ECOSYSTEMS-ECOLOGY

Essential info in accrdance to question usually asked

ABIOTIC FACTORS

1. Sunlight

2. Humidity

3. Temperature

4. Moistness

5. Mineral Availability

6. pH levels

7. Oxygen

8. Soil composition

BIOTIC FACTORS

1. Predation

2. Food availability

3. Competition for resources/mates

4. Disease and parasites

5. symbiotic processes (Mutualism, Commensalism and parasitism

Food chains, webs

A food chain is a linear pathway through which energy and nutrient transfer is layed out from producers to consumers (useful but oversimplified)

KEY ROLES: Trophic levels

Primary producers (autotrophs) create their own food using inorganic materials and inorganic energy.

Consumers (primary, secondary, tertiary) - heterotrophs

Apex Predator/Quaternary Consumer

Decomposers : gain energy by feeding on dead or waste organic material

(UNUSUAL TO HAVE MORE THAN 5 TROPHIC LEVELS, because more and more energy is lost to the surroundings in searching for mobile prey + less energy enters the system

Because so much energy is lost as heat through metabolic processes, movement and waste at each step, there is significantly less energy available for carnivores.

At some point: energy required to hunt > energy gained from feeding

A food web is a linkage with many overlapping chains where species may have many food sources and feed at more than 1 trophic level. more accurate representation of how one biological community interacts with another - in reality, organisms can prey on multiple different variety of organisms, occupying diferent trophic levels

energy flow:

as we move up the food cycle, energy decreases and is lost as heat and used for metabolism.

energy transfer is not 100% efficient, it is only 10%. (90% is LOST TO THE ENVIRONMENT)

producer: makes its own energy using an energy source (usually sunlight)

consumer: absorb/gain energy by eating other organisms

Biomass

chemical energy stored in living matter - it decreases as we go up the food cycle (producer —> consumers)

Keystone species

The population part of a food cycle which has a disproportionate impact on an ecosystem in comparison to/despite its abundance/population size.

A keystone species must have a profound impact on its ecoystem such as a whales, elephants (which are herbivores) etc.

Ecosystem stability:

If a top predator’s population size suddenly decreases, the primary consumer/herbivore population increases, resulting in a reduced producer/plant biomass.