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Populations and Communities
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Populations and Communities

Feb 23, 2016

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Populations and Communities. = Population. A group of individuals of the same species, living in a shared space at a specific point in time. Factors affecting population size. births. deaths. Population. Emigration. Immigration. How big is this population?. 11. 6. 6. - PowerPoint PPT Presentation
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Page 1: Populations and Communities

Populations and Communities

Page 2: Populations and Communities

• A group of individuals of the same species, living in a shared space at a specific point in time

= Population

Page 3: Populations and Communities

Factors affecting population size

births deaths

Population

Immigration Emigration

Page 4: Populations and Communities

• How big is this population?

6

11

6

Page 5: Populations and Communities

Counting populations I

- Counting individuals

- Counting by sampling:

Population size =

Average number of individuals per section

xArea of section

total study area

- Counting by recapture %:

Page 6: Populations and Communities

Counting by recapture %

d

d

d

# of marked recaptured animals# of captured animals

# of marked animalsPopulation size=

Page 7: Populations and Communities

Population density

• Factors influencing population density:– Access to water and food– Presence of predators– Parasites, diseases

Pop. Density =# of individuals

Space occupied (area / volume)

Page 8: Populations and Communities

Population distribution

= the way in which individuals are dispersed

within their habitat

clumped

random

uniform

http://www.youtube.com/watch?v=1yKxUNP_XVo&list=PL9CE54703E2B8E92F

Page 9: Populations and Communities

clumpedrandom

uniform

Page 10: Populations and Communities

Ecological factors

= aspect of a habitat that can affect the organisms living there

• amount of light• soil / water pH• terrain• temperature• air humidity

• birth rate• disease• amount of food• predation• competition• human activity

Related to the action of living

organismsPhysical or

chemical origin

Abiotic Biotic

Page 11: Populations and Communities

Limiting factor• A factor that limits the growth of a population– Light– Temperature– Water– Food / nutrients– …

Page 12: Populations and Communities

Limiting factor• Is low temperature limiting growth of vampire

bat population?

• Vampire bat colonies

Mean minimal temperature for January > 10°C

Page 13: Populations and Communities

12 m200 mDistance between nest boxes

Dens

ity (p

airs

/ ha

)

pied flycatcher

Is nesting space limiting?

Providing more nesting spaces increases population density

Nesting space was limiting

Page 14: Populations and Communities

Biological cycles in populations

• Population cycles are composed of alternating rise and fall of population size.• Periods are of fixed duration and are repeated continually.

Page 15: Populations and Communities

Populations

• Counting methods• Density (number/ area)• Distribution (clumped/ random / uniform)• Ecological factors – limiting factors

Polpulation cycles

commuities

Page 16: Populations and Communities

organism

population community

Communities: A set of populations of different species sharing the same habitat

Page 17: Populations and Communities

BiodiversityThe variety of species living in a community

Species richness:Number of different species in a community

Relative species abundance:Number of individuals of one species in relation to total community

Page 18: Populations and Communities

Same species richness;

community 2: species abundance not even

Lower biodiversity

Biodiversity is high when:• number of species high• relative abundance of species similar

Page 19: Populations and Communities

Interactions between individualsCompetition:Living organisms seek access to the same resource in their habitat.

PredationOne feeds on the other.

Mutualism:Interaction between two species beneficial to both.

Commensalism:One organism benefits from relationship while other remains unaffected.

Page 20: Populations and Communities

Competition

interspecific

intraspecific

Page 21: Populations and Communities

Predation:

predator prey

prey may or may not die

parasite hostParasite lives either on or inside the host. Host is harmed from the interaction.

Page 22: Populations and Communities

mutualism

Bee gains foodFlower gains fertilization

Clown fish gains protectionAnemone gains prey (attracted by clown fish)

Page 23: Populations and Communities

Commensalism

Bird gains foodHuman remains unaffected

Bird gains protectiontree remains unaffected