Chap 20 Flashcards
Population Density
Is defined as the # of individual organisms (N) in a given area (A) or volume (V).
• [Dp =N/A or Dp =N/V]
Growth rate (gr)
The change in the number of individuals in a population (^N) over a specific time frame (^t)
(Population crash and explosion for decrease and increase)
Three distribution patterns
Distribution patterns influenced by the distribution of resources in a habitat and the interactions among members of population/community
-3 types
3 distribution:
- uniform: artificial populations like orchards
- random: resources are abundant and populations don’t compete
- clumped: common as members are closer together for resources
Growth equation
gr= ^N/^t
Individuals over time
Per capita growth
Can be determined by calculating the change in the number of individuals(^N) relative to N (original individuals)
• {gr= ^N/N or Nfinal-N/N}
Factors that affect population growth
1) biotic factors
2) abiotic factors
3) limiting factors
Biotic Potential (r)
The highest possible “cgr” population
- # of offspring per reproductive cycle
- # of offspring that survive long enough to reproduce
- age of reproductive maturity
- life span of individuals
Exponential Growth Pattern
Brief lag phase followed by a steep increase in the growth curve. (J-shaped curve)
Ex) bacteria growth
Logistic Growth patterns
An s-shaped curve (sigmoidal)
Carrying Capacity (K)
Green line running through a curve
•theoretical maximum of population size that environment can sustain over time.
~without depleting resources
Density-dependent factors
Are BIOTIC
•increase with the density of a population
Density-independent factors
Are ABIOTIC and include harsh weather (drought flood fires)
•limit growth of a population regardless of density
Environmental resistance
Interacting limiting factors
•prevents a population from growing at its biotic potential and determined the carrying capacity of the habitat
R-selected strategies
Species that REPRODUCE close to their biotic potential (r) •early reproductive age •short life span •no parental care Ex) algae
K-selected strategies
Populations that live close to the carrying capacities (K) of their habitat
•few offspring per cycle
•parental care
•pinger life span
Ex) bison
Population types
Open system: immigration vs emigration
Closed system: nothing is added or removed from the environment
1) competition
- intraspecific
* interspecific
intraspecific
Competition for limited resources among members of the SAME species
Interspecific
Competition between 2 OR MORE populations for resources (light, space)
-can’t share niches
2) predator and prey
-producer consumer interaction
•peak for predators = crash for prey
~next year they will crash to restart
3) symbiotic relationships
- mutualism(++)
- commensalism
- parasitism (-+)
4) succession
•pioneer community first to colonize
•climax community becomes stable
A) primary succession: ongoing eras
B) secondary succession: disturbance (fire)
Primary succession and secondary
1) NO SOIL. An event occurs that changes structure if a community
2) soil REMAINS. Recolonization of Ana area after disturbances
Sustainability
The concept of living in a way that meets out needs without compromising health of future generations or planet
Age pyramid
Are tools that demographers use to help them assess a populations potential for growth. (Cgr)
•shows % of males and females in separate categories
