unit 12—ecology (& populations) ch. 30 populations & communities (sec. 1 & 4) 200

Unit 12—Ecology (& Populations)Ch. 30 Populations & Communities

(sec. 1 & 4)

200

Populations, Communities, & Ecosystems• What is a population?

– All organisms of same type (species) living in an area

• What is a community?– All different organisms (populations) living in an area

• What is an ecosystem?– A community interacting with the non-living (abiotic)

factors in an area

• What can cause an increase in the population size of an area?– births– immigration

Population Changes

• What can cause a decrease in the population size of an area? – deaths– emigration

Population Changes

• population pyramids (a.k.a. age structure diagrams)– basic shape can help us predict what’s going to happen to

the population in the future…– What do you think will happen to the population in each pyramid???

Rapid GrowthGuatemala

NigeriaSaudi Arabia

Negative GrowthGermanyBulgariaSweden

Zero GrowthSpain

AustriaGreece

Slow GrowthU. S.

AustraliaCanada

Ages 0-14 Ages 45+Ages 15-44

Visualizing Population Structures & Predicting Future Changes

How Population Pyramids Are Made Video

Animated Population Pyramid

Developing Countries– wide base– high #s of pre- &

reproductive age• high birth rates

– fast growth

Developed Countries– slightly wider base, width is same,

or inverted pyramid– lower #s of pre- & reproductive age– low birth rates

• slow growth, zero growth, negative growth (pop. shrinks)

Population Pyramids(Age Structure Diagrams)

Population growth rate by country

Census Bureau International Data-Pyramids

Population Clock

What event???

Population Growth• Types of population

growth:– exponential growth

• represents species’ biotic potential

– ideal conditions

– logistic growth• population reaches

“carrying capacity”

point of maximum growth

Logistic Growth

Exponential Growth

Population Growth• Why don’t populations

increase forever?– limiting factors

• provide environmental resistance

• prevent population from growing indefinitely

– reach “carrying capacity”

• can be:– abiotic (non-living)– biotic (living)

Examples of Abiotic Limiting Factors

Examples of Biotic Limiting Factors• living factors in an ecosystem

Decomposers are heterotrophs & must be part of every ecosystem to break down dead material & recycle nutrients!

Biotic Limiting Factors

• usually described in terms of interactions– especially

who eats whom or trophic levels

First trophic levelPrimary producers

autotrophs

Second trophic levelPrimary consumers

herbivores

Fourth trophic levelTertiary consumers

Carnivores/omnivores

Third trophic levelSecondary consumers

carnivores

Energy Flow: Food Chains

Decomposers are heterotrophs & must be part of every ecosystem to break down dead material & recycle nutrients!

heterotrophs

Energy Flow: Food Chains• Does energy only flow through individual

organisms?– No… through community

• in food chains & webs ***Arrow always points toward organism taking in energy & away from the organism “giving up” energy.

Where do almost all communities get their energy?

Food Web Interactive

• Energy cannot be recycled, it can only be transferred & transformed.– ~90% is lost as heat &/or used by

previous organism for life functions– ~10% passed to next level

• 10% Rule of Ecological Efficiency

Energy Flow: Energy Pyramids

Amount of energy passed on to the

next level.

Lost Energy

Lost Energy

20

J

80

• Another name for autotrophs?– producers

• How do they get nutrients?– make their own food

(sugars)• most by photosynthesis

– What is the equation for photosynthesis?

Energy Flow: Food Chains

Another name for heterotrophs?consumers

How do they get nutrients?absorptioningestion

Energy Flow: Food Chains

• Types of heterotrophs?– herbivores (eat plants)

– carnivores (eat animals)• scavengers (feed on dead animals)

– ex. vultures, buzzards, crabs

– omnivores (eat plants & animals)

– decomposers (break down dead material & recycle nutrients)

• Must be part of EVERY ecosystem!

Energy Flow: Food Chains

Carbon Cycle

Nutrients in An Ecosystem

• Nutrients can be recycled!– Biogeochemical or nutrient cycles

• Ex. carbon cycle & nitrogen cycle

• Decomposers play major role…

Other Relationships in a Community

Predation• one organism benefits

(predator), the other is harmed & usually killed (prey) (+, -)

Competition• both organisms are

harmed (not necessarily killed) (-, -)

Other Relationships in a Community• symbiosis

– when 2 species live closely together in a relationship over (a long) time

• commensalism• mutualism• parasitism

Other Relationships in a Community: Commensalism

• one partner benefits from the relationship & the other neither benefits, nor is harmed (+, 0)

Other Relationships in a Community: Mutualism

• both partners benefit from the relationship (+, +)

Other Relationships in a Community: Parasitism

• one partner benefits (parasite) & the other is harmed, but not usually killed (host) (+, -)