Topic 13: Ecology
Topic 13: Ecology
Chapter Overview
Chapter 52: Sections 52.1, 52.4
Chapter 53: Sections 53.1-53.3
Chapter 54: Sections 54.1-54.2
Chapter 55: Sections 55.1-55.3
Learning Outcomes
Upon successful completion of this topic, students will be able to:
Explain the relationship between weather and climate.
Describe the primary causes of seasonal variation.
Describe conditions that can produce microclimates.
Explain how climate and competition limit an organism’s ability to survive in an area.
Describe the structural features of populations.
Describe the dynamic features of populations.
Diagram hypothetical survivorship curves.
Compare exponential and logistic population growth.
Summarize the different meanings of biodiversity.
Explain competitive exclusion and compare fundamental and realized niches.
Explain how predation affects the populations of predators and prey.
Summarize types of symbiosis discussed in class and interpret examples.
Compare food chains and food webs.
Explain how keystone species influence community structure.
Describe how communities change through succession and how an intermediate disturbance regime maximizes biodiversity.
Diagram the flow of energy and cycling of nutrients within an ecosystem, compare the trophic efficiency of different animal groups, and diagram and interpret a trophic pyramid.
52.1 Introduction to Ecology
Definition of Ecology: Ecology is the rigorous study of climate and interactions with other species to understand how these factors influence the distribution and abundance of organisms.
Utilizes:
Quantitative Approach: Western scientific methodology.
Traditional Ecological Knowledge (TEK): Integrating indigenous knowledge.
Subfields of Ecology
Organismal Ecology: Focuses on how an organism’s structure, physiology, and behavior affect its survival in the environment.
Example: How flamingos mate?
Population Ecology: Analyzes factors that affect population size and temporal changes.
Example: Environmental factors affecting reproductive rates of flamingos.
Community Ecology: Examines interactions between species and their effects on community structure and organization.
Example: Factors influencing species diversity in an area.
Landscape Ecology: Focuses on interactions across multiple ecosystems regarding energy, material, and organism exchanges.
Example: Nutrient effects from terrestrial ecosystems on lake organisms.
Ecosystem Ecology: Emphasizes energy flow and chemical cycling between organisms and their environments.
Example: Factors controlling photosynthetic productivity in aquatic ecosystems.
Global Ecology: Examines the influence of regional energy and material exchanges on organism distribution and ecosystem dynamics.
Example: Effects of global air circulation patterns on species distribution.
52.1 Earth's Climate Varies by Latitude and Season
Climate: Long-term prevailing weather conditions in an area influenced by several factors:
Temperature, Precipitation, Sunlight, Wind.
Major drivers of climate:
Solar Energy: Affects global climate patterns through insolation (intensity of sunlight in a specific area over time).
Evaporation: Warm temperatures in tropics lead to evaporation and moisture release (rain)
Dry air leads to desert formation around 30°N/S latitudes.
Factors Determining Climate
Seasonality: Earth's axial tilt and orbit cause seasonal variations affecting:
Day length
Solar radiation
Temperature
Rainfall patterns, wind, and ocean currents.
Water Bodies: Ocean currents influence climate by altering air temperatures.
Coastal areas often receive more precipitation than inland areas.
Specific heat capacity of water moderates local climates.
Afternoon temperature differences between land and ocean impact wind patterns.
Mountains: Affect climate by creating rain shadows.
Windward sides receive more rainfall while leeward sides are drier (i.e., deserts).
Temperature decreases with elevation (~6°C drop per 1,000 m).
Microclimates
Microclimates: Localized climatic variations caused by:
Abiotic Factors: Temperature, light, water, nutrients.
Biotic Factors: Organisms such as trees moderating climate by providing shade.
Climate Change Effects: Burning fossil fuels and deforestation shift climate patterns, challenging species' adaptability.
52.4 Interactions Limit the Distribution of Species
Distribution Influences: Physical land characteristics and climatic factors affect species distribution.
Example: Kangaroos in Australia’s unique environment.
Dispersal Limiting Factors: Include:
Abiotic Factors: Temperature, salinity, water levels, sunlight, soil nutrients affect survival.
