Chapter 4.2 What shapes an ecosystem?

BIOTIC AND ABIOTIC FACTORS: Biotic factor-biological influence on organisms within an ecosystem  Example: frog, bears, trees, mushrooms, bacteria Abiotic factor-physical or nonliving factor that shapes an ecosystem  Example: temperature, climate, rocks, wind, nutrient availability Together, biotic and abiotic factors determine the survival and growth of an organism and the productivity of the ecosystem in which the organism lives.

 Habitat-the area where an organisms lives, including the biotic and abiotic factors that affect the organism.

NICHE Niche-is full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions. A niche includes the type of food the organism eats, how it obtains this food, and which other species use the organism as food. It also includes physical conditions for an organism to survive and reproduction.

Niche

COMMUNITY INTERACTIONS: 1. Competition  Resource –any necessity of life, such a water, nutrients, light, food or space. Competition happens when organisms of the same or different species attempt to use an ecological resource in the same place at the same time.  Competitive exclusion principle- ecological rule that states that no two species can occupy the same exact niche in the same habitat at the same time 2. Predation  Predation-interaction in which one organism captures (predator) and feeds on another organism(prey). 3. Symbiosis  Symbiosis-relationship in which two species live closely together [symbiosis = living together].

Symbiosis a. Mutualism- symbiotic relationship in which both species benefit from the relationship  Example: Flowers depend on bees to pollinate seeds. Insects need flowers for nectar, pollen or other substance. OR the ant cares for aphids and protects them from predators. The aphids produce a sweet liquid that the ant drinks. b. Commensalism-symbiotic relationship in which one member of the association benefits and the other is neither helped nor harmed.  Example: The orchid benefits from growing on a tree as it absorbs water and minerals from rainwater and runoff, but the tree is not affected. c. Parasitism-symbiotic relationship in which one organism lives in or on another organism and harms it  Example: A flea market feeds on the blood of its host, when can be harmed by diseases the flea carries.

ECOLOGICAL SUCCESSION: As an ecosystem changes, older inhabitants gradually die out and new organisms move in, causing further changes in the community. Ecological succession-is a gradual change in living communities that follows a disturbance. Ecosystems are constantly changing in response to natural and human disturbances.

1. Primary succession - succession that occurs on surfaces where no soil exists.  Example: after volcanic eruptions, there is an empty land. OR bare rock land when glaciers melt.  Pioneer species- are first species to populate an area during primary succession.  Example: lichens, fungus, algae,

Primary succession

2. Secondary succession: -succession following a disturbance that destroys a community without destroying the soil.  Example: happens when land is cleared and plowed for farming is abandoned OR wildfire in Yellowstone National Park

Secondary succession

3. Succession in a marine ecosystem: can happen anywhere even in the dark deep ocean. There are three stages in the marine ecosystem. a. the disturbances starts when a whale dies and sinks the to the bottom of the ocean. It attracts scavengers and decomposers, amphipods, hagfishes, sharks b. within a year, a whale’s body is gone. The body supports only a small number of fishes, crabs snails and other marine animals. However, the soil is enriched by decomposed whale that attracts many marine worms. c. when the whale’s skeleton remains, a third community moves in. Heterotrophic bacteria start to decompose oils in the whale’s bone. When they decompose, they release chemicals that attract other bacteria called chemosynthesis autotrophs. In turn, these chemosynthesis bacteria support mussels, limpets, snails, worms, crabs, clams, and other organism that live on the bones and within the nearby sediments.

QUESTIONS: 1. What is the difference between a biotic factor and an abiotic factor?  A biotic factor is a living organism. An abiotic factor is nonliving.

2. Name three types of community interactions that can affect an ecosystem.  -competition  -predation  -symbiosis

3. What is the difference between primary succession and secondary succession? Primary succession occurs when any previously existing ecosystem has been removed. The area is then colonized by pioneer species, and soil forms, allowing more plants and animals to move in. Secondary succession occurs after an ecosystem has been disturbed by natural events or human activities. As secondary succession takes place, the disturbed area comes to resemble its surroundings.

4. How is an organism’ niche determined? An organism’s niche is determined by the physical and biological conditions in its environment and how it uses those conditions.

5. Critical thinking: how are the three types of symbiotic relationships different? How are they similar? In mutualism, both species benefit. In commensalisms, only one species benefits while the other is neither helped nor harmed. In parasitism, one species benefits while the other is harmed. In all three relationships, two species live closely together.