Notes on Biodiversity and Species Interactions

Each species occupies a specific niche in the community, which influences its existence.
- **Feeding Heights of Different Warblers:
  - Bay-Breasted Warbler: Feeds in the middle part of the tree.
  - Cape May Warbler: Feeds at the tips of branches near the top of the tree.
  - Yellow-Rumped Warbler: Feeds in the lower part of the tree and at the bases of the middle branches.**

What is Competition?
- Competition arises when multiple species vie for the same resources such as space, food, or light.
- Example: Connell's barnacle study illustrates competitive outcomes based on resource allocation.
Types of Competition:
- Intraspecific Competition: Competition within a single species.
- Interspecific Competition: Competition between different species.

Ecological Niche: The complete range of an organism's use of biotic and abiotic resources in the environment.
Fundamental Niche: The theoretical niche that a species could occupy without competition.
Realized Niche: The actual niche occupied by the species, which is often smaller than the fundamental niche due to competition.

Interspecific Competition:
- Occurs when two different species compete for a resource that is in limited supply.
- Niche Differentiation: Slight differences in habitat or feeding preferences can allow similar species to coexist.
- Example: The introduction of the American gray squirrel affected the native red squirrel population in Britain by causing a decline in its range due to competitive exclusion.

Example: Male zebras may engage in battles to claim territory, thereby securing breeding rights.

Resource Partitioning: Occurs when species diverge in order to exploit different resources thus minimizing competition for similar resources.

Primary Succession: The process of community development in lifeless areas with no soils. Examples include:
- Areas following volcanic eruptions (e.g., lava flows).
- Regions left by glacial retreats.
- Newly formed beaches or dunes.
Pioneer Species: The first species to colonize previously uninhabited areas (e.g., lichens, mosses).
- Characteristics of Pioneer Species:
- Notably hardy and often able to extract nutrients from rocks or through photosynthesis.

Stages of Growth:
- Lichens and mosses (pioneering species) initiate ecological succession on barren rocks.
- Following further growth, annual plants may establish, followed by perennial grasses and eventually shrubs and tress.
- Climax communities can evolve into mature forests over periods ranging from several decades to hundreds of years.

Secondary Succession: Describes the recovery of an ecosystem after disturbances such as fires, floods or human activities when the soil still remains intact.
Stages of Secondary Succession:
- Pioneer Species: (e.g., annual plants) arise between 0-1 years following disturbance.
- Intermediate Species: (e.g., grasses and perennials) emerge by 1-3 years.
- Climax Community: (e.g., mature oak and hickory forests) develop after 150+ years.

Ecological Disturbance: Events that physically disrupt an ecosystem, leading to changes and the possibility for succession.
Example: The aftermath of a forest fire, such as the conditions in Yellowstone National Park 10 years post-fire.

Carrying Capacity: Refers to the maximum number of individuals of a species that an environment can sustainably support over time due to resource limitations.
A population cannot expand indefinitely, constrained by available resources.
Population Growth Dynamics:
- Populations can exceed carrying capacity temporarily, referred to as overshooting.
- Population graphs illustrate fluctuations, demonstrating peaks and declines based on available resources and environmental factors.

Influences on Carrying Capacity:
- Overgrazing by herbivores can diminish habitats.
- Environmental changes such as climate variation, disasters, or invasive species impact pop. sizes.
Deer Population Case Study:
- An uncontrolled increase in deer populations can lead to habitat degradation, reducing the ecosystem's carrying capacity.
- Changes in population sizes can occur due to seasonal effects, food availability, natural predation, and human activity like hunting.

A case study involving the predator-prey dynamics between moose and wolves illustrates how populations oscillate over time, influenced by external and internal ecological pressures. Data spans decades noting peak populations in relation to resource availability and predator presence.