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Ecology Chapter 14
14.2 Community Interactions
when organisms live together in an ecological community they interact constantly.
Three types of interactions– Competition– Predation– Symbiosis
Competition- competing for resources
occurs due to a limited number of resources
Resource- any necessity of life. water, nutrients, light, food.
Competitive exclusion principle- no two species can occupy the same niche in the same habitat at the same time
Predation Predation- when
an organism captures and feeds on another organism.
Predator- hunter Prey- hunted
Symbiosis Symbiosis- any relationship where
two species live closely together. (3 types)– Mutualism– Commensalism– Parasitism
Symbiosis Mutualism- both
species benefit from a relationship.
Lichens (fungus and Algae)
One example is the lichens, little non-descript patches of stuff you see growing on rocks and tree bark. This is a symbiosis, consisting of a fungus and an alga. The fungus provides a protective home for the algae, and gathers mineral nutrients from rainwater and from dissolving the rock underneath. The alga gathers energy from the sun. There are thousands of species of lichen in the world; actually thousands of species of fungi with just a few species of algae which can form a partnership with almost any of them.
Symbiosis Commensalism –
One member of a symbiotic relationship benefits and the other is neither helped or harmed
Ex. Holes used by bluebirds in a tree were chiseled out by woodpeckers after it has been abandoned
Symbiosis Parasitism- One
creature benefits and one creature is harmed
Ex tapeworm. Feeds in a humans intestines absorbing his/her nutrients.
Relationships: Symbiosis = Living Togethera)
commensalism b) mutualism
c) parasitism
Identify these relationships
Chapter 14.4 – Population Growth Patterns
What is a population? What is exponential population
growth? What happens to a population when it
reaches its carrying capacity?
How many mice are in the following population?
Estimate!
Ready
SETSET
Go!
How many did you count?
What is the best way to count them?
SAMPLING
Population Sampling Sometimes, the entire population to be
studied is small enough for the researcher to include the entire population in the study.– This type of research is called a census study
because data is gathered on every member of the population.
Usually, the population is too large for the researcher to attempt to survey all of its members.– A small, but carefully chosen sample can be
used to represent the population.– The sample reflects the characteristics of the
population from which it is drawn
Sampling Methods There are LOTS ways to sample a
population including:– Biased sampling, Systematic sampling, Stratified
sampling, Judgment sampling, Quota sampling, Snowball sampling, Counting method, Hit-or-miss method, etc…
HOWEVER, the most common methods are:
– Random and non-random sampling
– Each gives you a “best estimate” of the population size
Population Size Factors that affect:
– Natality– Mortality/Fatality– Immigration – Emigration
Population Growth Curves Explain what is happening to the
populations below:
Population Growth Curves Explain what is happening to the
populations below:
Rate at which a population could grow if it had unlimited resources
If a population reached its biotic potential it would have exponential growth
Biotic Potential = Reproductive Potential
The “J” Curve: Exponential Growth
The “S” Curve: Logistic Growth
This graph shows a typical population growth curve. Under ideal conditions a population would have a growth with a slow start, then a very fast rate of increase and finally the growth slows down and stops.
Population Density
Environmental Limits on populations
Density-dependent– Disease– Food– Parasitism– Predation– Competition
Intraspecific Interspecific
Density-independent– Temperature– Storms– Floods– Drought– Habitat Disruption
Density Dependent Here is a dramatic
example of how competition among members of one species for a finite resource — in this case, food — caused a sharp drop in population.
The graph shows a population crash; in this case of reindeer on two islands in the Bering Sea. Inter or Intra?
Density Dependent This graph shows the effect of interspecific competition on the population
size of two species of paramecia, Paramecium aurelia and Paramecium caudatum.
When either species was cultured alone — with fresh food added regularly — the population grew exponentially at first and then leveled off.
However, when the two species were cultured together, P. caudatum proved to be the weaker competitor. After a brief phase of exponential growth, its population began to decline and ultimately it became extinct. The population of P. aurelia reached a plateau, but so long as P. caudatum remained, this was below the population density it achieved when grown alone.
Density Independent This graph shows the
decline in the population of one of Darwin's finches on Daphne Major, a tiny (100-acre) member of the Galapagos Islands. The decline (from 1400 to 200 individuals) occurred because of a severe drought that reduced the quantity of seeds on which this species feeds. The drought ended in 1978, but even with ample food once again available the finch population recovered only slowly.
Limiting Factors Definition?
What factors would limit these communities?
Organism Interactions Limit Populations
Predation Competition
– Both types Parasitism Crowding/stress
The Human Population
Figure 4.10 pg 104
Demography Vocabulary Age Structure Immigration Emigration Birth/Death Rate
Age Structure Pyramids These pyramids compare the age structure of the populations of France
and India in 1984. The relative number (%) of males and females is shown in 5-year cohorts. Almost 20% of India's population were children — 15 years or less in age — who had yet to begin reproduction. When the members of a large cohort like this begin reproducing, they add greatly to birth rates. In France, in contrast, each cohort is about the size of the next until close to the top when old age begins to take its toll.
Age Structure Pyramids These population pyramids show the baby-boom
generation in 1970 and again in 1985 (green ovals). Profound changes (e.g. enrollments in schools and
colleges) have occurred — and continue to occur — in U.S. society as this bulge passes into ever-older age brackets.
Chapter 14.5 Ecological Succession
Vocabulary to Know:– Succession
Primary Secondary Pioneer Species
– Climax Community
Community
All the populations that live together in a
habitat
Habitat is the type of place where
individuals of a species typically live
Type of habitat shapes a community’s
structure
What is Succession & what causes it?
Changes to a community
Biotic Factor
Abiotic Factors
2 Types of succession Primary
– From nothing– Even the soil must be “created”
Secondary– From soil– Disaster can strike and make it start over
Primary Succession
Secondary Succession
Pioneer Species
Species that colonize barren habitats
Lichens, small plants with brief
life cycles
Improve conditions for other species
who then replace them
Climax Community
Stable array of species that persists
relatively unchanged over time
Succession does not always move
predictably toward a specific climax
community; other stable communities
may persist
Pioneer stage Climax Community
The trend of Succession