Ecology Part 3 Flashcards
Population
A group of organisms of the same species inhabiting the same area at the
same time
Community
Interacting populations occupying the same area
Ecological species
A set of organisms occupying the same niche
Biological species
Closely related organisms capable of interbreeding and producing fertile
(viable) offspring
How is Population size (number of individuals in a population) affected?
Birth (increases population size)
Death (decreases population size)
Migration (increases or decreases population size)
What is recruitment?
Number of birthed offspring attaining maturity (added adults)
What is Biotic Potential?
Maximum rate at which population can increase in ideal conditions
What is Environmental Resistance?
Set by a combination of biotic and abiotic factors
Establishes the Carrying Capacity (max population size supported)
What is biotic potential detailed?
Rate at which population increases in ideal conditions
No competition
Unlimited resources
Therefore, unrestricted exponential growth
Which are the influential factors of biotic potential?
Age at sexual maturity
Average frequency of reproduction
Average number of offspring produced per batch
Average reproductive life span
Average death rate under ideal conditions
What happens in Exponential Growth? (Biotic Potential)
Growth without limits
What happens in Logistic Growth? (Environmental resistance)
Competition limits growth.
What is environmental resistance and some examples?
Environmental limits set by biotic and abiotic factors
Food availability Habitat space Competition (intraspecific and interspecific) Disease Parasitism
Increases death rate and lowers birth rate
Balances population size around an ideal density
Population quickly reaches set limit and then fluctuates around it
What are growth curves?
Graphical representation of population growth
Population growth pattern is often repetitive on a small scale
Many mini booms and mini busts (depending on environmental resistance)
Graphs more complex than simple curve
Factors of an S Shaped (Sigmoid) Growth Curve?
Density dependent growth
As numbers increase, growth slows down
Factors of a J Shaped Growth Curve?
Density independent growth
Growth continues to speed up exponentially until the carrying capacity is exceeded
J-Shaped Growth Curve (detailed)
Lag phase is followed by a log phase until the population suddenly crashes
Also called the “boom and bust” cycle
Growth is Density Independent
Population grows quickly and then crashes
this cycle is repeated incessantly
Influential factors include:
Seasonality, breeding phases, human intervention (e.g. pesticides), seasonal climatic extremes (e.g.floods, fires or droughts)
what is the exponential growth equation?
dN/dt = rN
S-Shaped growth curve (detailed)
Growth is Density Dependent
Curve is Logistic
Lag phase (slow growth due to adjustment and few numbers) Log phase (max birth rate growth speeds up as numbers increase) Deceleration phase (environmental resistance increases with increasing density) Stationery phase (recruitment and death even out)
Saturation Value or Carrying Capacity is reached
Death phase (death rate exceeds birth rate due to increasing environmental resistance)
Fast growth when density is low; slow growth when density is high
Influential factors include competition, (including predation) parasitism (including disease), overcrowding and stress
What is the logistic growth equation?
dN/dt = rN (K-N/K)
Which are the population strategies?
r-strategist
K-strategist
What are opportunist species?
Also called r selected species or r strategists
high growth rate
produce many offspring with low probability of surviving
Exploit less crowded ecological niches
Predominate in disturbed or unstable environments
What are Equilibrium species?
Also called K selected species or K strategists
Low growth rate
Produce few offspring with increased probability of survival
Better competitors (can survive in more crowded niches)
Predominate in stable and predictable environments
How many Survivorship Curves types are there?
