Abiotic and Biotic Components in Ecosystems

Source: Jones, M and G. Jones 1995 Biology. Cambridge University Press.

United Kingdom

Abiotic and Biotic FactorsAbiotic: Non-living components of the

ecosystemPhysicalChemical

Biotic: Living componentsBiotic interactionsBiotic indexes

Studying Abiotic Factors

Abiotic Physical FactorspH (of soil and water): important factor in

the process of absorption of nutrients from the soil. Acidic soils inhibit absorption and decreases biological diversity.

Salinity: amount of dissolved salts. This factor has an effect on the absorption of H2O by osmosis. Some plants are adapted to soil with high salinity

Climate: influences natural populations The two most important factors are temperature

and precipitation

Temperature: temperatures higher than optimum denature enzymes; low temperatures inactivate enzymes. Has negative effects on growth, productivity and reproduction

Water (precipitation): Needed for vital activities (enzyme activity, transport, photosynthesis, support)

Light (intensity and duration): Important for photosynthesis, flowering, reproduction, phototropism. In dark areas of the world where there is low light intensity and duration

Abiotic Chemical Factors Soil: affects plants and therefore animals.

Plants rely on it for many of their requirements Provides: anchorage, nutrient minerals, water, air;

habitat

Oxygen: needed by most living organisms. Can quite often be in short supply in water (in

riffles there is large supply; in pools is sometimes depleted due to decomposition

BOD (biochemical oxygen demand) DO (dissolved oxygen)

Nutrients Phosphorus

Mineral Nutrients: Plants need a continuous supply of nutrients from the soil for manufacturing enzymes, proteins, vitamins, nucleotides and other compounds Phosphorus Mg Fe

Studying Biotic Factors

Biotic FactorsInclude descriptions of the following factors:

Availability of foodPredatorsParasitesCompetitionBiotic Indexes

Abundance or Pop. Size (random sampling)Density (# of organisms per area or volume)Biological diversity (biodiversity index)

Distribution (type):RandomClumpedUniform

Studying biotic components of ecosystemsRandom sampling: Using randomly selected representative samples. Including a large portion (sample) of the populationRandom Sampling using Quadrats: It can be any size, but one with sides of about 0.5 m is convenient in the fieldTransects: Allows us to see distribution of organisms in the field. A line crossing the field. A long calibrated line or tape could be used to record all plants/organisms touching the field or at certain intervalsMark-release-recapture: Use with animals that move around a lot.

Classification and Identification of Organisms

Why do we classify?To identify organismsTo make inferences about characteristicsTo establish evolutionary links

How do we name organisms?Binomial System

Five KingdomsProkaryota

Protoctista

Fungi

Plantae

Animalia

Classification from species to Kingdom HUMAN BLUE

WHALE

Kingdom Animalia Animalia

Phylum Chordata Chordata

Class Mammalia Mammalia

Order Vertebrata Cetacea

Family Hominidae Balaenopteridae

Genus Homo Balaenoptera

species sapiens musculus

Evidence used in classificationFossil record

Biochemical evidence

Anatomical Structures

Geographical Distribution

Identifying OrganismsDichotomous or Taxonomic Key

Practice: Taxonomic Key for snakes and for

salamanders