Investigative Science – NOTES: WEEK 31
Tuesday March 31, 2015
Perry High School
Notebook page: 11
MR. POMERANTZ_____________________________________________________________Page 1 of 4
Students are responsible for having the following notes in their notebooks.
Biotic and abiotic factors
An ecosystem is composed of biotic and abiotic factors. Biotic factors are living components of an ecosystem
(plants and animals). All of the biotic factors in an ecosystem comprise a community. The smallest part of an
ecological community is an organism (a single living individual – or a single biotic factor). Abiotic factors are the
non-living components (sunlight, water, rocks, water). Energy travels between biotic factors and is organized into
“trophic levels”.
Trophic levels are the feeding position in a food chain
Lower trophic levels provide food (energy) for levels above them. This means there must be more “biomass” in lower
trophic level in comparison to higher levels. Biomass is collective mass of all living things in a trophic level or ecosystem.
Trophic levels are summarized in Figure 1.
Example of moving down the levels
Feeding 1 person a year…..
It will require 300 trout….
The trout will eat 90,000 frogs….
The frogs will consume 27 million grasshoppers….
The grasshopper will devour 2 million pounds of grass….
The original source of energy for everything is the sun
Figure 1: Trophic levels
Quaternary
consumers
Notice how the populations grow as we move down the trophic levels. Populations in higher trophic
levels have less energy available to them. All the Earth’s energy originates with the sun. The Sun’s
energy is transferred into plants, which incorporate energy from the sun into carbohydrates (energy in
the form of sugars and starches). First order consumers eat the plants and incorporate carbohydrates
into proteins (muscle) and lipids (fats), both of which store energy. Second order consumers eat first
order consumers and incorporate the proteins and lipids (energy) into their own bodies. Dead plants
and animals decompose, their energy (carbohydrates, proteins, fats) is used by the decomposers.
At all levels, the organisms use some of the energy for metabolism, movement, and growth,
reproduction, and neural activity– these are basic life activities.
Once used, this energy is lost from the system (biosphere) as heat. This means there is less
energy available to higher trophic levels.
Only 10% of available energy transfers up from one level to the next. This 10% of energy is
incorporated while 90% of energy at each level is lost. Each trophic level has a numerical
name: Primary producers (plants), Primary consumers (animals that eat plants), Secondary
(meaning second level) consumers, Tertiary (meaning third level consumers, and
Quaternary (meaning fourth level) consumers. It is very rare to have a fifth level because
there will be little to no energy left to pass along to that level.
Figure 2 shows an example of transferring energy between trophic levels. Notice as the energy depletes
so does the biomass and only 10% of the mass (an energy) transfer up to the next level.
Hawk 1kg
10% transfers up
Bluebird 10kg
10% transfers up
Caterpillar 100kg
10% transfers up
Oak tree1000kg
Tertiary
consumers
Secondary
consumer
s
Primary
consumer
s
Primary
producers
Investigative Science – NOTES: WEEK 31
Tuesday March 31, 2015
Perry High School
Notebook page: 11
MR. POMERANTZ_____________________________________________________________Page 2 of 4
Carrying capacity
The carrying capacity is the maximum number of individuals in a population that can be supported in an ecosystem. The
carrying capacity will be higher for populations that occupy lower trophic levels. Populations that exceed their capacity will
shrink. Populations that are below their capacity are likely to grow. Figure 3 shows how a deer population changes with a
changing capacity.
Figure 3:
Max population
When a population exceeds its carrying capacity there is likely not enough energy in the community to maintain the
population. In figure 3 the deep population reaches a maximum value, well above its capacity. This is possible when a
population starts small and grows quickly. However a maximum amount of individuals is not always a sustainable amount of
individuals.
Investigative Science – NOTES: WEEK 31
Tuesday March 31, 2015
Perry High School
Notebook page: 11
MR. POMERANTZ_____________________________________________________________Page 3 of 4
Week 31 review:
1. Draw an ecosystem representing central Arizona. Label three biotic and three abiotic factors. Circle the biotic
factors in green and abiotic factors in red.
2.
Give three examples of a population found in central Arizona as well as the definition of a population.
3.
Explain the difference between a community and a population.
4.
Define carrying capacity. Explain the difference between the concept of a carrying capacity and the peak
(maximum) of a population.
5.
What is unique about plants versus animals in terms of gathering and producing food?
Investigative Science – NOTES: WEEK 31
Tuesday March 31, 2015
Perry High School
Notebook page: 11
MR. POMERANTZ_____________________________________________________________Page 4 of 4
6. If a kestrel eats a mouse that eats grass, the kestrel is in what trophic level? Draw a food chain showing the
relationship. If the biomass of the mouse trophic level is 2,500 kg what is the biomass of the grass and the kestrel
trophic levels?
7.
The first organism in a food chain is always a what? How much of its energy is passed to the next level?
8.
In an energy pyramid, which level has the most available energy?
9.
Create a graph showing how Biomass (as the DV) relates to trophic position (as the IV). Be sure to label each axis
properly.
10. If there are 25,000,000 calories of energy available in the secondary consumer trophic level of a community, how
many calories are available at the primary producer level, primary consumer level and tertiary consumer level?
Organize your answer into a data table.