Population and Community Ecology Flashcards
What is ecology?
Study of the relationships of organisms to one another and the environment
Involves examination of:
-distribution and abundance of organisms
-biotic interactions (between organisms)
-abiotic interactions (organisms and non-living environment)
List the levels of study of ecology from smallest to largest
- Organisms: survival/reproduction; unit of natural selection
- Population: unit of evolution
- Community: interactions among populations
- Ecosystem: energy flux and cycling of nutrients
- Biosphere: global processes
Population Ecology
The study of populations in relation to the environment
Define population
All the individuals of a single species that live/reproduce within a given area
Population Structure: (Patterns in space/time). List these characteristics
- size
- density/biomass
- distribution
- dispersion
Population dynamics: (Changes over time). List these characteristics
- age distribution
- sex ratios
- demography
- survivorship curves
Define size
Number of individual organisms present at given time
Does not indicate space occupied/involved
Numbers can increase, decrease or remain static
Define density
Number of individuals per unit area or volume
Determining density of natural populations is possible but difficult
Define distribution/dispersion
Special arrangement of individuals
- random
- clustered/clumped
- uniform
Define demography
Study size/structure/distribution over time
What are survivorship curves?
Gives average timing of deaths of individuals in a population
Classified into 3 types
What are the types of survivorship curves?
Type I: survive early years but decline in later years (humans)
Type II: steady decrease throughout life (birds)
Type III: death early in life but live longer in later years (turtles)
Age and sex distribution do what?
Reveal trends in population state
Uniform throughout ages (France)
More younger children then less older individuals (India)
How do populations grow?
Natality: births within population
Mortality: deaths within population
Immigration: arrival of individuals from outside population
Emigration: departure of individuals from population
Growth under idea conditions is helpful to study population growth because…
- capacity of species for increase
- conditions facilitating this type of growth
Population growth is described by…
Exponential Growth Model DN/dt = (rmax)(N) N=number of individuals T=time Rmax=intrinsic rate of growth
When population increase is ideal it results in exponential growth, this means what and results in what?
Reproductive rate is at its maximum=intrinsic rate of increase (rmax) (species specific)
Results in J-shaped curve
Exponential growth can be sustained indefinitely
TRUE OR FALSE
FALSE
What is a more realistic population model?
Logistic Growth Model
What is the Logistic Growth Model?
Per capita rate of increase declines as carry capacity is reached
Expressed as: dN/dt = (rmax)(N) ((K-N)/K)
N=number of individuals
T=time
R=rate of growth
K=carrying capacity
What is K
Carrying Capacity: maximum population size that an environment can support
Logistic growth Model results in a what-shaped curve
S-shaped curve
List the types of population regulation
- Density-Independent regulation: birth/death rates not affected by density but by other factors
- Density-dependent regulation: birth rates fall and death rates rise with population density
What are some factors that affect populations regardless of density?
- weather phenomena
- natural catastrophes
- random events (extraterrestrial/terrestrial)
What are some factors that affect populations because of density?
- Competition for resources
- Territoriality
- Predation
- Health (spread of disease)
- Toxic waste accumulation
- Intrinsic factors
What are the 2 life history strategies?
R-selection (density-independent)
K-selection (density-dependent)
What is r-selection?
Selects for life history traits that maximize reproduction
What is K-selection?
Selects for life history traits that are sensitive to population density
Characterisitcs of r-selected species: Maturation time: Life span: Mortality rate: Reproductive episodes: Time of 1st reproduction: Clutch/brood size: Size of offspring: Active parental care: Population size: Tolerance of environmental change:
Characterisitcs of r-selected species: Maturation time: short Life span: short Mortality rate: usually high Reproductive episodes: usually one Time of 1st reproduction: early Clutch/brood size: usually large Size of offspring: small Active parental care: little or none Population size: fluctuating Tolerance of environmental change: generally poor
Characterisitcs of K-selected species: Maturation time: Life span: Mortality rate: Reproductive episodes: Time of 1st reproduction: Clutch/brood size: Size of offspring: Active parental care: Population size: Tolerance of environmental change:
Characterisitcs of K-selected species: Maturation time: long Life span: long Mortality rate: usually low Reproductive episodes: usually several Time of 1st reproduction: late Clutch/brood size: usually small Size of offspring: large Active parental care: often extensive Population size: relatively stable Tolerance of environmental change: generally good
Define metapopulations
Large populations made up of many small populations linked by migrations
Define biogeography
Study of patterns of distributions of populations, species, and communities among biogeographic regions
**Geological history of regions influences kind of organisms found
What 3 scientific advances occurred to determine causes o species distribution?
