21.3 Interactions among living things pg 722 Key concepts: How do an organism’s adaptations help it to survive? What are the major ways in which organisms in an ecosystem interact? What are the three types of symbiotic relationships? Key terms: natural selection, adaptations, niche, competition, predation, predator, prey, symbiosis, mutualism, commensalism, parasitism, parasite, host

Adapting to the environment Natural Selection – a process that selects individuals better suited to their environments to reproduce. It results in adaptations. Adaptations – the behaviors and physical characteristics that allow organisms to live successfully in their environments. Individuals who are poorly suited to the environment are less likely to survive and reproduce.

Niche Every organism has a variety of adaptations that are suited to its specific living conditions. The role of an organism in its habitat is its niche. Includes type of food, how it gets food, which others use the same food Also includes how and when the organism reproduces and the physical conditions it needs to survive

Competition There are three major types of interactions among organisms: competition, predation, and symbiosis Competition is the struggle between organisms to survive as they attempt to use the same limited resource (food, water, shelter)

Predation An interaction in which one organism kills another for food. Predator – does the killing Prey – gets killed Effect of predation on population size: if there are many predators, a decrease in prey population will occur. When that happens, the predators will die from lack of food.

Predator adaptations Speed, poisons, bigger eyes

Prey adaptations Speed, defensive mechanisms (smelliness, ability to puff up or pretend to be bigger, pretending to be a different species, etc) Mimicry False coloring Camouflage Protective covering

Symbiosis Symbiosis is a close relationship between two species that benefits at least one of the species Three types occur: mutualism, commensalism, parasitism

Mutualism Both species benefit E.g. saguaro cactus and long- eared bats Bats get food and cactus gets pollen transfer

Commensalism One species benefits and the other is not helped nor harmed Red tailed hawk with saguaro cactus Hawk gets a nest, cactus not affected

Parasitism One organism living on or inside another and harming it. Organism that benefits is a parasite Organism that is used is a host Common parasites are ticks, fleas, leeches

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