Biology Name: _____________________Unit 1 Ecology Date: ____________ Hour: ___

Food Web Assignment The flow of materials (and energy) in an ecosystem is the result of predator-prey relationships. These relationships establish a long chain of events. They always begin with a producer and end with consumers.

1. For the food chain above, indicate the:

a) producer: grass

b) primary (1st) consumer: grasshopper

c) secondary (2nd) consumer: frog

d) tertiary (3rd) consumer: snake

e) quarternary (4th) consumer: eagle

f) herbivore: grasshopper

g) first carnivore: frog

h) top carnivore: eagle 2. Complete each of the following food chains with an appropriate animal:

a) in a woodlot: leaves worm ___bird_____

b) in a pond: algae insect ___frog____

eagle snake frog grasshopper grass

c) in a forest: grass rabbit ___fox______

3. Use the food chain below to answer the following questions.

sapling wolf a) If the deer population increases, what will happen to:

i) the sapling population? (increase or decrease)

ii) the wolf population? (increase or decrease)

b) The changes in the sapling and wolf population will cause a change in the number of deer. What happens to the deer population as a result? (increase or decrease)

c) As a result of the change in (b) what will now happen to:

i) the sapling population? (increase or decrease)

ii) the wolf population? (increase or decrease)

4. The area in which the above food chain occurs contains other organisms such as grass, mice, rabbits, hawks, frogs, snakes, and insects. We can connect all these animals together in a food web as shown below.

deer

The food web represents a more realistic situation. In the above food chain;

a) What are the two foods that the deer eats? Grass and saplings

b) What does the wolf feed on? mouse, deer, rabbit

c) Why is it advantageous for the deer and the wolf to have more than one food source?

If one food source decreases in number, the animal will likely be OK b/c there are others to fall back on.

d) Are there any omnivores in the above food web? If so, name them. NO.

e) The food web contains 16 food chains. Identify 4 of these chains:

i) Grass → mouse→ snake→ hawk

ii) Sapling→ Deer→ Wolf iii) Grass → insect→ frog iv) Sapling → mouse→ Hawk

frog insect grass

hawk rabbit

wolf deer aplings

snake ousem

f) If the number of rabbits were to increase, what would happen to each of the following populations:

i) grass (increase or decrease)

ii) hawks (increase or decrease)

g) Will the changes in (f) have any effect on the number of mice in the area? EXPLAIN.

The mice may decrease because they have less food (grass) and more predators (hawks)

5. One important organism omitted from our food chain and food web is the decomposer. a) What is the role of a decomposer? Break things down (cause decay).

They release the nutrients back to the environment.

b) Why are decomposers important? They release the nutrients back to the environment. They can then be used again. Nutrients are needed to carry out life’s functions.

6. Consider the food chain below. At each level in this food chain, energy is lost. Approximately 90% of the energyconsumed by the caterpillar is used in its day-to-day metabolism, and only 10% can be passed on to the bird who eats it.

10 kJ kJ100 1000 kJ ENERGY

bird caterpillar lowerf

900 kJ lost 90 kJ lost

a. Food chains rarely go beyond 5 trophic levels. Explain why, using the food chain above for reference.

Most of the energy is gone by the time you reach the upper trophic levels. There is very little usable energy available with which to make a living.

Food Chains and Food Webs

1. Identify all the producers. Trees and grass 2. Construct a food chain that has four (4) trophic levels. Grass→ Rabbit→ Fox →Mountain Lion 3. Identify three (3) herbivores. Rabbits, mice, squirrel, beaver, grasshopper, 4. Identify three (3) secondary consumers. Mountain lion, owl, frog, bird, fox, hawk

Trees

Grasshopper Bird Frog

Mouse Rabbit

Squirrel Beaver

Snake

Owl

Hawk

Fox Mountain Lion

Grasses

5. Identify all omnivores (if there are any). NONE. 6. Identify any organisms that occupy more than one possible trophic level. Mountain lion, owl, hawk 7. Explain what might happen to the fox and the hawk populations if a disease

dramatically reduced the mouse population.

They may have a decline in population due to a reduction in available food. They would focus more on the other prey.

Energy Movement in Ecosystems

Draw a food web for the following ecosystems and identify: • Producers (first trophic level) • Primary consumers (second trophic level) • Secondary consumers (third trophic level) • Tertiary consumers (fourth trophic level) A. In a pond, floating plants are found on the surface and phytoplankton (algae) are found

just below the surface. The floating plants serve as food for muskrats, which are eaten by snapping turtles. The phytoplankton is food for both tadpoles and minnows in the pond. Both the tadpoles and minnows are eaten by the Kingfisher bird. Snapping turtles also eat the tadpoles.

B. In a forest ecosystem, land plants act as producers and provide food for mice, bears,

insects, and grouse (a bird). The mice, in turn, are eaten by hawks and snakes. The insects are eaten by both grouse and spiders. The grouse are eaten by foxes. Black bears in the area feed on plants and fish. The fish eat crayfish in the streams, while the crayfish eat microscopic plants in the water.