Ch 27 Ch 28 Unit 14—Ecology Populations, Communities, & Ecosystems • Population – A group of organisms of the same species living in an area at the same time • Community – All the different populations living & interacting in an area • Ecosystem – Interaction of community with the non-living environment Visualizing population structures & predicting future 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 How Population Pyramids Are Made Video Animated Population Pyramid Rapid Growth Guatemala Nigeria Saudi Arabia Ages 0-14 Slow Growth U. S. Australia Canada Ages 15-44 Zero Growth Negative Growth Spain Germany Austria Bulgaria Greece Sweden Ages 45+ Population growth rate by country Population Pyramids (Age Structure Diagrams) Developing Countries Developed Countries – Wide base – High #s of reproductive/ pre-reproductive age – High birth rates – slightly wider base, width ~ same, or inverted pyramid – fewer people of reproductive age or younger • the higher educational level of – low birth rates women, the lower the birth rate – Population will grow fast • slow growth, zero growth, negative growth (pop. shrinks) •Population clock •http://www.census.gov/main/www/popclock.html Population Growth • Limiting factors: circumstances or resources that limit growth, reproduction, or distribution of organisms (provide environmental resistance) – prevents population from growing indefinitely • “carrying capacity” – can be: • abiotic or biotic Examples of Abiotic Factors Organisms have optimal ranges of abiotic factors in which they thrive • Is temperature a limiting factor for these fish species? Optimal temperature Biotic Factors • Living factors in an ecosystem – Usually described in terms of interactions • especially who eats whom or trophic levels Energy Flow: Food Chains Fourth trophic level Tertiary consumers Carnivores/omnivores Third trophic level Secondary consumers carnivores Second trophic level Primary consumers herbivores Decomposers Heterotrophs Break down dead material & recycle nutrients First trophic level Primary producers autotrophs Autotrophs vs. Heterotrophs • Another name for autotrophs? – How do they get nutrients? Another name for heterotrophs? How do they get nutrients? What categories can we break heterotrophs into? herbivores carnivores scavengers omnivores decomposers Part of EVERY ecosystem Energy Flow: Food Chains • Does energy only flow through Where do individual organisms? almost all –No… through community • food chains & webs ***Arrow always points toward organism taking in the energy & away from the organism “giving up” the energy.*** communities get their energy? Energy Flow: Energy Pyramids • 10% Rule of Ecological Efficiency – ~10% passed to next level • Nutrients are recycled – Ex. carbon cycle • Energy is transferred & degraded. – ~90% is lost as heat Carbon Cycle Other relationships - Symbiosis • When two species live closely together in a relationship that lasts over time symbiosis occurs. Commensalism • One partner benefits from the relationship & the other neither benefits, nor is harmed Mutualism • Both partners benefits from the relationship. Parasitism • One partner benefits, the other is harmed.