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