Chapter 9 p. 292-309

Population and Communities

Studying Populations

- Definition: ______________________________________________________________________________________________________________________________________________________________________________

They have a lot of interactions and share the same resources:

- Water, food, sunlight…To describe a population the area that is occupied needs to be specified.

- Three main characteristics used to describe populations:

A) ___________________________

B) ___________________________

C) ___________________________

A) Population Size

- Definition: _____________________________________________________________________________________.

Population size is affected by births, deaths, immigration and emigration.

- Birth: _________________________________________- Death: ________________________________________- Immigration:

___________________________________________________________________________________________________________________________________________________________________________

- Emigration: _______________________________________________________________________________

______________________________________________________________________________________________

The population size will remain the same if:

__________________ + ______________________ = ______________________ + __________________________

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Chapter 9 p. 292-309

Measuring Population Size

A number of methods exist to measure the size of populations. The most common methods are counting individuals, counting by sample area and mark-recapture.

1. Counting Individuals

- If possible, count all the individuals within the area occupied by the population.

______________________________________________________________________OR

______________________________________________________________________

2. Counting by Sample Area

- ___________________________________________________________________________________________

A) Section off sample area into quadrats (rectangular areas marked off with rope or ribbon).

B) The number of individuals are counted in that area and used in the equation below:

Population size =

Example: quadrat is a rectangle (3 m x 4 m = 12 m2), total study area (100 m x 72 m = 7200 m2), average number of individuals (40)

Population size = ________________________________________________________________________________

3. Mark and Recapture

Method used when population moves a lot (sharks, fish etc…)

1. Catch individuals (nets or cages).2. ________________________________________________________________________

___

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3. ___________________________________________________________________________

4. Recapture individuals (nets or cages). 5. Count the individuals with separate count for marked individuals. 6. ________________________________________________________________________

___

Population size =

Example: 30 ducks are captured, marked and released. If on the second capture, 10 of 40 captured ducks are tagged (marked), then the population of ducks is estimated to be:

B) Population Density

Definition: ________________________________________________________________________________________

______________________________________________________________________________________________________

- Example: there are 21 white-tailed deer per square kilometer on the island of Anticosti.

Population Density Example

a) Area: A population of 10 000 maple trees is contained within a 300 km2 forest. The density of the maple tree population is 33.3 maple trees per km2 .

b) Volume: A pond contains 2500 L of water and 17 lily pads. The density of lily pads is 0.0068 lily pads per liter of water.

The density of a population can vary depending on the habitat.

a) The presence of predators, parasites or disease can affect the density.

- Increased presence of predators, parasites or disease = ___________________________

- Decreased presence of predators, parasites or disease = __________________________

b) Natural or “man-made” disasters can affect the density.

- Deforestation = ______________________________

c) The climate and resources within the habitat can affect the density.

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- More resources = ___________________________________- Fewer resources = __________________________________

C) Population Distribution

Definition: ________________________________________________________________________________________

______________________________________________

Three types of population distribution

- ________________________________________- ________________________________________- ________________________________________

Population Distribution

A) clumped: most common, occurs when certain areas of the habitat offer better living conditions (shelter, food, water …)

Example: fish moving in schools.

B) uniform: ______________________________________________________________________________.

Example: certain birds are uniformly distributed to allow each bird a certain minimal territory.

C) random: ____________________________________________

Example: bushes and trees are randomly dispersed because they cannot clump together or spread out uniformly.

Ecological Factors

Definition: ________________________________________________________________________________________

______________________________________________________________________________________________________

Different factors of a habitat can affect the individuals of a population population density affected.

2 types of ecological factors:

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A) abiotic (non-living): _________________________________________________________________________

B) biotic (living): _________________________________________________________________________________

______________________________________________________________________________________________________

Abiotic factors: soil or water pH, amount of light, depth of snow, temperature, air humidity, terrain (land topography).

Biotic factors: predation, birth rate, disease, amount of food, competition, human activity.

Limiting Factor: If the effect of the factor is dramatic

(reduces the population density or prevents its growth),

the ecological factor is called the limiting factor.

Definition: ________________________________________________________________________________________

______________________________________________________________________________________________________

An ecological factor becomes limiting if:

1. ________________________________________________ (no sunlight) 2. ________________________________________________ (too cold – not enough heat) 3. ____________________________________________ (too much water causes cactus root to rot)

Biological Cycles in Populations

• Definition: ________________________________________________________________________

______________________________________________________________________________________

Example: The population of the hare and the lynx rise and fall together.

The hare population rises the lynx have more food reproduce a lot lynx population increases more hares are hunted hare population

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decreases less food for the lynx lynx population decreases hare population increases etc….

Studying Communities

• Definition: ___________________________________________________

______________________________________________________________________________________

Biodiversity

Definition: ________________________________________________________________________________________

______________________________________________________________________________________________________

We must consider the following to measure biodiversity:

1) The number of species in the community (species richness).

2) Relative abundance of each species, meaning the number of individuals of a particular species in relation to the total number of individuals in the community.

Factors affecting Biodiversity

- The biodiversity of a community is high when:o _____________________________________________ (NOT the number of

individuals)o The relative abundance of different species is similar (percentage of

each species is similar across species)

Four main types of interaction between individuals in a community are:

- __________________________________- __________________________________- __________________________________- __________________________________

Competition

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Definition: ________________________________________________________________________________________

______________________________________________________________________________________________________

Example of resources: limited precipitation in a desert allows for competition between plant species.

Competition cannot exist without _______________________________________ (resource).

2 Types of Competition

- Intraspecific competition occurs between individuals of the ____________ species.

- Interspecific competition occurs between individuals of _________________ species.

Predation

• Definition: ________________________________________________________________________

______________________________________________________________________________________

Predator (the one eating) versus prey (the one being eaten)

Mutualism

• Definition: ________________________________________________________________________

______________________________________________________________________________________

Commensalism

Definition: commensalism is the interaction between two living organisms in which one organism benefits from the relationship, while the other remains unaffected.

Type of Interaction Effect on Population A Effect on Population BCompetitionPredation and ParasitismMutualismCommensalism

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