Ecosystems & Populations

1. Ecosystems & Populations Chapters 4 & 5

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

11. 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.

12. 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.