1.3 I NTERACTIONS IN E COSYSTEMS pp

L EARNING G OALS By the end of this lesson, you should: Understand the three different symbiotic relationships Know what a predator – prey relsationship is and why they are important Know what competition is and what the two types of competitive relationships are Understand the concept of equilibrium and how limiting factors contribute to creating it (e.g. carrying capacity)

B IOTIC I NTERACTIONS Organisms in a community interact with one another in many ways. Three main ways are through symbiosis, predation, and competition.

S YMBIOTIC R ELATIONSHIPS (3 TYPES ) Symbiosis is a close interaction between two different species in which members of one species live in, on, or near members of another species. 1. Commensalism + / 0 relationship One partner benefits without significantly affecting the other Example – Clown fish and anemone

S YMBIOTIC R ELATIONSHIPS (3 TYPES ) 2. Mutualism + / + relationship Both organisms benefit Example – Bees and flowers, crocodiles and dikkop birds 3. Parasitism +/ - relationship One organism, the parasite, harms the host Example – Deer, tick

PREDATOR – PREY RELATIONSHIPS When one organism consumes a second organism Example – Lions and Zebras Some species use mimicry to avoid predators one species looks like another species. Monarch butterflyViceroy Butterfly

C OMPETITIVE R ELATIONSHIPS (2 TYPES ) Where organisms compete for an important resource such as food, shelter or possibly mates. May have negative effects on one another. Actual fighting or exploitative competition 1. Intraspecific Between members of the same species Individuals may compete over food, water, light, space, safe sites, or mates. Important factor limiting the population size of many species.

C OMPETITIVE R ELATIONSHIPS (2 TYPES ) 2. I NTERSPECIFIC 2. Interspecific Between 2 or more species As the population of one species increases, it may limit the density of the competing species

C HARACTERISTICS OF P OPULATIONS As populations grow the resources available to each individual gets smaller. When resources are decreased the number of births will decrease and the number of deaths will increase. Eventually the number of births will equal the number of deaths. This is called an equilibrium.

L IMITING F ACTOR Limiting Factor - Environmental factor that prevents an increase in the number of organisms in a population or prevents them from moving into new habitats.

L IMITING F ACTOR Abiotic Limiting Factors Sunlight, water, soil, and air, natural disturbances such as storms, fires, droughts, and logging. Biotic Limiting Factors Competition among organisms for resources, presence of predators, reliance on other organisms for survival, and the presence of disease causing organisms.

C ARRYING CAPACITY The maximum number individuals that an ecosystem can support without reducing its ability to support future generations of the same species. Exceeding the carrying capacity hurts the environment.

C ARRYING C APACITY The figure shows a rabbit population after it was introduced to an ecosystem. At first the population grows quickly and then it slows down to the point where the number of births equals the number of deaths.

L EARNING G OALS By the end of this lesson, you should: Understand the three different symbiotic relationships Know what a predator – prey relsationship is and why they are important Know what competition is and what the two types of competitive relationships are Understand the concept of equilibrium and how limiting factors contribute to creating it (e.g. carrying capacity)

H OMEWORK Read pp. 36 – 42 Answer the following questions: p. 42 # 1, 3 p. 46 # 1 – 4, 7