Survival of the Fittest in Action

Three Basic Types of Interactions 1. Competition 2. Predation 3. Symbiosis

Competition All living things require resources such as: Food Water Living Space Sunlight Mates Competition occurs when two organisms try to use the same resources, especially when resources are limited.

Types of Competition Within a species (intraspecific): Dolphins swimming in a pod compete for squid to eat Between species (interspecific): Coyotes and foxes both compete for the same rabbit prey Competition leads to changing population sizes. When resources are abundant populations grow. When they are scarce, they shrink.

Predation Many interactions involve one organism eating another In order to eat and avoid being eaten, both predators and prey have evolved useful adaptations. Fish swim in schools so that there are more individuals on the look out for predators. Octopus have entirely soft bodies to squeeze through rocks to avoid predators. Killer whales use echolocation to find their prey.

Symbiosis Any type of close interaction between two different species. Often these interactions are so vital that their lives depend on them. Three Types: Mutualism - both benefit (+/+) Commensalism - one benefits, other unharmed (+/0) Parasitism - one benefits, other is harmed (+/-)

Let’s watch a BrainPop about Symbiosis

Mutualism (+/+) Examples Corals provide a home for algae, algae provide extra food through photosynthesis. Spider crab gets camouflage from algae and algae gets living space. Blue-Spotted Stingray gets parasites removed by Cleaner fish and the fish get food.

Commensalism (+/0) Remora feeds on scraps left by the shark, the shark is unaffected. Barnacles travel on whales. They rely on currents to get their food, whales are unaffected.

Parasitism (+/-) Parasitic Barnacle attaches to reproductive system of Swimming Crab and destroys it. Sea Lampreys attach to various fish and secrete an protein that keeps the fish blood from clotting so it can feed off it until the fish dies.