ecology, ecosystems, and the environment chapter 19 great idea: ecosystems are interdependent...
TRANSCRIPT
Ecology, Ecosystems, and the Environment
Chapter 19
Great Idea:Ecosystems are interdependent communities of
living things that recycle matter while energy flows through.
Ecology and Ecosystems
• Ecology– Natural living systems
• Ecosystems– Biotic and abiotic components
• Community– Producers, consumers, decomposers
Characteristics of Ecosystems
• Every ecosystem consists of both living and nonliving parts
• Energy flows through ecosystems• Matter is recycled by ecosystems
Characteristics of Ecosystems – cont.
• Every organism occupies an ecological niche
• Stable ecosystems achieve a balance among their populations
• Ecosystems are not permanent, but change over time
Energy Flows through Ecosystems
• Food Web– Interactions of organisms
• Trophic Levels– Photosynthetic organisms– Herbivores– Carnivores– Decomposers
• Most energy is lost as heat– 10% is transferred
Every Organism Occupies an Ecological Niche
• Ecological niche– Mode of survival
• Each plant/animal fills a niche– Organisms compete for dominance
Stable Ecosystems Achieve a Balance among Their Populations
• Homeostasis– Balance among populations
• Resources are limited– Some variation in populations– Overall relatively constant
The Law of Unintended Consequences
• It is virtually impossible to change one aspect of a complex system without affecting other parts of the systems, often in as-yet unpredictable ways.
The Problem of Urban Landfills
• Solid Waste– Nothing is ever thrown away
• Landfills– Decay slowed enormously
• Response – Recycling– Large depositories
Acid Rain and Urban Air Pollution
• Burning introduces chemicals– Nitrogen oxides, sulfur compounds,
hydrocarbons• Effects
– Air pollution• Production of bad ozone
– Acid rain• Reduction
– Reduce emissions• Power plants• Vehicles
The Ozone Problem
• Ozone– Molecule of 3 oxygen atoms– Absorbs ultraviolet radiation
• The ozone layer– Detection
• Aircraft sampling• Measure spectral lines from molecule
– Stratosphere• Highest concentration
The Greenhouse Effect
• Greenhouse effect– Traps heat on earth
• Global warming– Climate change
• 3 main points– CO2 is a greenhouse gas– Burning fossil fuels increases CO2
– Average global temperature has significantly increased• 1990s warmest decade
Debates about Global Climate Change
• Increased CO2 levels– Responsible for temperature increase?
• World’s oceans– CO2 exchange with atmosphere
– Current circulation
• Solar energy output– Varies over time
Evolution
Chapter 25
Great Idea:All life on Earth evolved from single-celled
organisms by the process of natural selection.
The Fact of Evolution
• Evolution– Ongoing process of change
• Scientists accept evolution as fact– Debate various theories of HOW it
occurs, but no credible scientist denies that fact that it does occur.
The Fossil Record
• Fossils– Organism’s hard parts preserved
• Turned to rock• Replaced by minerals
• Fossil record– Fossils found, catalogued, and analyzed– Shows transitions– Incomplete
The Fossil Record – cont.
• Three key ideas– Older fossils more different– Increasing complexity with time– Most species have gone extinct (99%)
The Biochemical Evidence
• DNA– Evidence for evolution
– Changes slowly
– Also compare amino acid sequences• Cytochrome c
– Humans and chimps identical
– Rattlesnake 86% overlap
Evidence from Anatomy:Vestigial Organs
• Vestigial organs– Internal features– No useful function
• Examples– Appendix: humans– Wings: penguins– Hind legs: whales
Black Smokers
• Black Smokers– Deep-ocean floor– Vents of mineral rich hot water– Diverse ecosystem
• Most primitive bacteria
• Hydrothermal zones– Site of life’s origin?
• Protected• Ideal chemical environment
Natural Selection
• Charles Darwin
• Natural Selection– Variation in populations
• Some variation heritable
– More individuals born than will survive
• Adaptation
• Artificial selection
The Story of Life
• First cell– Natural selection
• Mutations
• Mutations– Random– Most not beneficial
• Environment– Impacts evolution
Mass Extinctions and the Rate of Evolution
• Rate of extinction– 10%-20% extinct in 5-6 million years
• Mass extinctions– 30%-90% extinct
• Mechanisms– Asteroid
• Evolution – Gradualism– Punctuated equilibrium