Interactions in Ecosystems

Habitat vs Niche Habitat Niche The habitat is the place where an organism lives out its life. It is where the organism finds food, shelter and mates. A niche is its role in the community and how it interacts with the environment. How it obtains food, mates and protection from predators.

Red Squirrel Habitat Niche Lives in the trees of the coniferous forest, this is its address, so to speak. Spends much of its time searching for nuts and seeds Builds its nest in trees, Is food source for the great horned owl. It also fills an important role in the forest by spreading and burying seeds which later germinate into trees.

Two Types of Niches 1. Fundamental niche- the set of resources a population is theoretically capable of using under ideal conditions 2. Realized niche- the resources a population actually uses Thus, 2 species cannot coexist in a community if their niches are identical

Competitive Exclusion Competitive Exclusion- two species competing for the same resources cannot coexist The one that uses the resources more efficiently will eliminate the other

Competitive Exclusion For example, the three species of North American warblers shown all live in the same trees and feed on insects. But one species feeds on high branches; another feeds on low branches, and another feeds in the middle.

Competition Competition- two species use the same resources Ex. lion and hyena

Predation Predation- one organism killing the other for food

Coevolution Coevolution- back and forth evolution adjustments between interacting members of a community.

Symbiotic Relationships Symbiosis- relationship between two or more species - 3 types of symbiotic relationships 1) mutualism 2) commensalism 3) parasitism

Mutualism Mutualism- both species benefit Ex. Butterfly and flower

Commensalism Commensalism- one benefits, one is unaffected Ex. Clown fish and sea anemone

Parasitism Parasitism- one benefits, one is harmed The parasite usually doesn’t kill the host Ex. Wasp eggs on caterpillar

Tapeworm on Oprah Video

Practice Problems Example #1 Bacteria and the human colon: Bacteria live in the colon of humans and are able to feed off the indigestible food that the human body cannot break down (cellulose of plants). In the process of breaking down the food, the bacteria also make much-needed vitamins that the human body in turn can use to keep healthy. Organism 1:  helped harmed not harmed/not helped Organism 2:  helped harmed not harmed/not helped Symbiotic Relationship: _____________________________ Example #2 Remora and the shark: Remora fish are small fish that make their niche by picking up the scraps that sharks leave behind while feeding. The shark makes no attempt to prey on the remora fish.  

Quiz 1. Bacteria and the human colon: Bacteria live in the colon of humans and are able to feed off the indigestible food that the human body cannot break down (cellulose of plants). In the process of breaking down the food, the bacteria also make much-needed vitamins that the human body in turn can use to keep healthy. _____________:  helped harmed not harmed/not helped Symbiotic Relationship: __________________ 2. Remora and the shark: Remora fish are small fish that make their niche by picking up the scraps that sharks leave behind while feeding. The shark makes no attempt to prey on the remora fish. ______________:  helped harmed not harmed/not helped Symbiotic Relationship: ____________________

Succession Ecological succession- transition in species composition over ecological time

Primary Succesion Primary Succession - begins in an area begun in a lifeless area; no soil, perhaps volcanic activity or retreating glacier

1st Step in Primary Succession Pioneer Species- first to colonize barren rock Example- Lichen and Mosses

Pioneer Species Lichens Mosses

Succession Continuing 2nd Step- soil 3rd Step- grasses and small shrubs 4th Step- pine trees 5th Step- mature oak-hickory forest (Climax community) - Climax Community- usually a stable forest

Secondary Succession Secondary Succession- an existing community has been cleared by some disturbance that leaves the soil intact