Population Ecology Flashcards

$4.5\text{ Billion Years}$ Ago ("Carbon Day")
- Formation of Earth.
$4\text{ Billion Years}$ Ago
- The planet cools down.
- Oceans form.
$3.5\text{ Billion Years}$ Ago
- Emergence of primitive bacteria (prokaryotes).
$2.5\text{ Billion Years}$ Ago
- Diversification of bacteria.
- There was no land; the environment was entirely marine.
- The first life forms were anaerobes that did not require oxygen ( $O_2$ ).
- Anaerobic organisms predominated until microorganisms started photosynthesizing, generating $O_2$ for aerobes.
$2\text{ Billion Years}$ Ago
- Eukaryotes develop (nucleated cells).

Atmospheric Composition
- Present-day atmosphere contains approximately $20\%$ oxygen ( $O_2$ ).
Photosynthetic Proportions and Patterns
- Photosynthesis is the main producer of oxygen on Earth.
- $50\%$ of photosynthesis occurs in marine environments; $50\%$ occurs in terrestrial environments.
- Rates of photosynthesis vary drastically across latitudinal gradients.
Earth Surface Composition
- 70% water.
- $30\%$ land.
Axial Tilt and Temporal Dynamics
- Earth operates on an axial tilt, which determines seasons as well as sunrise and sunset patterns, creating temporal change.
- Hypothetical planetary conditions without an axial tilt:
  - No seasonal variation.
  - Loss of biodiversity and geographical diversity.

Latitudinal Gradient of Biomes
- $70^\circ\text{N}$ to $90^\circ\text{N}$ (Tundra)
  - Freeze/thaw ecosystem.
  - No water shortage.
  - Contains extreme biodiversity.
- $60^\circ\text{N}$ (Boreal Forest / Taiga)
  - Comprises much of the land area in the Northern Hemisphere.
  - Experiences constant rain with no water shortage.
  - Subject to freeze/thaw cycles, but possesses a longer growing period than tundra.
  - Functions as a huge producer of oxygen ( $O_2$ ).
- $45^\circ\text{N}$ (Temperate Forest)
  - Not typical of the entire planet.
  - Generally rainy, but susceptible to drought and progressively getting hotter.
- $30^\circ\text{N/S}$ (Desert)
  - Hot, arid latitude.
  - No rain, resulting in severe water scarcity.
- $0^\circ$ (Tropical Rainforest)
  - Located at the equator.
  - Huge producer of oxygen ( $O_2$ ).
Geographical Controls on Precipitation
- Geographical features within latitudinal zones cause localized variations in precipitation.
- Rain Shadow Deserts: Caused by a combination of altitude, latitude, and the direction of precipitation. Topography blocks moisture, creating a rainy slope on the windward side and a dry rain shadow on the leeward side.
- Marine Currents: Proximity to ocean currents significantly alters local precipitation and climate.

Distribution Range and Habitation
- Habitation range is defined by two primary aspects:
  - Geographical distribution.
  - Ecological distribution (e.g., elevation gradients).
- Elevational Rule of Thumb: Every $1000\,\text{A}$ change in elevation mirrors changes observed in latitude.
- Elevation gradients serve as model systems used to study dispersion and spread patterns.
Dispersion and Spatial Patterns
- Dispersion refers to the specific ways organisms spread across an environment.
- Influenced by latitudinal gradients.
- Three primary patterns of dispersion:
  - Clumped
  - Uniform
  - Random
- Range dynamics and dispersion analysis also incorporate concepts of rarity.

Core Assessment Goals in Population Ecology
- Determining abundance: How many individuals are present in a population?
- Evaluating trajectory: Is the population growing, decreasing, or stagnant?
- Identifying $3$ core factors to predict future population numbers.
- Model organism example: Iguanas.
Population Attributes
- Strategies are applied to calculate specific attributes:
  - Distribution
  - Dispersion
  - Size and density
  - Age structure
  - Sex ratio
- Age Structure Analysis: Evaluates demographic breakdown to address why only a specific subset of a population actively reproduces.
Models of Population Growth
- Intrinsic Growth Rate ( $r$ ): Measures how fast a population can grow when no limiting factors are holding it back (also known as exponential growth).
- Exponential Growth Model: Characterizes unrestricted, linear-rate growth over time on logarithmic scales.
- Carrying Capacity ( $K$ ): The maximum population size that a specific environment can sustainably handle.
- Logistic Growth Model: Models population expansion leveling off as it approaches carrying capacity ( $K$ ).
- Limiting Factors: Environmental attributes that directly influence or determine carrying capacity ( $K$ ). These include:
  - Water
  - Space
  - Food
  - Predators and predation
  - Competition
  - Disease and pathogens

Schedule and Assignments
- Quizzes and assignments take place on Fridays.
- Note-taking resources: $3$ reliable names for class notes include "anna 10".
Weekly Planning Method
- Friday Routine: Reflect on the week (evaluating the good, the bad, and the ugly).
- Sunday Routine: Map out the upcoming week.