- Acceptance of theory of continental drift/plate tectonics
- Development of phylogenetic taxonomy
- Development of the theory of island biogeography
Outline the key points of Island biogeography
The rate of arrival of new species on an island drops as species accumulate over time
The extinction rate increases over time as individuals from different species compete for resources
Eventually these rates balance at a point of equilibrium
Because populations are small, it may increase the probability of extinction
How does the size of the island affect populations?
Larger islands have more colonists and lower rates of extinction moving the equilibrium number of species to higher values
How does distance from mainland of the island affect populations?
Far islands have lower rates of colonization-equilibrium number of species moves lower
Extinction rates are not influences
List the scenarios of small-large island and close-far island in terms of equilibrium number
Small & far < Large & far < Small & near < Large & near
List the levels of community ecology from smallest to largest
- Organism: unit of natural selection
- Population: unit of evolution
- Community: interactions among populations
- Ecosystem: energy flux and cycling of nutrients
- Biosphere: Global processes
Define Community Ecology
Study of communities in relation to the environment
Define Community
Assemblage of all the populations that live an interact within a given area at a given time
Define Niche
A species’ special ecological role in its community
A multidimensional habitat that allows a species to practice its way of life
Due to competition and other species’ interactions what happens to niches?
Realized niche may be smaller than fundamental niche
Define intraspecific species interaction
Occurs when 2+ individuals from same species interact (population ecology)
Define Interspecific species interaction
Occurs when 2+ different species interact (community ecology)
What does Antagonism involve?
Species interaction is either both negative (-/-) or positive for only one (+/-) Competition Predation Herbivory Parasitism
Competition
(-/-)
Intraspecific and interspecific
Resources are limited due to consumption
What is the competitive exclusion principal?
2 species with the same niche cannot co-exist 1 species (the stronger one) will exclude the other species
What is resource partitioning?
Solution to direct competition and competitive exclusion by dividing resources by partitioning
Predation
(+/-)
Predator hunts prey
Important for food chains/webs
Herbivory
(+/-)
Animals feed on tissues of plants
Natural selection leads to evolution
Adaptions of plants to avoid herbivory: chemicals, physical (thorns, spines)
Parasitism
(+/-)
Parasite exploits host by gaining benefits and causing harm
Mutualism includes what types of species interaction?
Mutualism and Commensalism
Mutualism
(+/+)
Both species benefit (symbiosis)
Commensalism
(+/0)
One species benefits and other remains unaffected
Ex. Facilitation
Define Dominant species
A species which is most numerous and forms the bulk of biomass
Define Keystone species
Species that exerts strong control of community despite not being the most abundant
Removal of keystone species has significant ripple effect: alters food chain
Define Engineering species
Species that can change an ecosystem through its activities
Make new habitats or destroy habitats
What do interactions among species determine?
- Structure
- Function
- Species composition of the community
Define Invasive species
Species that spreads widely and rapidly becoming dominant and changing the normal function of a community
Many are non-native and have no natural controls
What is community succession?
Predictable series of changes in a community following a disturbance
Primary Succession
Occurs after a disturbance that eliminates all vegetation/soil life
Pioneer species
First species to arrive in a primary succession area (lichens)
Usually favours r-selected species
Secondary succession
Occurs after a disturbance that dramatically alters, but does not destroy all local organisms or the soil. (Fire , hurricanes, farming, logging, mining)
Remaining organisms form building-blocks
Climax Community
Community resulting from successful succession to mature community
Usually favours K-selected species
