unit 3 notes

An exploration of species classifications and their adaptations, discussed through various ecological phenomena.

Historical Context: Early 1600s, Europeans found extensive temperate seasonal forests rich in species like maple, beech, pine, hemlock. Over time, deforestation occurred due to agriculture and development.
Deforestation Peaks: In the 1800s, up to 80% of New England forests were cleared. Post-1850, urban migration led to the abandonment of farms, causing ecological recovery.
Visual Evidence: Stone walls remain as historical markers of prior farmland.

The transformation of abandoned farmland to forests involves complex interactions of species. After farmland abandonment:
- Initial Colonizers: Grasses and wildflowers were spread by wind and birds, leading to rapid plant growth.
- Dominance of Goldenrods: This specialist plant flourished due to its ability to outcompete for sunlight, but was eventually challenged by herbivores such as leaf beetles (Microrhopala vittata).
- Succession Dynamics: Goldenrods support a diverse array of herbivorous insects, including generalist and specialist species, affecting population dynamics.
- Ecological Interactions: Increased beetle populations led to reduced goldenrod populations, allowing for plant diversity resurgence.

White Pine (Pinus strobus): A generalist species thriving in varying conditions replaced the goldenrods as they shaded out other species:
- Growth Conditions: Adaptable to both sunny fields and shaded understory conditions.
- Later Harvesting Effects: Intensive logging in the early 1900s opened spaces for broadleaf species like American beech (Fagus grandifolia) and sugar maple (Acer saccharum).

The patterns of species interactions illustrate the impact of human activities on ecosystem dynamics:
- Generalist vs. Specialist Dynamics: Generalist species often adapt better to changing environments, while specialists are more vulnerable to habitat loss.
- Historical Human Impacts: Deforestation and urbanization continuously reshape natural habitats, affecting species populations and interactions over time.

Generalists vs. Specialists: Differentiate between species that thrive under varying ecological conditions versus those limited to specific habitats.
K- and r-selected Species: Compare reproductive strategies, defining characteristics:
- K-selected species: Long-lived, few offspring, and extensive parental care.
- r-selected species: Short-lived, many offspring, and low parental care.
Survivorship Curves: Analyze organisms' survival patterns throughout their lifespan, with types:
- Type I: High survival rates until late life (e.g., humans).
- Type II: Constant survivorship across all ages (e.g., some birds).
- Type III: Low early life survival with a few reaching adulthood (e.g., many fish).

Environmental Tolerance: Each species has optimal habitats; thus their presence varies across ecosystems:
- Generalist Niche: Broad range of conditions; e.g., stickleback fish.
- Specialist Niche: Narrow range; e.g., koala dependent on eucalyptus leaves.
- Comparative Vulnerability: Specialization limits adaptability in face of environmental change.
- Practical Implications: In light of climate change, generalists are likely to adapt better than specialists.

Lower Growth Rate: Population increases slowly until reaching carrying capacity.
Traits:
- Often large organisms with later reproductive maturity.
- Produce few, larger offspring.
- Expend energy on parental care (e.g., elephants).
Population Stability: Generally near the ecosystem's carrying capacity, showing resistance to rapid population swings.

Higher Growth Rate: Populations grow quickly, often overshooting carrying capacity.
Traits:
- Smaller organisms, early reproductive maturity.
- Produce many small offspring with little to no parental care (e.g., house mice).
Population Fluctuations: Populations can dramatically increase and decrease in size, showing less stability than K-selected species.

Graphical Representation: Population survival rates plotted against age, showing distinct survival patterns based on life history strategies:
- Type I (K-selected): High survival until old age followed by rapid decline.
- Type II: Constant mortality rate throughout life.
- Type III: High mortality in early life but longer survival for those who reach maturity.

Carrying Capacity (K): Maximum population size an environment can sustain, influenced by resource availability.
Population Dynamics: Understanding how population size changes based on growth models, resource limitations, and environmental effects.

Exponential Growth Model:
- Describes continuous, unrestricted population growth leading to a J-shaped curve on a graph.
- Represented by the equation $\text{Growth Rate} = (b - d)$ , where b is the birth rate and d is the death rate.
- Often seen in r-selected species when resources are abundant.
Logistic Growth Model:
- Illustrates population growth that is initially exponential but slows as it approaches carrying capacity, depicted as an S-shaped curve.
- Both models highlight the influence of resource availability on population dynamics.

K and r Differences: K-selected grow slowly near maximum sustainable limit; r-selected oscillate widely, potentially overshooting carrying capacity.
Density-Dependent and Density-Independent Factors: Influence survival and reproduction, shaping population dynamics and resource availability.

Population management in conservation to regulate endangered species.
Impacts of K and r strategies on biodiversity management, invasive species, and human population policies.