Ecology and Global Systems

3.1 Introduction to Global Systems

  • Learning Objectives:
    • Explain why ecology is important.
    • Describe the methods used to study ecology.
    • Explain how biotic and abiotic factors influence an ecosystem.
    • Explain how we can understand global systems and the changes they undergo.

Ecology

  • Ecology is the scientific study of interactions among organisms and between organisms and their physical environment.

Species and Populations

  • Species: A group of similar organisms that can breed and produce fertile offspring.
  • Population: A group of individuals that belong to the same species and live in the same area.

Community

  • Community: An assemblage of different populations that live together in a defined area.

Ecosystem

  • Ecosystem: all the organisms that live in a place and their physical environment

Biome

  • Biome: a group of ecosystems that share similar climates and typical organisms

Biosphere

  • Biosphere: the entire planet with all its organisms and physical environments
  • Includes atmosphere, geosphere & hydrosphere
  • Extends from about 8 km above Earth’s surface to about 11 km below the surface of the ocean

Gathering Ecological Data

  • Observation
  • Experimentation
  • Modeling

Biotic and Abiotic Factors

  • Biotic Factors: The biological influences on organisms within an ecosystem
  • Abiotic Factors: The physical, or nonliving, factors that shape ecosystems

3.2 Climate, Weather, and Life

  • Learning Objectives:
    • Explain how weather and climate differ.
    • Describe how Earth’s climate and average temperature are determined.
    • Explain the causes of ocean currents.
    • Identify the factors that shape regional climates.
    • Explain the processes involved in climate change.

Climate and Weather

  • Weather: Day-to-day conditions of Earth's atmosphere.
  • Climate: Long-term patterns of temperature and precipitation over many years.
  • Climate = Temperature + Precipitation
    • Wind
    • Clouds
    • Weather/Extreme Events

Solar Energy and the Greenhouse Effect

  • Energy enters as light. Much of the energy is trapped as heat. Smaller amount of energy passes back through walls.

The Greenhouse Effect on Earth

  • Sunlight: Some solar energy is reflected, some is absorbed, and some is reradiated as heat.
  • Heat is lost to space.
  • Heat is reradiated.
  • Heat is absorbed and reradiated by greenhouse gases and retained in the earth system.
  • Greenhouse gases in the atmosphere include:

Latitude and Solar Energy

  • Earth’s climate zones are produced by unequal distribution of the sun’s heat on Earth’s surface.
  • Polar regions receive less solar energy per unit area, and therefore less heat, than tropical regions do.
  • The tilt of Earth’s axis causes the distribution of sunlight to change over the course of the year.
  • Because of the distance Earth is from the sun, we cannot feel the heat from the sun. When we experience the sun’s warmth, we are experiencing the transformation of light energy to heat energy.

Global Winds

  • Unequal distribution of heat between the equator and the poles (differences in density of cold air vs warm air) creates winds.

Ocean Currents

  • Illustration depicting cold and warm surface currents, as well as deep flow currents, relative to the equator and latitudes.

Regional Climate

  • Upwind side: Air rises and cools, releasing moisture.
  • Downwind side: Air descends, warms, and becomes drier, decreasing moisture.

Changes in Climate

  • Climate change involves changes in temperature, clouds, winds, patterns and amounts of precipitation, and the frequency and severity of extreme weather events.

Nonhuman Causes of Climate Change

  • Not all factors that impact climate change are human caused.
  • Causes:
    • Solar output
    • Earth's tilt and orbit
    • Meteorite impact
    • Distribution of continents
    • Mountain building
    • Volcanism & oceans

4.1 Energy, Producers, & Consumers

  • Learning Objectives
    • Define primary producers.
    • Describe how consumers obtain energy and nutrients.

Primary Producers

  • All living systems require energy for growth, reproduction, and metabolic processes, but no organism can create energy - can only use energy from other sources
  • Organisms that can capture energy from nonliving sources and convert it into forms that living cells can use are called autotrophs (or primary producers)

Energy from the Sun

  • Photosynthesis: process that uses energy from the sun to convert carbon dioxide and water into carbohydrates and oxygen

Life Without Light

  • Chemosynthesis: process that uses chemical energy to produce carbohydrates
  • Carbon dioxide + Hydrogen sulfide + Oxygen --> Carbohydrates + Sulfur compounds + Chemical Energy

Energy Sources

  • Energy cannot be created or destroyed, but it can change form
  • Photosynthesis: Carbon dioxide + Water + Light Energy \rightarrow Carbohydrates + Oxygen
  • Chemosynthesis: Carbon dioxide + Oxygen + Hydrogen sulfide + Chemical Energy \rightarrow Carbohydrates + Sulfur compounds

Consumers

  • Organisms that rely on other organisms for energy and nutrients
    • Carnivore
    • Herbivore
    • Omnivore

More Consumers

  • Decomposer
  • Detritivore
  • Scavenger

4.2 Energy Flow in Ecosystems

  • Learning Objectives
    • Explain how energy flows through ecosystems.
    • Explain how ecological pyramids help analyze energy flow through trophic levels.

