Phylogenies and The History of Life

How to Estimate Phylogenies

Phylogenies are evolutionary trees that depict relationships among species. Estimating phylogenies involves analyzing shared characteristics and genetic information.

• Create a Data Matrix: Closely related species should share more characters; distantly related species share fewer characters. Data matrices are used to organize these traits.

• Use the Data Matrix to Estimate a Tree: The cladistic approach is based on synapomorphies (shared derived traits) that identify monophyletic groups.

• Large Scale Patterns in Life's History – Adaptive Radiation:

  • When a single species rapidly produces many descendant species (rapid speciation), usually when new resources or niches become available.

  • Niche: Refers to the range of conditions that a species can tolerate and the range of resources it can use.

Mechanisms that Can Trigger Adaptive Radiation

• Extrinsic Factors: Environmental changes.

• Intrinsic Factors: Evolution of morphological, physiological, or behavioral modifications.

• Adaptive Radiation by Ecological Opportunity:

  • Occurs when there is the availability of more resources or new types of resources.

  • Example: Descendants of original colonizing species begin to live in a wide range of habitats.

• Adaptive Radiation by Morphological, Physiological, or Behavioral Innovation:

  • New key traits evolve, allowing species to exploit new resources.

  • Example: Flowers in angiosperms (organism group).

Mass Extinctions

Mass extinctions are rapid, large reductions in the number of species, often driven by short-term environmental catastrophes.

• Background Extinctions: Smaller, more gradual extinction events due to normal environmental changes.

• Mass Extinctions: Events like the extinction of dinosaurs, with extinction rates much higher than background rates.

Introduction to Ecology

Definition and Scope

Ecology is the scientific study of how organisms interact with each other and their environment. It is closely related to evolution, as the diversity of life is the result of evolutionary processes.

• Ecology is dynamic, collaborative, and interdisciplinary.

• Human health depends on healthy ecosystems.

Levels of Ecological Study

• Organismal Ecology: Focuses on how individual organisms interact with their environment, including morphological, physiological, and behavioral adaptations.

• Population Ecology: Studies groups of individuals of the same species living in the same area at the same time.

• Community Ecology: Examines populations of different species that interact within a defined area.

• Ecosystem Ecology: Considers all organisms in an area plus abiotic components (air, water, soil, sunlight).

• Global Biosphere Ecology: Studies the biosphere, the thin layer surrounding Earth where all life exists, including global impacts and movement of invasive species.

• Conservation Ecology: Efforts to study, preserve, and restore threatened populations, communities, and ecosystems.

What Determines Distribution and Abundance of Organisms?

• Biogeography: The study of how organisms are distributed geographically.

• Niche: The range of conditions a species can tolerate and the range of resources it can use, determined by biotic and abiotic factors.

Abiotic Factors Affecting Distribution

• Temperature: Affects physiological processes such as growth, survival, and reproduction.

• Water: Essential for photosynthesis and water balance in organisms.

• Nutrients: Availability affects growth and survival.

• Salinity: Influences water movement and organism distribution.

• Interactions with Other Species: Includes competition, predation, mutualism, and commensalism.

Biomes

Definition and Classification

Biomes are regions characterized by distinct abiotic factors and dominant types of vegetation.

• Each biome contains species adapted to particular sets of conditions.

• Primary Productivity (NPP): The total amount of biomass generated by carbon fixation (photosynthesis) minus the amount of fixed carbon oxidized during cellular respiration.

• Formula:

Major Terrestrial Biomes

• Arctic Tundra: Low precipitation, very cold, very short growing season.

• Boreal Forest: Moderate precipitation, cold, acidic soils, conifers.

• Temperate Forest: Moderate precipitation and temperature, winter freezing, deciduous trees.

• Temperate Grasslands: Dry summers, cold winters, moderate precipitation, grasses.

• Tropical Wet Forest: Warm and wet year-round, rapid nutrient cycling, high productivity.

Aquatic Biomes

• Freshwater: Includes lakes, ponds, streams, rivers, and wetlands.

• Marine: Oceans, estuaries (where freshwater meets saltwater).

Population Ecology

Introduction

Population ecology integrates morphological, behavioral, and physiological studies to understand how populations change over time.

Population Distribution and Abundance

• Distribution: Explains where populations of a species live, their abundance, density, and dispersion.

• Geographic Range: The total area occupied by a population.

• Population Abundance: The total number of individuals within a defined area.

• Population Density: Number of individuals per unit area.

• Population Dispersion: The spacing of individuals within the geographic range (random, clumped, uniform).

Demography

Demography studies factors that determine the size and structure of populations through time.

• Birth Rates

• Death Rates

• Immigration Rates

• Emigration Rates

• Fecundity: The number of female offspring produced by each female in the population.

• Survivorship: The proportion of offspring that survive to a particular age.

  • Type I Curve: High survivorship throughout life.

  • Type II Curve: Constant mortality throughout life.

  • Type III Curve: High death rates early in life.

• Life Tables: Summarize the probability that an individual survives and reproduces at each age.

Community Ecology

Types of Species Interactions

• Commensalism (+/0): One species benefits, the other is unaffected.

• Competition (-/-): Both species are harmed by the interaction.

• Consumption (+/-): One species benefits, the other is harmed (includes predation, herbivory, parasitism).

• Mutualism (+/+): Both species benefit.

Dispersal and Invasive Species

• Dispersal: Movement of individuals from their place of origin to new locations.

• Invasive Species: Species introduced to an area where they would not normally live, often causing ecological disruption.

Climate and Biomes

Weather and Climate

• Weather: Short-term atmospheric conditions (temperature, precipitation, sunlight, wind).

• Climate: Long-term patterns of weather in a region.

Major Factors Affecting Climate

• Atmospheric Circulation: Driven by the uneven heating of the earth, major cycles include Hadley cell, Ferrel cell, and Polar cell.

• Seasonality: Caused by the tilt of Earth's axis.

• Regional Effects: Mountains and oceans affect local climate (rain shadow effect, moderation by water).

Summary Table: Types of Species Interactions

Additional info:

• Some explanations and examples were expanded for clarity and completeness.

• Definitions and formulas were added to ensure the notes are self-contained and suitable for exam preparation.