Unit 14—Ecology Ch 28 Ch 27

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

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 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 Animated Population Pyramid How Population Pyramids Are Made Video

Developing Countries –Wide base –High #s of reproductive/ pre-reproductive age –High birth rates the higher educational level of women, the lower the birth rate –Population will grow fast Developed Countries –slightly wider base, width ~ same, or inverted pyramid –fewer people of reproductive age or younger –low birth rates slow growth, zero growth, negative growth (pop. shrinks) Population Pyramids (Age Structure Diagrams) Population growth rate by country

Population clock

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

Decomposers Heterotrophs Break down dead material & recycle nutrients 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

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 individual organisms? –No… through community food chains & webs ***Arrow always points toward organism taking in the energy & away from the organism “giving up” the energy.*** Where do almost all communities get their energy?

10% Rule of Ecological Efficiency –~–~10% passed to next level Nutrients are recycled –E–Ex. carbon cycle Energy is transferred & degraded. –~–~90% is lost as heat Energy Flow: Energy Pyramids

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.