Assignment Community Ecology Part 1 Two Species Interactions One way to categorize interactions between two different species is to define the interaction by the outcomes A mutualism is an interaction that benefits both species Almost always Competition mutualisms involve the exchange of two different types of resources Food for protection for example is an interaction between two species both attempting to use the same resource when the resource is in limited supply Thus both species are hurt by the interaction Predation which one species benefits and one species is hurt Parasitism Herbivory We have three terms for interactions in o Predators kill and eat the prey species o Parasites eat or live on their hosts but do not always kill the host o Herbivores are animals that eat plant tissues o But notice that in each case one species benefits from the presence of the other species while the other species is hurt Commensalism is an interaction in which one species benefits and the other species is not particularly affected It can be hard to define a commensalism because interactions tend to affect the species involved and any effect will shift a commensalism into a mutualism or a predation type interaction Read the interaction scenarios below and decide whether the interaction is competition commensalism predation parasitism herbivory or mutualism Fill in the information on the table below Scenario A On the edge of an alpine meadow a beaver cuts down an aspen tree It eats the bark uses some of the timber to shore up its dam and stores some of the branches underwater for it to eat later in the winter Scenario B You are camping in the meadow A female mosquito smells you She finds a piece of exposed skin drills her proboscis through your skin to find a capillary and sucks up your blood Scenario C That evening you watch as an elk and a white tailed deer both grazing ungulates eat the same kinds of plants in an alpine meadow Scenario D The next day you notice some colorful flowers A butterfly walks over a brightly blooming inflorescence It finds nectar stored inside the flowers and eats the nectar In the process it gets pollen smeared on its body When it is finished hunting for nectar it flies to another flower of the same species a little ways away to find more nectar Some of the pollen gets scraped off onto the second flower Adapted from a case study by Eric Ribbens Department of Biological Sciences Western Illinois University Scenario E A hawk soars over the meadow Its sharp eyes spot a field mouse The hawk drops into a steep dive and catches the mouse in its talons Then it flies away to feed the dead mouse to its nestlings Scenario F On the edge of the meadow is a large tree Growing on the tree s bark is a circular gray green lichen about 6 inches in diameter The lichen is using the tree for habitat The trunk gets sun and the lichen isn t competing with other organisms for space The tree hardly notices the lichen it isn t eating the tree or taking resources from the tree Scenario G In the wetter part of the meadow there is standing water In the shallow water a cattail a tall grassy plant and a rush another kind of grassy plant are both growing The cattail and the rush both prefer the same kind of habitat both need sunlight and both are sucking up nitrogen and other nutrients from the marsh mud Scenario Type of Interaction A B C D E F G HERBIVORY COMPETITION HERBIVORY PARASITISM MUTUALISM PREDATION COMMENSALISM COMPETITION Part 2 Symbiosis Symbiosis is another type of two species interaction It literally means living together and refers to pairs of species that live in close physical proximity with the other species for a major part of their life cycles Some examples of symbiosis include You and the microorganisms that live in your intestines bark beetles burrowing in pine tree trunks Monarch butterfly caterpillars and milkweed plants and Adapted from a case study by Eric Ribbens Department of Biological Sciences Western Illinois University Dinoflagellates living in coral tissues Can you think of any symbiotic interactions that are commensal or parasitic Fill in examples for each in the blank cells in the table below Interaction Mutualism Monarch butterfly caterpillars and milkweed plants Dinoflagellates living in coral Examples tissues trunks Commensalism bark beetles burrowing in pine tree Parasitism You and the microorganisms that live in your intestines Part 3 Facultative vs Obligatory Interactions Another idea especially applied to mutualism is whether the interaction is facultative or obligatory A facultative interaction is one that is not essential for the survival of the species involved while an obligatory interaction is essential for one or both of the species involved Classify the following examples as mutualism parasitism or commensalism Determine if each example is obligatory or facultative Fill in the information in the tale below Example 1 The interaction between a fungus and an algae cell forms lichen The fungi provide the algal cell with water and nutrients from the environment The algae provide the fungi with carbohydrates produced during photosynthesis These organisms cannot be cultures alone when separated the organisms cannot grow or reproduce successfully Example 2 Cattle egrets are insectivores The cattle egret will eat insects that have been disturbed when the cattle forage Example 3 A spider building a web on a tree this allows the spider to easily capture prey Example 4 Aphids are tiny insects that use their pointed snout to suck fluids from the phloem of plants Adapted from a case study by Eric Ribbens Department of Biological Sciences Western Illinois University Example 5 Yucca moths and yucca plants have a reciprocal obligate relationship the plants cannot make seeds without the yucca moth and the moth larvae only reach maturity if they eat developing yucca seeds Example 6 Fig wasps lay eggs on figs The male fig wasp is wingless and does not leave the fig tree Female fig wasps fly great distances to lay eggs and fertilize the fig trees that she visits Figs can only be pollinated by fig wasps Example Type of Interaction 1 MUTUALISM Obligatory or Facultative OBLIGATORY 2 3 4 5 6 COMMENSALISM FACULTATIVE COMMENSALISM OBLIGATORY PARASITISM OBLIGATORY MUTUALISM OBLIGATORY MUTUALISM OBLIGATORY Part 4 Coevolution in Newts Watch the Toxic Newts video and read the background plain text URL https unctv pbslearningmedia org resource tdc02 sci life evo toxicnewts