There are different interactions between the species of a community. Populations may be linked by 4 interactions: competition, predation, mutualism, and commensalism COMMUNITY ECOLOGY: Interspecific Interactions

Interspecies Interaction: Competition Interspecific competition is: The competitive exclusion principle is:

The ecological niche is the sum total of an organism’s use of abiotic/biotic resources in the environment. An organism’s niche is its role in the environment. VideoVideo The competitive exclusion principle: two species cannot coexist in a community if their niches are identical.

Classic experiments confirm this (Video).(Video).

Resource partitioning is VideoVideo Fig. 53.2

Interspecies Interaction: Predation Predation is: Herbivory is: parasitism is: Pathogens are disease-causing organisms that can be considered predators/predation.

Plant defenses against herbivores include chemical compounds that are toxic. Animal defenses against predators. Behavioral defenses include fleeing, hiding, self- defense, noises, and mobbing. Camouflage includes cryptic coloration, deceptive markings.

More Animal defenses against predators. Mechanical defenses include spines. Chemical defenses include odors and toxins Warning colors, sometimes associated with other defenses (toxins).

More Animal defenses against predators. Mimicry – Batesian mimicry – Müllerian mimicry -

Mutualism – Commensalism – Example barnacles attached to a whale. Interspecies Interactions: Mutualism/Commensalism

Coevolution and interspecific interactions. Coevolution refers to reciprocal evolutionary adaptations of two interacting species. When one species evolves, it exerts selective pressure on the other to evolve to continue the interaction. When a prey evolves better defenses against its predator, this selects for predators that are able to overcome this. As the predator evolves to better catch prey, exerts pressure on the prey to evolve even better defenses.

Summary: 4 Interactions Between Species: Interspecific interactions of Table 53.1, note the positive, negative or no affect of the interaction on the individual populations.

What’s the interaction? 1.Cow and Grass? 2.Tiger and ape?Tiger and ape? 3.Moss on trees? 4.Lion and cheetah? 5.Man & sheep-dog?Man & sheep-dog? 6.Human & this animal?Human & this animal? live in our home, eat our food,eat our food wake us when we are sleeping!

Dominant species are: abundance and biomass If we remove a dominant species from a community, it can change the entire community structure. Dominant and keystone species exert strong controls on community structure

Keystone species exert an important regulating effect on other species in a community.

If they are removed, community structure is greatly affected. Video on keystone speciesVideo on keystone species ©

Next Class: Topics on Man’s Interaction w/ Biosphere Working in groups to learn a topic, present your findings to the class. Split into groups (2/topic, each group must quickly decide how to split the work). Turn in worksheet for points. Five topics: 1.Birth defects 2.Frog populations 3.Increasing testicular cancer 4.Autism (ask older students if they knew of any when they were in grade school) 5.Bees

Extra Credit Find New Articles (w/I a year) discussing these topics and if possible, a theory on its cause. Must be good (reliable) articles, but can be newspaper or internet or some other source. I will keep the articles, so make a second copy if you want the article.