bio unit 8

Table of Contents

• A. Ecology Basics —Pages 3-4

• B. Population Ecology—Page 5-17

• C. Measuring Population Size—Pages 5-6

• D. Patterns of Dispersion—Pages 6-7

• E. Survivorship Curves—Pages 9

• F. Age-Sex Structures—Pages 10-11

• G. Life History Strategies—Pages 11-12

• H. Population Dynamics—Pages 12-18

• I. Community Ecology—Pages 17-22

• J. Interspecific/Interpopulation Interactions—Pages 17-21

• K. Communication Between Organisms—Pages 21-22

• L. Community Structure—Pages 22-25

• M. Simpson’s Diversity Index—Pages 23-24

• N. Ecological Succession—Pages 26-27

• O. Ecosystem Ecology—Pages 27-40

• P. Responses to the Environment—Pages 29-30

• Q. Energy and Matter in Ecosystems—Pages 30-40

• R. Energy Flow and Primary Productivity—Pages 36

• S. Thermoregulation—Pages 36-39

• T. Biogeochemical Cycles—Pages 39-44

• U. Carbon Cycle—Pages 39-40

• V. Nitrogen Cycle—Pages 41-42

• W. Phosphorus Cycle—Pages 42-43

• X. Water Cycle—Page 44

• Y. Movement of Water Through a Plant—Pages 45-46

• Z. Biological Magnification—Pages 46-47

• AA. Ecology and Evolution—Page 47

Important Ideas/Enduring Understandings

• The timing and coordination of biological mechanisms involved in growth, reproduction, and homeostasis depend on organisms responding to environmental cues.

• Transmission of information results in changes within and between biological systems.

• The highly complex organization of living systems requires constant input of energy and the exchange of macromolecules.

• Living systems are organized in a hierarchy of structural levels that interact.

• Communities and ecosystems change based on interactions among populations and disruptions to the environment.

• Naturally occurring diversity among and between components within biological systems affects interactions with the environment.

• Evolution is characterized by change in the genetic make-up of a population over time and is supported by multiple lines of evidence.

• Competition and cooperation are important aspects of biological systems.

Ecology Basics

• Ecology: The study of the interactions between organisms and their environment, including how distribution and abundance of organisms are affected by abiotic and biotic factors.

Abiotic Factors

• Definition: Environmental elements that are not living.

• Examples:

  • Temperature

  • Light

  • Water

  • Nutrients

  • Soil

  • Wind

Biotic Factors

• Definition: Environmental elements that are living or related to living things.

• Examples:

  • Bacteria

  • Protists

  • Fungi

  • Plants

  • Animals

  • Competition

  • Symbiosis

Levels of Ecology

1. Organism Level: Study of individual organisms and their adaptations.

2. Population Level: Study of groups of the same species in the same area (size, density, structure).

3. Community Level: Study of interactions between different populations in the same area.

4. Ecosystem Level: Study of energy flow and nutrient recycling in communities interacting with their environment.

5. Biosphere Level: Study of interactions between ecosystems affecting the overall Earth.

Population Ecology

• Population: A group of organisms of the same species that live in the same area and show signs of reproduction with each other.

• Demography: Statistical study of populations and how they change over time.

• Population Size (N): The total number of individuals in a population.

• Population Density: The number of individuals per unit of area or volume.

Measuring Population Size

• Ideal methods for counting:

  • Counting all members is often impractical.

  • Sampling Methods:

  1. Quadrat Method: Best for stationary organisms; squares are marked out, and individuals counted in each.

  2. Mark-Recapture Method: Best for mobile organisms; individuals are captured, marked, released, and later recaptured to estimate total population based on the proportion of marked to unmarked individuals.

Patterns of Dispersion

• Dispersion Patterns: How individuals are distributed in space.

  • Clumped/Aggregated: Individuals clustered in groups (e.g., schools of fish).

  • Uniform: Evenly spaced throughout habitat (e.g., territorial animals).

  • Random: No predictable pattern (e.g., wind-dispersed plants).

Life Tables

• Life Tables: Summarize birth and death rates for organisms at different life stages; used to predict future population growth.

• Mortality Rate: Calculated by dividing the number of deaths in an age interval by the number surviving at the start of that interval.

Survivorship Curves

• Survivorship Curve: Graph showing the proportion of individuals surviving to each age for a species.

• Types of Survivorship Curves:

  1. Type I: High survival early in life; increased death in older age (e.g., large mammals).

  2. Type II: Constant death rate at all ages (e.g., lizards, hydra).

  3. Type III: Low survival early on, survival improves at older ages (e.g., insects, fish).

Age-Sex Structures

• Age-Sex Structure: Important characteristic represented by age-sex pyramids.

• Interpreting Age-Sex Pyramids:

  • Left side: male population

  • Right side: female population

  • X-axis: number of individuals or percentage per age group

  • Y-axis: age groups (typically in five-year increments)

  • Growth Patterns: Rapid growth shows a sharp pyramid, slow growth shows a more gradual shape, and zero growth or decline shows a dome shape.

Life History Strategies

• Darwinian Fitness: Evaluated by the number of offspring left that survive to reproduce. Life strategies are shaped by natural selection.

• Life History Strategies: Age and stage-specific patterns or timing of key life events (birth, maturity, offspring production, parental investment).

• r-selection vs K-selection:

  • r-selection: High reproductive rate, low parental care, typical of unstable environments (e.g., many fish, insects).