Fundamental niches define the conditions enabling survival.
Example: High/low temperature extremes impact cell survival.
Biotic Factors: Predators, food sources, disease can restrict survival and reproduction.
Role of Humans: Human activity can prevent natural range expansions affecting ecosystem dynamics.
53.1 Biological Processes Affect Population Dynamics
Populations: Groups of individuals from the same species within a defined area interacting and interbreeding.
Density: Number of individuals per unit area or volume, assessed using methods like mark-recapture.
Births and deaths influence population size changes.
Immigration: Influx of individuals from other populations.
Emigration: Movement of individuals from a population to new locations.
Population Dispersion Patterns
Dispersion: The spacing pattern of individuals within a population:
Clumped: Grouped in patches.
Uniform: Evenly spaced.
Random: Independent spacing with no pattern.
Demographics in Population Studies
Demography: Study of population statistics and changes.
Life Tables: Summarize survival and reproductive rates based on age groups.
Birth Rates: Frequency of offspring.
Death Rates (Mortality): Frequency of deaths observed.
Survivorship Curves: Graphs showing the proportion of individuals alive at various ages:
Type I: Low early death rate (e.g., humans).
Type II: Constant death rate across lifespan (e.g., squirrels).
Type III: High early death rate (e.g., fish).
Reproductive Rates
Female Reproductive Output varies with age and can be estimated through various methods including genetic testing.
Methods include mark-recapture and molecular tools (e.g., PCR).
53.2 Change in Population Size
Population growth is determined by births, immigration, deaths, and emigration with the basic formula of:
Where B = births and D = deaths over time.
Per Capita Change: Represents average contributions of individuals to population change, represented as:
Mathematical Model:
Where r denotes per capita growth rate.
Exponential Growth
Characterized by rapid increase when conditions are favorable, leading to a “J-shaped” curve in graphs representing population growth.
Example: Population may increase by a fixed number (
e.g., 40 individuals) at a certain growth rate regardless of total population size.
53.3 Logistic Growth
Carrying Capacity (K): The maximum sustainable population within an environment.
Logistic Growth Models: Describe how per capita growth slows as population reaches K:
Population growth rate slows as resources become limited, experiencing overshoots.
54.1 Community Interactions Are Dynamic
A Biological Community is a group of populations of different species living close enough to interact.
Interspecific Interactions: Interactions between species, categorized as:
Competition: -/- (none benefits)
Predation: +/- (one benefits, one harmed)
Herbivory: +/- (plants eaten)
Parasitism: +/- (one benefits, one harmed)
Mutualism: +/+ (both benefit)
Commensalism: +/0 (one benefits, the other unaffected)
Impact of Interactions on Community Composition
Interactions can alter species abundance and influence evolutionary processes affecting morphology, physiology, and behavior.
Example: Kelp forests provide habitats, but can be affected by predators like sea urchins.
Competition and Resource Limitations
Interspecific Competition: Competing species for limited resources (e.g., soil, nutrients).
Competitive Exclusion: Dominance of one species over another leading to local elimination:
G.F. Gause’s work on Paramecium illustrates this phenomenon.
Ecological Niches
Ecological Niches: Encompass both abiotic and biotic resources a species requires to survive.
Resource Partitioning: Mechanisms allowing coexistence by using portions of shared niches.
Fundamental vs. Realized Niches: Fundamental niches are theoretical while realized niches are actual occupied niches based on competition.
Exploitative Interactions
Predation: Interaction where one organism consumes another; influences community structure.
Herbivory: Involves plant consumption without killing plants, thus impacting plant abundance and ecosystem health.
Parasitism: Derives nutrients from host organisms, which can weaken them.
54.2 Species Diversity and Trophic Structure
Species Diversity: Includes species richness and relative abundance, vital in community ecology.
Trophic Structure: Feeding relationships in ecosystems, represented via food chains and webs.
Energy Transfer Efficiency: Production efficiency indicates how well energy is converted at trophic levels; usually around 10% due to energy loss in metabolic processes.