Chapter 53 Population Ecology Flashcards
What is ecology?
Study of interactions between organisms and their environment
How do populations, communities, and ecosystems, relate to each other?
Populations: group of individual organisms that interbreed
Communities: populations of different species that interact with each other within a habitat
Ecosystems: all living organisms, intergrating with each other and with non living elements of an area
Populations make communities. Communities make ecosystems
What is population ecology?
Focuses on the population, not the individual. Group of organisms of the same species in a certain geographic region
How are populations distributed?
Clumped
Uniform
Random
Clumped
- Most common, patches
- resource availability: ex plants will grow together in a desert
- offspring dispersed together: sponges or corals go off together and then pick a place to stay and don’t move (coral reef)
- social groups: protection, schools of fish, herd of zebra
Uniform
- individuals more evenly spaced
- form territories that they defend because of competition for food and mates
- ex: mountain lions claims an area or range of land for its own and defend its home from other mountain lions
- ex: desert shrub, roots compete for resources and release toxins, discourage close growth
Random
- Habitat conditions uniform, random where you find populations
- resource availability is constant, no competition, members do not attract or avoid each other
- ex: wolf spiders, solitary hunters, each burrow has equal advantage for prey
Immigration, Migration, Emmigration
Immigration: birth rates, individuals move into population, population size increases
Emigration: death rates, individuals move out of population, population size decreases
Migration: periodic movement between regions, seasonally, daily; individuals return to same starting point
How to calculate population growth
Birth rate: monthly birth rate/population
Death rate: monthly death rate/population
Per capacita growth rate:
per capita birth rate - per capita death rate
Population growth: per capita growth rate x # of I do ideals = population growth per unit time
This gives the # of new individuals to population. ADD WHAT U GET TO TOTAL POPULATION
What is exponential growth? Why is exponential growth not seen in natural populations?
- population with per capita growth rate that is constant and greater than zero
- grows at a rate proportional to current size (human growth rate)
- not seen in nature because in nature there is something to keep the population in check. (Predators, resources,)
What are density dependent factors?
- limiting factor on population growth
- essential resources are short in supply
- increases competition
- diseases and parasites
What is logistic growth?
- a population in an environment with limited resources
- the quantity of resources affects how large the population will be
What is carrying capacity K
- the max number of individuals of a species that a givens environment can sustain indefinitely
- if pop approaches K the death rate increases emigration rate increases birth rate reduces
What are density independent factors
- not influenced by population density
- increases death rates
- decreased birth rates
- populations may never reach K
- earthquakes, fires, snowstorm, floods, habitat destruction by humans
What is a rise and crash growth pattern? What kind of species interaction influences this pattern?
- not as clear cut as logistic growth or exponential, depends on available resources
- predator and prey exert pressure on each other
- ex: lynx and snowshoe hare. If hare pop goes up lynx come in and decrease hare pop. If hare pop goes down lynx pop goes down. Rise and crash pattern
- ex locusts: large amount of food they swarm and eat a lot and when there’s no food their pop crashes
