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 Growth Guatemala Nigeria Saudi Arabia Negative Growth Germany Bulgaria Sweden Zero Growth Spain Austria Greece Slow Growth U. S. Australia Canada Ages 0-14Ages 45+Ages 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 level Primary producers autotrophs Second trophic level Primary consumers herbivores Fourth trophic level Tertiary consumers Carnivores/omnivores Third trophic level Secondary consumers carnivores Energy Flow: Food Chains Decomposers are heterotrophs & must be part of every ecosystem to break down dead material & recycle nutrients! heterotrophsheterotrophs

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 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? absorption ingestion 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) (+, -)