Post on 13-Dec-2015
Ecosystems:How do They Work?
Unit 5
5-1 Earth’s Life-Support Systems1. The atmosphere2. The hydrosphere3. The geosphere4. The biosphere
The Biosphere
• Contains the living systems on Earth
3 Factors Sustain Life on Earth
1. One-way flow of high-quality to low-quality energy: -Sun→ organisms→ environment (mostly heat)→ space2. Cycling of nutrients through the biosphere -cycles can take seconds to centuries; governed by matter conservation laws3. Gravity
Ecosystems Have Living and Nonliving Components Abiotic:• Water • Air • Nutrients • Rocks • Heat • Solar energy
Biotic:• Living, once living
Energy and the Ecosystem
• Life begins with the sun’s energy• Trophic levels: biotic energy pathways which include: -primary producers -consumers -decomposers
Energy and the Ecosystem
• Photosynthesis: process by which plants, algae, and some bacteria use sunlight, carbon dioxide, and water to produce carbohydrates and oxygen.• End result: carbohydrate (sugar molecules).• Gives energy to do daily activities.
Primary Producers
• AKA autotrophs•Make organic molecules (glucose) from inorganic
compounds • Primary producers: green plants (trees, phytoplankton), specialized bacteria -photosynthesis: 6CO₂ + 6H₂ → C₆H₁₂O₆ + 6O₂ (2% sunlight) -chemosynthesis: occurs near thermal vents (no sunlight)
FYI Chemosynthesis
• Deep-ocean communities of worms, clams, crabs, mussels, and barnacles, exist in total darkness on the ocean floor, where photosynthesis cannot occur.• Producers are bacteria that use hydrogen sulfide.• Other underwater organisms eat the bacteria or the organisms that
eat the bacteria.
Consumers
• AKA heterotrophs• Gain energy by breaking down organic molecules to release
energy -aerobic (cell) respiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂ • Food is oxidized (burned) for repair, growth, maintenance•Wastes products: cellulose, CO₂, H₂O, other compounds
Primary Consumers
• Herbivores• Adapted for plant eating only ex. Giraffes, caterpillars, zooplankton
Secondary Consumers
• Carnivores adapted to feed on herbivores ex: spiders, lions, most small fish
Tertiary Consumers
• Carnivores adapted to feed on other carnivores ex. tigers, hawks, orcas
Omnivores
• Adapted to feed on both plants and animals ex. pigs, bears, humans
Detritivores/Decomposers
• Detritivores/decomposers feed on wastes or remains of organisms -break down organic compounds -return nutrients to ecosystem ex. earthworms, vultures, bacteria, fungi
Energy Flow in the Ecosystem
•Most ecosystems use sunlight as their energy source• Food chain: movement of energy and nutrients from one
trophic level to the next -determines how energy, nutrients move from organism to organismFood web: network of interconnected food chains
Loss of Energy
• Energy degrades with each use so less is available to next organism• 10% Rule: 90% of energy is “lost” from one trophic level to
another
5-2 Biochemical Cycling
• 2nd basic principle of ecosystem sustainability: ecosystem dispose of waste and replenish nutrients by recycling:
-hydrologic cycle -carbon cycle -nitrogen cycle -phosphorus cycle -sulfur cycle
FYI: The Science of Water
Properties of water due to hydrogen bonds between water molecules: • Exists as a liquid over a large range of temperature • Changes temperature slowly • High boiling point: 100˚C • Adhesion and cohesion • Expands as it freezes • Solvent • Filters out harmful UV
Hydrologic Cycle
Movement of water between surface and atmosphereThree major processes renew water:• Evaporation • Precipitation • Transpiration: movement of water through leaves -90% of water that evaporates into atmosphere
Hydrologic Cycle
Human Impact on Hydrologic Cycle•Withdrawal of large amounts of freshwater at rates faster
than nature can replace it • Clearing vegetation increases runoff, erosion• Draining wetlands increases flooding
The Carbon Cycle
•Movement of carbon from the nonliving environment into organisms and back• Carbon is essential component of proteins, fats, and
carbohydrates, which make up all organisms
The Carbon Cycle• Photosynthesis: producers convert carbon dioxide
from the atmosphere into carbohydrates.• Consumers obtain carbohydrates from the producers
they eat.
The Carbon Cycle• Cellular respiration: carbon is released back into the
atmosphere as carbon dioxide.• Carbon is stored in limestone, one of the largest
“carbon sinks” on Earth.
The Carbon Cycle
• Fossil fuels store carbon left over from bodies of organisms that died millions of years ago:• Coal• Oil (petroleum)• Natural gas
The Carbon Cycle
• Burning fossil fuels releases carbon into the atmosphere as carbon dioxide. • Increased levels of carbon dioxide may contribute to
global warming.• Global warming: increase in the temperature of the
Earth.
Humans Impact on the Carbon Cycle
The Nitrogen Cycle
•Movement of nitrogen among air, soil, water, plants, and animals. •Makes up 78 percent of gases in the atmosphere• All organisms need nitrogen to build proteins- building blocks
of cells.
The Nitrogen Cycle• Nitrogen must be “fixed” by special
bacteria before organisms can use it.• Nitrogen-fixing bacteria and are found
only in roots of legumes (soy, peanut plants, clover).• -convert nitrogen to ammonia• -excess nitrogen is released into soil
The Nitrogen Cycle
• Decomposers return nitrogen to the soil• Soil bacteria convert small amount of the nitrogen into
nitrogen gas• Nitrogen gas returns to the atmosphere, completing the cycle.
Decomposers and the Nitrogen Cycle
Human Impacts on Nitrogen CycleOver-fertilizing crops creates nitrogen runoff in waterways, reducing O₂ and depleting aquatic life.Burning fossil fuels releases NO, a component of acid rain.
The Phosphorus Cycle
•Movement of phosphorus between environment and organisms-does not involve atmosphere.• Phosphorus make up cells and ATP (energy molecule)• Plants get the phosphorus from soil and water• Animals get phosphorus by consuming plants or herbivores.
The Phosphorus Cycle
• Erosion of rock creates small amounts of phosphate, which moves into the soil.• Plants absorb phosphates in soil through roots.• Some phosphorus runs off into ocean and accumulates as
sediment.
The Phosphorus Cycle
Human Impacts on Phosphorus Cycle
Over-fertilizing crops creates phosphate runoff in waterways, causing rapid algal bloom.-too much algae reduces O₂, depleting aquatic life.