3 types of curves
Explain type 1 curve
High probability of survival throughout their life with a sudden drop at a specific
age
Parental care, low birth rates, and extended social networks (herds, packs, or colonies)
improve survival rates
E.g. Elk, White tailed Deer, Grey Wolves, and Humans
Explain type 2 curve
Steadily declining probability of survival throughout their life
Parental care, moderate to low birth rates, and extended social networks but small to
moderate in size and are a key prey source of prey
E.g. Sandhill Cranes and Coyotes
Explain type 3 curve
Very rapid decline in probability of survival early in life and then a good probability
of survival late in life
Large body size or physical/behaviour defence mechanisms
E.g. Northern Pike, Water Hyacinth, and Autumn Olive
Population size information card
Population size fluctuates even when stable
Abiotic and biotic factors continue to influence population size
Sometimes these factors are cyclical
Some factors affect birth rate (population growth)
Other factors affect death rate (population decline)
Intraspecific factor- Density Dependent Factors (mostly biotic)
Effect increases with increasing population density
E.g. food shortage, territorial behaviour, overcrowding and dispersal
Intraspesific factor- Density Independent Factors (mostly abiotic)
Effect is not related to population size
E.g. edaphic factors, climatic factors, natural disasters, and pollution
Food Shortage information card
Individuals suffer the effects of malnutrition
Increased mortality
Especially young
Reduced resistance to disease and parasites
Reduced fecundity (or altogether absent)
Inherent defensive behaviour may be lost
In severe starvation cases, animals may seek food beyond adequate cover against discovery by predators
This leads to increased mortality through
predation
Water shortage is just as debilitating
Territorial Behaviour (Territoriality) information card
Low population density
One or both individuals in a pair establish a territory
The extent of the territory is marked chemically, visually, or through calls
Challengers are seen off after a ritual fight
There is no overlap between individual territories
High population density
Territorial size diminishes
Only the toughest maintain adequate territories
These individuals survive and/or reproduce to the detriment of others of the same species (Intraspecific Competition)
This is also called Regulation through Spatial Interaction
Overcrowding information card
Low population density
Population behaves normally
High population density
Effects of Social Stress are observed in small mammals
Diminished reproductive organs
Reduced reproductive rate
Slower growth
Reduced disease resistance
Reduced parental care
Young abandon nest early and die more often as a consequence
Cannibalism of the young (Intraspecific Competition)
These symptoms appear even in cases of high food availability
what are examples of interspecific interactive relationships?
Predator prey relationships
Parasite host relationships
Interspecific competition for resources
Predator-Prey interactions
Predator species feed on their designated prey species
Predators control prey populations
This is a density dependent interaction
Experiments in the lab show that predator and prey populations interactions
follow a distinct pattern
- A crash in a prey population leads to a similar predator population crash
- The reduced number of predators boosts the prey population which recovers
- The now abundant prey population boots the predator population
- The increase in predators cause the prey population to crash (cycle complete)
The two populations are slightly out of sync
it takes some time for the effect to be felt
Lab conditions preclude predators selecting alternative prey so field results could be
different (also, other density dependant factors may apply, e.g. disease and overgrazing)
Parasite-Host Interactions information card
Parasites only attack designated host species
Parasites weaken hosts and may make them more vulnerable to disease or predators
This is another density dependant interaction
Overcrowding means parasites spread faster and wider
Under normal circumstances, parasites have limited mobility
Many parasitic strategies have evolved
E.g. conventional parasite, parasitoid and parasitic castrator
Interspecific Competition
Predators and parasites keep populations within the k limit
They cull the least fit individuals
Only most fit individuals survive to reproduce
Target species involved in “arms race” with predators and
parasites
This is called Coevolution
It is a major evolutionary drive
Keystone Species
•
Disproportionately large effect on the community
Maintain biodiversity by controlling dominant species
Provide critical resources for a wide variety of species
Fundamental community structure changes if this species is removed
Not all communities include keystone species
If present, they are critical to the environment and community
Examples of keystone species
E.g. Pisaster ochraceus (starfish)
Major predator of the mussel Mytilus
When the starfish is removed, mussels take over the community and displace the other 25 or so species of invertebrates and algae in the environment
Other examples
Sea otters and sea urchins; grey wolves in the Greater Yellowstone ecosystem
Ecological Niche
How an organism utilises its environment
E.g. spatial utilisation, food consumption, temperature range, mating
requirements, moisture conditions, etc
Fundamental (Potential) niche
Full range of conditions in which organism can survive
Realised (Actual) niche
Actual range of conditions occupied by the organism
Chthalamus vs Semibalanus information card
Study carried out along the coast of Scotland
Competitive interactions between two types of barnacles
Chthalamus stellatus can withstand a wide range of
submersion/exposure
However it is the weaker competitor
Semibalanus balanoides cannot withstand long exposure
It is the stronger competitor
If present alone, C . stellatus occupies the shallow and deep
zones
The presence of S . balanoides in deeper zones prevents C . stellatus from occupying its full niche as it is outcompeted
Niche Strategies- Generalist Species
Characteristics
Wide fundamental niche
Can exist in many different environments
Can use a wide range of resources
Good opportunistic species
Generally successful at colonising new
environments
Good at surviving environmental changes
Can tolerate a wide variety of conditions
Generally evolve at a faster pace
Tend to be put under greater environmental
pressures
Examples
Omnivores, humans, weeds
Niche Strategies-Specialist Species
Characteristics
Narrow fundamental niche
Can exist only in specific environments
Limited to a narrow range of resources
Often equilibrium species
Need stable environment
Generally outcompete the generalists
Not likely to survive environmental changes
Narrow tolerance limits
More vulnerable to extinction
Not likely to be flexible enough to survive change
Examples
Pandas, koalas, giraffes, xerophytes
