour pattern, shape or behaviour to avoid predation (ex wasp colouration on flies) - there are two types 1. Batesian is a trick (non harmful mimics harmful) and 2. Mullerian (both animals are harmful and look similar)

They are when  first degree consumers and first degree producers are so connected they form a relationship with each other. They end up limiting each others populations and can elad to boom and bust cycles. ex: snowshoe hare and lynx. It leads to co-evolution due to similar environmental resistances.

Sucession is the gradual changes in vegetation from a pioneer community to a climax community, "pioneer pave the way for climax" (best adapted). There is primary succesion which is when no community existed before and secondary which is after a destructive event like a flood, fire or tsunami. The three types of organisms in succession are first pioneer which are the first to arrive, are always r selected, resistant to direct sun and fluctuating soil temperature and their dead bodies produce soil (ex: lichens,grasses and weeds), the second type are seral/intermediate, they live longer, require more nutrients and shade undergrowth (ex: shrubs and soft wood trees), the thridr type are climax species and they have the longest lifespans, can tolerate shade and stabilize the environment (ex: hardwood trees).

THey are species that have an influential ecological role, they exert important regulating effects on other species in the community, "they hold everything up", when they are present they increase diversity in the ecosystem. Ex: sea otters and urchins.