  • K-selection: Low reproductive rate, high parental care, typical of stable environments (e.g., elephants, whales).

Population Dynamics

• Population Dynamics: Study of how populations change in size and structure over time due to resource availability and environmental factors.

• General Equation for Population Growth Rate: $rN=\frac{dN}{dT}$

  • Where:

  • $r$ = per capita rate of increase

  • $N$ = population size

  • $T$ = time

• Exponential Growth: Occurs when resources are unlimited. - Equation: $\frac{dN}{dT}=r_{max}N$

• Logistic Growth: Occurs as resources become limited, leading to a carrying capacity (K). Growth becomes S-shaped.

Community Ecology

Community Structure and Interactions

• Community: Different populations interacting within a habitat.

• Interspecific Interactions:

  1. Competition (-,-)—both species are harmed (Competitive Exclusion Principle).

  2. Predation (+,-)—one benefits at the expense of another.

  3. Symbiosis:

  • Mutualism (+,+)—both species benefit (e.g., plants and pollinators).

  • Commensalism (+,0)—one benefits, other unaffected (e.g., bacteria on skin).

  • Parasitism (+,-)—one benefits, the other is harmed (e.g., humans and tapeworms).

Competition and Resource Partitioning

• Resource partitioning occurs when competing species evolve to limit competition for resources, leading to niche differentiation.

Trophic Ecology

• Trophic Cascades: Top-down effects from predators affecting the entire community structure. Example: Reintroduction of wolves in Yellowstone and its impact on elk and plant life.

Communication Between Organisms

• Communication: Mechanisms include visual, auditory, tactile, electrical, and chemical signaling.

• Examples:

  • Territorial Marking in mammals (scent marking).

  • Coloration in flowers to attract pollinators.

  • Bird Songs for mating calls and territory defense.

  • Aposematic Coloration in warning species (e.g., poison dart frogs).

Community Structure

• Species Composition and Diversity:

  • Species Richness: Number of different species.

  • Species Diversity: Includes both richness and relative abundance.

• Diverse communities are more stable and recover better from disturbances.

Simpson’s Diversity Index

• Formula for Simpson’s Diversity Index: $D=1-\sum\left(\frac{n}{N}\right)^2$

  • Where:

  • $n$ = number of each species present

  • $N$ = total number of organisms

  • Ranges from 0 (no diversity) to 1 (infinite diversity).

• Example Calculation provided in the original notes.

Foundation and Keystone Species

• Foundation Species: Create and define community structures (e.g., kelp forests, coral reefs).

• Keystone Species: Disproportionately affect community structure (e.g., the sea star Pisaster ochraceus and its impact on biodiversity).

Invasive Species

• Invasive Species: Non-native species that disrupt local ecosystems, compete for resources, and outcompete native species (examples: kudzu, Asian carp).

Ecological Succession

• Succession: Progressive changes in community composition over time.

  • Primary Succession: Occurs on newly formed or exposed land (e.g., after volcanic eruptions).

  • Secondary Succession: Re-colonization after disturbances (e.g., wildfires).

Ecosystem Ecology

• Ecosystem: A community plus its physical environment.

• Fluctuations and changes are influenced by geological and meteorological events, as well as human impacts such as climate change and introduction of new species.

Responses to the Environment

• Plant Responses:

  • Phototropism: Growth towards light (positive) or away from light (negative).

  • Photoperiodism: Development and physiological changes based on day length. - Examples: flowering times.

• Animal Responses: Include kinesis (random movement) and taxis (directional movement).

  • Circadian Rhythms: Behavioral patterns occurring in cycles around 24 hours.

Energy and Matter in Ecosystems

• Matter Recycled: Nutrients are recycled while energy flows through ecosystems.

• Matter is absorbed by organisms and returned through decomposition.

Energy Flow and Primary Productivity

• GPP (Gross Primary Productivity): Total energy captured by photosynthesis.

• NPP (Net Primary Productivity): GPP - energy lost through respiration.

• Measured through changes in dissolved oxygen (DO) levels.

Thermoregulation

• Ectotherms: Regulate body temperature behaviorally; dependent on external temperature.

• Endotherms: Maintain a constant internal temperature; can live in diverse habitats but require more energy for metabolism.

Biogeochemical Cycles

Carbon Cycle

• Major processes include photosynthesis and respiration. Human activities have led to increased atmospheric CO2 levels and climate change impacts.

Nitrogen Cycle

• Includes nitrogen fixation, ammonification, nitrification, and denitrification. Human impacts lead to eutrophication of water systems.

Phosphorus Cycle

• Phosphorus in rock, soil, and organic matter; human activity can lead to excessive nutrient loading of aquatic systems.

Water Cycle

• Water is cycled through evaporation, condensation, precipitation, and transpiration. Human activity can affect local and regional water cycles.

Movement of Water Through a Plant

• Water is absorbed through roots, moves up via xylem, and is lost through transpiration. Factors influencing rate: temperature, humidity, wind, soil moisture, and plant type.

Biological Magnification

• Concentration of toxins increases up the food chain (e.g., mercury); exemplified by historical impacts on bald eagle populations due to DDT.

Ecology and Evolution

• Natural selection acts on phenotypic variations; mutations provide the raw material for evolution. Climate change can shift selective pressures on populations, leading to changes in gene frequencies.