Food Chains & Webs

  • A food chain is series of organisms in which energy is transferred from one organism to another.
  • A food web is a network of feeding interactions, through which both energy and matter move.

Earth’s Recycling Center

  • Decomposers and detritivores play a role as the recyclers of ecosystems, releasing nutrients that can be used by primary producers

Food Webs and Disturbance

  • Illustrates a complex food web involving producers, herbivores, carnivores, omnivores, detritivores, scavengers, and decomposers within an ecosystem.

Pyramid of Energy

  • Ecological pyramids are models that show the relative amount of energy or matter contained within each trophic level (each step in a food chain or food web)
  • Only a small portion of the energy that enters any trophic level is available to organisms at the next level
  • Organisms spend much of the energy they acquire on life processes, such as respiration, movement, growth, and reproduction
  • Most of the remaining energy is released into the environment as heat

Pyramids of Biomass and Numbers

  • Biomass = total amount of living tissue within a given trophic level
  • A pyramid of biomass is a model that illustrates the relative amount of living organic matter available at each trophic level in an ecosystem

4.3 Cycles of Matter

  • Learning Objectives
    • Explain how matter flows between trophic levels and among ecosystems.
    • Explain how water cycles globally.
    • Identify the importance of the main nutrient cycles.
    • Explain how nutrient availability affects primary productivity.

Recycling in Nature

  • Energy flow is strictly a one- time, one-way movement
  • Matter flows through trophic levels and then flows through biogeochemical cycles that reuse, or recycle, nutrients within and between ecosystems
  • These cycles are powered by the flow of energy

Processes That Cycle Matter

  • Biological Processes
  • Geological Processes
  • Physical and Chemical Processes
  • Human Activities

Water Cycle

  • Evaporation & transpiration à cools to form clouds à precipitation falls to Earth’s surface à runoff carries to bodies of water OR absorbed as groundwater

Nutrient Cycles

  • Nutrients = chemical substances that every organism needs to sustain life (build tissues, chemical reactions, etc).
  • Oxygen participates in parts of the carbon, nitrogen, and phosphorus cycles by combining with these elements and cycling with them through parts of their journeys

Carbon Cycle

  • Major component of all organic compounds
  • Carbon reservoirs include atmospheric carbon (CO_2 gas), fossil fuels (coal, oil, and natural gas), forests, dissolved carbon dioxide, carbon in marine sediments, and carbonate rocks.
  • Carbon cycles through biological, human, geological, and physical/chemical processes.

The Carbon Cycle

  • Carbon Reservoirs (storage of carbon)
    • Animal skeletons & rocks
    • carbon dioxide in atmosphere & dissolved in oceans
    • fossil fuels
    • Living organism tissues in carbs, lipids, proteins & nucleic acids
  • Activities that RECYCLE Carbon
    • Photosynthesis & cell respiration
    • Decomposition
    • Making or burning of fossil fuels
    • Volcanic eruptions
    • Burning forests

Nitrogen Cycle

  • Nitrogen cycle involves nitrogen fixation, biological processes, human activities, and physical/chemical processes.
  • Nitrogen is found in atmospheric nitrogen (N2 gas), soil nitrogen (NH4, NO3^-, NO2^-$), and dissolved nitrogen.
  • Denitrification is also a key process.

The Nitrogen Cycle

  • Nitrogen Reservoirs
    • Nitrogen gas (N_2$$) makes up 78 % of Earth’s atmosphere, but not usable for most organisms
    • Soil, wastes & dead organic matter
    • Dissolved in bodies of water (increased amounts caused by fertilizer runoff)
    • Living tissue in proteins & nucleic acids
  • Processes that RECYCLE Nitrogen
    • Nitrogen fixation & denitrification - bacteria (or lightning) convert between nitrogen gas and ammonia/nitrates/nitrites
    • Absorbed by producers, consumed by heterotrophs & released by decomposers

Phosphorus Cycle

  • Phosphorus cycle involves biological, human, and geological processes.
  • Phosphorus is found in soil phosphates, phosphate rock, dissolved phosphates, and phosphates in marine sediments.

The Phosphorus Cycle

  • Although phosphorus is of great biological importance (DNA & RNA) it is not abundant in the biosphere.
  • Phosphorus Reservoirs
    • inorganic (not part of living tissue) phosphate remains mostly on land (rock and soil minerals) and in the ocean, as dissolved phosphate and sediments.
  • Processes that recycle Phosphorus
    • rock formation & wear down
    • absorbed by plants from soil or water à food web.
    • excretion and decomposition
    • Mined and added to fertilizers, which is applied to the land and often becomes part of runoff, where it enters bodies of water.

Nutrient Limitation

  • The rate at which primary producers create organic material and the long-term survival of species are dependent on changing resource bases that are limited
  • The nutrient whose supply limits productivity is called the limiting nutrient.
    • Soil – N, P, or K
    • Salt water ecosystems – N
    • Freshwater ecosystems - P