Chapter 2Chapter 2

EcosystemsEcosystems

Ecosystems: What are they?Ecosystems: What are they?

• The biotic and abiotic factors in a specified area that interact with each other.

• Plants and animals’ interaction with their abiotic environment– Organisms try to reduce the effects of factors

by adapting: waxy coats, pine needles, cactus spines

abioticabiotic bioticbiotic• Radiation

• Space

• Rainfall

• Temperature

• Elevation

• Humidity

• Wind

• Landform

• pH

• Salinity

•Food•Immigration•Emigration•Natality•Mortality•Predation•Parasitism•Scavenging•Competition

Structure of EcosystemsStructure of Ecosystems

• Feeding relationships

• Non-feeding relationships

• Limiting factors

Feeding relationships: Feeding relationships: Trophic CategoriesTrophic Categories

• Producers create organic molecules by capturing light energy and converting into food energy

• Consumers feed on producers and without such would not exist

• Primary consumers (herbivores):• Secondary consumers (carnivores): • Omnivores:

• Detritus feeders and decomposers• Detritus feeders can be primary or secondary• Decomposers are primary detritus feeders

Trophic relationshipsTrophic relationships• Food chains are feeding pathways such as

predator-prey and parasite-host

• Food webs: are complex diagrams of feeding relationships

• Trophic levels exist:– All producers are on the first level– All primary consumers are on the second level– All carnivores (secondary consumers) are on the

third level

Biomass pyramidBiomass pyramid• All organic matter is biomass

• All biomass can be related to the producers

• About 10% of energy from one level moves to the next:– Because so little energy is transferred, it is

necessary that most organisms are on the first level – limitations on this transferral create the pyramid

– If organisms eat high on the pyramid, then fewer organisms can be supported.

Non-feeding Non-feeding RelationshipsRelationships

• Mutualism

• Competition– Reduction can be achieved by habitat and

niche formation– If niches overlap, the competition increases

Limiting FactorsLimiting Factors• Availability of factors affect the survival of

an organism such as temperature, light, oxygen, CO2, and precipitation

↓Law of Limiting Factors: quantities of any

single factor above or below optimum levels will limit growth, reproduction, and survival

Global BiomesGlobal Biomes

• Climate– temperature and pecipitation determine

biomes

• Microclimate and abiotic factors:

-light intensity, soil types, topography

• Biotic factors: organisms’ presence affecting another (shade, chemicals, presence of producers)

World Distribution of BiomesWorld Distribution of Biomes

Implications for HumansImplications for Humans3 revolutions:

• Neolithic:

– Special skills

– Settlements

– Agriculture

• Industrial: creation of modern world

• Energized by fossil fuels

• More concentrated waste

• Greater increase in human population

• Environmental:

• Need to create sustainable human systems

• Need to reduce concentrated waste and use waste as a resource