Partial recovery since listed as endangered in 1977
Reasons to care about sea otters
Five types of species interactions
Interspecific competition
Predation
Parasitism
Mutualism
Commensalism
Interspecific competition
Competition between different species to use the same limited resources
Competitive exclusion principle
Two species cannot occupy the same niche
Resource partitioning
Different species evolve specialized traits that allow them to share the same resources
Predation
Predator feeds directly on all or part of a member of another species (prey)
Strong effect on population sizes and other factors in ecosystems
Methods of predation
Herbivores walk, swim, or fly to plants
Carnivores use speed, flight, and senses to locate prey
Predators adapt camouflage and chemical warfare
Prey adapt protective shells, bark, spines, and thorns
Prey species adaptations
Camouflage
Chemical warfare
Warning coloration
Mimicry
Behavioral strategies
Giant kelp anchored to ocean floor and grow toward surface
Fast growing
Resistant to storm and wave damage
Support many marine plants and animals
Sea urchins prey on kelp plants
Southern sea otter helps control sea urchin population
Coevolution
Changes in the gene pool of one species can cause changes in the gene pool of the other
Coevolution example
Bats and moths
Echolocation of bats and sensitive hearing of moths
Parasitism
One species (parasite) lives on another organism
Parasites harm but rarely kill the host
Parasitism examples
Tapeworms
Sea lampreys
Fleas
Ticks
Mutualism
Interaction that benefits both species
Nutrition and protective relationship
Not cooperation—mutual exploitation
Mutualism 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
Commensalism
Benefits one species and has little effect on the other
Commensalism examples
Epiphytes (air plants) attach themselves to trees
Birds nest in trees
Primary ecological succession
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
Secondary ecological succession
Series of terrestrial communities or ecosystems develop in places with soil or sediment
Examples: abandoned farmland, burned or cut forests, and flooded land
Factors affecting rate of secondary succession
Facilitation of area by one species for another
Inhibition hinders growth
Tolerance occurs when organisms are not in direct competition
Traditional view of ecological succession
Proceeds to stable climax communities
Equilibrium called balance of nature
Current view of ecological succession
Leads to a more complex, diverse, and resilient ecosystem
Can withstand changes if not too large or too sudden
Ecological inertia or persistence
Ability of a living system to survive moderate disturbances
Resilience
Ability of a living system to be restored through secondary succession after a moderate disturbance
Population
Group of interbreeding individuals of the same species
Variables that govern changes in population size
Births
Deaths
Immigration
Emigration
Age structure
Pre-reproductive stage
Reproductive stage
Post-reproductive stage
Limiting factors
Precipitation (on land)
Water temperature, depth, clarity, and other factors (in aquatic environments)
Population density
Density-dependent factors
shaped growth curve
Some species can reproduce exponentially
Reproduce at an early age
Have many offspring each time they reproduce
Short intervals in between reproductive cycles
Environmental resistance
Sum of all factors that limit population growth
Carrying capacity
Maximum population of a given species that a particular habitat can sustain indefinitely
selected species
Species with capacity for a high rate of population growth
May go through irregular and unstable cycles in population sizes
Tend to be opportunists
selected species
Species that reproduce later in life
Have few offspring
Have long life spans
Can be vulnerable to extinction
1900: deer habitat destruction and uncontrolled hunting
1920s–1930s: laws to protect deer
Current deer population explosion in suburban areas
Increased deer-vehicle collisions and Lyme disease
Factors in declining sea otter population
Increased predation by orcas
Toxic algae and pollutants released into the ocean
Low reproductive rate
Rising mortality rate
Other threats: oil spills and fishing traps
Otter population rising in last several years
Survivorship curve
Shows the percentages of members of population surviving at different ages
Late loss (K-selected species)
Early loss (r-selected species)
Constant loss (many songbirds)
Mature white oak (Quercus alba) produces thousands of acorns per year, which serve as an important food source for many animals. Mature trees have an average lifespan of 300 years.
Technological, social, and cultural changes have expanded earth's carrying capacity for the human species today