ecology chapter 14. 14.2 community interactions when organisms live together in an ecological...

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