C4.1 Populations and communities Flashcards
Population
group of individual organisms of the same species in a defined area, where members can interbreed with each other
Standard deviation
Measure of the variability of data in dataset
Lower SD shows little variation between values
High SD shows lots of variation
Sessile organisms
Organisms that are fixed in one place
Quadrat
square sample area
Motile organisms
Organisms that are capable of moving from place to place
Carrying capacity
Max size of population that the environment can support due to limited availability of resources
Density dependent factors
Factors that have increasing effects as population increase
eg. competition, predation
Density independent factors
Factors that have same effect regardless of population size
eg. flooding, fires
Lag phase
Population still small but starting to increase
Exponential growth phase
Population increases rapidly, limited threats, abundant resources
Transitional phase
DDF start to impact population growth
Plateau phase
Population remains close to carrying capacity
Stable equilibrium
When population aligns with carrying capacity
Intraspecific relationships
Interactions between members of same species
Competition or cooperation
Competition
Same species have same ecological niche and need same resources
Coorperation
Relationships where both species benefit
Community
Group of populations living together in an area and interacting with each other
Includes all populations in a specific area
Herbivory
Primary consumers eating plants
Producer may or may not be killed
Predation
One consumer species killing and eating another
Interspecific competition
Two or more species using the same resource
Mutualism
Two species living in close association
Both species benefit
Parasitism
One specifies (Parasite) lives on/in another species (host)
Parasite benefits, host is harmed
Pathogenicity
One species (pathogen) living inside other (host), causing disease in host
Pathogen benefits, host harmed
Commensalism
Relationship where one species benefits from another while the other is not affected
Antibiosis
Two organisms interact in a way that harms one of both of them
Endemic species
Species that occur naturally in an area
Alien species
Species introducted to an area by humans
Invasive species
If alien species increase in number and spreads
Dynamic equilibirum
Balance between opposing forces
Cyclical oscillations
Rise and fall of populations in a cyclical nature
Direct interaction
Predator feeds on prey/herbivore feeds on producer
Indirect interaction
Population size of predator can affect the population of producers from impact on herbivore prey
Top down control
Process where higher level species regulate lower level species
Bottom up control
Process where lower level species regulate higher level species
Antibiotics
Compounds secreted by microorganisms to kill or prevent growth of other microorganisms
Penicillium
A saprotrophic fungi that lives in soil that secretes digestive enzymes and absorb digestion of organic molecules, reducing competition that interfere with bacterial cell wall formation
Allelopathic agents
Compounds secreted into soil by plants to influence growth, survival or reproduction of others
Inhibiting nearby growth reduces competition, increases availability of resources
Chi squared test
Statistical test used to examine whether two variables are independent in influencing test statistic
Statistical significance
Outcome of statistical hypothesis test
Usual significance level
5%/p=0.05
Chi squared test method
- State null and alternative hypothesis
- Contingency table with observed values
- Contingency table with expected values and calculate expected frequency
- Determine degrees of freedom
- Find critical value
- Find Chi squared value
- Compare Chi squared value to critical value, if X^2> critical value, reject null and accept H1
Expected frequency formula
(Row totale * column total)/Grand total
Degrees of freedom formula
(m-1)(n-1)
m = number of rows
n = number of columns
