Ecosystems & Populations Chapters 4 & 5

Levels of Organization in Ecology Ecologists study individual organisms, but this only provides part of the story of its life cycle. An individual organism interacts with others of its species; it is also dependant on other organisms for food, shelter, reproduction and protection.

Levels of Organization in Ecology cont. Population – a group of organisms of one species that interbreed and live in the same place at the same time Members of the same population may compete with each other for food, water, and other resources. How organisms share the resources determines how far apart organisms live and the size of the population.

Levels of Organization in Ecology cont. Community – a collection of interacting populations A change in one population in a community will cause changes in the other populations.

Levels of Organization in Ecology cont. Ecosystem – made up of the interactions among the populations in a community and the community’s physical surroundings Terrestrial, freshwater and saltwater (marine) ecosystems are the three major kinds.

Levels of Organization in Ecology cont. Biome – a large region characterized by a specific climate and certain plants and animals Biosphere – the portion of Earth that supports life The biosphere extends from high in the atmosphere to the bottom of the ocean.

Organisms in Ecosystems Habitat – the place where an organism lives out its life Niche – the role and position a species has in its environment – how it meets its needs for food and shelter, how it survives and how it reproduces.

Niche Several species may share a habitat, but the food, shelter, and other resources of that habitat are used in different ways. These differences lead to reduced competition. It is an advantage for a species to occupy a niche different from those of other species.

Living Relationships Predator-Prey Relationship – beneficial for one species and harmful to another, involves a fight for survival. However, some species enhance their chances of survival by forming close, permanent relationships with other species - symbiosis.

Symbiotic Relationships Commensalism –relationship in which one species benefits and the other species is neither harmed nor benefited The clownfish lives among the stinging tentacles of an anemone and is protected from potential predators not immune to the sting of the anemone.

Symbiotic Relationships cont. Mutualism – relationship in which both species benefit Some fish and shrimp clean the bodies and mouths of large fish and turtles. The cleaner fish get a meal while the large fish have parasites removed.

Symbiotic Relationships cont. Parasitism – relationship in which one organism derives benefit at the expense of the other. Ticks are parasites of animals like dogs, obtaining nutrients from the blood of their host. Parasites harm, but usually do not kill, the host.