Unit 4

• Live in giant kelp forests on Pacific coast • Hunted almost to extinction by early 1900s • Partial recovery since listed as endangered in 1977 Reasons to care about sea otters: - Keystone species - Ethics - Tourism dollars

• Competition • Predation • Parasitism • Mutualism • Commensalism

• Most common interaction is competition Interspecific competition - Competition between different species to use the same limited resources Resource partitioning - Occurs when different species evolve specialized traits that allow them to share the same resources - Species may use only parts of resource - At different times In different ways

• Competition between different species to use the same limited resources

• Occurs when different species evolve specialized traits that allow them to share the same resources • Species may use only parts of resource • At different times In different ways

• Predator feeds directly on all or part of a member of another species (prey) • Strong effect on population sizes and other factors in ecosystems

• Walk, swim, or fly • Camouflage • Chemical warfare

• Camouflage • Chemical warfare • Warning coloration • Mimicry • Behavioral strategies

• Changes in the gene pool of one species can cause changes in the gene pool of the other • Example: bats and moths • Echolocation of bats and sensitive hearing of moths

Animals with better defenses against predation tend to leave more offspring

• One species (parasite) lives on another organism • Parasites harm but rarely kill the host • Examples: tapeworms, sea lampreys, fleas, and ticks

• Interaction that benefits both species • Nutrition and protective relationship • Not cooperation—mutual exploitation • Example: clownfish live within sea anemones • Gain protection and feed on waste matter left by anemones’ meals Clownfish protect anemones from some predators and parasites

• Benefits one species and has little effect on the other • Examples: • Epiphytes (air plants) attach themselves to trees • Birds nest in trees

• Normally gradual change in structure and species composition in a given system

• Involves gradual establishment of communities in lifeless areas • Need to build up fertile soil or aquatic sediments to support plant community • Pioneer species such as lichens or mosses

• Series of terrestrial communities or ecosystems develop in places with soil or sediment • Examples: abandoned farmland, burned or cut forests, and flooded land

Facilitation of area by one species for another Inhibition hinders growth

Ability of a living system to survive moderate disturbances

Ability of a living system to be restored through secondary succession after a moderate disturbance

Group of interbreeding individuals of the same species

• May increase, decrease, or remain the same in response to changing environmental conditions • Scientists use sampling techniques to estimate Variables that govern changes in population size: - Births, deaths, immigration, and emigration

• Most populations live together in clumps or groups • Organisms cluster for resources • Protection from predators

• Distribution of individuals among various age groups • Pre-reproductive, reproductive, and post-reproductive stages

can be used to determine abundance, density, and distribution of species