Energy Flow & Trophic Pyramids
In a typical energy pyramid, which organisms form the base?
Producers, such as plants or algae.
What is a keystone species?
A species whose ecological impact is unusually large relative to its abundance.
What does gross primary productivity measure?
The total rate at which producers capture energy and store it as chemical energy through photosynthesis.
Why did we let the tap water sit out uncovered for 48 hours prior to adding dead leaves and other materials?
Tap water is treated with chlorine to kill any bacteria/pathogens in it. Since we wanted to grow and ecosystem complete with bacteria, fungi, and plants, we have to first let the chlorine evaporate out of the water before adding components to the jar.
Two eagles battle it out for the same Chinook salmon. What type of symbiotic relationship is this and what are the symbols to indicate who benefits/suffers/is unaffected)? (+, -, 0)
Competition (-/-)
They both are expending energy to compete. Therefore, they both lose!
Why does the available energy generally decrease at higher trophic levels?
Organisms use much of the energy they obtain for life processes, and some energy is released as heat. Less energy is transferred to the next trophic level.
What is a trophic cascade?
A chain of effects across trophic levels that occurs when a change to one population affects other populations and ecosystem processes
What does net primary productivity represent?
The energy or biomass producers retain after accounting for their own respiration.
What is the correct starting objective when focusing on a new slide, and why?
Start with the lowest-power objective because it gives a wider field of view and makes it easier to locate the specimen.
If a meadow of grass has 2,000 kJ of energy. How much energy would the SECONDARY consumers (Swallow birds) have?
Grass --> Insects (primary consumers) --> Swallows (secondary consumers)
10% of what the insects have --> 2,000/10 = 200 --> 200/10 = 20 kJ (we are going up TWO trophic levels, so we have to find 10% of the energy received from the level below TWICE.
What does each of these pyramids represent: a pyramid of numbers, a pyramid of biomass, and a pyramid of energy?
Numbers shows the number of organisms at each trophic level; biomass shows the total mass of living material at each level; energy shows energy transferred or available at each level over time.
In a coastal food web, sea otters eat sea urchins, and urchins graze on kelp. Predict what could happen to kelp if otters decline.
Urchin numbers may increase, leading to heavier grazing and reduced kelp abundance.
Complete the relationship: net primary productivity equals gross primary productivity minus what?
Producer respiration.
Formula: Net Primary Productivity = Gross Primary Productivity - Respiration
NPP = GPP - R
How do you prepare a basic wet mount slide?
Place a drop of water and the specimen on a clean slide, lower a coverslip at an angle to limit air bubbles, and follow classroom safety procedures.
Why did we leave the tap water to sit out in the jars over the weekend?
Our tap water is treated with chlorine to kill of any bacteria present. This could also kill any of the organisms that we will introduce to our jars with the dead leaves and such. Therefore, we needed to leave the water out for the chlorine to evaporate off.
A forest has one large tree supporting many insects. Which pyramid could be inverted, and why?
The pyramid of numbers could be inverted because one producer can support many consumers.
Describe one way great whales can influence marine productivity after feeding at depth and releasing nutrients near the surface.
Their nutrient release can increase nutrient availability near the surface, supporting phytoplankton growth and potentially affecting other organisms in the food web.
Two ecosystems receive similar sunlight, but one has more available water and nutrients. Which might have higher productivity, and why?
The ecosystem with more available water and nutrients may have higher productivity because these resources can support photosynthesis and producer growth.
A microscope has a 10× eyepiece/ocular lens and a 40× high-power objective lens. What is the total magnification?
10 × 40 = 400, so the total magnification is 400×
We have had some very intense wildfire seasons for the past few years. After a wildfire rips through a forest, what do you think would be one of the first organisms to occupy environment once the soil is replenished?
Weed-like plants like Fireweed!
Explain why an energy pyramid cannot be inverted, even when a pyramid of numbers or biomass is inverted.
Energy is lost between trophic levels, largely through metabolism and heat. Therefore, less energy is available at each successive level, so producers must have the greatest energy base.
A predator is removed, herbivores increase, and plant cover declines. Explain the trophic cascade and predict one possible ecosystem effect.
Predator loss can allow herbivores to increase, which can intensify plant consumption. Reduced plant cover may alter habitat or food availability for other species, changing community structure.
Why would a warm, wet tropical forest have high net primary productivity, while a desert often has lower productivity.
Tropical forests generally have abundant warmth and water that support year-round photosynthesis. Deserts have limited water, which restricts plant growth and photosynthesis.
A specimen spans about half the field of view under low power. When switching to high power, what happens to the field of view, and how can you estimate the specimen’s size?
The field of view becomes SMALLER.
Estimate the high-power field of view using the inverse relationship between magnification and field diameter
Formula: [(Total Magnification of Low-Power)(Field of View width for Low-Power)] / Total Magnification of High-Power
Example: (40X)(4mm) / (400X) = 4/10 = 0.4 mm --> 400 micrometers
What is the name of the resilient, microscopic organism that some of you may get to see when you look at a Succession Jar water sample under the microscope?
Tardigrade (aka water bear)!!!!