Definitions
the maximum population size of a species that can be sustained by that specific environment, given the food, habitat, water, and other resources available
carrying capacity
A Brazilian farming company cuts down 100,000 acres of rainforest and burns the trees in order to make room to raise cows. How does this impact the carbon cycle?
Increases atmospheric CO2 levels (which increases the rate of climate change)
Which of these terms applies to a rabbit:
a) producer
b) predator
c) autotroph
d) omnivore
b) predator
Picture a trophic pyramid. What often occurs when you remove a tertiary consumer from the top, such as a wolf?
trophic cascade
Name the 4 biogeochemical cycles we have studied
-nitrogen
-phosphorus
-water
-carbon
Define the symbiotic relationship between a bee and a flower
mutualism: both species benefit
The population of rabbits on our nature trail hill has a carrying capacity of 100 rabbits. Their limiting factor is the amount of food available. In the last few weeks, the rabbits had a lot of babies. There are now 150 rabbits living on the hill. What will happen next, and why?
Approximately 50 rabbits will die from starvation because they exceeded the carrying capacity. They died specifically from famine because the limiting factor was food.
What limits a population from exponentially growing forever?
a limiting factor
Imagine a trophic pyramid. Where is the base of the pyramid getting energy from?
the sun
What two things are able to "fix" nitrogen from the air into a useable form for plants?
- bacteria in the soil
- Lightning
an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter
consumer / heterotroph
Imagine a scenario where there are two species of tree in a forest. One of the two trees grows faster than the other, absorbs nutrients quicker, grows above the other species and deprives them of sunlight, and eventually outcompetes them and completely removes them from the area. What is this scenario called?
Competitive Exclusion
When performing an experiment, what is the independent variable?
The one thing that you change
Which type of survivorship curve illustrates an insect population?
Type III
Explain the effects of both burning fossil fuels and planting millions of trees on the carbon cycle.
Burning fossil fuels increases the amount of carbon dioxide in the atmosphere. Planting more trees decreases the amount of carbon dioxide in the atmosphere.
Define the 10% rule
when energy is passed in an ecosystem from one trophic level to the next, only ten percent of the energy will be passed on
A student draws a food chain of an environment near their high school. This food chain includes 8 different organisms, from the producer at to bottom to 7 trophic levels of consumers above them. What is unrealistic about this scenario?
There would most likely not be enough producers to support 7 trophic levels above it. Due to the 10% rule, there is rarely enough energy at the base level to support more than a tertiary consumer.
Most plants absorb more nitrogen from the soil than they release. Legumes (such as beans and peas) are a type of plant that return more nitrogen to the soil. How can this be beneficial?
Farmers can periodically plant legumes to increase their nitrogen levels in their soil without having to apply more synthetic fertilizer than necessary.
What type of survivorship curve do humans have? Prior to technological advancements and healthcare, what curve were we closer to?
We are now type 1, but we used to be more similar to type 2!
Name both limiting factors for plants that we synthetically add into fertilizer
- nitrogen
- phosphorus
Define and give one example of resource partitioning
When species divide a niche to avoid competition for resources.
EX: Hawks hunting during the day, owls hunting at night.
Some fish eating in shallow waters, other fish eating in deep.
A population of bacteria are growing in a flask of ideal medium at optimum temperature over a 24-hour period. They have no limiting factor other than space, and it will take them weeks to reach that point. What will their population growth curve look like after the 24 hours?
J-curve
Provide an example of a density dependent factor
Large scale weather events
Picture a graph of a population of deer. At first the deer population grows exponentially (J-shaped curve) but then it levels out. Their population wiggles up and down in a small wave. Why has their population stopped exponentially growing, and why does the line wiggle?
The population has reached carrying capacity, but populations never stay perfectly level. Populations will overshoot the carrying capacity which will lead to a die-off from exceeding the bounds of their limiting factor.
Humans are currently altering all four biogeochemical cycles that we discussed in class. Name one example of how we can mitigate (lessen) our effects on these cycles.
Water cycle - ex: plant native plants that are drought tolerant to decrease our water consumption
Carbon cycle - take government subsidies from fossil fuels and give them to renewable energy sources to decrease the amount of carbon we put in the air and change our habits sooner rather than later.
Phosphorus - Use fertilizer during dry seasons to limit the amount of runoff into nearby watersheds, creating less algal blooms and dead zones
Nitrogen - Plant less nitrogen-needy crops - use synthetic fertilizers less frequently