Detailed Study Notes on Species Interactions, Ecological Succession, and Population Control

Habitat:
- Live in giant kelp forests along the Pacific coast.
Conservation Status:
- Hunted almost to extinction by the early 1900s.
- Partial recovery since being listed as endangered in 1977.
Reasons to Care About Sea Otters:
- Keystone Species: A species that has a disproportionately large effect on its environment relative to its abundance.
- Ethics: Responsibility towards species and biodiversity.
- Tourism Dollars: Importance of sea otters in promoting eco-tourism.

Most Common Interaction: Competition.
Interspecific Competition:
- Definition: Competition between different species to use the same limited resources.
Competitive Exclusion Principle:
- States that two species cannot occupy the same niche indefinitely.

Occurs when different species evolve specialized traits to share the same resources.
Methods:
- Species may use only parts of resource at:
- Different times.
- In different ways.

Definition:
- A predator feeds directly on all or part of a member of another species (prey).
- Impact: Strong effect on population sizes and ecosystem factors.
Methods of Predation:
- Different strategies utilized by herbivores and carnivores.
- Herbivores: Walk, swim, or fly to plants.
- Carnivores: Utilize speed, flight, and senses.
Adaptations:
- Predators: Camouflage and chemical warfare.
- Prey: Protective shells, bark, spines, and thorns.

Definition: Changes in the gene pool of one species influence changes in the gene pool of another species.
Example: Bats and moths, involving echolocation in bats and sensitive hearing in moths.

Parasitism: One species (the parasite) lives on another organism (the host), harming it but rarely killing it.
- Examples: Tapeworms, sea lampreys, fleas, and ticks.
Mutualism: Interaction that benefits both species involved, involving nutrition and protection.
- Example: Clownfish living within sea anemones, gaining protection and feeding on waste while also safeguarding anemones.
Commensalism: One species benefits while the other is unaffected.
- Examples: Epiphytes attaching to trees and birds nesting in trees.

Definition: A gradual change in structure and species composition in an ecosystem.
Primary Ecological Succession: Establishment of communities in lifeless areas, requiring fertile soil or aquatic sediments.
- Pioneer Species: Lichens or mosses are necessary for initiating this process.
Secondary Ecological Succession: Development of communities in pre-existing environments with soil.
- Examples: Abandoned farmland, burned or cut forests, flooded land.
- Factors Affecting Rate:
- Facilitation by one species for another.
- Inhibition hinders growth.
- Tolerance occurs when organisms are not in direct competition.

Traditional View: Ecological succession leads to stable climax communities (Balance of Nature).
Current View: Succession results in more complex, diverse, and resilient ecosystems that can withstand changes unless they are too large or sudden.

Population Definition: A group of interbreeding individuals of the same species.
Variables Governing Changes in Population Size:
- Births, deaths, immigration, and emigration.
Age Structure: Divided into three categories:
- Pre-reproductive stage.
- Reproductive stage.
- Post-reproductive stage.

Range of Tolerance: The variation in physical and chemical environments under which a population can survive.
Limiting Factors Include:
- Precipitation on land.
- Water temperature, depth, clarity in aquatic environments.
- Density-dependent factors.

Some species reproduce exponentially; factors include reproductive age, offspring number, and reproductive intervals.
J-Curves and S-Curves: Exponential Growth Concepts
- J-Curve: Characterizes species like bacteria that have high reproductive potential.
- S-Curve: Represents populations that stabilize as they reach carrying capacity.
Environmental Resistance: Factors that limit population growth.
Carrying Capacity: Maximum sustainable population size for a given species in an environment; overshoot can lead to population crashes.

r-Selected Species:
- High reproductive potential.
- Work through irregular and unstable cycles.
- Examples: Algae, bacteria, most insects, and many fish.
K-Selected Species:
- Reproduce later in life with few offspring.
- Long life spans; examples include large mammals like whales and humans.

Trait	r-Selected Species	K-Selected Species
Reproductive potential	High	Low
Population growth rate	Fast	Slow
Time to reproductive maturity	Short	Long
Number of reproductive cycles	Many	Few
Number of offspring	Many	Few
Size of offspring	Small	Larger
Degree of parental care	Low	High
Life span	Short	Long
Population size	Variable with crashes	Stable near carrying capacity
Role in environment	Usually prey	Usually predators

Change from habitat destruction and uncontrolled hunting in the 1900s.
Legislative protections during the 1920s and 1930s helped populations recover, leading to current population explosions in suburban areas.
Consequences include increased deer-vehicle collisions and Lyme disease.
Various methods now employed to control the deer population.

Factors in Decline: Increased predation by orcas, toxic algae and pollutants, low reproductive rates, and rising mortality rates. Threats include oil spills and fishing traps.
Notably, the otter population has been rising in recent years.

Definition: Illustrate percentages of a population surviving at different ages.
- Types include:
- Late loss (K-selected species).
- Early loss (r-selected species).
- Constant loss (many songbirds).

Historical examples of population control due to environmental factors include:
- Ireland's Potato famine due to crop failure.
- Bubonic plague's impact on Europe's population.
Notably, technological and cultural changes currently expand Earth’s carrying capacity for humans.

Keystone Role of Sea Otters:
- Feed on sea urchins to prevent destruction of kelp forests.
Importance of biodiversity in promoting solar energy and nutrient cycling, providing alternate paths for energy flow and nutrient economies.