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 barnacle rides on a whale and gets access to food. The whale gets nothing. What symbiotic relationship is this?
commensalism
Which of these terms applies to a rabbit:
a) producer
b) predator
c) tertiary consumer
d) omnivore
predator
Picture a food web. What often occurs when you remove a tertiary consumer from the top, such as a wolf?
trophic cascade
Name one limiting factor for plants that we synthetically add into fertilizer
- nitrogen
- phosphorus
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.
Weather events such as floods and tornadoes are density dependent factors on populations.
false
Imagine a trophic pyramid. Where is the base of the pyramid getting energy from?
the sun
Name the 4 biogeochemical cycles we have studied
-nitrogen
-phosphorus
-water
-carbon
define a density depepndent factor
something that can influence the survival rate of a population DEPENDING on how close/dense they are
ex: disease
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.
What limits a population from exponentially growing forever?
a limiting factor
In a model of the carbon cycle, what could be seen as a carbon sink? (sink = absorbs more than it releases)
- plants
- ocean
- sediment
What two things are able to "fix" nitrogen from the air into a useable form for plants?
- bacteria in the soil
- Lightning
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
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
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.
Write the name of the only biogeochemical cycle we discussed that does not have an atmospheric phase (meaning there is not of that nutrient in the air)
phosphorus
We influence 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
This is the term for the measurement of organisms that move out of an area
emigration
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
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 for farmers?
Farmers can periodically plant legumes to increase their nitrogen levels in their soil without having to apply more synthetic fertilizer than necessary.
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.
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.