Growth-

Density- total number of individuals of a specific species divided by the area/volume occupied by the population D= N/S.

Density can be deceiving because of unused space within a habitat. Thus ecologist distinguish between crude density and ecological density

Crude density - number of individuals of the same species/ per total unit area

ecological density- number of individuals/ per used area by individuals

Distribution-

Dispersion- the general pattern in of individuals that are distributed through a specified area. Biologists have three main dispersion patters; clumped, uniform, and random.

Clumped dispersion- Most populations display clumped dispersion, organisms are densely grouped in areas of the habitat best for survival/ have favourable conditions

Uniform dispersion - Individuals are evenly distributed in the habitat. This dispersion may be a result of competition between individuals, for feeding, breeding, or nesting.

Farmer’s fields, orchards, and tree plantations are often uniformly dispersed.

Random dispersion- the pattern when individuals are spread throughout a habitat in a unpredictable manner. This dispersion is a result of minimal influences by interaction with other individuals, and habitat conditions are virtually uniform. Rain forests exhibit random dispersion

carrying Capacity - the maximum number of organisms that can be sustained by available resources over a specific period of time

Minimum viable size-

Population size- number of individual of a specific species in a given area/ volume at a specific time

Measuring Population characteristics

quadrat- sampling frame used fir estimating population size. It is most effective for stationary species ( forest, tree species)

Mark -recapture method - sampling technique for mobile wildlife population (fish). The sample of animals is captured, marked, then released. Finally recaptured, comparing the proportion fo marked and unmarked animals in a given area.

Fluctuation of population

Population dynamics are changes in population characteristics determined by birth, mortality, immigration, and emigration rates.

Fecundity is the potential for a species to produce offspring in one lifetime

Type 1 survivorship- (humans) late loss

Type 2 survivorship - (birds) constant loss, independent of age

Type 3 survivorship- (small fishes) Early loss

Calculating changes in population size

Open Vs. Closed population

An open population is when the change in number and density is affected by births,deaths, immigration and emigration. Whereas a closed population is only affected by birth rates and death rates. ( immigration and emigration do not occur)

Closed populations are rare. But populations that exist on secluded islands can be thought of as closed populations. ( ex. Peary Caribou an Arctic ocean island)

population Growth models

geometric growth - a pattern of population growth where organisms reproduce at fixed intervals at a constant rate

lambda = geometric growth

N = the initial population size in year (t + 1)

t = years

exponential growth- a pattern of growth where organisms reproduce continuously at a constant rate.

Modelling logistic Growth

logistic growth takes into consideration carrying capacity

logistic growth represents the effect of carrying capacity on the growth of a population

lag phase - initial stage, population growth is slow, since small population

log phase - stage where population growth is rapid

environmental resistance - factors that limit population’s ability to realize biotic potential. exceeds carrying capacity ; reproduction slows, and deaths increase.

biotic potential - max rate a population can increase in ideal conditions

stationary phase - population reaching carrying capacity, thus growth rates decrease . It is said to be dynamic equilibrium at this stage.

Dynamic equilibrium - birthrate = death rate

Density dependent factors Vs. Independent factors

density dependent factors are a factor that influences a population regulation, having a greater impact as population density increases or decreases.

the struggle for survival includes factors as competition, predation, disease, and other biological factors

Infraspecific competition- same species compete for resources in habitat

as population density increases, more competition, thus growth rate decreases

predation- predator killing prey ( 2 diff species usually)

disease is more easily spread in overcrowded populations , pathogens are able to move from host to host easily, since more host available in close proximity

allele effect- population cannot survive/ reproduce when the population density is too low.

Independent factors

• temperatures

• insecticide applications -→ killing entire food chain begining with intended insect

• limiting factor - any essential resource in short supply

Interaction within communities

community - all populations in given ecosystem

ecological niche- an organism’s biological characteristics ( food, shelter, mate). How an organism fits into an ecosystem.

Fundamental niche vs. Realized niche

fundamental niche is theoretical niche

realized niche is actual niche

Interspecific competition

interspecific competition occurs between different species for the same resources

Interference competition is actual fighting

exploitative competition is shared consumption or use if a resource

The population size if the weaker could decline.

resource partitioning avoidance of competition by occupying different niche

predation

as the predator population density increases , prey population density decreases

decline in prey then leads to reductuon in predator species

Predator-prey relationships have resulted in diverse defence mechanisms

• morphological ( thorns, hooks, spines, and needles)

• chemical defences against herbivores

disruption of community equlibrium

interspecific interactions help maintain necessary equilibrium that sustain communities

disruption can occur when natural disaster or invasive species

Energy pyramid - a model that illustrates energy flow from producers at the beginning of food chains to consumers farther along.

humans can obtain more energy from consuming more autotrophs ( grains vegetables, and fruits)

GMO- crops are being genetically modified to withstand extreme temperatures, to be resistant to pests and herbicides, to have better flavour, and nutritional content

Pollution can contaminate water

overconsumption result in over use of freshwater resources

climate change has caused glaciers to melt rapidly, thus depleting the time we can use them for fresh water

Acid deposition- a mixture of sulfur dioxide and nitrogen oxide pollutants that reach earth in the form of rain, gas, or solid ( acid precipitation)

acid deposition affects soil pH and aquatic systems

Greenhouse effect - a result of certain atmospheric gases, such as CO2, water vapour, and methane, trapping heat in the atmosphere by letting visible sunlight penetrate to Earth’s surface, while absorbing most wavelengths of infrared radiation that radiate from Earth’s surface

Causes of greenhouse gases are human activity ( burning fossil fuels)