Unit 5 Lecture 26 Flashcards
What does community mean?
Groups of interacting species
- Interaction can include competition, predation, herbivory, mutualism, etc.
What does tropic levels mean?
Groups of species that have similar ways of obtaining energy (often exclude parasites)
- Transfer of energy from resource to consumers
How to tell what species in a food web is an omnivore?
Species that feed on multiple trophic levels
When arrows are going downward, it represents _______ when arrows are going upward in trophic levels it represents __________
- represents effect of one species on another (otters have a negative effect ON urchins)
- Arrows representing energy flow (energy flows from the sea urchins to the otters)
What do dashed lines mean in trophic cascades?
Indirect effect: sea otters don’t directly eat kelp but they do have a positive effect on them
Whats the difference between bottom-up control and top-down control?
Bottom-up: means that a lower trophic level in the biological network affects the community structure of higher trophic levels by means of resource restriction
Top-down: predation by higher trophic levels affect the accumulation of biomass at lower trophic levels.
In the absence of other (more dominant) species what can happen
Consumers reduce the resource until reaching carrying capacity
- When predators come in, they can reduce herbivore population and allow plants (primary producers) to flourish
Explain the trophic cascades with sea urchins
Sea otters (carnivore) have a negative impact on sea urchins (herbivore) (they eat sea urchins), and sea urchins have a negative impact on kelp (primary producer). Since sea otters eat urchins, that is an indirect positive impact on the kelp
What would happen if you took out sea otters?
Sea urchin abundance would go up, and kelp population would go down
What is the definition of trophic cascade?
When you have a system in which the levels of the food web are maintained through the addition of an apex predator
What would happen if a whale was added to the cascade?
It would have a indirect negative impact on the kelp because they would eat the sea otters.
Why did orcas suddenly begin to eat sea otters?
Killer whales never ate otters before 1991
- In the 40s-70s whales were being harvested
- Once harvesting became illegal, the orca population started increasing
- They first ate great whales, but then they disappeared
- then ate seeds, but started to disappear
- then ate sea lions but started to disappear
- Now eating sea otters, but are starting to disappear
Explain the Yellowstone study
In the early 1900s wolves were removed from the park, which cause deer to overgraze the forest, causing plant life to decrease, and tree life, there fore beaver life
Why was there a decrease in tree recruitment before elk population increased
“Landscape of fear”
- The presence/absence of predators can change the foraging behavior of herbivores (where and how much)
- Since wolves were gone, deer were able to graze everywhere again
