Ecosystems & Communities
Chapter 4
Dr. Donna HowellBiology IBlacksburg High School
EcosystemsTwo factors shape an ecosystem:
Biotic factors – biological influences
Plants, other animals, etc.Abiotic factors – nonliving influences
Climate, rainfall, wind, sunlight, etc.
HabitatTogether, the biotic and abiotic factors of an ecosystem determine the survival and growth of organisms and make up their habitat.
NicheA niche is the place an organism occupies in an ecosystem. A bullfrog’s niche would be what it eats, when it reproduces, and where it lives.
Community Interactions
There are three main types of community interactions:
CompetitionPredationSymbioses
CompetitionCompetition occurs when organisms have to use the same resources, such as food.
PredationPredation is when one organism captures and feeds on another. Lion and antelope
SymbiosesAny relationship where two organisms live closely together is called a symbiosis.There are 3 main types:
MutualismCommensalismParasitism
MutualismMutualism is a type of symbiosis where both species benefit.Example: bees and flowers
CommensalismCommensalism is a symbiosis where one member benefits, and the other is not harmed nor does it benefit.Example: barnacles on a whale
ParasitismParasitism is a symbiosis where one organism harms the other one.Example: mosquito sucking on human blood
Ecological Succession
Ecosystems are constantly changing over time.The series of predictable changes that occurs over time is called ecological succession.
Primary Succession
Primary succession occurs where no soil exists. Example: years after a volcanic eruption covers ground with lava.
Primary Succession
The first species to populate an area after such an event is called the pioneer species.
Secondary Succession
Secondary succession happens after a disturbance, such as a wildfire.The community interactions restore the ecosystem to its original condition.
BiomesA biome is a complex of terrestrial communities that covers a large area.
Tropical Rain Forest
Hot and wet year-round.Large trees with canopies.Huge variety of wildlife.Ex: Costa Rica
Tropical Dry Forest
Warm year-round, alternating wet and dry seasons.Deciduous trees with canopyTigers, monkeysEx: Mexico
Tropical SavannaWarm; seasonal rainfalls; frequent lightning firesTall grassesLions, cheetahEx: Africa
DesertHot year-round; little rainfallCactiScorpions, roadrunnersMiddle East
Temperate Grassland
Hot summers; cold winters; seasonal rainfallGrassesBison, Prairie chickensEx: central North America
Temperate Woodland
Hot dry summers; cool moist wintersEvergreen shrubsCoyotes, deerEx: West coast of North America
Temperate ForestWarm summers; cold winters; year-round rainfallDeciduous treesBears, bobcatsEx: Eastern US
Boreal ForestLong cold winters, short mild summersConifersLynxes & mooseEx: Washington State, US
Northwestern Coniferous Forest
Mild temperatures, lots of precipitationRedwoods and hemlocksElk, owlsEx: Pacific coast of US
Tundra Permafrost; long, cold wintersMosses, lichensCaribou, Arctic foxEx: Northern North America
Aquatic Ecosystems
In addition to land biomes, we also have aquatic biomes.Freshwater, estuaries, ocean, etc
Aquatic Ecosystems
The base of aquatic food chains are tiny free-floating creatures called plankton and zooplankton.
The End
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