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