Food Chains/ Food Web
What is the role of grass in a food chain?
Producer
Grass makes its own food through photosynthesis.
What is the main source of energy for most ecosystems?
The Sun
What is a limiting factor?
Anything that restricts population growth or size.
What are the three types of symbiotic relationships?
Mutualism, commensalism, and parasitism.
A grasshopper eats grass. Is the grasshopper a producer or consumer?
What do arrows in a food chain represent?
The direction energy flows.
Energy flows from the organism being eaten to the organism eating it.
What percentage of energy typically transfers between trophic levels?
10%
What does carry capacity mean?
The maximum population an environment can support over time.
What does the code (+/+) represent?
Mutualism
Question: Two ecosystems experience the loss of one species. Ecosystem A has a simple food chain, while Ecosystem B has a complex food web with multiple feeding relationships.
Which ecosystem is more likely to remain stable if one organism disappears? Explain why.
Ecosystem B, the food web, is generally more stable because organisms may have alternative food sources if one species disappears.
Grass → Rabbit → Fox. What type of consumer is the fox?
Secondary consumer
The fox eats the primary consumer.
If grass has 1,000 energy units, how many typically reach primary consumers?
100 units
A habitat has 10 rabbits and resources for 15. What is its carrying capacity in our model?
15 rabbits
A bird builds a nest in a tree without affecting the tree. What is the relationship and relationship code?
Commensalism, (+, 0)
A drought kills much of the grass. Predict one effect on rabbits.
The rabbit population may decrease.
The rabbits have less food.
What might happen to foxes if the rabbit population greatly decreases?
The fox population may decrease.
Less prey is available to support the foxes.
Why do organisms at higher trophic levels receive less energy?
Most energy is used by organisms or released as heat.
A rabbit population has plenty of food and water, but a new predator enters the ecosystem. The rabbit population begins to decrease.
What limiting factor caused the decrease, and did the carrying capacity necessarily change?
Predation. The rabbit population decreased, but the resource-based carrying capacity did not necessarily change because food and water were still available.
A tick feeds on a dog, while two lions compete for the same food. Give the relationship code for EACH interaction.
Parasitism: (+/−). Competition: (−/−). Both competing organisms expend energy or lose access to resources.
A disease kills rabbits but food resources stay the same. Does that necessarily lower carrying capacity?
No.
Population size can decrease without reducing the habitat's resource-based carrying capacity.
Why can removing one species affect an entire food web?
Organisms are interconnected and depend on one another.
Changes in one population can affect its predators, prey, and other organisms.
Why do food chains typically have a limited number of trophic levels?
Too little energy remains to support many additional levels.
A forest can support 100 deer. After a wildfire, the habitat loses much of its vegetation, and the deer population begins to decline.
Explain how the wildfire affected the carrying capacity and why the deer population decreased.
The wildfire reduced available food and habitat, lowering the carrying capacity. With fewer resources, the ecosystem could no longer support as many deer.
Two different species of birds compete for limited nesting space. Identify the relationship, give its code, and explain what happens if space becomes scarce.
Competition (−/−). Both species are negatively affected by competing for limited space. One or both populations may decrease.
Grass-> Grasshopper ->Frog -> Snake- > Hawk
Identify:
The herbivore
The carnivores
The tertiary consumer
Apex Predator
Herbivore: Grasshopper
Carnivores: Frog, Snake, Hawk
Tertiary consumer: Snake
Apex predator: Hawk