Biology 391Ch. 24

Ecosystems:Structure &

Function

What is going on in this picture?

Can you explain all of the arrows?

What do you think each represents?

• How does this define ecology?• Hints:

Nutrients, energy, biomass, abiotic,

biotic

24.1 Abiotic Factors

• Examples?• Abiotic affects biotic

– Distribution, adaptations, etc.– Trade-off adaptation to live in one envi.

Usually means exclusion for another• Biotic can affect abiotic

– EX: Soil development by lichens

All life on Earth is interconnected.

All life interacts with the nonliving

environment.

ECOSYSTEMSA. ABIOTIC

1. Includes: Water, air, temperature, soil, light levels, precipitation, salinity, pH

2. Sets tolerance limits for populations and communities3. Some are limiting factors that structure the abundance

of populations

B. BIOTIC – trophic structure1. Producers, consumers, decomposers in a food chain, web and pyramid2. Interactions lead to transfer of energy and biomass

ENERGYSUN Autotrophs Heterotrophs (producers) (consumers)

• Autotrophs- plants, algae, phytoplankton

• Heterotrophs- – Herbivores- eat plants– Carnivores- eat meat– Omnivores- eat meat or plants– Scavengers- eat dead material – Decomposers- final breakdown of dead material- returning

nutrients to soil/water

Energy Pyramid

• Shows transfer of energy through trophic levels (who eats what)

Producers primary consumers secondary consumers tertiary consumers, etc.

• 10% Rule– Only 10% of the energy in the previous trophic level is passed

on

• Biomass– Total quantity of living matter at each trophic level

Where does the 90% go? What law is this?

Relationships in Ecosystems• What is a niche?• Predation

– Predator/prey• Competition

– **Competitive Exclusion Principle• Symbiosis

– Mutualism– Parasitism– Commensalism

Ecosystem Dynamics – nutrient cycles

Nitrogen Cycle

What gases compose air?

Nitrogen is NOT usable by plants & animals

Must change molecular forms (nitrogen fixation)

Ammonia & nitrate preferred by plants

Decay & denitrification return N2 to air

Limiting Factors• Abiotic factors that limit the population• Examples?

Population Dynamics• Carrying capacity• Exponential growth vs.

Logistic growth• Boom-bust cycle• Predator-prey cycle

http://desip.igc.org/mapanim.htmlhttp://www.poodwaddle.com/clocks2.htm

Recap• Can an herbivore be a secondary consumer?

Secondary trophic level? Why/why not?• How many trophic levels typically exist in a food

web? Explain.• Why could the Earth support more people if we all

ate at lower trophic levels?• List 3 abiotic factors and describe how each can

act as a limiting factor.• What is the relationship between K and limiting

factors?

Chapter 25

• Biomes– Types of ecosystems usually defined by the

most conspicuous vegetation• Tropical rain forest• Savanna• Deserts• Temperate grasslands• Temperate deciduous forests• Taiga• Tundra

Aquatic Biome

• Vertical zones– Photic zone– Aphotic zone

• Benthic and abyssal zones can be within here

• Horizontal zones– Intertidal zone– Neritic zone– Oceanic zone